Corsica (table S1 and fig. S1). This island’s dry northern interior today receives~ 30% less precipitation than its margins (fig. S2A), whereas this difference was~ 50% during the LGM (fig. S4C). Although this prediction cannot (yet) be confirmed with the data available outside Corsica, it does agree with patterns seen in LGM reconstructions with the high-resolution climate model HadRM (23). As mentioned above, locally enhanced precipitation would largely reduce the local lapse rate, so that much of the initially (first-order) inferred temperature anomaly pattern in fact reflects the impact of precipitation anomalies. Although care must be taken not to simply ascribe past regional property distributions to modern climate oscillation patterns (24), it remains useful to consider instrumental records and proxy data in order to develop a sense of realistic analogous climate patterns over the study region (25). The contrast between strongly reduced SST in the western basin and much less reduced SST in the central Mediterranean basin during the LGM (Fig. 1) indicates a preferentially meridional geostrophic circulation, with a polar trough that frequently protruded into the western Mediterranean. Such a circulation is favored by northward extension of the Azores High toward Iceland (North Atlantic ridge) or Greenland, blocking moisture supply by the westerlies. It is further enhanced by expansion and intensification of the Siberian High in winter during glacial times (26). A similar configuration is thought to have been common during the late Little Ice Age, notably the Maunder Minimum (2, 27). The invasion of polar air as shown by our data, channeled by the topography of mountain ranges and ice sheets in Europe, would have generated cyclone formation in the Gulf of Genoa more frequently than at present, enhancing precipitation along various storm tracks in easterly directions. Our observations do not support a straightforward zonal LGM atmospheric circulation, as inferred from climate models (19, 28). Instead, we propose that frequent meridional circulation during cold seasons (characterized by the LGM ELA pattern) may have alternated with more zonal circulation during warm seasons. A more comprehensive quantitative assessment of the preferential LGM atmospheric circulation requires the use of both nested model simulation and high-resolution global climate model studies (4, 5, 8, 28), which should fully resolve the changing topography of glaciated mountain ranges and ice sheets. The validation of such models with our three-dimensional LGM climate proxy data ranging from the sea surface to alpine altitudes is a great future challenge.