Contraction and warming of Antarctic Bottom Water in the Amundsen Sea

Antarctic Bottom Water (AABW) plays an important role in the meridional overturning circulation and contributes significantly to global heat transport and sea level rise (SLR). Based on the Global Ocean (1/12)° Physical Reanalysis (GLORYS12V1) products and conductivity-temperature-depth instrument data from the World Ocean Circulation Experiment hydrographic program, we analyzed the trends in the thickness, volume, temperature, salinity, and neutral density of the AABW in the Amundsen Sea from 1993 to 2017. Over the past 25 years, the volume has decreased by 3.45×1012 m3/a, thinning at a rate of 5 m/a. In the vertical direction, the contraction of the AABW is compensated by the volume expansion of the Circumpolar Deep Water. As the volume of AABW decreases, the temperature of the AABW increases by about 0.002°C/a. This warming is equivalent to a heat flux of 0.27 W/m2. A local SLR is produced due to thermal expansion of 0.35 mm/a. During the study period, the neutral density decreased by 0.000 3 kg/(m3·a) due to warming. In the horizontal direction, the volume of AABW flowing from the Ross Sea into the Amundsen Sea gradually decreases and the temperature of the AABW increases continuously. The horizontal transport loss of the AABW volume is 4.07×1014 m3 and the horizontal heat transport results in a 0.03°C increase in the temperature of the AABW.