The Western Arctic Ocean is a host to major ocean circulation systems, many of which generate eddies that can transport water masses and corresponding tracers over long distances from their formation sites. However, comprehensive observations of critical eddy characteristics are currently not available and are limited to spatially and temporally sparse in situ observations. Here we use high-resolution spaceborne synthetic aperture radar measurements to detect eddies from their surface imprints in ice-free sea surface roughness, and in sea ice patterns throughout marginal ice zones. We provide the first estimate of eddy characteristics extending over the seasonally ice-free and marginal ice zone regions of the Western Arctic Ocean, including their locations, diameters, and monthly distribution. Using available synthetic aperture radar data, we identified over 4,000 open ocean eddies, as well as over 3,500 eddies in marginal ice zones from June to October in 2007, 2011, and 2016. Eddies range in size between 0.5 and 100 km and are frequently found over the shelf and near continental slopes but also present in the deep Canada Basin and over the Chukchi Plateau. We find that cyclonic eddies are twice more frequent compared to anticyclonic eddies at the surface, distinct from the dominating anticyclonic eddies observed at depth by in situ moorings and ice-tethered profilers. Our study supports the notion that eddies are ubiquitous in the Western Arctic Ocean even in the presence of sea ice and emphasizes the need for improved ocean observations and modeling at eddy scales. Plain Language SummaryOcean eddies play an important role in the transport of heat, salt, and pollutants over long distances from their formation sites. However, their observations in the Arctic Ocean are complex due to severe weather and sea ice cover. Here we present results of high-resolution satellite observations over the ice-free ocean and in the marginal ice zones. Detailed eddy characteristics are for the first time presented for the Western Arctic Ocean. These results provide observational evidence that eddies are ubiquitous in this Arctic region even in the presence of sea ice and emphasize the need for improved ocean observations and modeling at eddy scales. Key Points: • First account of eddies in the Western Arctic Ocean is presented based on satellite observations over open ocean and marginal ice zones • Eddies range in size between 0.5 and 100 km and are ubiquitous over deep and shelf regions of the Western Arctic Ocean • Cyclonic eddies are twice more frequent compared to anticyclones

<p>The Arctic Ocean is a host to major ocean circulation systems, many of which generate eddies that can transport water masses and corresponding tracers over long distances from their formation sites. However, comprehensive observations of critical eddy characteristics are currently not available and are limited to spatially and temporally sparse in situ observations.</p><p>Here we use multi-mission high‐resolution spaceborne synthetic aperture radar (SAR) measurements to detect eddies over open ocean and marginal ice zones (MIZ) of Fram Strait and Beaufort Gyre regions. We provide the first estimate of eddy properties, including their locations, size, vorticity sign and monthly distribution during summer period (from June to October). The results of historical Envisat ASAR observations for 2007 and 2011 are then compared to Sentinel-1 and ALOS-2 PALSAR-2 measurements acquired in 2016 and 2018, to infer the possible changes in the intensity and locations of eddy generation over the last decade.</p><p>The most prominent feature of the obtained results is that cyclonic eddies strongly dominate over anticyclones. Eddies range in size between 0.5 and 100 km and are frequently found over the shelf and near continental slopes but also present in the deep basin. For MIZ eddies, the number of eddies clearly depends on sea ice concentration with more eddies detected at the ice edge and over low ice concentration regions. The obtained results clearly show that eddies are ubiquitous in the Arctic Ocean even in the presence of sea ice and emphasize the need for improved ocean observations and modeling at eddy scales.</p><p>A special focus is also given to infer eddy dynamics over the Arctic marginal ice zones. The use of sequential Sentinel-1 SAR images enables to retrieve high-resolution velocity field over MIZ on a daily basis and observe eddy-driven MIZ dynamics down to submesoscales. The obtained eddy orbital velocities are in agreement with historical observations and may reach up to 0.5-0.7 m/s. We believe that this information is critical for better understanding of the key dynamical processes governing the MIZ state, as well as for improving and validation of sea ice and coupled ice-ocean models.</p><p>The analysis of eddies in this work was supported by RFBR grant 18‐35‐20078. Processing and analysis of Sentinel‐1 and ALOS‐2 Palsar‐2 data were done within RSF grant 18‐77‐00082. Software development for data analysis in this work was made under the Ministry of Science and Higher Education of the Russian Federation contract 0555‐2019‐0001.</p>

В работе представлены результаты анализа основных характеристик океанских вихрей в морях Чукотском и Бофорта, полученные на основе выделения их поверхностных проявлений (ПП) в спутниковых радиолокационных изображениях Envisat ASAR за летне-осенний период 2007 и 2011 гг. В ходе анализа определялись районы наблюдения вихрей, их диаметр, знак вращения, тип проявления и глубина места, соответствующая положению центра вихря. Полученные результаты обобщены для вихрей, наблюдаемых на участках открытой воды (ОВ), а также для вихрей в прикромочной зоне льда (ПЗЛ). Всего в ходе анализа выделено 2724 ПП вихревых структур, из которых 52 %-для вихрей открытой воды, 48 %-для вихрей ПЗЛ. Показано, что 64 % от общего числа вихрей являются циклоническими, причём это соотношение примерно одинаково как для вихрей ОВ, так и для вихрей ПЗЛ. Диапазон наблюдаемых диаметров вихрей составил от 1 до 50 км, но около 80 % всех вихрей имели диаметры менее 10 км. Поскольку радиус деформации Россби для района исследований в летнее время составляет 1-15 км, значительная часть наблюдаемых вихрей может относиться к субмезомасштабу.