Abstract
Abstract Climate change west of the Antarctic Peninsula is the most rapid of anywhere in the Southern Hemisphere, with associated changes in the rates and distributions of freshwater inputs to the ocean. Here, results from the first comprehensive survey of oxygen isotopes in seawater in this region are used to quantify spatial patterns of meteoric water (glacial discharge and precipitation) separately from sea ice melt. High levels of meteoric water are found close to the coast, due to orographic effects on precipitation and strong glacial discharge. Concentrations decrease offshore, driving significant southward geostrophic flows (up to ~30 cm s−1). These produce high meteoric water concentrations at the southern end of the sampling grid, where collapse of the Wilkins Ice Shelf may also have contributed. Sea ice melt concentrations are lower than meteoric water and patchier because of the mobile nature of the sea ice itself. Nonetheless, net sea ice production in the northern part of the sampling grid is inferred; combined with net sea ice melt in the south, this indicates an overall southward ice motion. The survey is contextualized temporally using a decade-long series of isotope data from a coastal Antarctic Peninsula site. This shows a temporal decline in meteoric water in the upper ocean, contrary to expectations based on increasing precipitation and accelerating deglaciation. This is driven by the increasing occurrence of deeper winter mixed layers and has potential implications for concentrations of trace metals supplied to the euphotic zone by glacial discharge. As the regional freshwater system evolves, the continuing isotope monitoring described here will elucidate the ongoing impacts on climate and the ecosystem.
Highlights
The western Antarctic Peninsula (WAP; Fig. 1) is the most rapidly warming region in the Southern Hemisphere (King 1994)
The WAP is unusual compared with other sectors of Antarctica, where katabatic winds and other circulations lead to atmospheric flows with significant southerly components and coastal atmospheric temperatures that depend comparatively little on sea ice extent
Temperatures at the WAP are especially sensitive to sea ice because the mean winds have a strong westerly component associated with the eastern limb of the Amundsen Sea low (ASL; the dominant feature of atmospheric circulation between the WAP and the Ross Sea); these winds cross the sea ice before reaching land
Summary
The western Antarctic Peninsula (WAP; Fig. 1) is the most rapidly warming region in the Southern Hemisphere (King 1994). The extent of sea ice adjacent to the WAP is known to be a significant influence on local atmospheric temperatures, with years of extensive sea ice being markedly colder (King 1994; King and Harangozo 1998; Smith and Stammerjohn 2001; Turner et al 2005). In this respect, the WAP is unusual compared with other sectors of Antarctica, where katabatic winds and other circulations lead to atmospheric flows with significant southerly components and coastal atmospheric temperatures that depend comparatively little on sea ice extent. The influence of sea ice on coastal temperature at the WAP was elucidated further by Turner et al (2013), who demonstrated that there has been a progressive tendency toward polynya-like conditions adjacent to Faraday/Vernadsky station (mid-WAP) and who showed that this is instrumental in the reduced frequency of very cold winters there
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