Abstract
Abstract. High-resolution MODIS thermal infrared satellite data are used to infer spatial and temporal characteristics of 17 prominent coastal polynya regions over the entire Arctic basin. Thin-ice thickness (TIT) distributions (≤ 20 cm) are calculated from MODIS ice-surface temperatures, combined with ECMWF ERA-Interim atmospheric reanalysis data in an energy balance model for 13 winter seasons (2002/2003 to 2014/2015; November to March). From all available MODIS swath data, daily thin-ice thickness composites are computed in order to derive quantities such as polynya area and total thermodynamic (i.e., potential) ice production. A gap-filling approach is applied to account for cloud and data gaps in the MODIS composites. All polynya regions combined cover an average thin-ice area of 226.6 ± 36.1 × 103 km2 in winter. This allows for an average total winter-accumulated ice production of about 1811 ± 293 km3, whereby the Kara Sea region, the North Water polynya (both 15 %), polynyas on the western side of Novaya Zemlya (20 %), as well as scattered smaller polynyas in the Canadian Arctic Archipelago (all combined 12 %) are the main contributors. Other well-known sites of polynya formation (Laptev Sea, Chukchi Sea) show smaller contributions and range between 2 and 5 %. We notice distinct differences to earlier studies on pan-Arctic polynya characteristics, originating in some part from the use of high-resolution MODIS data, as the capability to resolve small-scale (> 2 km) polynyas and also large leads are increased. Despite the short record of 13 winter seasons, positive trends in ice production are detected for several regions of the eastern Arctic (most significantly in the Laptev Sea region with an increase of 6.8 km3 yr−1) and the North Water polynya, while other polynyas in the western Arctic show a more pronounced variability with varying trends. We emphasize the role of the Laptev Sea polynyas as being a major influence on Transpolar Drift characteristics through a distinct relation between increasing ice production and ice area export. Overall, our study presents a spatially highly accurate characterization of circumpolar polynya dynamics and ice production, which should be valuable for future modeling efforts of atmosphere–ice–ocean interactions in the Arctic.
Highlights
The sea-ice cover in the Arctic is subject to continuous changes through a variety of thermodynamic and dynamic processes, which are driven by atmosphere and ocean dynamics
Vast fast-ice areas, e.g., along the Siberian coast, can be detected from monthly Thin-ice thickness (TIT) frequencies, as these areas usually appear at fixed locations attached to the shore and TIT frequencies tend towards zero as the ice quickly thickens by congelation ice growth
In the present study we analyzed circumpolar polynya dynamics and ice production in the Arctic based on highresolution Moderate Resolution Imaging Spectroradiometer (MODIS) thermal infrared imagery and atmospheric reanalysis from the ERA-Interim data set
Summary
The sea-ice cover in the Arctic is subject to continuous changes through a variety of thermodynamic and dynamic processes, which are driven by atmosphere and ocean dynamics. Areas of open water and thin ice, i.e., polynyas and leads, are characteristic features in this icescape with a huge influence on local physical, biological and chemical processes at the interface between the atmosphere and the ocean (Barber and Massom, 2007). In contrast, far more variable both in space and time (Willmes and Heinemann, 2016). Regular monitoring of these open-water and thin-ice areas with a high spatial accuracy is a crucial step to be able to detect long-term changes, potential linkages and feedbacks to other environmental compartments as well as spatial and temporal patterns
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