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Boghosian AL, Pitcher LH, Smith LC, Kosh E, Alexander PM, Tedesco M, Bell RE. Development of Ice-Shelf Estuaries Promotes Fractures and Calving. NATURE GEOSCIENCE 2021; 14:899-905. [PMID: 34917170 PMCID: PMC8670399 DOI: 10.1038/s41561-021-00837-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Accepted: 09/08/2021] [Indexed: 06/14/2023]
Abstract
As the global climate warms, increased surface meltwater production on ice shelves may trigger ice-shelf collapse and enhance global sea-level rise. The formation of surface rivers could help prevent ice-shelf collapse if they can efficiently evacuate meltwater. Here, we present observations of the evolution of a surface river into an ice-shelf estuary atop the Petermann Ice Shelf in northwest Greenland, and identify a second estuary at the nearby Ryder Ice Shelf. This surface hydrology process can foster fracturing and enhance calving. At the Petermann estuary, sea ice was observed converging at the river mouth upstream, indicating a flow reversal. Seawater persists in the estuary, after the surrounding icescape is frozen. Along the base of Petermann estuary, linear fractures were initiated at the calving front and propagated upstream along the channel. Similar fractures along estuary channels shaped past large rectilinear calving events at the Petermann and Ryder Ice Shelves. Increased surface melting in a warming world will enhance fluvial incision, promoting estuary development, longitudinal fracturing orthogonal to ice-shelf fronts, and increase rectilinear calving. Estuaries could develop in Antarctica within the next half-century, resulting in increased calving and accelerating both ice loss and global sea-level rise.
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Affiliation(s)
- Alexandra L. Boghosian
- Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York, NY 10964
- Department of Earth and Environmental Sciences, Columbia University, Palisades, New York, NY 10964
| | - Lincoln H Pitcher
- Cooperative Institute for Research in Environmental Science (CIRES), University of Colorado Boulder, Boulder, CO 80309
- Institute at Brown for Environment and Society, Brown University, Providence, RI 02912
| | - Laurence C. Smith
- Institute at Brown for Environment and Society, Brown University, Providence, RI 02912
- Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI, 029123
| | - Elena Kosh
- Environmental Science Department, Barnard College, New York, NY 10027
| | - Patrick M. Alexander
- Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York, NY 10964
- NASA Goddard Institute for Space Studies, New York, NY 10025
| | - Marco Tedesco
- Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York, NY 10964
- NASA Goddard Institute for Space Studies, New York, NY 10025
- Data Science Institute at Columbia University, New York, NY 10027
- Institute of Economics, Scuola Superiore Sant-Anna, Pisa, Italy
| | - Robin E. Bell
- Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York, NY 10964
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2
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Irvine-Fynn TDL, Edwards A, Stevens IT, Mitchell AC, Bunting P, Box JE, Cameron KA, Cook JM, Naegeli K, Rassner SME, Ryan JC, Stibal M, Williamson CJ, Hubbard A. Storage and export of microbial biomass across the western Greenland Ice Sheet. Nat Commun 2021; 12:3960. [PMID: 34172727 PMCID: PMC8233322 DOI: 10.1038/s41467-021-24040-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Accepted: 05/21/2021] [Indexed: 11/23/2022] Open
Abstract
The Greenland Ice Sheet harbours a wealth of microbial life, yet the total biomass stored or exported from its surface to downstream environments is unconstrained. Here, we quantify microbial abundance and cellular biomass flux within the near-surface weathering crust photic zone of the western sector of the ice sheet. Using groundwater techniques, we demonstrate that interstitial water flow is slow (~10−2 m d−1), while flow cytometry enumeration reveals this pathway delivers 5 × 108 cells m−2 d−1 to supraglacial streams, equivalent to a carbon flux up to 250 g km−2 d−1. We infer that cellular carbon accumulation in the weathering crust exceeds fluvial export, promoting biomass sequestration, enhanced carbon cycling, and biological albedo reduction. We estimate that up to 37 kg km−2 of cellular carbon is flushed from the weathering crust environment of the western Greenland Ice Sheet each summer, providing an appreciable flux to support heterotrophs and methanogenesis at the bed. Microbes that colonise ice sheet surfaces are important to the carbon cycle, but their biomass and transport remains unquantified. Here, the authors reveal substantial microbial carbon fluxes across Greenland’s ice surface, in quantities that may sustain subglacial heterotrophs and fuel methanogenesis.
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Affiliation(s)
- T D L Irvine-Fynn
- Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, UK.
| | - A Edwards
- Institute of Biological Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, UK
| | - I T Stevens
- Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, UK.,School of Geography, Politics and Sociology, Newcastle University, Newcastle-upon-Tyne, UK.,Department of Environmental Science, Aarhus University, Frederiksborgvej, Roskilde, Denmark
| | - A C Mitchell
- Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, UK
| | - P Bunting
- Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, UK
| | - J E Box
- Department of Glaciology and Climate, Geological Survey of Denmark and Greenland, Copenhagen, Denmark
| | - K A Cameron
- Institute of Biological Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, UK.,Department of Glaciology and Climate, Geological Survey of Denmark and Greenland, Copenhagen, Denmark.,School of Geographical and Earth Sciences, University of Glasgow, Glasgow, UK
| | - J M Cook
- Institute of Biological Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, UK.,Department of Environmental Science, Aarhus University, Frederiksborgvej, Roskilde, Denmark.,Department of Geography, University of Sheffield, Sheffield, UK
| | - K Naegeli
- Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, UK.,Institute of Geography and Oeschger Center for Climate Change Research, University of Bern, Bern, Switzerland
| | - S M E Rassner
- Institute of Biological Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, UK
| | - J C Ryan
- Institute at Brown for Environment and Society, Brown University, Providence, RI, USA
| | - M Stibal
- Department of Ecology, Faculty of Science, Charles University, Prague, Czechia
| | - C J Williamson
- Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, Bristol, UK
| | - A Hubbard
- Centre for Gas Hydrate, Environment and Climate, Department of Geosciences, UiT-The Arctic University of Norway, Tromsø, Norway.,Geography Research Unit, University of Oulu, Oulu, Finland
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Glacio-Nival Regime Creates Complex Relationships between Discharge and Climatic Trends of Zackenberg River, Greenland (1996–2019). CLIMATE 2021. [DOI: 10.3390/cli9040059] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Arctic environments experience rapid climatic changes as air temperatures are rising and precipitation is increasing. Rivers are key elements in these regions since they drain vast land areas and thereby reflect various climatic signals. Zackenberg River in northeast Greenland provides a unique opportunity to study climatic influences on discharge, as the river is not connected to the Greenland ice sheet. The study aims to explain discharge patterns between 1996 and 2019 and analyse the discharge for correlations to variations in air temperature and both solid and liquid precipitation. The results reveal no trend in the annual discharge. A lengthening of the discharge period is characterised by a later freeze-up and extreme discharge peaks are observed almost yearly between 2005 and 2017. A positive correlation exists between the length of the discharge period and the Thawing Degree Days (r=0.52,p<0.01), and between the total annual discharge and the annual maximum snow depth (r=0.48,p=0.02). Thereby, snowmelt provides the main source of discharge in the first part of the runoff season. However, the influence of precipitation on discharge could not be fully identified, because of uncertainties in the data and possible delays in the hydrological system. This calls for further studies on the relationship between discharge and precipitation. The discharge patterns are also influenced by meltwater from the A.P. Olsen ice cap and an adjacent glacier-dammed lake which releases outburst floods. Hence, this mixed hydrological regime causes different relationships between the discharge and climatic trends when compared to most Arctic rivers.
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Remote Sensing of River Discharge: A Review and a Framing for the Discipline. REMOTE SENSING 2020. [DOI: 10.3390/rs12071107] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Remote sensing of river discharge (RSQ) is a burgeoning field rife with innovation. This innovation has resulted in a highly non-cohesive subfield of hydrology advancing at a rapid pace, and as a result misconceptions, mis-citations, and confusion are apparent among authors, readers, editors, and reviewers. While the intellectually diverse subfield of RSQ practitioners can parse this confusion, the broader hydrology community views RSQ as a monolith and such confusion can be damaging. RSQ has not been comprehensively summarized over the past decade, and we believe that a summary of the recent literature has a potential to provide clarity to practitioners and general hydrologists alike. Therefore, we here summarize a broad swath of the literature, and find after our reading that the most appropriate way to summarize this literature is first by application area (into methods appropriate for gauged, semi-gauged, regionally gauged, politically ungauged, and totally ungauged basins) and next by methodology. We do not find categorizing by sensor useful, and everything from un-crewed aerial vehicles (UAVs) to satellites are considered here. Perhaps the most cogent theme to emerge from our reading is the need for context. All RSQ is employed in the service of furthering hydrologic understanding, and we argue that nearly all RSQ is useful in this pursuit provided it is properly contextualized. We argue that if authors place each new work into the correct application context, much confusion can be avoided, and we suggest a framework for such context here. Specifically, we define which RSQ techniques are and are not appropriate for ungauged basins, and further define what it means to be ‘ungauged’ in the context of RSQ. We also include political and economic realities of RSQ, as the objective of the field is sometimes to provide data purposefully cloistered by specific political decisions. This framing can enable RSQ to respond to hydrology at large with confidence and cohesion even in the face of methodological and application diversity evident within the literature. Finally, we embrace the intellectual diversity of RSQ and suggest the field is best served by a continuation of methodological proliferation rather than by a move toward orthodoxy and standardization.
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Molod A, Hackert E, Vikhliaev Y, Zhao B, Barahona D, Vernieres G, Borovikov A, Kovach RM, Marshak J, Schubert S, Li Z, Lim YK, Andrews LC, Cullather R, Koster R, Achuthavarier D, Carton J, Coy L, Freire JLM, Longo KM, Nakada K, Pawson S. GEOS-S2S Version 2: The GMAO High Resolution Coupled Model and Assimilation System for Seasonal Prediction. JOURNAL OF GEOPHYSICAL RESEARCH. ATMOSPHERES : JGR 2020; 125:e2019JD031767. [PMID: 33959467 PMCID: PMC8098100 DOI: 10.1029/2019jd031767] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The Global Modeling and Assimilation Office (GMAO) has recently released a new version of the Goddard Earth Observing System (GEOS) Sub-seasonal to Seasonal prediction (S2S) system, GEOS-S2S-2, that represents a substantial improvement in performance and infrastructure over the previous system. The system is described here in detail, and results are presented from forecasts, climate equillibrium simulations and data assimilation experiments. The climate or equillibrium state of the atmosphere and ocean showed a substantial reduction in bias relative to GEOS-S2S-1. The GEOS-S2S-2 coupled reanalysis also showed substantial improvements, attributed to the assimilation of along-track Absolute Dynamic Topography. The forecast skill on subseasonal scales showed a much-improved prediction of the Madden-Julian Oscillation in GEOS-S2S-2, and on a seasonal scale the tropical Pacific forecasts show substantial improvement in the east and comparable skill to GEOS-S2S-1 in the central Pacific. GEOS-S2S-2 anomaly correlations of both land surface temperature and precipitation were comparable to GEOS-S2S-1, and showed substantially reduced root mean square error of surface temperature. The remaining issues described here are being addressed in the development of GEOS-S2S Version 3, and with that system GMAO will continue its tradition of maintaining a state of the art seasonal prediction system for use in evaluating the impact on seasonal and decadal forecasts of assimilating newly available satellite observations, as well as to evaluate additional sources of predictability in the earth system through the expanded coupling of the earth system model and assimilation components.
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Affiliation(s)
- Andrea Molod
- NASA, Goddard Space Flight Center, Greenbelt, MD 20771
| | - Eric Hackert
- NASA, Goddard Space Flight Center, Greenbelt, MD 20771
| | - Yury Vikhliaev
- NASA, Goddard Space Flight Center, Greenbelt, MD 20771
- SSAI, Science Systems and Applications, Inc. Lanham, MD 20706
| | - Bin Zhao
- NASA, Goddard Space Flight Center, Greenbelt, MD 20771
- SSAI, Science Systems and Applications, Inc. Lanham, MD 20706
| | | | | | - Anna Borovikov
- NASA, Goddard Space Flight Center, Greenbelt, MD 20771
- SSAI, Science Systems and Applications, Inc. Lanham, MD 20706
| | - Robin M. Kovach
- NASA, Goddard Space Flight Center, Greenbelt, MD 20771
- SSAI, Science Systems and Applications, Inc. Lanham, MD 20706
| | | | - Siegfried Schubert
- NASA, Goddard Space Flight Center, Greenbelt, MD 20771
- SSAI, Science Systems and Applications, Inc. Lanham, MD 20706
| | - Zhao Li
- NASA, Goddard Space Flight Center, Greenbelt, MD 20771
- SSAI, Science Systems and Applications, Inc. Lanham, MD 20706
| | - Young-Kwon Lim
- NASA, Goddard Space Flight Center, Greenbelt, MD 20771
- Goddard Earth Sciences Technology and Research, I. M. Systems Group, College Park, MD 20740
| | | | - Richard Cullather
- NASA, Goddard Space Flight Center, Greenbelt, MD 20771
- University of Maryland, College Park, MD
| | - Randal Koster
- NASA, Goddard Space Flight Center, Greenbelt, MD 20771
| | - Deepthi Achuthavarier
- NASA, Goddard Space Flight Center, Greenbelt, MD 20771
- Goddard Earth Sciences Technology and Research, Universities Space Research Association, Columbia, MD
| | | | - Lawrence Coy
- NASA, Goddard Space Flight Center, Greenbelt, MD 20771
- SSAI, Science Systems and Applications, Inc. Lanham, MD 20706
| | - Julliana L. M. Freire
- NASA, Goddard Space Flight Center, Greenbelt, MD 20771
- Center for Weather Forecast and Climate Studies, National Institute for Space Research (INPE), Cachoeira Paulista, Sao Paulo, Brazil
| | - Karla M. Longo
- NASA, Goddard Space Flight Center, Greenbelt, MD 20771
- Goddard Earth Sciences Technology and Research, Universities Space Research Association, Columbia, MD
| | - Kazumi Nakada
- NASA, Goddard Space Flight Center, Greenbelt, MD 20771
- SSAI, Science Systems and Applications, Inc. Lanham, MD 20706
| | - Steven Pawson
- NASA, Goddard Space Flight Center, Greenbelt, MD 20771
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Applications of Unmanned Aerial Vehicles in Cryosphere: Latest Advances and Prospects. REMOTE SENSING 2020. [DOI: 10.3390/rs12060948] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Owing to usual logistic hardships related to field-based cryospheric research, remote sensing has played a significant role in understanding the frozen components of the Earth system. Conventional spaceborne or airborne remote sensing platforms have their own merits and limitations. Unmanned aerial vehicles (UAVs) have emerged as a viable and inexpensive option for studying the cryospheric components at unprecedented spatiotemporal resolutions. UAVs are adaptable to various cryospheric research needs in terms of providing flexibility with data acquisition windows, revisits, data/sensor types (multispectral, hyperspectral, microwave, thermal/night imaging, Light Detection and Ranging (LiDAR), and photogrammetric stereos), viewing angles, flying altitudes, and overlap dimensions. Thus, UAVs have the potential to act as a bridging remote sensing platform between spatially discrete in situ observations and spatially continuous but coarser and costlier spaceborne or conventional airborne remote sensing. In recent years, a number of studies using UAVs for cryospheric research have been published. However, a holistic review discussing the methodological advancements, hardware and software improvements, results, and future prospects of such cryospheric studies is completely missing. In the present scenario of rapidly changing global and regional climate, studying cryospheric changes using UAVs is bound to gain further momentum and future studies will benefit from a balanced review on this topic. Our review covers the most recent applications of UAVs within glaciology, snow, permafrost, and polar research to support the continued development of high-resolution investigations of cryosphere. We also analyze the UAV and sensor hardware, and data acquisition and processing software in terms of popularity for cryospheric applications and revisit the existing UAV flying regulations in cold regions of the world. The recent usage of UAVs outlined in 103 case studies provide expertise that future investigators should base decisions on.
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Williams JJ, Gourmelen N, Nienow P. Dynamic response of the Greenland ice sheet to recent cooling. Sci Rep 2020; 10:1647. [PMID: 32015394 PMCID: PMC6997348 DOI: 10.1038/s41598-020-58355-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 01/13/2020] [Indexed: 11/08/2022] Open
Abstract
The subglacial hydrological system critically controls ice motion at the margins of the Greenland Ice Sheet. However, over multi-annual timescales, the net impact of hydro-dynamic coupling on ice motion remains poorly understood. Here, we present annual ice velocities from 1992-2019 across a ~10,600 km2 land-terminating area of southwest Greenland. From the early-2000s through to ~2012, we observe a slowdown in ice motion in response to increased surface melt, consistent with previous research. From 2013 to 2019 however, we observe an acceleration in ice motion coincident with atmospheric cooling and a ~15% reduction in mean surface melt production relative to 2003-2012. We find that ice velocity speed-up is greater in marginal areas, and is strongly correlated with ice thickness. We hypothesise that under thinner ice, increases in basal water pressure offset a larger proportion of the ice overburden pressure, leading to reduced effective pressure and thus greater acceleration when compared to thicker ice further inland. Our findings indicate that hydro-dynamic coupling provides the major control on changes in ice motion across the ablation zone of land terminating margins of the Greenland Ice Sheet over multi-annual timescales.
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Affiliation(s)
- Joshua J Williams
- School of Geosciences, University of Edinburgh, Edinburgh, EH8 9XP, UK.
| | - Noel Gourmelen
- School of Geosciences, University of Edinburgh, Edinburgh, EH8 9XP, UK
| | - Peter Nienow
- School of Geosciences, University of Edinburgh, Edinburgh, EH8 9XP, UK
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8
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An Integrated View of Greenland Ice Sheet Mass Changes Based on Models and Satellite Observations. REMOTE SENSING 2019. [DOI: 10.3390/rs11121407] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The Greenland ice sheet is a major contributor to sea level rise, adding on average 0.47 ± 0.23 mm year − 1 to global mean sea level between 1991 and 2015. The cryosphere as a whole has contributed around 45% of observed global sea level rise since 1993. Understanding the present-day state of the Greenland ice sheet is therefore vital for understanding the processes controlling the modern-day rates of sea level change and for making projections of sea level rise into the future. Here, we provide an overview of the current state of the mass budget of Greenland based on a diverse range of remote sensing observations to produce the essential climate variables (ECVs) of ice velocity, surface elevation change, grounding line location, calving front location, and gravimetric mass balance as well as numerical modelling that together build a consistent picture of a shrinking ice sheet. We also combine these observations with output from a regional climate model and from an ice sheet model to gain insight into existing biases in ice sheet dynamics and surface mass balance processes. Observations show surface lowering across virtually all regions of the ice sheet and at some locations up to −2.65 m year − 1 between 1995 and 2017 based on radar altimetry analysis. In addition, calving fronts at 28 study sites, representing a sample of typical glaciers, have retreated all around Greenland since the 1990s and in only two out of 28 study locations have they remained stable. During the same period, two of five floating ice shelves have collapsed while the locations of grounding lines at the remaining three floating ice shelves have remained stable over the observation period. In a detailed case study with a fracture model at Petermann glacier, we demonstrate the potential sensitivity of these floating ice shelves to future warming. GRACE gravimetrically-derived mass balance (GMB) data shows that overall Greenland has lost 255 ± 15 Gt year − 1 of ice over the period 2003 to 2016, consistent with that shown by IMBIE and a marked increase compared to a rate of loss of 83 ± 63 Gt year − 1 in the 1993–2003 period. Regional climate model and ice sheet model simulations show that surface mass processes dominate the Greenland ice sheet mass budget over most of the interior. However, in areas of high ice velocity there is a significant contribution to mass loss by ice dynamical processes. Marked differences between models and observations indicate that not all processes are captured accurately within models, indicating areas for future research.
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