FY 1996

Atmosphere-ocean interactions in the Marginal Ice Zones of the Nordic Seas

Guest, P.S., K.L. Davidson, J.E. Overland, and P.A. Frederickson

In Arctic Oceanography: Marginal Ice Zones and Continental Shelves, Coastal and Estuarine Studies, 49, 51–95 (1995)

Atmospheric-ocean interactions occur on a variety of time and space scales in marginal ice zones (MIZs). The most important momentum and heat flux events in the MIZs of the Nordic Seas occur during the passage of synoptic-scale cyclones, many of which follow the general axis of the warmest waters in the Norwegian Sea and cross the MIZ near Svalbard or in the Barents Sea. If deep layers of mid-latitude marine air penetrate over the ice, intense cyclogenesis can occur in situ. The low-level baroclinicity associated with MIZs alone is not enough to cause strong cyclogenesis, but it can generate moderate mesoscale cyclones. If other forcing mechanisms are present, these mesoscale cyclones may become intense polar lows which affect the MIZ, but usually polar low development occurs a few hundred kilometers or more seaward of the ice edge. Based on our measurements, we find that during the spring, the median height of the temperature inversion base varies from 155 m over the pack ice to 1240 m over the open ocean for off-ice winds, and 160 m to 1490 m for on-ice winds. Corresponding median 10 meter air temperatures are -13°C to 0°C and -13°C to -7°C and median wind speeds are 4.5 m s to 9 m s and 3 m s to 8 m s. The median, upward, bulk-derived, combined sensible and latent, surface heat fluxes are 178 Wm just off ice edge to 136 Wm at locations between 100 km and 150 km seaward of the ice edge during off-ice winds and 101 Wm to 41 Wm during on-ice winds. During the summer, the median height of the temperature inversion base varies from 160 m over the pack ice to 505 m over the open ocean for off-ice winds, and 155 m to 680 m for on-ice winds. Summer median air temperatures are -2°C to 2°C and -1°C to 4°C and median wind speeds are 3 m s to 7 m s and 4.5 m s to 9 m s. The systematic wind speed gradients caused by boundary layer depth and surface heat flux gradients have effects on wind stress that are as significant as surface roughness gradients. As a result, there is typically a wind stress minimum over the inner pack ice and two maxima, one over the rough MIZ ice and one in the open ocean, where the wind speed is highest.