Improving ice core interpretation using in situ and reanalysis data

• Published in: Journal of Geophysical Research. B. Solid Earth Vol. 114; no. D20
• Main Authors: Thomas, E. R., Bracegirdle, T. J.
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 28-10-2009; American Geophysical Union
• Subjects: Annual precipitation; Antarctic Peninsula; Atmospherics; Climate; Earth sciences; Earth, ocean, space; Exact sciences and technology; ice cores; Marine; Precipitation; Proxy client servers; Sea ice; Trajectories; Transport; Antarctic Ocean; polar regions; Antarctica; Weddell Sea; Bellingshausen Sea; Antarctic Peninsula; PSW, Bellingshausen Sea; PSW, Antarctica, Antarctic Peninsula; PSW, Weddell Sea; Weather forecast; Westerly wind; atmospheric precipitation; Summer; Isotopic composition; low pressure; climate; transport; variability; trajectory; in situ; Antarctic oscillation; drill cores; Air mass; Meteorological station; correlation; interpretation; circulation; sea ice; Reanalysis; Snow accumulation; glacial extent
• ISSN: 0148-0227; 2169-897X; 2156-2202; 2169-8996
• DOI: 10.1029/2009JD012263

Back trajectory analysis, provided by the British Atmospheric Data Centre using meteorological parameters from the European Centre for Medium‐Range Weather Forecasts (ECMWF) reanalysis ERA‐40 (1980–2001) and operational analysis (2002–2006), is used to investigate transport pathways and source regions of climate proxies preserved in a new ice core (Gomez) from the southwestern Antarctic Peninsula. The ECMWF data are compared with automatic weather station data and ice core annual accumulation records to demonstrate that the ECMWF data capture a large proportion of the annual and subseasonal precipitation variability at the site. The back trajectories reveal that precipitation preserved in the ice core accumulation record, and hence climate proxies contained therein, originate from the low‐pressure systems from the Bellingshausen Sea transported via circumpolar westerly winds. Hence, precipitation‐dependent ice core proxies, such as isotopic composition, will be influenced by both localized sea ice extent and large‐scale circulation changes, such as the Southern Annular Mode. Sea ice proxies from the ice core are expected to be dominated by sea ice extent in the Bellingshausen Sea but also influenced by sea ice in the Weddell Sea, with a small proportion of air mass trajectories originating from this region during the summer. Comparison with other ice core sites reveals a stronger influence of easterly transport at more northerly locations, thus explaining the observed differences in snow accumulation records between ice cores and the poor correlation with instrumental records at these sites.