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Mapping the Bathymetry of Melt Ponds on Arctic Sea Ice Using Hyperspectral Imagery. REMOTE SENSING 2020. [DOI: 10.3390/rs12162623] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Hyperspectral remote-sensing instruments on unmanned aerial vehicles (UAVs), aircraft and satellites offer new opportunities for sea ice observations. We present the first study using airborne hyperspectral imagery of Arctic sea ice and evaluate two atmospheric correction approaches (ATCOR-4 (Atmospheric and Topographic Correction version 4; v7.0.0) and empirical line calibration). We apply an existing, field data-based model to derive the depth of melt ponds, to airborne hyperspectral AisaEAGLE imagery and validate results with in situ measurements. ATCOR-4 results roughly match the shape of field spectra but overestimate reflectance resulting in high root-mean-square error (RMSE) (between 0.08 and 0.16). Noisy reflectance spectra may be attributed to the low flight altitude of 200 ft and Arctic atmospheric conditions. Empirical line calibration resulted in smooth, accurate spectra (RMSE < 0.05) that enabled the assessment of melt pond bathymetry. Measured and modeled pond bathymetry are highly correlated (r = 0.86) and accurate (RMSE = 4.04 cm), and the model explains a large portion of the variability (R2 = 0.74). We conclude that an accurate assessment of melt pond bathymetry using airborne hyperspectral data is possible subject to accurate atmospheric correction. Furthermore, we see the necessity to improve existing approaches with Arctic-specific atmospheric profiles and aerosol models and/or by using multiple reference targets on the ground.
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Horvat C, Jones DR, Iams S, Schroeder D, Flocco D, Feltham D. The frequency and extent of sub-ice phytoplankton blooms in the Arctic Ocean. SCIENCE ADVANCES 2017; 3:e1601191. [PMID: 28435859 PMCID: PMC5371420 DOI: 10.1126/sciadv.1601191] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Accepted: 02/10/2017] [Indexed: 05/05/2023]
Abstract
In July 2011, the observation of a massive phytoplankton bloom underneath a sea ice-covered region of the Chukchi Sea shifted the scientific consensus that regions of the Arctic Ocean covered by sea ice were inhospitable to photosynthetic life. Although the impact of widespread phytoplankton blooms under sea ice on Arctic Ocean ecology and carbon fixation is potentially marked, the prevalence of these events in the modern Arctic and in the recent past is, to date, unknown. We investigate the timing, frequency, and evolution of these events over the past 30 years. Although sea ice strongly attenuates solar radiation, it has thinned significantly over the past 30 years. The thinner summertime Arctic sea ice is increasingly covered in melt ponds, which permit more light penetration than bare or snow-covered ice. Our model results indicate that the recent thinning of Arctic sea ice is the main cause of a marked increase in the prevalence of light conditions conducive to sub-ice blooms. We find that as little as 20 years ago, the conditions required for sub-ice blooms may have been uncommon, but their frequency has increased to the point that nearly 30% of the ice-covered Arctic Ocean in July permits sub-ice blooms. Recent climate change may have markedly altered the ecology of the Arctic Ocean.
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Affiliation(s)
- Christopher Horvat
- Department of Applied Mathematics, School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
- Corresponding author.
| | - David Rees Jones
- Atmospheric, Oceanic and Planetary Physics, Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, U.K
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, U.K
| | - Sarah Iams
- Department of Applied Mathematics, School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - David Schroeder
- Centre for Polar Observation and Modelling, Department of Meteorology, University of Reading, Reading, U.K
| | - Daniela Flocco
- Centre for Polar Observation and Modelling, Department of Meteorology, University of Reading, Reading, U.K
| | - Daniel Feltham
- Centre for Polar Observation and Modelling, Department of Meteorology, University of Reading, Reading, U.K
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Pućko M, Stern GA, Macdonald RW, Jantunen LM, Bidleman TF, Wong F, Barber DG, Rysgaard S. The delivery of organic contaminants to the Arctic food web: why sea ice matters. THE SCIENCE OF THE TOTAL ENVIRONMENT 2015; 506-507:444-52. [PMID: 25437762 DOI: 10.1016/j.scitotenv.2014.11.040] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 11/10/2014] [Accepted: 11/11/2014] [Indexed: 05/02/2023]
Abstract
For decades sea ice has been perceived as a physical barrier for the loading of contaminants to the Arctic Ocean. We show that sea ice, in fact, facilitates the delivery of organic contaminants to the Arctic marine food web through processes that: 1) are independent of contaminant physical-chemical properties (e.g. 2-3-fold increase in exposure to brine-associated biota), and 2) depend on physical-chemical properties and, therefore, differentiate between contaminants (e.g. atmospheric loading of contaminants to melt ponds over the summer, and their subsequent leakage to the ocean). We estimate the concentrations of legacy organochlorine pesticides (OCPs) and current-use pesticides (CUPs) in melt pond water in the Beaufort Sea, Canadian High Arctic, in 2008, at near-gas exchange equilibrium based on Henry's law constants (HLCs), air concentrations and exchange dynamics. CUPs currently present the highest risk of increased exposures through melt pond loading and drainage due to the high ratio of melt pond water to seawater concentration (Melt pond Enrichment Factor, MEF), which ranges from 2 for dacthal to 10 for endosulfan I. Melt pond contaminant enrichment can be perceived as a hypothetical 'pump' delivering contaminants from the atmosphere to the ocean under ice-covered conditions, with 2-10% of CUPs annually entering the Beaufort Sea via this input route compared to the standing stock in the Polar Mixed Layer of the ocean. The abovementioned processes are strongly favored in first-year ice compared to multi-year ice and, therefore, the dynamic balance between contaminant inventories and contaminant deposition to the surface ocean is being widely affected by the large-scale icescape transition taking place in the Arctic.
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Affiliation(s)
- Monika Pućko
- Centre for Earth Observation Science, University of Manitoba, Wallace Building, 125 Dysart Road, Winnipeg R3T 2N2, Canada.
| | - Gary A Stern
- Centre for Earth Observation Science, University of Manitoba, Wallace Building, 125 Dysart Road, Winnipeg R3T 2N2, Canada
| | - Robie W Macdonald
- Centre for Earth Observation Science, University of Manitoba, Wallace Building, 125 Dysart Road, Winnipeg R3T 2N2, Canada; Institute of Ocean Sciences, Department of Fisheries and Oceans, 9860 West Saanich Road, Sidney, British Columbia V8L 4B2, Canada
| | - Liisa M Jantunen
- Air Quality Processes Research Section, Environment Canada, 6248 Eighth Line, Egbert, Ontario L0L 1N0, Canada
| | | | - Fiona Wong
- Air Quality Processes Research Section, Environment Canada, 6248 Eighth Line, Egbert, Ontario L0L 1N0, Canada; Department of Applied Environmental Science (ITM), Stockholm University, Stockholm SE-106 91, Sweden
| | - David G Barber
- Centre for Earth Observation Science, University of Manitoba, Wallace Building, 125 Dysart Road, Winnipeg R3T 2N2, Canada
| | - Søren Rysgaard
- Centre for Earth Observation Science, University of Manitoba, Wallace Building, 125 Dysart Road, Winnipeg R3T 2N2, Canada; Department of Geological Sciences, University of Manitoba, Wallace Building, 125 Dysart Road, Winnipeg R3T 2N2, Canada; Greenland Climate Research Centre, Greenland Institute of Natural Resources, 3900 Nuuk, Greenland; Arctic Research Centre, Aarhus University, 8000 Aarhus, Denmark
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Pućko M, Stern GA, Barber DG, Macdonald RW, Warner KA, Fuchs C. Mechanisms and implications of α-HCH enrichment in melt pond water on Arctic sea ice. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2012; 46:11862-9. [PMID: 23039929 DOI: 10.1021/es303039f] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
During the summer of 2009, we sampled 14 partially refrozen melt ponds and the top 1 m of old ice in the pond vicinity for α-hexachlorocyclohexane (α-HCH) concentrations and enantiomer fractions (EFs) in the Beaufort Sea. α-HCH concentrations were 3 - 9 times higher in melt ponds than in the old ice. We identify two routes of α-HCH enrichment in the ice over the summer. First, atmospheric gas deposition results in an increase of α-HCH concentration from 0.07 ± 0.02 ng/L (old ice) to 0.34 ± 0.08 ng/L, or ~20% less than the atmosphere-water equilibrium partitioning concentration (0.43 ng/L). Second, late-season ice permeability and/or complete ice thawing at the bottom of ponds permit α-HCH rich seawater (~0.88 ng/L) to replenish pond water, bringing concentrations up to 0.75 ± 0.06 ng/L. α-HCH pond enrichment may lead to substantial concentration patchiness in old ice floes, and changed exposures to biota as the surface meltwater eventually reaches the ocean through various drainage mechanisms. Melt pond concentrations of α-HCH were relatively high prior to the late 1980-s, with a Melt pond Enrichment Factor >1 (MEF; a ratio of concentration in surface meltwater to surface seawater), providing for the potential of increased biological exposures.
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Affiliation(s)
- M Pućko
- Centre for Earth Observation Science, University of Manitoba, 460 Wallace Building, 125 Dysart Road, Winnipeg, R3T 2N2, Canada.
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Ehn JK, Mundy CJ, Barber DG, Hop H, Rossnagel A, Stewart J. Impact of horizontal spreading on light propagation in melt pond covered seasonal sea ice in the Canadian Arctic. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010jc006908] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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