| Variation in the Arctic Ocean stratification will exert a tremendous impact on the Arctic Ocean sea ice,circulation,water mass variation,and even global climate change.In the past,due to limited observational data and conditions,there was little awareness of the stratification in the Arctic Ocean,especially the hydrological characteristics of the subsurface.Based on the ocean reanalysis data ORAP5 of the European Center for Medium-Range Weather Forecasts(ECMWF),the multi-scale temporal and spatial changes of the upper ocean stratification in the Arctic Ocean basin are statistically analyzed.The multi-scale temporal and spatial variation of the upper ocean stratification in the entire Arctic Ocean basin are statistically analyzed.The seasonal signal of mixed layer depth of the Arctic Ocean is obvious,but the regional difference is not significant.While the seasonal characteristic of the halocline depth is not,and the properties of the halocline in the Eurasian Basin and Amerasian Basin have great differences.Strong stratification,which is found in the most of the Arctic Ocean,prevents vigorous AW ventilation.This ventilation in the western Nansen Basin leads to the reduction of sea-ice thickness.In the past,these conditions have been limited to the western EB,because winter ventilation of AW in the eastern EB was constrained by stronger stratification there.Therefore,studying on the phenomenon of halocline ventilation is very significant for comprehending sea ice conditions.In our research,we propose a new criterion to identify halocline ventilation.According to this criterion,we describe the ventilation phenomenon of the Eurasian basin in detail,and reveal its variation and relationship between the depths of halocline.The results show that the shallower the halocline,the weaker the stability of ocean stratification,and the easier ventilation phenomena occurs.In view of the significant negative correlation on interdecadal scale between the halocline depth of the Beaufort Gyre and of the eastern Eurasian basin.This paper combines the ERA5 10m wind speed data and the OSI-SAF sea ice concentration data to calculate the freshwater content and the Ekman pumping velocity,aiming at the opposite phenomenon of the interdecadal variation of halocline depth in the Beaufort Gyre and Eastern Eurasian Basin.Studies have shown that when the intensity of the Beaufort Gyre increases,the downward Ekman pumping velocity increases,resulting a downwelling,which is conducive to the convergence of fresh water in the Arctic Ocean basin to the Canadian basin,resulting halocline depth of Canadian Basin deepens.Due to the decrease of fresh water content in the Eastern Eurasian Basin,the stratification stability weakens,and then the halocline depth becomes shallow;On the contrary,when the Beaufort Gyre intensity weakens,the reduced Ekman pumping velocity cannot maintain the fresh water storage in the Canadian Basin.The fresh water transport to the Eurasian Basin,and enhances local stratification,then the halocline depth will be deeper.The halocline depth can change the ocean stratification stability,thereby causing or inhibiting the occurrence of ventilation phenomena. |
