Air-Ice-Ocean Coupling During a Strong Mid-Winter Cyclone, Part 1:
Observing Coupled Dynamic Interactions Across Scales
Abstract
Arctic cyclones are key drivers of sea ice and ocean variability. During
the 2019-2020 Multidisciplinary drifting Observatory for the Study of
Arctic Climate (MOSAiC) expedition, joint observations of the coupled
air-ice-ocean system were collected at multiple spatial scales. Here, we
present observations of a pair of strong mid-winter cyclones that
impacted the MOSAiC site as it drifted in the central Arctic pack ice,
with analytic emphasis on the second cyclone. The sea ice dynamical
response showed spatial structure at the scale of the evolving
atmospheric wind field. Internal ice stress and the ocean stress play
significant roles, resulting in timing offsets between the atmospheric
forcing and the ice response and post-cyclone inertial ringing in the
ice and ocean. A structured response of sea ice motion and deformation
to cyclone passage is seen, and the consequent ice motion then forces
the upper ocean currents through frictional drag. The strongest impacts
to the sea ice and ocean from the passing cyclone occur as a result of
the surface impacts of a strong atmospheric low-level jet (LLJ) behind
the trailing cold front. Impacts of the cyclone are prolonged through
the coupled ice-ocean inertial response. The local impacts of the
approximately 120 km wide LLJ occur over a 12 hour period or less and at
scales of a kilometer to a few tens of kilometers, meaning that these
impacts occur at smaller spatial scales and faster time scales than many
satellite observations and coupled Earth system models can resolve.