Distribution Characteristics Of Amery Ice Shelf Water, Antarctica

Amery Ice Shelf(AIS) is located in the Indian Ocean sector, Antarctica. It has a less area than Ross Ice Shelf and Filchner-Ronne Ice Shelf. As Lambert Glacier mainly flows through it to the Southern Ocean, its mass balance has a direct influence on the Antarctic ice sheet, and even potentially changes the global sea level and climate. Ice shelf water(ISW) is generated by the ocean-ice shelf interaction, and the temperature of which is lower than the freezing point. Comparing with the surrounding water, it is relatively colder and saltier. Thus it can be a good indicator to estimate the mass balance of Amery Ice Shelf, and has a great significance to evaluate the dynamic changes of the polar ice glacier.However, by the limit of Antarctic severe climate condition, it is still relatively difficult for us to carry out field investigations on AIS in winter, and our knowledge on the distribution characteristics of ISW is urgent to be promoted. In order to understand winter, even full-year distributions of ISW in front of AIS, and provide a basis for evaluating the mass balance of AIS quantitively, CTD and mooring observations by the Australian Amery Ice Shelf Ocean Research(AMISOR) in February 2001 and 2002, the elephant seal CTD observations by the Australia Integrated Marine Observing System(IMOS) in 2011 and 2012, and the Antarctic ice sheet elevations by ICESat from 2003 to 2009 were all adopted in our study. According to temperature-salinity profiles and water mass structures, firstly we made a redefinition of ISW; then summer and winter distributions of ISW were discussed systematically, seasonal and annual variations of ISW were highlighted as well, and annual volume fluxes of ISW were calculated quantitively; finally, based on the variations of ISW, dynamic balance of AIS was discussed briefly. The main conclusions are as follows:Firstly, ISW has a temperature lower than-1.90℃ and has a salinity between 33.60 and 34.60, thereinto Low Salinity Ice Shelf Water has a salinity between 33.60 to 34.00 and High Salinity Ice Shelf Water has a salinity between 34.40 to 34.60. In summer, ISW generally distributes beneath the seasonal thermocline, and in the central and western front of AIS. ISW can uplift from east to west obviously. However, the spatial distribution of ISW presents remarkable annual variation. Compared to 2002, ISW distributed in wider areas with different depth in 2001, also distributed in wider areas with different longitude and latitude. But the intensity of ISW in 2002 is larger than that in 2001.Secondly, in winter, ISW mainly occupies at the depth between 4 to 678 meters with a temperature between-1.95 to-2.23℃ and a salinity between 33.60 to 34.60, and the spatial distribution of ISW varies with year as well. Compared 2012 with 2011, the thickness of ISW was increased slightly, but there was little change of the maximum depth where ISW exsited in. What’s more, the peak not only of thickness but also of the maximum depth was appeared closer to the western front of AIS.Thirdly, the spatial distribution of ISW indeed differs with season remarkablely. During winter, ISW mainly distributes to the west of 73.5°E and between 350 to 600 meters, but there is no ISW observed to the east of 73.5°E, and the flux of ISW is-0.53 mSv. During summer, ISW mainly distributes to the east of 72.5°E and between 350 to 580 meters, yet there is no water observed to the west of 72.5°E of the front edge, and the flux of ISW is 10.48 mSv. The flux of ISW in winter is fewer than that in summer, and it shows outflow from the basis of Amery Ice Shelf into Prydz Bay as the main characteristic of ISW.Finally, in spite of 2003 and 2004, the mass balance of Amery Ice Shelf was appeared material output from winter to summer, which indicates that there must be mass of ISW outflow from the Amery Ice Shelf.