Department of Geological Sciences, Stockholm University, Stockholm, Sweden.
Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden.
Nat Commun. 2023 May 13;14(1):2763. doi: 10.1038/s41467-023-38425-5.
The hydrological cycle is expected to intensify in a warming climate. However, observational evidence of such changes in the Southern Ocean is difficult to obtain due to sparse measurements and a complex superposition of changes in precipitation, sea ice, and glacial meltwater. Here we disentangle these signals using a dataset of salinity and seawater oxygen isotope observations collected in the Indian sector of the Southern Ocean. Our results show that the atmospheric water cycle has intensified in this region between 1993 and 2021, increasing the salinity in subtropical surface waters by 0.06 ± 0.07 g kg per decade, and decreasing the salinity in subpolar surface waters by -0.02 ± 0.01 g kg per decade. The oxygen isotope data allow to discriminate the different freshwater processes showing that in the subpolar region, the freshening is largely driven by the increase in net precipitation (by a factor two) while the decrease in sea ice melt is largely balanced by the contribution of glacial meltwater at these latitudes. These changes extend the growing evidence for an acceleration of the hydrological cycle and a melting cryosphere that can be expected from global warming.
水文循环预计在气候变暖的情况下会加剧。然而，由于测量稀疏且降水、海冰和冰川融水变化的复杂叠加，在南大洋很难获得这种变化的观测证据。在这里，我们使用在南大洋印度区收集的盐度和海水氧同位素观测数据集来解混这些信号。我们的结果表明，在 1993 年至 2021 年期间，该地区的大气水循环已经加强，亚热带表层海水的盐度每十年增加 0.06±0.07 g kg，亚表层海水的盐度每十年减少 0.02±0.01 g kg。氧同位素数据允许区分不同的淡水过程，表明在亚极地区，淡水的增加主要是由净降水（增加了两倍）驱动的，而海冰融化的减少主要与这些纬度的冰川融水的贡献相平衡。这些变化扩展了从全球变暖中可以预期的水文循环加速和融冰圈缩小的证据。
