OSD Ocean Science Discussions OSD Ocean Sci. Discuss. 1812-0822 Göttingen, Germany 10.5194/os-2021-7 Observational Study on the Variability of Mixed Layer Depth in the Bering Sea and the Chukchi Sea in the Summer of 2019 Jiao Xiaohui 1 Zhang Jicai https://orcid.org/0000-0001-7916-6289 1 Li Chunyan 2 Institute of Physical Oceanography, Ocean College, Zhejiang University, Zhoushan 316021, China Department of Oceanography and Coastal Sciences, College of the Coast and Environment, Louisiana State University, Baton Rouge 70803, U.S.A. 15 02 2021 2021 1 40 Copyright: © 2021 Xiaohui Jiao et al. 2021 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://os.copernicus.org/preprints/os-2021-7/ The full text article is available as a PDF file from https://os.copernicus.org/preprints/os-2021-7/os-2021-7.pdf

<p>Based on the high-resolution CTD data from 58 stations in the Bering Sea and the Chukchi Sea in the summer of 2019, the mixed layer depth (MLD) was obtained according to the density difference threshold method. It was verified that the MLD could be estimated more accurately by using a criterion of 0.125&thinsp;kg/m<sup>3</sup> in this region. The MLD in the Bering Sea basin was larger than that in the Bering Sea shelf, and both of them were smaller than that in the Bering Sea slope. The MLD increased northward both in the Chukchi Sea shelf and the Chukchi Sea slope. The farther northward, the greater the difference between the MLD calculated from temperature (MLDt) and the MLD calculated from density (MLDd) was, and the more important the role of salinity was in determining the MLD. The larger MLD (refer to MLDd specifically) in the Bering Sea slope might be due to the enhancement of mixing caused by the Bering Slope Current (BSC) and eddies. The horizontal advection of the Bering Sea Anadyr Water and the Alaska Coastal Water in the Bering Sea shelf led to the shallower MLD in the central transition zone. The northward increase of the MLD in the Chukchi Sea might be related to the low-salinity seawater resulting from the melting of sea ice in summer. The spatial variation of MLD was more closely related to the surface momentum flux than the sea surface buoyancy flux, and the wave had little effect.</p>

 National Key Research and Development Program of China 2017YFC1404000 2017YFA0604100 National Natural Science Foundation of China 41876086 41206001