The Winter Heat Budget of Sea Ice in Kotzebue Sound: Residual Ocean Heat and the Seasonal Roles of River Outflow

• Published in: Journal of geophysical research. Oceans 2021-09, Vol.126 (9), p.n/a
• Main Authors: Witte, Carson R., Zappa, Christopher J., Mahoney, Andrew R., Goodwin, John, Harris, Cyrus, Schaeffer, Robert J., Schaeffer, Roswell, Betcher, Sarah, Hauser, Donna D. W., Laxague, Nathan J. M., Lindsay, Jessica M., Subramaniam, Ajit, Turner, Kate E., Whiting, Alex
• Format: Article
• Language: English
• Subjects: Bridges; Geophysics; Heat; Heat budget; Ice formation; Ice melting; indigenous knowledge; knowledge co‐production; Oceans; Outflow; Partnerships; residual ocean heat; River channels; River outflow; Rivers; Sea ice; Seasonal variations; Spring; Spring (season); Summer; Water outflow; Winter
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1029/2020JC016784

The winters of 2017/18 and 2018/19 saw unprecedented sea ice minima in the Bering and Chukchi Seas. Kotzebue Sound, located in the southeastern corner of the Chukchi Sea, remained largely ice‐free throughout the winter in a stark departure from both recorded history and Indigenous oral history. The only sea ice that persisted throughout the winter was landfast ice and most of this occupied a small corner of the Sound near the outflow of the Noatak and Kobuk Rivers. We present oceanographic and atmospheric time series from a heavily instrumented “ice‐tethered observatory” located on this landfast ice above the river outflow channel. This observing station was deployed as part of the Ikaaġvik Sikukun (Iñupiaq for “Ice Bridges”) project, in which hypotheses and subsequent observational programs were co‐produced in partnership with an Indigenous Elder Advisory Council in Kotzebue. The measurements allow us to quantify the heat budget of the ice above the outflow channel, and identify the ocean as the primary source of heat contributing to thinning of the ice, which began in early February and accelerated rapidly before the recovery of the station in April of 2019. In concert with the ice‐tethered observations, we use 2 years of oceanographic measurements from the mouth of Kotzebue Sound to characterize the influence of river outflow on the heat budget of the landfast ice, revealing a seasonal pattern in which the rivers promote ice formation and growth in the fall/winter, but help to drive melting of the ice in spring and early summer. Plain Language Summary A study of sea ice was undertaken as part of the Ikaaġvik Sikukun (Iñupiaq for “Ice Bridges”) project, in which scientific objectives were developed in partnership with an Indigenous Elder Advisory Council in Kotzebue, Alaska. One of these objectives was to explain why there was so little sea ice in Kotzebue Sound during the winters of 2017/18 and 2018/19. We set out to answer this question by making direct observations of the flow of heat into and out of the ice, and identified the ocean as the main source of heat driving ice melt during the winter. We also found that the outflow from several rivers was promoting ice growth during the fall and winter, but helping to drive ice melt in the spring and early summer. Key Points The winter of 2018/19 saw unprecedentedly low sea ice cover in the Bering Strait region and Kotzebue Sound In‐situ observations identify the ocean as the primary source of heat input to