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Jaegyu Knoll is located in Antarctic Sound, between Trinity Pen- insula and islands of the Joinville Island Group, on the northern Antarctic Peninsula (Fig. 1a). Jaegyu Knoll is interpreted as a Holocene submarine intraplate volcano based on its morphology, in situ observations such as bottom videos and high-resolution photographs (Quinones et al. 2005), a rock dredge that recovered fresh volcanic rock (Hatfield et al. 2004) and a measured geother- mal anomaly (Hatfield et al. 2004). All aspects of the knoll are con- sistent with recent volcanic activity, which appears to have been persistent in the northern Antarctic Peninsula region from Meso- zoic times to the present (e.g. Baker et al. 1973; Gonza ́lez-Ferra ́n 1991; Gracia et al. 1997). The knoll, and at least two other smaller volcanic features in Antarctic Sound (Fig. 1a), lie within an over- deepened glacial trough that was presumably sculpted by ice dur- ing the Last Glacial Maximum (LGM; 23–19 ka BP). 

Top-down rather than bottom-up change The Larsen-B Ice Shelf in Antarctica collapsed in 2002 because of a regional increase in surface temperature. This finding, reported by Rebescoet al., will surprise many who supposed that the shelf's disintegration probably occurred because of thinning of the ice shelf and the resulting loss of support by the sea floor beneath it. The authors mapped the sea floor beneath the ice shelf before it fell apart, which revealed that the modern ice sheet grounding line was established around 12,000 years ago and has since remained unchanged. If the ice shelf did not collapse because of thinning from below, then it must have been caused by warming from above. Science, this issue p.1354