Arctic | Climate and Oceanography
Physical controls of the seasonal stratification in the northeastern Chukchi Sea Presenter: Jiaxu Zhang , jiaxuzh@uw.edu, University of Washington and NOAA/PMEL Wei Cheng , wei.cheng@noaa.gov, Cooperative Institute for Climate, Ocean, and Ecosystem Studies, University of Washington Phyllis Stabeno , phyllis.stabeno@noaa.gov, NOAA Pacific Marine Environmental Laboratory
Wilbert Weijer , wilbert@lanl.gov Milena Veneziani , milena@lanl.gov Ryan McCabe , ryan.mccabe@noaa.gov
Using a 10-km ocean-sea ice hindcast simulation of 1958-2016, we identify seasonal transitions of the water-column stratification and its associated thermohaline signatures over the northeastern Chukchi Sea (NECS), and explore the physical processes that contribute to strong vs. weak summer stratifications. The model shows that warm summers have reduced stratification, resulting from salty anomalies on top and freshening anomalies at the bottom. In contrast, cold summers have enhanced stratification with opposite salinity anomalies. We find that warm summers are associated with strong advection of Bering inflow, which brings warmer and saltier water relative to the upper layer of the summer NECS while bringing relatively warm and fresh water to the bottom layer, and vice versa for cold summers. Meanwhile, warm summers have low ice production over NECS in the previous winters, keeping the lower layer fresh by reduced brine rejections in winters while keeping the upper layer salty through low meltwater release in the following springs, both of which help maintain a low vertical density gradient. Both factors (advection of Bering inflow and ice production rates in previous winters) are likely controlled by Aleutian Low and its associated east-northeast winds, with reduced Aleutian Low and reduced ENE winds leading to warm summers. The identified stratification patterns in warm vs. cold summers have implications for local nutrient supply through vertical mixing and remote nutrient supply through Bering inflow.
Alaska Marine Science Symposium 2023 123
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