Response of Antarctic continental shelf conditions to increased meltwater — Australian Meteorological and Oceanographic Society

Response of Antarctic continental shelf conditions to increased meltwater (#146)

Ruth Moorman 1 , Andrew McC. Hogg 1 , Adele K. Morrison 1
  1. Research School of Earth Sciences, Australian National University, Canberra, ACT, Australia

The implications of ocean freshening from accelerating Antarctic land-ice loss are poorly understood, largely due to the high spatial and temporal resolution required to resolve Antarctic continental shelf processes in ocean models. Here, a high-resolution global ocean – sea-ice model is used to investigate the response of Antarctic continental shelf circulation to increasing meltwater inputs. Two freshwater perturbation experiments are conducted using projected Antarctic ice-loss under RCP4.5 and RCP8.5 scenarios at 2100. The freshwater perturbations are spatially variable, with forcing patterns generated by amplifying present-day estimates of Antarctic runoff in regions where land-ice thinning has been observed over recent decades. We find that the additional freshwater input reduces the production of Dense Shelf Water (DSW), particularly in the Ross Sea, leading to a slowdown in the Antarctic Bottom Water (AABW) overturning cell. The simulations further suggest that surface freshening induces warm anomalies both at the surface and at depth near ice-shelves in the Amundsen and Bellingshausen Seas, the Ross Sea, and parts of East Antarctica, indicating a positive feedback that may further enhance ice-shelf melt. The temperature response is spatially inhomogeneous, with substantial cold anomalies generated off the Adélie Coast. Regional heat budgets and analysis of along and cross-shelf transports are used to reveal the mechanisms controlling these shifts in temperature and DSW production, which have critical implications for sea-level rise and ocean ventilation.

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