Observations of the heat budget of thinning coastal Arctic sea ice under the influence of a river outflow

Abstract:

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 shorefast 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 shorefast ice above the river outflow channel. This observing station was deployed as part of the Ikaaġvik Sikukun 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, and identify the ocean as the primary source of heat contributing to thinning of the ice in the outflow channel, which began in early February and accelerated rapidly before recovery of the station in April. We then use oceanographic measurements from the Bering Strait and the mouth of Kotzebue Sound in concert with the ice-tethered observations to identify the transport pathways for heat in the Sound and the influence of river outflow over the course of a seasonal cycle. These results are presented and discussed in the context of the multi-disciplinary research questions developed under the co-production framework of Ikaaġvik Sikukun, focused specifically on the implications of changing ice conditions on marine ecosystems and Indigenous ways of life in Kotzebue.