EVIDENCE FOR STABILITY ENHANCEMENT OF SEA ICE IN THE GREENLAND AND LABRADOR SEAS

Malmberg proposed in 1969 that anomalously low surface (upper 200 m) salinities in the Iceland seas during the late 1960s could increase the stability of the water column sufficiently to prevent deep convection. The increased stability would then enhance the formation of sea ice during winter in this region because even at the freezing point (-1.8-degrees-C), the surface water density is sufficiently low to prevent mixing with the water below. Hence only a small portion of the water column need be cooled before freezing can occur and ice formation is enhanced. Here we explore this concept further by examining hydrographic data from three locations bordering Greenland and Iceland and then compare these with colocated sea ice concentrations. For the period 1953-1980, it is shown that the lag correlations between surface salinity and sea ice anomalies show a common structure for the case where salinity anomalies lead sea ice anomalies. It is shown that this correlation structure can be reproduced by a simple statistical feedback model using a nonstationary negative feedback coefficient to account for salinity forcing of ice anomalies. The data presented are all consistent with the concept of stability enhancement of sea ice formation.