The Study on Near Surface Temperature Maximum in the Canada Basin for 2003-2008 in Response to Sea Ice Variations

摘要

The vertical properties and the space-time variations of the upper waterrnmass in the Canada Basin are investigated using CTD data collectedrnfrom 2003 to 2008. In most areas there were four temperaturernmaximum waters in the Canada Basin in summer which named NorthrnAtlantic Intermediate Water (NAIW), Alaskan Coastal Water (ACW),rnsummer Bering Sea Water (sBSW) and Near Surface TemperaturernMaximum (NSTM). The temperature of the NSTM was higher than thernfreezing point and lower than ACW except in ice-free area where thernmaximum temperature might reach 2℃. In this paper, the verticalrnstructures of temperature show that the maxima of NSTM in 2007 werernhigher, while the salinity, density and depth of NSTM were lower thanrnthat in other years.rnThe observations suggest the following ice-ocean processes arernoccurring. The melting ice water reduced the salinity and density of thernmixed layer water when the sea ice melts earlier in summer. The solarrnradiation heated the water more with lower sea ice concentration andrnice extent. At the same time the intensification of air-sea heat exchangernmight accelerate the upward heat flux and reduce the net downwardsrnheat transport, which led to the depth of temperature peak of NSTMrndeeper than before. In Canada Abyssal Plain, the NSTM occurredrnnearly every year but in 2003. In 2008, the NSTM for the first timernoccurred in the north of 80°N. The reduction of the Arctic sea ice couldrnincrease and enhance the NSTM occurrence.