Effect of summertime wind conditions on lateral and bottom melting in the central Arctic

Abstract

AbstractTo understand the role of wind conditions on the summertime surface ocean system, the ocean, ice and atmosphere in the central Arctic Ocean were observed using two drifting buoys, one in 2002 under stormy conditions, one in 2003 under calm conditions. Although the ice concentration near the North Pole was the same in 2002 and 2003 during early summer, the heat used in bottom melting in 2003 was only about half of that in 2002. To obtain the total heat input into the upper ocean, heat used in lateral melting was additionally derived from a time series of ice concentration in 2002. Assuming the same heat input into the upper ocean, the heat used in lateral and bottom melting was estimated and compared between the years. It is thought that the warm fresh water embedded within the ice cover was mixed downward during the frequently stormy mid-summer of 2002, enhancing bottom melting. By contrast, the warm water in 2003 tended to be used for lateral melting due to the relatively calm conditions, suggesting that a continuously weak wind favours ice-cover decrease during summer. A simple calculation of the ice-cover evolution reveals that the difference in ice concentration during August between 2002 and 2003 reached 10%, which is consistent with the satellite-derived ice concentration.