Winter ocean-ice interactions under thin sea ice observed by IAOOS platforms during N-ICE2015: salty surface mixed layer and active basal melt
Koenig, Z and Provost, C and Villacieros-Robineau, N and Sennechael, N and Meyer, A, Winter ocean-ice interactions under thin sea ice observed by IAOOS platforms during N-ICE2015: salty surface mixed layer and active basal melt, Journal of Geophysical Research: Oceans, 121, (10) pp. 7898-7916. ISSN 2169-9275 (2016) [Refereed Article]
IAOOS (Ice Atmosphere Arctic Ocean Observing System) platforms, measuring physical
parameters at the atmosphere‐snow‐ice‐ocean interface deployed as part of the N‐ICE2015
campaign, provide new insights on winter conditions North of Svalbard. The three regions
crossed during the drifts, the Nansen Basin, the Sofia Deep, and the Svalbard northern
continental slope featured distinct hydrographic properties and ice‐ocean exchanges.
In the Nansen Basin, the quiescent warm layer was capped by a stepped halocline (60
and 110 m) and a deep thermocline (110 m). Ice was forming and the winter mixed layer
salinity was larger by ∼0.1 g/kg than previously observed. Over the Svalbard continental
slope, the Atlantic Water (AW) was very shallow (20 m from the surface) and extended
offshore from the 500 m isobath by a distance of about 70 km, sank along the slope
(40 m from the surface) and probably shed eddies into the Sofia Deep. In the Sofia
Deep, relatively warm waters of Atlantic origin extended from 90 m downward. Resulting
from different pathways, these waters had a wide range of hydrographic characteristics.
Sea‐ice melt was widespread over the Svalbard continental slope and ocean‐to‐ice heat
fluxes reached values of 400 W m−2 (mean of ∼150 W m−2 over the continental slope). Sea‐ice melt events were associated with near 12 h fluctuations
in the mixed‐layer temperature and salinity corresponding to the periodicity of tides
and near‐inertial waves potentially generated by winter storms, large barotropic tides
over steep topography, and/or geostrophic adjustments.