Winter Water Formation in Coastal Polynyas of the Eastern Chukchi Shelf: Pacific and Atlantic Influences

Abstract

Water properties and formation processes of Alaskan Coastal Winter Water (ACWW) over the eastern Chukchi shelf along the Alaska coast, the so‐called Barrow Canyon pathway, are examined using data from moorings, atmospheric reanalysis, satellite‐derived sea‐ice production (SIP), and a numerical tracer experiment. Along this pathway, Pacific Winter Water (PWW) can be modified to produce ACWW through SIP accompanied by production of cold, saline polynya water in the coastal polynyas, upwelling of warm Atlantic Water (AW), and mixing processes on the shelf. Three different types of ACWW are formed: (i) a mixture of AW and PWW, (ii) a mixture of AW and polynya water, and (iii) hypersaline polynya water. The northeasterly winds, correlated with the north‐south atmospheric pressure gradient between Beaufort High and Aleutian Low, are common triggers of polynya SIP episodes and AW upwelling in the Barrow Coastal Polynya (BCP). Due to the dual impact of northeasterly winds, PWW modification processes in the BCP are more complicated than what occurs elsewhere in the Chukchi Polynya. The impact of AW upwelling on the ACWW formation is most prominent in the BCP, usually centered along the coast. All types of ACWW are thought to be basically transported westward or northwestward with the Chukchi slope current and/or Beaufort Gyre and finally contribute to maintenance of the lower halocline layer especially over the Chukchi Borderland, Northwind Ridge, and southern Canada Basin. Even in the Pacific sector of the Arctic Ocean, ACWW properties are strongly influenced by both Atlantic‐origin and Pacific‐origin waters.

Retrieval of Wintertime Sea Ice Production in Arctic Polynyas Using Thermal Infrared and Passive Microwave Remote Sensing Data

“…Accumulated IP ranges between 25 and 125 km 3 per winter, and likewise to POLA there are no significant trends. Supporting that finding, Hirano et al () also found an absence of any significant trend or transition in the magnitude of IP between 1992 and 2014, and postulated that the year‐to‐year variability in IP is related to varying winter northeasterly wind stress. Derived metrics from AMSR‐E and MODIS agree very well, with only 4% to 8% difference for both POLA and IP (Tables and ).…”

“…Similar to the Laptev Sea, the Chukchi Sea has been subject to a huge number of in situ, remote sensing and modeling studies related to sea ice and dense‐water formation (Cavalieri & Martin, ; Fukamachi et al, ; Hirano et al, , ; Iwamoto et al, , ; Martin et al, , ; Tamura & Ohshima, ; Weingartner et al, ; Winsor & Björk, ; Winsor & Chapman, , among various others). Regular forming coastal polynyas appear along the Alaskan coastline due to strong offshore winds from northerly to easterly directions, most frequently around Point Barrow in the north over to Wainwright and Icy Cape down to Cape Lisburne in the south.…”

“…A oceanic contribution to the surface energy balance could reduce the thermodynamic ice growth by around 23-27% in case of the NOW polynya (Tamura & Ohshima, 2011;Iwamoto et al, 2014) due to a potential influence of the West Greenland Current in northern Baffin Bay (Steffen, 1985;Yao & Tang, 2003). Further, for certain areas of the Chukchi Sea (Hirano et al, 2016;Hirano et al, 2018) and the Canadian Arctic Archipelago (CAA) (Hannah et al, 2009;Melling et al, 2015) it is either known or assumed that there is an oceanic influence on wintertime polynya dynamics.…”

Introduction to Special Collection on Arctic Ocean Modeling and Observational Synthesis (FAMOS) 2: Beaufort Gyre Phenomenon

“…Aksenov et al, 2016;Jones, 2001;McLaughlin et al, 2002;Steele et al, 2004;Timmermans et al, 2014). In this special collection, Spall et al (2018), Zhong et al (2019), Hirano et al (2018), and Hu and Myers (2019) discuss the most recent findings associated with the circulation of the Pacific water layers and factors influencing their dynamics and properties.…”

Favorable Conditions for Suspension Freezing in an Arctic Coastal Polynya

“…The coastal polynya system of the northeastern Chukchi Sea along the Alaskan coast, with significant wind‐driven offshore ice transport, has been identified as a major source of ice production (Martin et al, , ; Tamura & Ohshima, ; Iwamoto et al, ; Figure ). Saline water, that is, brine, excluded from growing sea ice in these polynyas results in dense water, which contributes to formation of the cold halocline layer in the Arctic Ocean (Hirano et al, ; Itoh et al, ; Martin et al, ). Previous work, tracing back highly sediment laden ice based on ice drift trajectories from buoys and a simple model, indicates significant particle entrainment into sea ice in this region (Eicken et al, ).…”