Altered Weddell Sea warm- and dense-water pathways in response to 21st-century climate change
Abstract. The transport of water masses with ocean circulation is a key component of the global climate system. In this context, the Filchner Trough in the southern Weddell Sea is critical, as it is a hotspot for the cross-shelf-break exchange of Dense Shelf Water and Warm Deep Water. We present results from Lagrangian particle tracking experiments in a global ocean-sea ice model (FESOM-1.4) which includes ice-shelf cavities and has eddy-permitting resolution on the southern Weddell Sea continental shelf. With backward and forward experiments, we assess changes between a present-day and a future (SSP5-8.5) time slice in the origin of waters reaching the Filchner Ice Shelf front and the fate of waters leaving it. We show that particles reaching the ice-shelf front from the open ocean originate from 173 % greater depths by 2100 (median), while waters leaving the cavity towards the open ocean end up at 35 % shallower depths. Simultaneously, median transit times between the Filchner Ice Shelf front and the continental shelf break decrease (increase) by 6 (9.5) months in the backward (forward) experiments. Pathways of water leaving the continental shelf increasingly occur in the upper ocean, while the on-shelf flow of waters that might reach the ice shelf cavity, i.e., at deeper layers, becomes more important by 2100. In conclusion, our study demonstrates the sensitivity of regional circulation patterns in the southern Weddell Sea to on-going climate change, with direct implications for ice-shelf basal melt rates and local ecosystems.
