Interaction of ocean temperature advection, surface heat fluxes and sea ice in the marginal ice zone during the North Atlantic Oscillation in the 1990s: A modeling study

A moderately fine-resolution (0.4 degrees, 40 vertical levels), global, coupled ice-ocean model was configured and run for 24 years (1979-2002), forced with high-frequency National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) atmospheric fluxes. The model consists of the Los Alamos National Laboratory Parallel Ocean Program (POP) and sea ice model (CICE). The fidelity of the simulated mean climatological state and variability of key variables such as ice concentration, total ice area, ice thickness and drift were compared to observational data sets from satellite and ice drift buoy measurements. Basin-scale changes in the lower atmosphere/surface ocean/sea-ice in the simulated Arctic and Nordic Seas before and after the North Atlantic Oscillation (NAO) phase switch in 1995 were examined using winter composite analyses over the period 1990-1999. Ice cover changes between the two NAO phases were consistent with observations in that reduced concentrations were found in the Nordic and Barents Seas and increased values occurred in the Labrador Sea. Next we regionally evaluated the relative importance of winter anomalies of upper-ocean mixed layer net heat fluxes and of ocean temperature advection on marginal ice zone variability in the Irminger, Greenland, and Barents Seas for this ten-year period. We found that the net heat flux winter anomaly was at least four times more important than the winter anomaly of ocean temperature advection in the Greenland and Barents Seas, while it was twice as important in the Irminger Sea. The Ekman ocean temperature advection component generally dominated the geostrophic component in all three regions.