Publications

Preusser, A; Ohshima, KI; Iwamoto, K; Willmes, S; Heinemann, G (2019). Retrieval of Wintertime Sea Ice Production in Arctic Polynyas Using Thermal Infrared and Passive Microwave Remote Sensing Data. JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 124(8), 5503-5528.

Abstract
Precise knowledge of wintertime sea ice production in Arctic polynyas is not only required to enhance our understanding of atmosphere-sea ice-ocean interactions but also to verify frequently utilized climate and ocean models. Here, a high-resolution (2-km) Moderate Resolution Imaging Spectroradiometer (MODIS) thermal infrared satellite data set featuring spatial and temporal characteristics of 17 Arctic polynya regions for the winter seasons 2002/2003 to 2017/2018 is directly compared to an akin low-resolution Advanced Microwave Scanning Radiometer-EOS (AMSR-E) passive microwave data set for 2002/2003 to 2010/2011. The MODIS data set is purely based on a 1-D energy-balance model, where thin-ice thicknesses (<= 20 cm) are directly derived from ice-surface temperature swath data and European Centre for Medium-Range Weather Forecasts Re-Analysis-Interim atmospheric reanalysis data on a quasi-daily basis. Thin-ice thicknesses in the AMSR-E data set are derived empirically. Important polynya properties such as areal extent and potential thermodynamic ice production can be estimated from both pan-Arctic data sets. Although independently derived, our results show that both data sets feature quite similar spatial and temporal variations of polynya area (POLA) and ice production (IP), which suggests a high reliability. The average POLA (average accumulated IP) for all Arctic polynyas combined derived from both MODIS and AMSR-E are 1.99x10(5) km(2) (1.34x10(3) km(3)) and 2.29x10(5) km(2) (1.31x10(3) km(3)), respectively. Narrow polynyas in areas such as the Canadian Arctic Archipelago are notably better resolved by MODIS. Analysis of 16 winter seasons provides an evaluation of long-term trends in POLA and IP, revealing the significant increase of ice formation in polynyas along the Siberian coast. Plain Language Summary The term "polynya" essentially describes the appearance of "holes" in an otherwise closed sea ice cover, that are kept free of thick sea ice due to strong physical forcing mechanisms such as wind or warmer ocean temperatures. The size of such a polynya can sometimes exceed several tens of thousands of square kilometers, indicating a high physical and biological importance. The contrast between the relatively warm ocean and the cold atmosphere creates a flow of heat to the atmosphere that causes intense freezing at the ocean surface. Gaining a more detailed knowledge about the total amount of new sea ice that is formed in these polynyas during the Arctic winter is highly important to understand the large-scale characteristics of the Arctic sea ice cover. Using different kinds of satellite data, this study follows the aim to analyze the difference in Arctic-wide polynya monitoring between two independent and previously published data sets. Our results show that both data sets show highly similar estimations of polynya size and new sea ice production, with the overall Arctic-wide difference being in the range of 2-15%. The results of this study enhance the confidence when using the data sets for other applications and when analyzing long-term developments and trends of Arctic polynyas.

DOI:
10.1029/2019JC014976

ISSN:
2169-9275