Characteristics of the modelled meteoric freshwater budget of the western Antarctic Peninsula

• Published in: Deep Sea Research Part II: Topical Studies in Oceanography
• Main Authors: van Wessem, J. M., Meredith, M. P., Reijmer, C. H., van den Broeke, M. R., Cook, A. J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2017
• Subjects: Climate; Freshwater budget; Ocean; Regional climate modelling; Western Antarctic Peninsula; Adelaide Island; Antarctic; Antarctic Peninsula; Bellingshausen Sea; Marguerite; Marguerite Bay; Antarc*; Sea ice
• Online Access: https://pure.uhi.ac.uk/en/publications/16bc2800-4055-490a-991c-b62638fe33a1; https://doi.org/10.1016/j.dsr2.2016.11.001; http://www.scopus.com/inward/record.url?scp=85006725515&partnerID=8YFLogxK; http://www.scopus.com/inward/citedby.url?scp=85006725515&partnerID=8YFLogxK

Rapid climatic changes in the western Antarctic Peninsula (WAP) have led to considerable changes in the meteoric freshwater input into the surrounding ocean, with implications for ocean circulation, the marine ecosystem and sea-level rise. In this study, we use the high-resolution Regional Atmospheric Climate Model RACMO2.3, coupled to a firn model, to assess the various contributions to the meteoric freshwater budget of the WAP for 1979–2014: precipitation (snowfall and rainfall), meltwater runoff to the ocean, and glacial discharge. Snowfall is the largest component in the atmospheric contribution to the freshwater budget, and exhibits large spatial and temporal variability. The highest snowfall rates are orographically forced and occur over the coastal regions of the WAP (>2000mm water equivalent (w.e.) y −1 ) and extend well onto the ocean up to the continental shelf break; a minimum (∼500mmw.e.y −1 ) is reached over the open ocean. Rainfall is an order of magnitude smaller, and strongly depends on latitude and season, being large in summer, when sea ice extent is at its minimum. For Antarctic standards, WAP surface meltwater production is relatively large (>50mmw.e.y −1 ), but a large fraction refreezes in the snowpack, limiting runoff. Only at a few more northerly locations is the meltwater predicted to run off into the ocean. In summer, we find a strong relationship of the freshwater fluxes with the Southern Annular Mode (SAM) index. When SAM is positive and occurs simultaneously with a La Niña event there are anomalously strong westerly winds and enhanced snowfall rates over the WAP mountains, Marguerite Bay and the Bellingshausen Sea. When SAM coincides with an El Niño event, winds are more northerly, reducing snowfall and increasing rainfall over the ocean, and enhancing orographic snowfall over the WAP mountains. Assuming balance between snow accumulation (mass gain) and glacial discharge (mass loss), the largest glacial discharge is found for the regions around Adelaide Island (10Gty −1 ), ...