Abstract
Abstract. The presence of melt ponds on the Arctic sea ice strongly affects the energy balance of the Arctic Ocean in summer. It affects albedo as well as transmittance through the sea ice, which has consequences for the heat balance and mass balance of sea ice. An algorithm to retrieve melt pond fraction and sea ice albedo from Medium Resolution Imaging Spectrometer (MERIS) data is validated against aerial, shipborne and in situ campaign data. The results show the best correlation for landfast and multiyear ice of high ice concentrations. For broadband albedo, R2 is equal to 0.85, with the RMS (root mean square) being equal to 0.068; for the melt pond fraction, R2 is equal to 0.36, with the RMS being equal to 0.065. The correlation for lower ice concentrations, subpixel ice floes, blue ice and wet ice is lower due to ice drift and challenging for the retrieval surface conditions. Combining all aerial observations gives a mean albedo RMS of 0.089 and a mean melt pond fraction RMS of 0.22. The in situ melt pond fraction correlation is R2 = 0.52 with an RMS = 0.14. Ship cruise data might be affected by documentation of varying accuracy within the Antarctic Sea Ice Processes and Climate (ASPeCt) protocol, which may contribute to the discrepancy between the satellite value and the observed value: mean R2 = 0.044, mean RMS = 0.16. An additional dynamic spatial cloud filter for MERIS over snow and ice has been developed to assist with the validation on swath data.
Highlights
Melt ponds on the Arctic sea ice affect the albedo, mass balance and heat balance of the ice (e.g. Perovich et al, 2009) by translating the increase of air temperature into drastic and rapid surface type changes
The data used for the present study are the pond fraction and broadband sea ice albedo swath data products retrieved from MERIS (Medium Resolution Imaging Spectrometer) swath Level 1b data over the ice-covered Arctic Ocean using the Melt Pond Detector (MPD) retrieval
Melt ponds on sea ice affect the radiative properties of the ice cover and its heat and mass balance
Summary
Melt ponds on the Arctic sea ice affect the albedo, mass balance and heat balance of the ice (e.g. Perovich et al, 2009) by translating the increase of air temperature into drastic and rapid surface type changes. The present work is dedicated to validation of a MPF and sea ice albedo retrieval algorithm, the Melt Pond Detector (MPD), described by Zege et al (2015). A detailed description of melt stages and melt water distribution mechanisms can be found in Polashenski et al (2012) These details of melt evolution are responsible for the spatial variability of MPF and sea ice albedo. The temporal variability of MPF is driven by air mass transport and changing air temperature This introduces complications in the MPF modelling and creates the need for an MPF and sea ice albedo data set of possibly high temporal and spatial resolution, which can be retrieved from satellite data.
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