Thin ice, deep snow and surface flooding in Kotzebue Sound: landfast ice mass balance during two anomalously warm winters and implications for marine mammals and subsistence hunting

Andrew R Mahoney,Alex V Whiting,Robert J Schaeffer,Sarah Betcher,John Goodwin,Nathan J M Laxague,Cyrus Harris,Carson R Witte,Ajit Subramaniam,Kate E Turner,Donna D W Hauser,Christopher J Zappa,Roswell Schaeffer,Jessica M Lindsay

doi:10.1017/jog.2021.49

Abstract

AbstractThe inaugural data from the first systematic program of sea-ice observations in Kotzebue Sound, Alaska, in 2018 coincided with the first winter in living memory when the Sound was not choked with ice. The following winter of 2018–19 was even warmer and characterized by even less ice. Here we discuss the mass balance of landfast ice near Kotzebue (Qikiqtaġruk) during these two anomalously warm winters. We use in situ observations and a 1-D thermodynamic model to address three research questions developed in partnership with an Indigenous Advisory Council. In doing so, we improve our understanding of connections between landfast ice mass balance, marine mammals and subsistence hunting. Specifically, we show: (i) ice growth stopped unusually early due to strong vertical ocean heat flux, which also likely contributed to early start to bearded seal hunting; (ii) unusually thin ice contributed to widespread surface flooding. The associated snow ice formation partly offset the reduced ice growth, but the flooding likely had a negative impact on ringed seal habitat; (iii) sea ice near Kotzebue during the winters of 2017–18 and 2018–19 was likely the thinnest since at least 1945, driven by a combination of warm air temperatures and a persistent ocean heat flux.

Highlights

As a large embayment on the northwest coast of Alaska, Kotzebue Sound (Fig. 1a) is a relatively sheltered environment in which to grow sea ice
The slow rates of growth observed at both mass-balance stations (MBSs) despite low air temperatures, relatively thin ice and shallow snow indicate that Fw was already ∼10 W m−2 in early January at the Channel MBS and 5 W m−2 at the Bay MBS
Our results do not provide exhaustive answers, by framing our conclusions in response to each question, we can improve our understanding of the connections between the mass balance of landfast ice, marine mammals and subsistence hunting in Kotzebue Sound

Summary

Introduction

As a large embayment on the northwest coast of Alaska, Kotzebue Sound (Fig. 1a) is a relatively sheltered environment in which to grow sea ice. Landfast ice that extends between shorelines like this is referred to as ‘landlocked’ (Hata and Tremblay, 2015; Mahoney, 2018) and Kotzebue Sound is perhaps the largest region in North America occupied by such ice outside of the Canadian Archipelago. The landlocked nature of wintertime Kotzebue Sound sea ice has historically allowed local residents to hunt marine mammals at the flaw lead in the Chukchi Sea (Lucier and VanStone, 1991; Huntington and others, 2016) and travel to coastal communities outside the Sound without having to follow the shoreline. For the last decade, sea ice has typically filled Kotzebue Sound, it has failed to become landlocked, leaving only a relatively narrow fringe of landfast ice attached to the coast and a discontinuous ice pack of mobile floes in the center

Results

Discussion

Conclusion