1
|
Dømgaard M, Schomacker A, Isaksson E, Millan R, Huiban F, Dehecq A, Fleischer A, Moholdt G, Andersen JK, Bjørk AA. Early aerial expedition photos reveal 85 years of glacier growth and stability in East Antarctica. Nat Commun 2024; 15:4466. [PMID: 38796492 PMCID: PMC11127979 DOI: 10.1038/s41467-024-48886-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Accepted: 05/15/2024] [Indexed: 05/28/2024] Open
Abstract
During the last few decades, several sectors in Antarctica have transitioned from glacial mass balance equilibrium to mass loss. In order to determine if recent trends exceed the scale of natural variability, long-term observations are vital. Here we explore the earliest, large-scale, aerial image archive of Antarctica to provide a unique record of 21 outlet glaciers along the coastline of East Antarctica since the 1930s. In Lützow-Holm Bay, our results reveal constant ice surface elevations since the 1930s, and indications of a weakening of local land-fast sea-ice conditions. Along the coastline of Kemp and Mac Robertson, and Ingrid Christensen Coast, we observe a long-term moderate thickening of the glaciers since 1937 and 1960 with periodic thinning and decadal variability. In all regions, the long-term changes in ice thickness correspond with the trends in snowfall since 1940. Our results demonstrate that the stability and growth in ice elevations observed in terrestrial basins over the past few decades are part of a trend spanning at least a century, and highlight the importance of understanding long-term changes when interpreting current dynamics.
Collapse
Affiliation(s)
- Mads Dømgaard
- Department of Geoscience and Natural Resource Management, University of Copenhagen, 1350, Copenhagen K, Denmark.
| | - Anders Schomacker
- Department of Geosciences, UiT The Arctic University of Norway, Postboks 6050 Langnes, NO-9037, Tromsø, Norway
| | | | - Romain Millan
- Univ. Grenoble Alpes, IRD, CNRS, INRAE, Grenoble INP, IGE, 38000, Grenoble, France
| | - Flora Huiban
- Department of Geoscience and Natural Resource Management, University of Copenhagen, 1350, Copenhagen K, Denmark
| | - Amaury Dehecq
- Univ. Grenoble Alpes, IRD, CNRS, INRAE, Grenoble INP, IGE, 38000, Grenoble, France
| | - Amanda Fleischer
- Department of Geoscience and Natural Resource Management, University of Copenhagen, 1350, Copenhagen K, Denmark
| | | | - Jonas K Andersen
- Department of Geoscience and Natural Resource Management, University of Copenhagen, 1350, Copenhagen K, Denmark
| | - Anders A Bjørk
- Department of Geoscience and Natural Resource Management, University of Copenhagen, 1350, Copenhagen K, Denmark
| |
Collapse
|
2
|
Miles BWJ, Bingham RG. Progressive unanchoring of Antarctic ice shelves since 1973. Nature 2024; 626:785-791. [PMID: 38383628 PMCID: PMC10881387 DOI: 10.1038/s41586-024-07049-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Accepted: 01/09/2024] [Indexed: 02/23/2024]
Abstract
Mass loss of the Antarctic Ice Sheet has been driven primarily by the thinning of the floating ice shelves that fringe the ice sheet1, reducing their buttressing potential and causing land ice to accelerate into the ocean2. Observations of ice-shelf thickness change by satellite altimetry stretch back only to 1992 (refs. 1,3-5) and previous information about thinning remains unquantified. However, extending the record of ice-shelf thickness change is possible by proxy, by measuring the change in area of the surface expression of pinning points-local bathymetric highs on which ice shelves are anchored6. Here we measure pinning-point change over three epochs spanning the periods 1973-1989, 1989-2000 and 2000-2022, and thus by proxy infer changes to ice-shelf thickness back to 1973-1989. We show that only small localized pockets of ice shelves were thinning between 1973 and 1989, located primarily in the Amundsen Sea Embayment and the Wilkes Land coastline. Ice-shelf thinning spreads rapidly into the 1990s and 2000s and is best characterized by the proportion of pinning points reducing in extent. Only 15% of pinning points reduced from 1973 to 1989, before increasing to 25% from 1989 to 2000 and 37% from 2000 to 2022. A continuation of this trend would further reduce the buttressing potential of ice shelves, enhancing ice discharge and accelerating the contribution of Antarctica to sea-level rise.
Collapse
|
3
|
Gao L, Yuan X, Cai W, Guo G, Yu W, Shi J, Qiao F, Wei Z, Williams GD. Persistent warm-eddy transport to Antarctic ice shelves driven by enhanced summer westerlies. Nat Commun 2024; 15:671. [PMID: 38253634 PMCID: PMC10803808 DOI: 10.1038/s41467-024-45010-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 01/09/2024] [Indexed: 01/24/2024] Open
Abstract
The offshore ocean heat supplied to the Antarctic continental shelves by warm eddies has the potential to greatly impact the melting rates of ice shelves and subsequent global sea level rise. While featured in modeling and some observational studies, the processes around how these warm eddies form and overcome the dynamic sub-surface barrier of the Antarctic Slope Front over the upper continental slope has not yet been clarified. Here we report on the detailed observations of persistent eddies carrying warm modified Circumpolar Deep Water (CDW) onto the continental shelf of Prydz Bay, East Antarctica, using subsurface mooring and hydrographic section data from 2013-2015. We show the warm-eddy transport is most active when the summer westerlies strengthen, which promotes the upwelling of CDW and initiates eddy formation and intrusions. Our study highlights the important role of warm eddies in the melting of Antarctica's ice shelves, both now and into the future.
Collapse
Affiliation(s)
- Libao Gao
- First Institute of Oceanography, Key Laboratory of Marine Science and Numerical Modeling, Ministry of Natural Resources, Qingdao, China.
- Laboratory for Regional Oceanography and Numerical Modeling, Laoshan Laboratory, Qingdao, China.
- Shandong Key Laboratory of Marine Science and Numerical Modeling, Qingdao, China.
| | - Xiaojun Yuan
- Lamont-Doherty Earth Observatory, Columbia University, New York, USA
| | - Wenju Cai
- Laboratory for Regional Oceanography and Numerical Modeling, Laoshan Laboratory, Qingdao, China.
- Centre for Southern Hemisphere Oceans Research, CSIRO Oceans & Atmosphere, Hobart, Australia.
- Physical Oceanography Laboratory, Ocean University of China, Qingdao, China.
| | - Guijun Guo
- First Institute of Oceanography, Key Laboratory of Marine Science and Numerical Modeling, Ministry of Natural Resources, Qingdao, China
- Laboratory for Regional Oceanography and Numerical Modeling, Laoshan Laboratory, Qingdao, China
- Shandong Key Laboratory of Marine Science and Numerical Modeling, Qingdao, China
| | - Weidong Yu
- Laboratory for Regional Oceanography and Numerical Modeling, Laoshan Laboratory, Qingdao, China
- School of Atmospheric Sciences, Sun Yat-Sen University, Zhuhai, China
| | - Jiuxin Shi
- Laboratory for Regional Oceanography and Numerical Modeling, Laoshan Laboratory, Qingdao, China
- Physical Oceanography Laboratory, Ocean University of China, Qingdao, China
| | - Fangli Qiao
- First Institute of Oceanography, Key Laboratory of Marine Science and Numerical Modeling, Ministry of Natural Resources, Qingdao, China
- Laboratory for Regional Oceanography and Numerical Modeling, Laoshan Laboratory, Qingdao, China
- Shandong Key Laboratory of Marine Science and Numerical Modeling, Qingdao, China
| | - Zexun Wei
- First Institute of Oceanography, Key Laboratory of Marine Science and Numerical Modeling, Ministry of Natural Resources, Qingdao, China
- Laboratory for Regional Oceanography and Numerical Modeling, Laoshan Laboratory, Qingdao, China
- Shandong Key Laboratory of Marine Science and Numerical Modeling, Qingdao, China
| | - Guy D Williams
- First Institute of Oceanography, Key Laboratory of Marine Science and Numerical Modeling, Ministry of Natural Resources, Qingdao, China
| |
Collapse
|
4
|
Greene CA, Gardner AS, Wood M, Cuzzone JK. Ubiquitous acceleration in Greenland Ice Sheet calving from 1985 to 2022. Nature 2024; 625:523-528. [PMID: 38233618 DOI: 10.1038/s41586-023-06863-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 11/09/2023] [Indexed: 01/19/2024]
Abstract
Nearly every glacier in Greenland has thinned or retreated over the past few decades1-4, leading to glacier acceleration, increased rates of sea-level rise and climate impacts around the globe5-9. To understand how calving-front retreat has affected the ice-mass balance of Greenland, we combine 236,328 manually derived and AI-derived observations of glacier terminus positions collected from 1985 to 2022 and generate a 120-m-resolution mask defining the ice-sheet extent every month for nearly four decades. Here we show that, since 1985, the Greenland Ice Sheet (GrIS) has lost 5,091 ± 72 km2 of area, corresponding to 1,034 ± 120 Gt of ice lost to retreat. Our results indicate that, by neglecting calving-front retreat, current consensus estimates of ice-sheet mass balance4,9 have underestimated recent mass loss from Greenland by as much as 20%. The mass loss we report has had minimal direct impact on global sea level but is sufficient to affect ocean circulation and the distribution of heat energy around the globe10-12. On seasonal timescales, Greenland loses 193 ± 25 km2 (63 ± 6 Gt) of ice to retreat each year from a maximum extent in May to a minimum between September and October. We find that multidecadal retreat is highly correlated with the magnitude of seasonal advance and retreat of each glacier, meaning that terminus-position variability on seasonal timescales can serve as an indicator of glacier sensitivity to longer-term climate change.
Collapse
Affiliation(s)
- Chad A Greene
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
| | - Alex S Gardner
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Michael Wood
- Moss Landing Marine Laboratories, San José State University, San José, CA, USA
| | - Joshua K Cuzzone
- Joint Institute for Regional Earth System Science and Engineering, University of California, Los Angeles, Los Angeles, CA, USA
| |
Collapse
|
5
|
Pelle T, Greenbaum JS, Dow CF, Jenkins A, Morlighem M. Subglacial discharge accelerates future retreat of Denman and Scott Glaciers, East Antarctica. SCIENCE ADVANCES 2023; 9:eadi9014. [PMID: 37889971 PMCID: PMC10610922 DOI: 10.1126/sciadv.adi9014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Accepted: 09/27/2023] [Indexed: 10/29/2023]
Abstract
Ice shelf basal melting is the primary mechanism driving mass loss from the Antarctic Ice Sheet, yet it is unknown how the localized melt enhancement from subglacial discharge will affect future Antarctic glacial retreat. We develop a parameterization of ice shelf basal melt that accounts for both ocean and subglacial discharge forcing and apply it in future projections of Denman and Scott Glaciers, East Antarctica, through 2300. In forward simulations, subglacial discharge accelerates the onset of retreat of these systems into the deepest continental trench on Earth by 25 years. During this retreat, Denman Glacier alone contributes 0.33 millimeters per year to global sea level rise, comparable to half of the contemporary sea level contribution of the entire Antarctic Ice Sheet. Our results stress the importance of resolving complex interactions between the ice, ocean, and subglacial environments in future Antarctic Ice Sheet projections.
Collapse
Affiliation(s)
- Tyler Pelle
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Jamin S Greenbaum
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Christine F Dow
- Department of Geography and Environmental Management, University of Waterloo, Waterloo, ON, Canada
| | - Adrian Jenkins
- Department of Geography and Environmental Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK
| | | |
Collapse
|
6
|
Davison BJ, Hogg AE, Gourmelen N, Jakob L, Wuite J, Nagler T, Greene CA, Andreasen J, Engdahl ME. Annual mass budget of Antarctic ice shelves from 1997 to 2021. SCIENCE ADVANCES 2023; 9:eadi0186. [PMID: 37824617 DOI: 10.1126/sciadv.adi0186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Accepted: 09/07/2023] [Indexed: 10/14/2023]
Abstract
Antarctic ice shelves moderate the contribution of the Antarctic Ice Sheet to global sea level rise; however, ice shelf health remains poorly constrained. Here, we present the annual mass budget of all Antarctic ice shelves from 1997 to 2021. Out of 162 ice shelves, 71 lost mass, 29 gained mass, and 62 did not change mass significantly. Of the shelves that lost mass, 68 had statistically significant negative mass trends, 48 lost more than 30% of their initial mass, and basal melting was the dominant contributor to that mass loss at a majority (68%). At many ice shelves, mass losses due to basal melting or iceberg calving were significantly positively correlated with grounding line discharge anomalies; however, the strength and form of this relationship varied substantially between ice shelves. Our results illustrate the utility of partitioning high-resolution ice shelf mass balance observations into its components to quantify the contributors to ice shelf mass change and the response of grounded ice.
Collapse
Affiliation(s)
| | - Anna E Hogg
- School of Earth and Environment, University of Leeds, Leeds, UK
| | - Noel Gourmelen
- School of Geosciences, University of Edinburgh, Edinburgh, UK
- Earthwave, Codebase, Office L2, 3 Lady Lawson St, Edinburgh, UK
| | - Livia Jakob
- Earthwave, Codebase, Office L2, 3 Lady Lawson St, Edinburgh, UK
| | - Jan Wuite
- ENVEO IT GmbH, Innsbruck 6020, Austria
| | | | - Chad A Greene
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Julia Andreasen
- Department of Soil, Water, and Climate, University of Minnesota, St. Paul, MN, USA
| | | |
Collapse
|
7
|
Robel AA, Sim SJ, Meyer C, Siegfried MR, Gustafson CD. Contemporary ice sheet thinning drives subglacial groundwater exfiltration with potential feedbacks on glacier flow. SCIENCE ADVANCES 2023; 9:eadh3693. [PMID: 37595049 PMCID: PMC10438444 DOI: 10.1126/sciadv.adh3693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 07/19/2023] [Indexed: 08/20/2023]
Abstract
Observations indicate that groundwater-laden sedimentary aquifers are extensive beneath large portions of the Greenland and Antarctic ice sheets. A reduction in the mechanical loading of aquifers is known to lead to groundwater exfiltration, a discharge of groundwater from the aquifer. Here, we provide a simple expression predicting exfiltration rates under a thinning ice sheet. Using contemporary satellite altimetry observations, we predict that exfiltration rates may reach tens to hundreds of millimeters per year under the fastest thinning parts of the Antarctic Ice Sheet. In parts of West Antarctica, predicted rates of exfiltration would cause the total subglacial water discharge rate to be nearly double what is currently predicted from subglacial basal melting alone. Continued Antarctic Ice Sheet thinning into the future guarantees that the rate and potential importance of exfiltration will only continue to grow. Such an increase in warm, nutrient-laden subglacial water discharge would cause changes in ice sliding, melt of basal ice and marine biological communities.
Collapse
Affiliation(s)
- Alexander A. Robel
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30318, USA
| | - Shi J. Sim
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30318, USA
| | - Colin Meyer
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA
| | - Matthew R. Siegfried
- Hydrologic Science and Engineering Program, Department of Geophysics, Colorado School of Mines, Golden, CO 80401, USA
| | - Chloe D. Gustafson
- U.S. Geological Survey, Geology, Geophysics, and Geochemistry Science Center, Lakewood, CO 80225, USA
| |
Collapse
|
8
|
Li R, Cheng Y, Chang T, Gwyther DE, Forbes M, An L, Xia M, Yuan X, Qiao G, Tong X, Ye W. Satellite record reveals 1960s acceleration of Totten Ice Shelf in East Antarctica. Nat Commun 2023; 14:4061. [PMID: 37429894 DOI: 10.1038/s41467-023-39588-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 06/21/2023] [Indexed: 07/12/2023] Open
Abstract
Wilkes Land and Totten Glacier (TG) in East Antarctica (EA) have been losing ice mass significantly since 1989. There is a lack of knowledge of long-term mass balance in the region which hinders the estimation of its contribution to global sea level rise. Here we show that this acceleration trend in TG has occurred since the 1960s. We reconstruct ice flow velocity fields of 1963-1989 in TG from the first-generation satellite images of ARGON and Landsat-1&4, and build a five decade-long record of ice dynamics. We find a persistent long-term ice discharge rate of 68 ± 1 Gt/y and an acceleration of 0.17 ± 0.02 Gt/y2 from 1963 to 2018, making TG the greatest contributor to global sea level rise in EA. We attribute the long-term acceleration near grounding line from 1963 to 2018 to basal melting likely induced by warm modified Circumpolar Deep Water. The speed up in shelf front during 1973-1989 was caused by a large calving front retreat. As the current trend continues, intensified monitoring in the TG region is recommended in the next decades.
Collapse
Affiliation(s)
- Rongxing Li
- Center for Spatial Information Science and Sustainable Development Applications, Tongji University, 1239 Siping Road, Shanghai, China
- College of Surveying and Geo-Informatics, Tongji University, 1239 Siping Road, Shanghai, China
| | - Yuan Cheng
- Institute for the Conservation of Cultural Heritage, School of Cultural Heritage and Information Management, Shanghai University, Shanghai, China.
| | - Tian Chang
- Center for Spatial Information Science and Sustainable Development Applications, Tongji University, 1239 Siping Road, Shanghai, China
- College of Surveying and Geo-Informatics, Tongji University, 1239 Siping Road, Shanghai, China
| | - David E Gwyther
- School of Earth and Environmental Sciences, The University of Queensland, St Lucia, QLD, 4072, Australia
| | - Martin Forbes
- National School of Surveying, University of Otago, Dunedin, New Zealand
| | - Lu An
- Center for Spatial Information Science and Sustainable Development Applications, Tongji University, 1239 Siping Road, Shanghai, China.
- College of Surveying and Geo-Informatics, Tongji University, 1239 Siping Road, Shanghai, China.
| | - Menglian Xia
- Center for Spatial Information Science and Sustainable Development Applications, Tongji University, 1239 Siping Road, Shanghai, China
- College of Surveying and Geo-Informatics, Tongji University, 1239 Siping Road, Shanghai, China
| | - Xiaohan Yuan
- Center for Spatial Information Science and Sustainable Development Applications, Tongji University, 1239 Siping Road, Shanghai, China
- College of Surveying and Geo-Informatics, Tongji University, 1239 Siping Road, Shanghai, China
| | - Gang Qiao
- Center for Spatial Information Science and Sustainable Development Applications, Tongji University, 1239 Siping Road, Shanghai, China
- College of Surveying and Geo-Informatics, Tongji University, 1239 Siping Road, Shanghai, China
| | - Xiaohua Tong
- Center for Spatial Information Science and Sustainable Development Applications, Tongji University, 1239 Siping Road, Shanghai, China
- College of Surveying and Geo-Informatics, Tongji University, 1239 Siping Road, Shanghai, China
| | - Wenkai Ye
- Center for Spatial Information Science and Sustainable Development Applications, Tongji University, 1239 Siping Road, Shanghai, China
- College of Surveying and Geo-Informatics, Tongji University, 1239 Siping Road, Shanghai, China
| |
Collapse
|
9
|
Jordan JR, Miles BWJ, Gudmundsson GH, Jamieson SSR, Jenkins A, Stokes CR. Increased warm water intrusions could cause mass loss in East Antarctica during the next 200 years. Nat Commun 2023; 14:1825. [PMID: 37005432 PMCID: PMC10067810 DOI: 10.1038/s41467-023-37553-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Accepted: 03/22/2023] [Indexed: 04/04/2023] Open
Abstract
The East Antarctic Ice Sheet (EAIS) is currently surrounded by relatively cool water, but climatic shifts have the potential to increase basal melting via intrusions of warm modified Circumpolar Deep Water (mCDW) onto the continental shelf. Here we use an ice sheet model to show that under the current ocean regime, with only limited intrusions of mCDW, the EAIS will likely gain mass over the next 200 years due to the increased precipitation from a warming atmosphere outweighing increased ice discharge due to ice-shelf melting. However, if the ocean regime were to become dominated by greater mCDW intrusions, the EAIS would have a negative mass balance, contributing up to 48 mm of SLE over this time period. Our modelling finds George V Land to be particularly at risk to increased ocean induced melting. With warmer oceans, we also find that a mid range RCP4.5 emissions scenario is likely to result in a more negative mass balance than a high RCP8.5 emissions scenario, as the relative difference between increased precipitation due to a warming atmosphere and increased ice discharge due to a warming ocean is more negative in the mid range RCP4.5 emission scenario.
Collapse
Affiliation(s)
- James R Jordan
- Department of Geography and Environmental Sciences, Faculty of Engineering and Environment, Northumbria University, Newcastle upon Tyne, UK.
- Laboratoire de Glaciologie, Université libre de Bruxelles (ULB), Brussels, Belgium.
| | - B W J Miles
- Department of Geography, Durham University, Durham, DH1 3LE, UK
- School of Geosciences, University of Edinburgh, Edinburgh, UK
| | - G H Gudmundsson
- Department of Geography and Environmental Sciences, Faculty of Engineering and Environment, Northumbria University, Newcastle upon Tyne, UK
| | - S S R Jamieson
- Department of Geography, Durham University, Durham, DH1 3LE, UK
| | - A Jenkins
- Department of Geography and Environmental Sciences, Faculty of Engineering and Environment, Northumbria University, Newcastle upon Tyne, UK
| | - C R Stokes
- Department of Geography, Durham University, Durham, DH1 3LE, UK
| |
Collapse
|
10
|
Davison BJ, Hogg AE, Rigby R, Veldhuijsen S, van Wessem JM, van den Broeke MR, Holland PR, Selley HL, Dutrieux P. Sea level rise from West Antarctic mass loss significantly modified by large snowfall anomalies. Nat Commun 2023; 14:1479. [PMID: 36932070 PMCID: PMC10023770 DOI: 10.1038/s41467-023-36990-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 02/27/2023] [Indexed: 03/18/2023] Open
Abstract
Mass loss from the West Antarctic Ice Sheet is dominated by glaciers draining into the Amundsen Sea Embayment (ASE), yet the impact of anomalous precipitation on the mass balance of the ASE is poorly known. Here we present a 25-year (1996-2021) record of ASE input-output mass balance and evaluate how two periods of anomalous precipitation affected its sea level contribution. Since 1996, the ASE has lost 3331 ± 424 Gt ice, contributing 9.2 ± 1.2 mm to global sea level. Overall, surface mass balance anomalies contributed little (7.7%) to total mass loss; however, two anomalous precipitation events had larger, albeit short-lived, impacts on rates of mass change. During 2009-2013, persistently low snowfall led to an additional 51 ± 4 Gt yr-1 mass loss in those years (contributing positively to the total loss of 195 ± 4 Gt yr-1). Contrastingly, extreme precipitation in the winters of 2019 and 2020 decreased mass loss by 60 ± 16 Gt yr-1 during those years (contributing negatively to the total loss of 107 ± 15 Gt yr-1). These results emphasise the important impact of extreme snowfall variability on the short-term sea level contribution from West Antarctica.
Collapse
Affiliation(s)
| | - Anna E Hogg
- School of Earth and Environment, University of Leeds, Leeds, UK
| | - Richard Rigby
- School of Earth and Environment, University of Leeds, Leeds, UK
| | - Sanne Veldhuijsen
- Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, the Netherlands
| | - Jan Melchior van Wessem
- Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, the Netherlands
| | - Michiel R van den Broeke
- Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, the Netherlands
| | | | | | | |
Collapse
|
11
|
Berthier E, Floriciou D, Gardner AS, Gourmelen N, Jakob L, Paul F, Treichler D, Wouters B, Belart JMC, Dehecq A, Dussaillant I, Hugonnet R, Kääb A, Krieger L, Pálsson F, Zemp M. Measuring glacier mass changes from space-a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2023; 86:036801. [PMID: 36596254 DOI: 10.1088/1361-6633/acaf8e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 01/03/2023] [Indexed: 06/17/2023]
Abstract
Glaciers distinct from the Greenland and Antarctic ice sheets are currently losing mass rapidly with direct and severe impacts on the habitability of some regions on Earth as glacier meltwater contributes to sea-level rise and alters regional water resources in arid regions. In this review, we present the different techniques developed during the last two decades to measure glacier mass change from space: digital elevation model (DEM) differencing from stereo-imagery and synthetic aperture radar interferometry, laser and radar altimetry and space gravimetry. We illustrate their respective strengths and weaknesses to survey the mass change of a large Arctic ice body, the Vatnajökull Ice Cap (Iceland) and for the steep glaciers of the Everest area (Himalaya). For entire regions, mass change estimates sometimes disagree when a similar technique is applied by different research groups. At global scale, these discrepancies result in mass change estimates varying by 20%-30%. Our review confirms the need for more thorough inter-comparison studies to understand the origin of these differences and to better constrain regional to global glacier mass changes and, ultimately, past and future glacier contribution to sea-level rise.
Collapse
Affiliation(s)
- Etienne Berthier
- LEGOS, Université de Toulouse, CNES, CNRS, IRD, UPS, Toulouse, France
| | - Dana Floriciou
- Remote Sensing Technology Institute (IMF), German Aerospace Center (DLR), Oberpfaffenhofen, Germany
| | - Alex S Gardner
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States of America
| | - Noel Gourmelen
- School of GeoSciences, University of Edinburgh, Edinburgh EH8 9XP, United Kingdom
- Earthwave Ltd, Edinburgh EH1 2EL, United Kingdom
- IPGS UMR 7516, Université de Strasbourg, CNRS, Strasbourg 67000, France
| | - Livia Jakob
- Earthwave Ltd, Edinburgh EH1 2EL, United Kingdom
| | - Frank Paul
- Department of Geography, University of Zurich, Zurich, Switzerland
| | | | - Bert Wouters
- Department of Physics, Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, The Netherlands
- Department of Geoscience and Remote Sensing, Delft University of Technology, Delft, The Netherlands
| | - Joaquín M C Belart
- National Land Survey of Iceland, Stillholt 16-18, 300 Akranes, Iceland
- Institute of Earth Sciences, University of Iceland, Reykjavik, Iceland
| | - Amaury Dehecq
- University Grenoble Alpes, CNRS, INRAE, IRD, Grenoble INP, IGE, Grenoble, France
| | - Ines Dussaillant
- Department of Geography, University of Zurich, Zurich, Switzerland
| | - Romain Hugonnet
- LEGOS, Université de Toulouse, CNES, CNRS, IRD, UPS, Toulouse, France
- Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zürich, Zürich, Switzerland
- Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Birmensdorf, Switzerland
| | - Andreas Kääb
- Department of Geosciences, University of Oslo, Oslo, Norway
| | - Lukas Krieger
- Remote Sensing Technology Institute (IMF), German Aerospace Center (DLR), Oberpfaffenhofen, Germany
| | - Finnur Pálsson
- Institute of Earth Sciences, University of Iceland, Reykjavik, Iceland
| | - Michael Zemp
- Department of Geography, University of Zurich, Zurich, Switzerland
| |
Collapse
|
12
|
Medley B, Lenaerts JTM, Dattler M, Keenan E, Wever N. Predicting Antarctic Net Snow Accumulation at the Kilometer Scale and Its Impact on Observed Height Changes. GEOPHYSICAL RESEARCH LETTERS 2022; 49:e2022GL099330. [PMID: 36589269 PMCID: PMC9787652 DOI: 10.1029/2022gl099330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 09/26/2022] [Accepted: 09/26/2022] [Indexed: 06/17/2023]
Abstract
Sub-grid-scale processes occurring at or near the surface of an ice sheet have a potentially large impact on local and integrated net accumulation of snow via redistribution and sublimation. Given observational complexity, they are either ignored or parameterized over large-length scales. Here, we train random forest (RF) models to predict variability in net accumulation over the Antarctic Ice Sheet using atmospheric variables and topographic characteristics as predictors at 1 km resolution. Observations of net snow accumulation from both in situ and airborne radar data provide the input observable targets needed to train the RF models. We find that local net accumulation deviates by as much as 172% of the atmospheric model mean. The correlation in space between the predicted net accumulation variability and satellite-derived surface-height change indicates that surface processes operate differently through time, driven largely by the seasonal anomalies in snow accumulation.
Collapse
Affiliation(s)
- B. Medley
- Cryospheric Sciences LaboratoryNASA Goddard Space Flight CenterGreenbeltMDUSA
| | - J. T. M. Lenaerts
- Department of Atmospheric and Oceanic SciencesUniversity of Colorado BoulderBoulderCOUSA
| | - M. Dattler
- Cryospheric Sciences LaboratoryNASA Goddard Space Flight CenterGreenbeltMDUSA
- Department of Atmospheric and Oceanic ScienceUniversity of Maryland College ParkCollege ParkMDUSA
| | - E. Keenan
- Department of Atmospheric and Oceanic SciencesUniversity of Colorado BoulderBoulderCOUSA
| | - N. Wever
- Department of Atmospheric and Oceanic SciencesUniversity of Colorado BoulderBoulderCOUSA
| |
Collapse
|
13
|
Dawson EJ, Schroeder DM, Chu W, Mantelli E, Seroussi H. Ice mass loss sensitivity to the Antarctic ice sheet basal thermal state. Nat Commun 2022; 13:4957. [PMID: 36104329 PMCID: PMC9474861 DOI: 10.1038/s41467-022-32632-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Accepted: 08/05/2022] [Indexed: 11/30/2022] Open
Abstract
Sea-level rise projections rely on accurate predictions of ice mass loss from Antarctica. Climate change promotes greater mass loss by destabilizing ice shelves and accelerating the discharge of upstream grounded ice. Mass loss is further exacerbated by mechanisms such as the Marine Ice Sheet Instability and the Marine Ice Cliff Instability. However, the effect of basal thermal state changes of grounded ice remains largely unexplored. Here, we use numerical ice sheet modeling to investigate how warmer basal temperatures could affect the Antarctic ice sheet mass balance. We find increased mass loss in response to idealized basal thawing experiments run over 100 years. Most notably, frozen-bed patches could be tenuously sustaining the current ice configuration in parts of George V, Adélie, Enderby, and Kemp Land regions of East Antarctica. With less than 5 degrees of basal warming, these frozen patches may begin to thaw, producing new loci of mass loss. This study uses ice sheet modeling experiments to show that thawing portions of the Antarctic ice sheet bed can increase century-scale mass loss, particularly in the Wilkes and Enderby Land regions of East Antarctica.
Collapse
|
14
|
How much of the Earth's ice is melting? New and old techniques combine to paint a sobering picture. Proc Natl Acad Sci U S A 2022; 119:e2213762119. [PMID: 36037390 PMCID: PMC9477384 DOI: 10.1073/pnas.2213762119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
15
|
Abstract
AbstractDespite the exclusion of the Southern Ocean from assessments of progress towards achieving the Convention on Biological Diversity (CBD) Strategic Plan, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) has taken on the mantle of progressing efforts to achieve it. Within the CBD, Aichi Target 11 represents an agreed commitment to protect 10% of the global coastal and marine environment. Adopting an ethos of presenting the best available scientific evidence to support policy makers, CCAMLR has progressed this by designating two Marine Protected Areas in the Southern Ocean, with three others under consideration. The region of Antarctica known as Dronning Maud Land (DML; 20°W to 40°E) and the Atlantic sector of the Southern Ocean that abuts it conveniently spans one region under consideration for spatial protection. To facilitate both an open and transparent process to provide the vest available scientific evidence for policy makers to formulate management options, we review the body of physical, geochemical and biological knowledge of the marine environment of this region. The level of scientific knowledge throughout the seascape abutting DML is polarized, with a clear lack of data in its eastern part which is presumably related to differing levels of research effort dedicated by national Antarctic programmes in the region. The lack of basic data on fundamental aspects of the physical, geological and biological nature of eastern DML make predictions of future trends difficult to impossible, with implications for the provision of management advice including spatial management. Finally, by highlighting key knowledge gaps across the scientific disciplines our review also serves to provide guidance to future research across this important region.
Collapse
|
16
|
Stokes CR, Abram NJ, Bentley MJ, Edwards TL, England MH, Foppert A, Jamieson SSR, Jones RS, King MA, Lenaerts JTM, Medley B, Miles BWJ, Paxman GJG, Ritz C, van de Flierdt T, Whitehouse PL. Response of the East Antarctic Ice Sheet to past and future climate change. Nature 2022; 608:275-286. [PMID: 35948707 DOI: 10.1038/s41586-022-04946-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 06/07/2022] [Indexed: 11/09/2022]
Abstract
The East Antarctic Ice Sheet contains the vast majority of Earth's glacier ice (about 52 metres sea-level equivalent), but is often viewed as less vulnerable to global warming than the West Antarctic or Greenland ice sheets. However, some regions of the East Antarctic Ice Sheet have lost mass over recent decades, prompting the need to re-evaluate its sensitivity to climate change. Here we review the response of the East Antarctic Ice Sheet to past warm periods, synthesize current observations of change and evaluate future projections. Some marine-based catchments that underwent notable mass loss during past warm periods are losing mass at present but most projections indicate increased accumulation across the East Antarctic Ice Sheet over the twenty-first century, keeping the ice sheet broadly in balance. Beyond 2100, high-emissions scenarios generate increased ice discharge and potentially several metres of sea-level rise within just a few centuries, but substantial mass loss could be averted if the Paris Agreement to limit warming below 2 degrees Celsius is satisfied.
Collapse
Affiliation(s)
| | - Nerilie J Abram
- Research School of Earth Sciences, Australian National University, Canberra, Australian Capital Territory, Australia.,Australian Centre for Excellence in Antarctic Science, Australian National University, Canberra, Australian Capital Territory, Australia
| | | | | | - Matthew H England
- Climate Change Research Centre, University of New South Wales, Sydney, New South Wales, Australia.,Australian Centre for Excellence in Antarctic Science, University of New South Wales, Sydney, New South Wales, Australia
| | - Annie Foppert
- Australian Antarctic Program Partnership, Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
| | | | - Richard S Jones
- School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria, Australia.,Securing Antarctica's Environmental Future, Monash University, Clayton, Victoria, Australia
| | - Matt A King
- School of Geography, Planning, and Spatial Sciences, University of Tasmania, Hobart, Tasmania, Australia.,Australian Centre for Excellence in Antarctic Science, University of Tasmania, Hobart, Tasmania, Australia
| | - Jan T M Lenaerts
- Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, CO, USA
| | - Brooke Medley
- Cryospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | | | - Guy J G Paxman
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA
| | - Catherine Ritz
- Institut des Géosciences de l'Environnement, Université Grenoble Alpes, Grenoble, France
| | - Tina van de Flierdt
- Department of Earth Science and Engineering, Imperial College London, London, UK
| | | |
Collapse
|
17
|
Woodworth PL. Advances in the observation and understanding of changes in sea level and tides. Ann N Y Acad Sci 2022; 1516:48-75. [PMID: 35811415 DOI: 10.1111/nyas.14851] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Climate change, of which sea level change is one component, is seldom out of the news. This paper reviews developments in the measurement and understanding of changes in sea level and tides, focusing on the changes during the past century. The main aim has been to demonstrate how sea level and tidal science are now connected intimately with the fields of climate change and geodesy.
Collapse
|
18
|
Miles BWJ, Stokes CR, Jamieson SSR, Jordan JR, Gudmundsson GH, Jenkins A. High spatial and temporal variability in Antarctic ice discharge linked to ice shelf buttressing and bed geometry. Sci Rep 2022; 12:10968. [PMID: 35768612 PMCID: PMC9243100 DOI: 10.1038/s41598-022-13517-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Accepted: 05/25/2022] [Indexed: 11/09/2022] Open
Abstract
Antarctica's contribution to global mean sea level rise has been driven by an increase in ice discharge into the oceans. The rate of change and the mechanisms that drive variability in ice discharge are therefore important to consider in the context of projected future warming. Here, we report observations of both decadal trends and inter-annual variability in ice discharge across the Antarctic Ice Sheet at a variety of spatial scales that range from large drainage basins to individual outlet glacier catchments. Overall, we find a 37 ± 11 Gt year-1 increase in discharge between 1999 and 2010, but a much smaller increase of 4 ± 8 Gt year-1 between 2010 and 2018. Furthermore, comparisons reveal that neighbouring outlet glaciers can behave synchronously, but others show opposing trends, despite their close proximity. We link this spatial and temporal variability to changes in ice shelf buttressing and the modulating effect of local glacier geometry.
Collapse
Affiliation(s)
- Bertie W J Miles
- School of Geosciences, Edinburgh University, Edinburgh, EH8 9XP, UK. .,Department of Geography, Durham University, Durham, DH1 3LE, UK.
| | - Chris R Stokes
- Department of Geography, Durham University, Durham, DH1 3LE, UK
| | | | - Jim R Jordan
- Department of Geography and Environmental Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK.,Laboratoire de Glaciologie, Université Libre de Bruxelles, Brussels, Belgium
| | - G Hilmar Gudmundsson
- Department of Geography and Environmental Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK
| | - Adrian Jenkins
- Department of Geography and Environmental Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK
| |
Collapse
|
19
|
Khan SA, Colgan W, Neumann TA, van den Broeke MR, Brunt KM, Noël B, Bamber JL, Hassan J, Bjørk AA. Accelerating Ice Loss From Peripheral Glaciers in North Greenland. GEOPHYSICAL RESEARCH LETTERS 2022; 49:e2022GL098915. [PMID: 35865910 PMCID: PMC9286807 DOI: 10.1029/2022gl098915] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Revised: 05/24/2022] [Accepted: 05/25/2022] [Indexed: 06/15/2023]
Abstract
In recent decades, Greenland's peripheral glaciers have experienced large-scale mass loss, resulting in a substantial contribution to sea level rise. While their total area of Greenland ice cover is relatively small (4%), their mass loss is disproportionally large compared to the Greenland ice sheet. Satellite altimetry from Ice, Cloud, and land Elevation Satellite (ICESat) and ICESat-2 shows that mass loss from Greenland's peripheral glaciers increased from 27.2 ± 6.2 Gt/yr (February 2003-October 2009) to 42.3 ± 6.2 Gt/yr (October 2018-December 2021). These relatively small glaciers now constitute 11 ± 2% of Greenland's ice loss and contribute to global sea level rise. In the period October 2018-December 2021, mass loss increased by a factor of four for peripheral glaciers in North Greenland. While peripheral glacier mass loss is widespread, we also observe a complex regional pattern where increases in precipitation at high altitudes have partially counteracted increases in melt at low altitude.
Collapse
Affiliation(s)
- Shfaqat A. Khan
- DTU SpaceTechnical University of DenmarkKongens LyngbyDenmark
| | - William Colgan
- Department of Glaciology and ClimateGeological Survey of Denmark and GreenlandCopenhagenDenmark
| | | | | | - Kelly M. Brunt
- NASA Goddard Space Flight CenterGreenbeltMDUSA
- Earth System ScienceInterdisciplinary CenterUniversity of MarylandCollege ParkMDUSA
| | - Brice Noël
- Institute for Marine and Atmospheric Research UtrechtUtrecht UniversityUtrechtThe Netherlands
| | - Jonathan L. Bamber
- Bristol Glaciology CentreUniversity of BristolBristolUK
- Department of Aerospace and GeodesyData Science in Earth ObservationTechnical University of MunichMunichGermany
| | - Javed Hassan
- DTU SpaceTechnical University of DenmarkKongens LyngbyDenmark
| | - Anders A. Bjørk
- Department of Geosciences and Natural ResourcesUniversity of CopenhagenCopenhagenDenmark
| |
Collapse
|
20
|
Crameri NJ, Ellison JC. Atoll inland and coastal mangrove climate change vulnerability assessment. WETLANDS ECOLOGY AND MANAGEMENT 2022; 30:527-546. [PMID: 35571150 PMCID: PMC9091136 DOI: 10.1007/s11273-022-09878-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 04/09/2022] [Indexed: 06/15/2023]
Abstract
UNLABELLED Climate change threatens global mangroves, which are already among the world's most impacted ecosystems. Vulnerability components of exposure, sensitivity and adaptive capacity were evaluated on mangroves of atoll settings on Jaluit Atoll, in the Marshall Islands, assessing spatial changes of mangrove cover 1945-2018/19, sea-level trends 1968-2019, and reviewing available information. Inland mangrove depressions occur on Jaluit, as well as coastal lagoon margin mangroves, and both were assessed using the same methods. Spatial analysis results showed both inland and coastal mangroves have increased in area. Inland mangroves on eight of Jaluit's islands mostly expanded after 1976 from 40 to 50 hectares, with progradation and tidal creek infill closing lagoon connections. Shoreline mangroves showed 88-100% of transects prograding 0.1-0.51 m year-1 and 0-11.5% of transects eroding 0-0.18 m year-1. Assessment of a combination of aerial/satellite images, literature and on-the-ground photos indicated that the mangroves are in healthy condition. Vulnerability assessment results showed both inland and coastal mangroves to have similar strengths and weaknesses in resilience, with intrinsic areas of vulnerability persisting during increased future sea level rise, limited sediment supply and extremely low elevations. SUPPLEMENTARY INFORMATION The online version contains supplementary material available at 10.1007/s11273-022-09878-0.
Collapse
Affiliation(s)
- Nicholas J. Crameri
- School of Geography, Planning and Spatial Sciences, University of Tasmania, Launceston, TAS 7250 Australia
| | - Joanna C. Ellison
- School of Geography, Planning and Spatial Sciences, University of Tasmania, Launceston, TAS 7250 Australia
| |
Collapse
|
21
|
Sergienko OV. No general stability conditions for marine ice-sheet grounding lines in the presence of feedbacks. Nat Commun 2022; 13:2265. [PMID: 35477962 PMCID: PMC9046188 DOI: 10.1038/s41467-022-29892-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 04/05/2022] [Indexed: 11/29/2022] Open
Abstract
The “marine ice-sheet instability” hypothesis continues to be used to interpret the observed mass loss from the Antarctic and Greenland ice sheets. This hypothesis has been developed for conditions that do not account for feedbacks between ice sheets and environmental conditions. However, snow accumulation and the ice-sheet surface melting depend on the surface temperature, which is a strong function of elevation. Consequently, there is a feedback between precipitation, atmospheric surface temperature and ice-sheet surface elevation. Here, we investigate stability conditions of a marine-based ice sheet in the presence of such a feedback. Our results show that no general stability condition similar to one associated with the “marine ice-sheet instability” hypothesis can be determined. Stability of individual configurations can be established only on a case-by-case basis. These results apply to a wide range of feedbacks between marine ice sheets and atmosphere, ocean and lithosphere. Using theoretical, numerical and data analyses, this study finds that there are no general stability conditions for marine ice sheets if feedbacks caused by interactions of ice sheets with atmosphere, ocean and lithosphere are taken into account.
Collapse
Affiliation(s)
- Olga V Sergienko
- Program in Atmospheric and Oceanic Sciences, Princeton University, Princeton, NJ, USA.
| |
Collapse
|
22
|
Khan SA, Bamber JL, Rignot E, Helm V, Aschwanden A, Holland DM, van den Broeke M, King M, Noël B, Truffer M, Humbert A, Colgan W, Vijay S, Kuipers Munneke P. Greenland Mass Trends From Airborne and Satellite Altimetry During 2011-2020. JOURNAL OF GEOPHYSICAL RESEARCH. EARTH SURFACE 2022; 127:e2021JF006505. [PMID: 35864950 PMCID: PMC9286656 DOI: 10.1029/2021jf006505] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 03/07/2022] [Accepted: 03/14/2022] [Indexed: 06/15/2023]
Abstract
We use satellite and airborne altimetry to estimate annual mass changes of the Greenland Ice Sheet. We estimate ice loss corresponding to a sea-level rise of 6.9 ± 0.4 mm from April 2011 to April 2020, with a highest annual ice loss rate of 1.4 mm/yr sea-level equivalent from April 2019 to April 2020. On a regional scale, our annual mass loss timeseries reveals 10-15 m/yr dynamic thickening at the terminus of Jakobshavn Isbræ from April 2016 to April 2018, followed by a return to dynamic thinning. We observe contrasting patterns of mass loss acceleration in different basins across the ice sheet and suggest that these spatiotemporal trends could be useful for calibrating and validating prognostic ice sheet models. In addition to resolving the spatial and temporal fingerprint of Greenland's recent ice loss, these mass loss grids are key for partitioning contemporary elastic vertical land motion from longer-term glacial isostatic adjustment (GIA) trends at GPS stations around the ice sheet. Our ice-loss product results in a significantly different GIA interpretation from a previous ice-loss product.
Collapse
Affiliation(s)
- Shfaqat A. Khan
- DTU SpaceTechnical University of DenmarkKongens LyngbyDenmark
| | - Jonathan L. Bamber
- Bristol Glaciology CentreUniversity of BristolBristolUK
- Department of Aerospace and GeodesyTechnical University MunichMunichGermany
| | - Eric Rignot
- Department of Earth System ScienceUniversity of California IrvineIrvineCAUSA
| | - Veit Helm
- Glaciology SectionAlfred Wegener InstituteBremerhavenGermany
| | | | - David M. Holland
- New York UniversityNew YorkNYUSA
- Center for Global Sea Level ChangeNew York UniversityAbu DhabiUAE
| | - Michiel van den Broeke
- Institute for Marine and Atmospheric Research UtrechtUtrecht UniversityUtrechtThe Netherlands
| | - Michalea King
- Applied Physics LaboratoryUniversity of WashingtonSeattleWAUSA
| | - Brice Noël
- Institute for Marine and Atmospheric Research UtrechtUtrecht UniversityUtrechtThe Netherlands
| | | | | | - William Colgan
- Department of Glaciology and ClimateGeological Survey of Denmark and GreenlandCopenhagenDenmark
| | - Saurabh Vijay
- Department of Civil EngineeringIndian Institute of Technology RoorkeeRoorkeeIndia
| | - Peter Kuipers Munneke
- Institute for Marine and Atmospheric Research UtrechtUtrecht UniversityUtrechtThe Netherlands
| |
Collapse
|
23
|
Khan SA, Choi Y, Morlighem M, Rignot E, Helm V, Humbert A, Mouginot J, Millan R, Kjær KH, Bjørk AA. Extensive inland thinning and speed-up of Northeast Greenland Ice Stream. Nature 2022; 611:727-732. [PMID: 36352226 PMCID: PMC9684075 DOI: 10.1038/s41586-022-05301-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Accepted: 08/31/2022] [Indexed: 11/11/2022]
Abstract
Over the past two decades, ice loss from the Greenland ice sheet (GrIS) has increased owing to enhanced surface melting and ice discharge to the ocean1-5. Whether continuing increased ice loss will accelerate further, and by how much, remains contentious6-9. A main contributor to future ice loss is the Northeast Greenland Ice Stream (NEGIS), Greenland's largest basin and a prominent feature of fast-flowing ice that reaches the interior of the GrIS10-12. Owing to its topographic setting, this sector is vulnerable to rapid retreat, leading to unstable conditions similar to those in the marine-based setting of ice streams in Antarctica13-20. Here we show that extensive speed-up and thinning triggered by frontal changes in 2012 have already propagated more than 200 km inland. We use unique global navigation satellite system (GNSS) observations, combined with surface elevation changes and surface speeds obtained from satellite data, to select the correct basal conditions to be used in ice flow numerical models, which we then use for future simulations. Our model results indicate that this marine-based sector alone will contribute 13.5-15.5 mm sea-level rise by 2100 (equivalent to the contribution of the entire ice sheet over the past 50 years) and will cause precipitous changes in the coming century. This study shows that measurements of subtle changes in the ice speed and elevation inland help to constrain numerical models of the future mass balance and higher-end projections show better agreement with observations.
Collapse
Affiliation(s)
- Shfaqat A. Khan
- grid.5170.30000 0001 2181 8870DTU Space, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Youngmin Choi
- grid.20861.3d0000000107068890Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA USA
| | - Mathieu Morlighem
- grid.254880.30000 0001 2179 2404Department of Earth Sciences, Dartmouth College, Hanover, NH USA ,grid.266093.80000 0001 0668 7243Department of Earth System Science, University of California, Irvine, Irvine, CA USA
| | - Eric Rignot
- grid.266093.80000 0001 0668 7243Department of Earth System Science, University of California, Irvine, Irvine, CA USA
| | - Veit Helm
- grid.10894.340000 0001 1033 7684Glaciology Section, Alfred Wegener Institute, Bremerhaven, Germany
| | - Angelika Humbert
- grid.10894.340000 0001 1033 7684Glaciology Section, Alfred Wegener Institute, Bremerhaven, Germany
| | - Jérémie Mouginot
- grid.450308.a0000 0004 0369 268XInstitut des Géosciences de l’Environnement, Université Grenoble Alpes, Grenoble, France
| | - Romain Millan
- grid.450308.a0000 0004 0369 268XInstitut des Géosciences de l’Environnement, Université Grenoble Alpes, Grenoble, France
| | - Kurt H. Kjær
- grid.5254.60000 0001 0674 042XSection for GeoGenetics, Globe Institute, University of Copenhagen, Copenhagen, Denmark
| | - Anders A. Bjørk
- grid.5254.60000 0001 0674 042XDepartment of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark
| |
Collapse
|
24
|
Slater T, Shepherd A, McMillan M, Leeson A, Gilbert L, Muir A, Munneke PK, Noël B, Fettweis X, van den Broeke M, Briggs K. Increased variability in Greenland Ice Sheet runoff from satellite observations. Nat Commun 2021; 12:6069. [PMID: 34725324 PMCID: PMC8560907 DOI: 10.1038/s41467-021-26229-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 09/17/2021] [Indexed: 11/28/2022] Open
Abstract
Runoff from the Greenland Ice Sheet has increased over recent decades affecting global sea level, regional ocean circulation, and coastal marine ecosystems, and it now accounts for most of the contemporary mass imbalance. Estimates of runoff are typically derived from regional climate models because satellite records have been limited to assessments of melting extent. Here, we use CryoSat-2 satellite altimetry to produce direct measurements of Greenland's runoff variability, based on seasonal changes in the ice sheet's surface elevation. Between 2011 and 2020, Greenland's ablation zone thinned on average by 1.4 ± 0.4 m each summer and thickened by 0.9 ± 0.4 m each winter. By adjusting for the steady-state divergence of ice, we estimate that runoff was 357 ± 58 Gt/yr on average - in close agreement with regional climate model simulations (root mean square difference of 47 to 60 Gt/yr). As well as being 21 % higher between 2011 and 2020 than over the preceding three decades, runoff is now also 60 % more variable from year-to-year as a consequence of large-scale fluctuations in atmospheric circulation. Because this variability is not captured in global climate model simulations, our satellite record of runoff should help to refine them and improve confidence in their projections.
Collapse
Affiliation(s)
- Thomas Slater
- Centre for Polar Observation and Modelling, School of Earth and Environment, University of Leeds, Leeds, UK.
| | - Andrew Shepherd
- Centre for Polar Observation and Modelling, School of Earth and Environment, University of Leeds, Leeds, UK
| | - Malcolm McMillan
- Lancaster Environment Centre, Lancaster University, Lancaster, UK
| | - Amber Leeson
- Lancaster Environment Centre, Lancaster University, Lancaster, UK
| | - Lin Gilbert
- Mullard Space Science Laboratory, Department of Space & Climate Physics, University College London, London, UK
| | - Alan Muir
- Mullard Space Science Laboratory, Department of Space & Climate Physics, University College London, London, UK
- Centre for Polar Observation and Modelling, Department of Earth Sciences, University College London, London, UK
| | - Peter Kuipers Munneke
- Institute for Marine and Atmospheric research Utrecht, Utrecht University, Utrecht, the Netherlands
| | - Brice Noël
- Institute for Marine and Atmospheric research Utrecht, Utrecht University, Utrecht, the Netherlands
| | - Xavier Fettweis
- SPHERES Research Unit, Department of Geography, University of Liège, Liège, Belgium
| | - Michiel van den Broeke
- Institute for Marine and Atmospheric research Utrecht, Utrecht University, Utrecht, the Netherlands
| | - Kate Briggs
- Centre for Polar Observation and Modelling, School of Earth and Environment, University of Leeds, Leeds, UK
| |
Collapse
|
25
|
Michaelides RJ, Bryant MB, Siegfried MR, Borsa AA. Quantifying Surface-Height Change Over a Periglacial Environment With ICESat-2 Laser Altimetry. EARTH AND SPACE SCIENCE (HOBOKEN, N.J.) 2021; 8:e2020EA001538. [PMID: 34595326 PMCID: PMC8459227 DOI: 10.1029/2020ea001538] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 06/09/2021] [Accepted: 06/29/2021] [Indexed: 06/13/2023]
Abstract
We use Ice, Cloud, and land Elevation Satellite 2 (ICESat-2) laser altimetry crossovers and repeat tracks collected over the North Slope of Alaska to estimate ground surface-height change due to the seasonal freezing and thawing of the active layer. We compare these measurements to a time series of surface deformation from Sentinel-1 interferometric synthetic aperture radar (InSAR) and demonstrate agreement between these independent observations of surface deformation at broad spatial scales. We observe a relationship between ICESat-2-derived surface subsidence/uplift and changes in normalized accumulated degree days, which is consistent with the thermodynamically driven seasonal freezing and thawing of the active layer. Integrating ICESat-2 crossover estimates of surface-height change yields an annual time series of surface-height change that is sensitive to changes in snow cover during spring and thawing of the active layer throughout spring and summer. Furthermore, this time series exhibits temporal correlation with independent reanalysis datasets of temperature and snow cover, as well as an InSAR-derived time series. ICESat-2-derived surface-height change estimates can be significantly affected by short length-scale topographic gradients and changes in snow cover and snow depth. We discuss optimal strategies of post-processing ICESat-2 data for permafrost applications, as well as the future potential of joint ICESat-2 and InSAR investigations of permafrost surface-dynamics.
Collapse
Affiliation(s)
| | - M. B. Bryant
- Institute of Geophysics and Planetary PhysicsScripps Institution of OceanographyUniversity of California San DiegoLa JollaCAUSA
| | | | - A. A. Borsa
- Institute of Geophysics and Planetary PhysicsScripps Institution of OceanographyUniversity of California San DiegoLa JollaCAUSA
| |
Collapse
|
26
|
Minowa M, Sugiyama S, Ito M, Yamane S, Aoki S. Thermohaline structure and circulation beneath the Langhovde Glacier ice shelf in East Antarctica. Nat Commun 2021; 12:4209. [PMID: 34244489 PMCID: PMC8270922 DOI: 10.1038/s41467-021-23534-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 04/29/2021] [Indexed: 11/20/2022] Open
Abstract
Basal melting of ice shelves is considered to be the principal driver of recent ice mass loss in Antarctica. Nevertheless, in-situ oceanic data covering the extensive areas of a subshelf cavity are sparse. Here we show comprehensive structures of temperature, salinity and current measured in January 2018 through four boreholes drilled at a ~3-km-long ice shelf of Langhovde Glacier in East Antarctica. The measurements were performed in 302–12 m-thick ocean cavity beneath 234–412 m-thick ice shelf. The data indicate that Modified Warm Deep Water is transported into the grounding zone beneath a stratified buoyant plume. Water at the ice-ocean interface was warmer than the in-situ freezing point by 0.65–0.95°C, leading to a mean basal melt rate estimate of 1.42 m a−1. Our measurements indicate the existence of a density-driven water circulation in the cavity beneath the ice shelf of Langhovde Glacier, similar to that proposed for warm-ocean cavities of larger Antarctic ice shelves. Basal melting of ice shelves is the principal driver of recent ice mass loss in Antarctica. The study reports comprehensive structures of temperature, salinity and current under an ice shelf in East Antarctica obtained by borehole measurements.
Collapse
Affiliation(s)
- Masahiro Minowa
- Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan.
| | - Shin Sugiyama
- Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
| | - Masato Ito
- Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan.,Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
| | - Shiori Yamane
- Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
| | - Shigeru Aoki
- Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
| |
Collapse
|
27
|
Increased Ice Thinning over Svalbard Measured by ICESat/ICESat-2 Laser Altimetry. REMOTE SENSING 2021. [DOI: 10.3390/rs13112089] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A decade-long pronounced increase in temperatures in the Arctic, especially in the Barents Sea region, resulted in a global warming hotspot over Svalbard. Associated changes in the cryosphere are the consequence and lead to a demand for monitoring of the glacier changes. This study uses spaceborne laser altimetry data from the ICESat and ICESat-2 missions to obtain ice elevation and mass change rates between 2003–2008 and 2019. Elevation changes are derived at orbit crossover locations throughout the study area, and regional volume and mass changes are estimated using a hypsometric approach. A Svalbard-wide annual elevation change rate of −0.30 ± 0.15 m yr−1 was found, which corresponds to a mass loss rate of −12.40 ± 4.28 Gt yr−1. Compared to the ICESat period (2003–2009), thinning has increased over most regions, including the highest negative rates along the west coast and areas bordering the Barents Sea. The overall negative regime is expected to be linked to Arctic warming in the last decades and associated changes in glacier climatic mass balance. Further, observed increased thinning rates and pronounced changes at the eastern side of Svalbard since the ICESat period are found to correlate with atmospheric and oceanic warming in the respective regions.
Collapse
|
28
|
Hugonnet R, McNabb R, Berthier E, Menounos B, Nuth C, Girod L, Farinotti D, Huss M, Dussaillant I, Brun F, Kääb A. Accelerated global glacier mass loss in the early twenty-first century. Nature 2021; 592:726-731. [PMID: 33911269 DOI: 10.1038/s41586-021-03436-z] [Citation(s) in RCA: 71] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Accepted: 03/09/2021] [Indexed: 02/02/2023]
Abstract
Glaciers distinct from the Greenland and Antarctic ice sheets are shrinking rapidly, altering regional hydrology1, raising global sea level2 and elevating natural hazards3. Yet, owing to the scarcity of constrained mass loss observations, glacier evolution during the satellite era is known only partially, as a geographic and temporal patchwork4,5. Here we reveal the accelerated, albeit contrasting, patterns of glacier mass loss during the early twenty-first century. Using largely untapped satellite archives, we chart surface elevation changes at a high spatiotemporal resolution over all of Earth's glaciers. We extensively validate our estimates against independent, high-precision measurements and present a globally complete and consistent estimate of glacier mass change. We show that during 2000-2019, glaciers lost a mass of 267 ± 16 gigatonnes per year, equivalent to 21 ± 3 per cent of the observed sea-level rise6. We identify a mass loss acceleration of 48 ± 16 gigatonnes per year per decade, explaining 6 to 19 per cent of the observed acceleration of sea-level rise. Particularly, thinning rates of glaciers outside ice sheet peripheries doubled over the past two decades. Glaciers currently lose more mass, and at similar or larger acceleration rates, than the Greenland or Antarctic ice sheets taken separately7-9. By uncovering the patterns of mass change in many regions, we find contrasting glacier fluctuations that agree with the decadal variability in precipitation and temperature. These include a North Atlantic anomaly of decelerated mass loss, a strongly accelerated loss from northwestern American glaciers, and the apparent end of the Karakoram anomaly of mass gain10. We anticipate our highly resolved estimates to advance the understanding of drivers that govern the distribution of glacier change, and to extend our capabilities of predicting these changes at all scales. Predictions robustly benchmarked against observations are critically needed to design adaptive policies for the local- and regional-scale management of water resources and cryospheric risks, as well as for the global-scale mitigation of sea-level rise.
Collapse
Affiliation(s)
- Romain Hugonnet
- LEGOS, Université de Toulouse, CNES, CNRS, IRD, UPS, Toulouse, France. .,Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zürich, Zürich, Switzerland. .,Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Birmensdorf, Switzerland.
| | - Robert McNabb
- School of Geography and Environmental Sciences, Ulster University, Coleraine, UK.,Department of Geosciences, University of Oslo, Oslo, Norway
| | - Etienne Berthier
- LEGOS, Université de Toulouse, CNES, CNRS, IRD, UPS, Toulouse, France
| | - Brian Menounos
- Geography Earth and Environmental Sciences, University of Northern British Columbia, Prince George, British Columbia, Canada.,Hakai Institute, Campbell River, British Columbia, Canada
| | - Christopher Nuth
- Department of Geosciences, University of Oslo, Oslo, Norway.,The Norwegian Defense Research Establishment, Kjeller, Norway
| | - Luc Girod
- Department of Geosciences, University of Oslo, Oslo, Norway
| | - Daniel Farinotti
- Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zürich, Zürich, Switzerland.,Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Birmensdorf, Switzerland
| | - Matthias Huss
- Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zürich, Zürich, Switzerland.,Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Birmensdorf, Switzerland.,Department of Geosciences, University of Fribourg, Fribourg, Switzerland
| | - Ines Dussaillant
- LEGOS, Université de Toulouse, CNES, CNRS, IRD, UPS, Toulouse, France.,Department of Geography, University of Zurich, Zurich, Switzerland
| | - Fanny Brun
- IGE, Université Grenoble Alpes, CNRS, IRD, Grenoble INP, Grenoble, France
| | - Andreas Kääb
- Department of Geosciences, University of Oslo, Oslo, Norway
| |
Collapse
|
29
|
Rignot E, An L, Chauche N, Morlighem M, Jeong S, Wood M, Mouginot J, Willis JK, Klaucke I, Weinrebe W, Muenchow A. Retreat of Humboldt Gletscher, North Greenland, Driven by Undercutting From a Warmer Ocean. GEOPHYSICAL RESEARCH LETTERS 2021; 48:e2020GL091342. [PMID: 34219836 PMCID: PMC8243930 DOI: 10.1029/2020gl091342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 01/17/2021] [Accepted: 01/21/2021] [Indexed: 06/13/2023]
Abstract
Humboldt Gletscher is a 100-km wide, slow-moving glacier in north Greenland which holds a 19-cm global sea level equivalent. Humboldt has been the fourth largest contributor to sea level rise since 1972 but the cause of its mass loss has not been elucidated. Multi-beam echo sounding data collected in 2019 indicate a seabed 200 m deeper than previously known. Conductivity temperature depth data reveal the presence of warm water of Atlantic origin at 0°C at the glacier front and a warming of the ocean waters by 0.9 ± 0.1°C since 1962. Using an ocean model, we reconstruct grounded ice undercutting by the ocean, combine it with calculated retreat caused by ice thinning to floatation, and are able to fully explain the observed retreat. Two thirds of the retreat are caused by undercutting of grounded ice, which is a physical process not included in most ice sheet models.
Collapse
Affiliation(s)
- Eric Rignot
- Department Earth System ScienceUniversity of California IrvineIrvineCAUSA
- Jet Propulsion LaboratoryCalifornia Institute of TechnologyPasadenaCAUSA
| | - Lu An
- Department Earth System ScienceUniversity of California IrvineIrvineCAUSA
| | | | - Mathieu Morlighem
- Department Earth System ScienceUniversity of California IrvineIrvineCAUSA
| | - Seongsu Jeong
- Department Earth System ScienceUniversity of California IrvineIrvineCAUSA
| | - Michael Wood
- Department Earth System ScienceUniversity of California IrvineIrvineCAUSA
- Jet Propulsion LaboratoryCalifornia Institute of TechnologyPasadenaCAUSA
| | - Jeremie Mouginot
- Department Earth System ScienceUniversity of California IrvineIrvineCAUSA
- Institut des Geosciences de l'EnvironnementUniversite Grenoble‐AlpesCNRSGrenobleFrance
| | - Josh K. Willis
- Jet Propulsion LaboratoryCalifornia Institute of TechnologyPasadenaCAUSA
| | - Ingo Klaucke
- GEOMAR Helmholtz Centre for Ocean Research KielKielGermany
| | | | - Andreas Muenchow
- School of Marine Science and PolicyUniversity of DelawareNewarkDEUSA
| |
Collapse
|
30
|
Hawkings JR, Skidmore ML, Wadham JL, Priscu JC, Morton PL, Hatton JE, Gardner CB, Kohler TJ, Stibal M, Bagshaw EA, Steigmeyer A, Barker J, Dore JE, Lyons WB, Tranter M, Spencer RGM. Enhanced trace element mobilization by Earth's ice sheets. Proc Natl Acad Sci U S A 2020; 117:31648-31659. [PMID: 33229559 PMCID: PMC7749357 DOI: 10.1073/pnas.2014378117] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Trace elements sustain biological productivity, yet the significance of trace element mobilization and export in subglacial runoff from ice sheets is poorly constrained at present. Here, we present size-fractionated (0.02, 0.22, and 0.45 µm) concentrations of trace elements in subglacial waters from the Greenland Ice Sheet (GrIS) and the Antarctic Ice Sheet (AIS). Concentrations of immobile trace elements (e.g., Al, Fe, Ti) far exceed global riverine and open ocean mean values and highlight the importance of subglacial aluminosilicate mineral weathering and lack of retention of these species in sediments. Concentrations are higher from the AIS than the GrIS, highlighting the geochemical consequences of prolonged water residence times and hydrological isolation that characterize the former. The enrichment of trace elements (e.g., Co, Fe, Mn, and Zn) in subglacial meltwaters compared with seawater and typical riverine systems, together with the likely sensitivity to future ice sheet melting, suggests that their export in glacial runoff is likely to be important for biological productivity. For example, our dissolved Fe concentration (20,900 nM) and associated flux values (1.4 Gmol y-1) from AIS to the Fe-deplete Southern Ocean exceed most previous estimates by an order of magnitude. The ultimate fate of these micronutrients will depend on the reactivity of the dominant colloidal size fraction (likely controlled by nanoparticulate Al and Fe oxyhydroxide minerals) and estuarine processing. We contend that ice sheets create highly geochemically reactive particulates in subglacial environments, which play a key role in trace elemental cycles, with potentially important consequences for global carbon cycling.
Collapse
Affiliation(s)
- Jon R Hawkings
- National High Magnetic Field Laboratory Geochemistry Group, Department of Earth, Ocean and Atmospheric Sciences, Florida State University, Tallahassee, FL 32306;
- Interface Geochemistry, German Research Centre for Geosciences (GFZ), 14473 Potsdam, Germany
| | - Mark L Skidmore
- Department of Earth Sciences, Montana State University, Bozeman, MT 59717
| | - Jemma L Wadham
- School of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, United Kingdom
| | - John C Priscu
- Department of Land Resources and Environmental Sciences, Bozeman, Montana State University, MT 59717
| | - Peter L Morton
- National High Magnetic Field Laboratory Geochemistry Group, Department of Earth, Ocean and Atmospheric Sciences, Florida State University, Tallahassee, FL 32306
| | - Jade E Hatton
- School of Earth Sciences, University of Bristol, Bristol, BS8 1RL, United Kingdom
| | - Christopher B Gardner
- School of Earth Sciences, Byrd Polar and Climate Research Center, The Ohio State University, Columbus, OH 43210
| | - Tyler J Kohler
- Stream Biofilm and Ecosystem Research Laboratory, School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne, Lausanne CH-1015, Switzerland
| | - Marek Stibal
- Department of Ecology, Faculty of Science, Charles University, CZ-12844, Prague, Czechia
| | - Elizabeth A Bagshaw
- School of Earth and Ocean Sciences, Cardiff University, Cardiff, CF10 3AT, United Kingdom
| | - August Steigmeyer
- Department of Earth Sciences, Montana State University, Bozeman, MT 59717
| | - Joel Barker
- Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis, MN 55455
| | - John E Dore
- Department of Land Resources and Environmental Sciences, Bozeman, Montana State University, MT 59717
| | - W Berry Lyons
- School of Earth Sciences, Byrd Polar and Climate Research Center, The Ohio State University, Columbus, OH 43210
| | - Martyn Tranter
- School of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, United Kingdom
| | - Robert G M Spencer
- National High Magnetic Field Laboratory Geochemistry Group, Department of Earth, Ocean and Atmospheric Sciences, Florida State University, Tallahassee, FL 32306
| |
Collapse
|
31
|
Early ICESat-2 on-orbit Geolocation Validation Using Ground-Based Corner Cube Retro-Reflectors. REMOTE SENSING 2020. [DOI: 10.3390/rs12213653] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The Ice, Cloud and Land Elevation Satellite-2 (ICESat-2), an Earth-observing laser altimetry mission, is currently providing global elevation measurements. Geolocation validation confirms the altimeter’s ability to accurately position the measurement on the surface of the Earth and provides insight into the fidelity of the geolocation determination process. Surfaces well characterized by independent methods are well suited to provide a measure of the ICESat-2 geolocation accuracy through statistical comparison. This study compares airborne lidar data with the ICESat-2 along-track geolocated photon data product to determine the horizontal geolocation accuracy by minimizing the vertical residuals between datasets. At the same location arrays of corner cube retro-reflectors (CCRs) provide unique signal signatures back to the satellite from their known positions to give a deterministic solution of the laser footprint diameter and the geolocation accuracy for those cases where two or more CCRs were illuminated within one ICESat-2 transect. This passive method for diameter recovery and geolocation accuracy assessment is implemented at two locations: White Sands Missile Range (WSMR) in New Mexico and along the 88°S latitude line in Antarctica. This early on-orbit study provides results as a proof of concept for this passive validation technique. For the cases studied the diameter value ranged from 10.6 to 12 m. The variability is attributed to the statistical nature of photon-counting lidar technology and potentially, variations in the atmospheric conditions that impact signal transmission. The geolocation accuracy results from the CCR technique and airborne lidar comparisons are within the mission requirement of 6.5 m.
Collapse
|
32
|
Washam P, Nicholls KW, Münchow A, Padman L. Tidal Modulation of Buoyant Flow and Basal Melt Beneath Petermann Gletscher Ice Shelf, Greenland. JOURNAL OF GEOPHYSICAL RESEARCH. OCEANS 2020; 125:e2020JC016427. [PMID: 33381361 PMCID: PMC7757208 DOI: 10.1029/2020jc016427] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 08/17/2020] [Accepted: 09/28/2020] [Indexed: 06/12/2023]
Abstract
A set of collocated, in situ oceanographic and glaciological measurements from Petermann Gletscher Ice Shelf, Greenland, provides insights into the dynamics of under-ice flow driving basal melting. At a site 16 km seaward of the grounding line within a longitudinal basal channel, two conductivity-temperature (CT) sensors beneath the ice base and a phase-sensitive radar on the ice surface were used to monitor the coupled ice shelf-ocean system. A 6 month time series spanning 23 August 2015 to 12 February 2016 exhibited two distinct periods of ice-ocean interactions. Between August and December, radar-derived basal melt rates featured fortnightly peaks of ∼15 m yr-1 which preceded the arrival of cold and fresh pulses in the ocean that had high concentrations of subglacial runoff and glacial meltwater. Estimated current speeds reached 0.20 - 0.40 m s-1 during these pulses, consistent with a strengthened meltwater plume from freshwater enrichment. Such signals did not occur between December and February, when ice-ocean interactions instead varied at principal diurnal and semidiurnal tidal frequencies, and lower melt rates and current speeds prevailed. A combination of estimated current speeds and meltwater concentrations from the two CT sensors yields estimates of subglacial runoff and glacial meltwater volume fluxes that vary between 10 and 80 m3 s-1 during the ocean pulses. Area-average upstream ice shelf melt rates from these fluxes are up to 170 m yr-1, revealing that these strengthened plumes had already driven their most intense melting before arriving at the study site.
Collapse
Affiliation(s)
- Peter Washam
- School of Earth and Atmospheric SciencesGeorgia Institute of TechnologyAtlantaGAUSA
- College of Earth, Ocean, and EnvironmentUniversity of DelawareNewarkDEUSA
| | - Keith W. Nicholls
- British Antarctic SurveyNatural Environment Research CouncilCambridgeUK
| | - Andreas Münchow
- College of Earth, Ocean, and EnvironmentUniversity of DelawareNewarkDEUSA
| | | |
Collapse
|
33
|
PhotonLabeler: An Inter-Disciplinary Platform for Visual Interpretation and Labeling of ICESat-2 Geolocated Photon Data. REMOTE SENSING 2020. [DOI: 10.3390/rs12193168] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
NASA’s ICESat-2 space-borne photon-counting lidar mission is providing global elevation measurements that will provide significant benefits to a variety of ecosystem related research applications. Given the novelty of elevation and the derived data products from the ICESat-2 mission, the research community needs software tools that can facilitate photon-level analyses to support product validation and development new analysis methods. Here, we describe PhotonLabeler, a free graphic user interface (GUI) for manual labeling and visualization of ICESat-2 Geolocated Photon data (ATL03). Developed in MATLAB, the GUI facilitates the reading and display of ATL03 Hierarchical Data Format (HDF) files, the manual labeling of individual photons into target classes of choice using a number of point selections tools and enables eventual saving of labeled data in ASCII format. Other capabilities include saving and loading of labeling sessions to manage labeling tasks over time. We expect labeled data generated using the application to serve two main purposes. First, serve as reference data for validating various products from ICESat-2 mission, especially for study sites around the world that do not have existing reference datasets such as airborne lidar. Second, serve as training and validation data in the development of new algorithms for generating various ICESat-2 data products. We demonstrate the first use case through a validation case study for the land and vegetation product (ATL08), which provides canopy and terrain height estimates, over two sites. For the first site, located in northwestern Zambia, we used ICESat-2 ATL03 data acquired at night and for our second site in Texas, US, we used ATL03 data acquired during the day. ATL08 canopy and terrain height data showed good agreement (mean R2 > 0.8) with corresponding height metrics generated from manually labeled data. A comparison between PhotonLabeler and ATL08 photon labels also showed good agreement −93.3% and 95.4% overall accuracies for the Texas and Zambia site, respectively. These results, while limited in scope, show how PhotonLabeler can facilitate photon-level analyses for ICESat-2 data products beyond the ATL08 product. The PhotonLabeler application is freely available as a compiled MATLAB binary to enable free access and utilization by interested researchers.
Collapse
|
34
|
Adusumilli S, Fricker HA, Medley B, Padman L, Siegfried MR. Interannual variations in meltwater input to the Southern Ocean from Antarctic ice shelves. NATURE GEOSCIENCE 2020; 13:616-620. [PMID: 32952606 PMCID: PMC7500482 DOI: 10.1038/s41561-020-0616-z] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2019] [Accepted: 06/19/2020] [Indexed: 05/27/2023]
Abstract
Ocean-driven basal melting of Antarctica's floating ice shelves accounts for about half of their mass loss in steady-state, where gains in ice shelf mass are balanced by losses. Ice shelf thickness changes driven by varying basal melt rates modulate mass loss from the grounded ice sheet and its contribution to sea level, and the changing meltwater fluxes influence climate processes in the Southern Ocean. Existing continent-wide melt rate datasets have no temporal variability, introducing uncertainties in sea level and climate projections. Here, we combine surface height data from satellite radar altimeters with satellite-derived ice velocities and a new model of firn-layer evolution to generate a high-resolution map of time-averaged (2010-2018) basal melt rates, and time series (1994-2018) of meltwater fluxes for most ice shelves. Total basal meltwater flux in 1994 (1090±150 Gt/yr) was not significantly different from the steady-state value (1100±60 Gt/yr), but increased to 1570±140 Gt/yr in 2009, followed by a decline to 1160±150 Gt/yr in 2018. For the four largest "cold-water" ice shelves we partition meltwater fluxes into deep and shallow sources to reveal distinct signatures of temporal variability, providing insights into climate forcing of basal melting and the impact of this melting on the Southern Ocean.
Collapse
Affiliation(s)
- Susheel Adusumilli
- Scripps Institution of Oceanography, University of California San Diego, CA, USA
| | - Helen Amanda Fricker
- Scripps Institution of Oceanography, University of California San Diego, CA, USA
| | - Brooke Medley
- Cryospheric Science Laboratory, NASA Goddard Space Flight Center, MD, USA
| | | | | |
Collapse
|