Abstract
Abstract. Arctic sea ice kinematics and deformation play significant roles in heat and momentum exchange between the atmosphere and ocean, and at the same time they have profound impacts on biological processes and biogeochemical cycles. However, the mechanisms regulating their changes on seasonal scales and their spatial variability remain poorly understood. Using position data recorded by 32 buoys in the Pacific sector of the Arctic Ocean (PAO), we characterized the spatiotemporal variations in ice kinematics and deformation for autumn–winter 2018/19, during the transition from a melting sea ice regime to a nearly consolidated ice pack. In autumn, the response of the sea ice drift to wind and inertial forcing was stronger in the southern and western PAO compared to the northern and eastern PAO. These spatial heterogeneities gradually weakened from autumn to winter, in line with the seasonal increases in ice concentration and thickness. Correspondingly, ice deformation became much more localized as the sea ice mechanical strength increased, with the area proportion occupied by the strongest (15 %) ice deformation decreasing by about 50 % from autumn to winter. During the freezing season, ice deformation rate in the northern PAO was about 2.5 times higher than in the western PAO and probably related to the higher spatial heterogeneity of oceanic and atmospheric forcing in the north. North–south and east–west gradients in sea ice kinematics and deformation within the PAO, as observed especially during autumn in this study, are likely to become more pronounced in the future as a result of a longer melt season, especially in the western and southern parts.
Highlights
The Pacific sector of the Arctic Ocean (PAO) includes the Beaufort, Chukchi, and East Siberian seas, as well as the Canadian and Makarov basins
The marginal ice zone (MIZ), defined as the area in which the sea ice concentration is less than 80 %, can reach as far north as 80◦ N (Strong and Rigor, 2013); the south– north gradient in sea ice properties in the PAO is expected to be larger compared to other sectors of the Arctic Ocean
The sea ice in the PAO is expected to be considerably impacted by these seasonal changes in atmospheric circulation patterns as a result of the enhanced northward advection of sea ice to the Atlantic sector of the Arctic Ocean (AAO) (e.g., Bi et al, 2019)
Summary
The Pacific sector of the Arctic Ocean (PAO) includes the Beaufort, Chukchi, and East Siberian seas, as well as the Canadian and Makarov basins. Under a positive Arctic dipole anomaly (DA), more sea ice from the PAO is transported to the Atlantic sector of the Arctic Ocean (AAO), i.e., promoting ice advection from the BG system to the Transpolar Drift Stream (TDS) (Wang et al, 2009) In summer, such a regime would stimulate the ice–albedo feedback and accelerate sea ice retreat in the PAO (Lei et al, 2016). RADARSAT data for example revealed that the length scaling law of ice deformation in the western Arctic Ocean increased in summer as the ice pack weakens and internal stresses cannot be transmitted over long distances compared to winter (Stern and Lindsay, 2009). We combined the data measured by these buoys with other available buoy data from the International Arctic Buoy Programme (IABP) to identify the spatial variability of sea ice kinematics and deformation in the PAO from melting to freezing seasons, and we linked these results to the atmospheric forcing responsible for the observed changes in ice dynamics
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