Shipboard Observations of the Meteorology and Near‐Surface Environment During Autumn Freezeup in the Beaufort/Chukchi Seas

Abstract

AbstractThe collection and processing of shipboard air, ice, and ocean measurements from the Sea State field campaign in the Beaufort/Chukchi Seas in autumn 2015 are described and the data used to characterize the near‐surface freezeup environment. The number of parameters measured or derived is large and the location and time of year are unique. Analysis was done of transits through the new, growing ice and of ice edge periods. Through differential surface energy fluxes, the presence of new, thin sea ice (<50 cm) produces lower tropospheric air temperatures in the ice interior that average ~4°C colder than those over open water near the ice edge, resulting in an ice edge baroclinic zone. This temperature difference doubles by late October and produces thermodynamic and dynamic feedbacks. These include off‐ice, cold‐air advection leading to enhanced surface heat loss averaging ~200 W/m2 over the open water, formation of low‐level jets, suppression of the ice edge baroclinic zone, and enhanced ice drift. The interior ice growth rate is thermodynamically consistent with a surface heat loss of ~65 W/m2 to the atmosphere and a heat flux of several tens of W/m2 from the ocean below. Ice drift at times contributes to the southward advance of the autumn ice edge through off‐ice winds. The ocean thermohaline structure is highly variable and appears associated with bathymetric features, small‐scale upper‐ocean eddies, and the growing ice cover. Lower salinity under the ice interior compared to the nearby ice edge is an upper‐ocean impact of this thin ice cover.