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The position and intensity of the southern westerly wind belt varies seasonally as a consequence of changes in sea surface temperature. During the austral winter, the belt expands northward and the wind intensity in the core decreases. Conversely, during the summer, the belt contracts, and the intensity within the core is strengthened. Reconstructions of the westerly winds since the last glacial maximum, however, have suggested that changes at a single site reflected shifts throughout the entire southern wind belt 1-4 . Here we use sedimentological and pollen records to reconstruct precipitation patterns over the past 12,500 yr from sites along the windward side of the Andes. Precipitation at the sites, located in the present core and northern margin of the westerlies, is driven almost entirely by the wind belt 5 , and can be used to reconstruct its intensity. Rather than varying coherently throughout the Holocene epoch, we find a distinct anti-phasing of wind strength between the core and northern margin over multi-millennial timescales. During the early Holocene, the core westerlies were strong whereas the northern margin westerlies were weak. We observe the opposite pattern in the late Holocene. As this variation resembles modern seasonal variability, we suggest that our observed changes in westerly wind strength can best be explained by variations in sea surface temperature in the eastern South Pacific Ocean.Chile is ideally located to reconstruct past variability of the southern westerly wind belt (SWW) as the SWW almost entirely controls precipitation on the western side of the Andes in southern South America with an extreme north-south rainfall gradient from the semiarid, winter-rain climate in central Chile to yearround hyper-humid conditions in the fjord region of southern Chile 5 (Supplementary Fig. S1). Therefore, any paleoclimatic proxy record primarily controlled by rainfall changes is suitable for reconstructing past changes in the SWW in this region. In present-day austral winters, the SWW extends northward, providing rainfall to central Chile (33 • -40 • S), but zonal winds are reduced in its core zone in southernmost Chile (50 • -55 • S; Fig. 1a). During austral summer, the zonal wind pattern shows a latitudinally more confined and intensified SWW with maxima over southernmost Chile (Fig. 1b). Previous reconstructions of the SWW were primarily based on single sites and generally suggested a northward migration and intensification of the SWW during colder periods 1,2,4 . Intensity variations across the wind belt have only recently been addressed and interpreted in terms of co-varying

Dust deposition in the Southern Ocean constitutes a critical modulator of past global climate variability, but how it has varied temporally and geographically is underdetermined. Here, we present data sets of glacial-interglacial dust-supply cycles from the largest Southern Ocean sector, the polar South Pacific, indicating three times higher dust deposition during glacial periods than during interglacials for the past million years. Although the most likely dust source for the South Pacific is Australia and New Zealand, the glacial-interglacial pattern and timing of lithogenic sediment deposition is similar to dust records from Antarctica and the South Atlantic dominated by Patagonian sources. These similarities imply large-scale common climate forcings, such as latitudinal shifts of the southern westerlies and regionally enhanced glaciogenic dust mobilization in New Zealand and Patagonia.

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Regional variations of weather pattern were analyzed along a west-to-east profile across the Southern Andes (53°S), one of the most pronounced climate-divides in the world. For the first time we present a meteorological record from an array of three automatic weather stations (AWS), operated by the authors, for the central part of the climate divide which, together with previously existing Chilean weather stations, complete the transect. These data cover a time period of 3 yr. from October 1999 until September 2002. Air temperatures along the profile are highly correlated. Annual precipitation drops from between 6000 mm and 7000 mm at sea level along the main divide of the mountains to only about 1000 mm at the eastern slopes of the Andes and to as little as 430 mm at Punta Arenas. The variations of rainfall with wind direction and synoptic weather types are markedly different between the central part of the Andes and Punta Arenas. At the center of the climate divide precipitation correlates positively with wind speed from the west, whereas at Punta Arenas, east of the Andes, higher rainfall rates occur with easterly air flow. It is assumed that this reflects the barrier effect of the mountain range of the Andes.The results indicate that in order to make references about present or past climatic variations in Patagonia, it is essential to consider the effect of changes in circulation patterns.

15384±578 cal. yr BP), Hudson (between 7707±185 and 7795±131 cal. yr BP) and Aguilera (<3596±230 cal. yr BP) volcanoes also occur in some of the cores as indicated by the characteristic compositions of their tephra glass, which differ both from each other and also from that of tephra derived from Mount Burney. Significant loss of alkali elements during alteration of the volcanic glass in the tephra layers was observed, especially within acid peat soils, and this may be an important factor in the plant nutrient supply.]]>

The Drake Passage (DP) is the major geographic constriction for the Antarctic Circumpolar Current (ACC) and exerts a strong control on the exchange of physical, chemical, and biological properties between the Atlantic, Pacific, and Indian Ocean basins. Resolving changes in the flow of circumpolar water masses through this gateway is, therefore, crucial for advancing our understanding of the Southern Ocean’s role in global ocean and climate variability. Here, we reconstruct changes in DP throughflow dynamics over the past 65,000 y based on grain size and geochemical properties of sediment records from the southernmost continental margin of South America. Combined with published sediment records from the Scotia Sea, we argue for a considerable total reduction of DP transport and reveal an up to ∼40% decrease in flow speed along the northernmost ACC pathway entering the DP during glacial times. Superimposed on this long-term decrease are high-amplitude, millennial-scale variations, which parallel Southern Ocean and Antarctic temperature patterns. The glacial intervals of strong weakening of the ACC entering the DP imply an enhanced export of northern ACC surface and intermediate waters into the South Pacific Gyre and reduced Pacific–Atlantic exchange through the DP (“cold water route”). We conclude that changes in DP throughflow play a critical role for the global meridional overturning circulation and interbasin exchange in the Southern Ocean, most likely regulated by variations in the westerly wind field and changes in Antarctic sea ice extent.

[1] Glacial millennial-scale paleoceanographic changes in the Southeast Pacific and the adjacent Southern Ocean are poorly known due to the scarcity of well-dated and high resolution sediment records. Here we present new surface water records from sediment core MD07-3128 recovered at 53°S off the Pacific entrance of the Strait of Magellan. The alkenone-derived sea surface temperature (SST) record reveals a very strong warming of ca. 8°C over the last Termination and substantial millennial-scale variability in the glacial section largely consistent with our planktonic foraminifera oxygen isotope (d 18 O) record of Neogloboquadrina pachyderma (sin.). The timing and structure of the Termination and some of the millennial-scale SST fluctuations are very similar to those observed in the well-dated SST record from ODP Site 1233 (41°S) and the temperature record from Drowning Maud Land Antarctic ice core supporting the hemispheric-wide Antarctic timing of SST changes. However, differences in our new SST record are also found including a long-term warming trend over Marine Isotope Stage (MIS) 3 followed by a cooling toward the Last Glacial Maximum (LGM). We suggest that these differences reflect regional cooling related to the proximal location of the southern Patagonian Ice Sheet and related meltwater supply at least during the LGM consistent with the fact that no longer SST cooling trend is observed in ODP Site 1233 or any SST Chilean record. This proximal ice sheet location is documented by generally higher contents of ice rafted debris (IRD) and tetra-unsaturated alkenones, and a slight trend toward lighter planktonic d18 O during late MIS 3 and MIS 2.