Climate of the Antarctic Periphery

Only a small number of ice core records from the Antarctic Ice Sheet periphery extend beyond the LGM. The 1,178 m deep ice core at Law Dome appears to reach into the last interglacial period (Morgan et al., 1997), although the whole of the last glacial period is held within the lowest 100 m, and no attempt has been made to provide an age scale for the oldest part. At least during the last deglaciation, the timing of the signal from this core appears at least similar to that from other Antarctic cores. Of most interest for the current paper is the finding that no isotopic values typical of inland ice are found anywhere in the core. This implies that, although the ice at Law Dome may have thickened during some parts of the glacial by up to 300 m (Delmotte et al., 1999), it was never overridden by inland ice during the last 100 ka.

Working clockwise around the continent, Taylor Dome (TD), adjacent to many of the marine core records, has yielded a 554 m deep core to bedrock (Steig et al., 1998). The age scale has been tentatively extended to 300 ka (Grootes et al., 2001); however, Termination II (130 ka) is only 23 m above bedrock, so the record is most useful only for one climatic cycle. Comparison with Vostok during the last climatic cycle shows a very similar pattern of variations, but with a larger amplitude for the equivalents of the A-events (large AIM). The assumptions made to create the time scale for the glacial part of the record preclude any discussion about the phasing of these changes in the TD record relative to those of central Antarctica. There has of course been a suggestion (Steig et al., 1998) that, at least during the last termination, TD may have shown a different pattern of change from other Antarctic sites, more in line with those of Greenland. This assertion has been strongly challenged (Mulvaney et al., 2000) because of issues about the TD time scale in this section, and must be considered doubtful.

The 1,004 m deep bedrock core at Siple Dome (SD), on the West Antarctic side of the Ross Sea, also covers much of the last glacial period. Careful synchronisation of this core to that of Byrd and to Greenland cores (Brook et al., 2005) shows a similar pattern and timing of millennial-scale change to that of Byrd, with recognisable A-events, and with SD (like Byrd) warming while Greenland remained cold, and apparently starting to cool when Greenland warmed. An abrupt climate change, not observed in other Antarctic cores, is seen at SD at 22 ka (Taylor et al., 2004); there is as yet no clear explanation for this apparently very local climate shift.

Two other near-coastal cores have already penetrated beyond the LGM, at Talos Dome and Berkner Island, although publications from them are still awaited. Early indications from Berkner Island (facing the Weddell Sea) suggest that it was also never overridden by inland ice during the last climatic cycle (Mulvaney et al., 2007) as some models suggest.

Taking all the records, from central East Antarctica, coastal cores and Byrd in central West Antarctica, it appears likely (despite the questions raised by the TD core) that the continent sees the main millennial- and orbital-scale changes more or less synchronously and with a similar pattern. Further work to separate changes in ice sheet altitude from changes in climate will elucidate the causes of somewhat different amplitudes for millennial-scale change at different sites. Finally in this section, we note the potential for coastal cores such as Law Dome and Berkner Island to provide critical constraints on the extent of the Antarctic Ice Sheet during at least the last glacial cycle.

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