Paper No. 8
Presentation Time: 3:25 PM
RESPONSE OF SOUTH AMERICAN PALEOLAKES 19-49°S TO CLIMATE CHANGE DURING THE LATE QUATERNARY
Desert South America showed a highly varied hydrologic response to climate change over the last 40 ka. Here we survey the chronology of lake size change using shoreline evidence from four paleolake systems across a broad latitudinal swath (19-49°S) of desert South America east of the Andes. In the sub-tropics climate was wettest when the ITCZ shifted southward during Heinrich events, the mirror image of the subtropical response of the Northern Hemispheric subtropics. The giant overflow paleolakes from Lake Titicaca into the Poopo-Coipasa-Uyuni basins ((19-22°S) are very well documented and show up to 5-6x expansions during Heinrich Events, especially H1. Hydrologic modeling suggests that rainfall increased in the arid Andes by ~2x to create these lakes. Lake Bebedero at 33.5°S also experienced its largest expansion during H1, suggesting a similar link to North Atlantic cooling and a southward shift in the ITCZ.
Further south at 41°S, Laguna Cari-Laufquen was most expansive during the early LGM ca. 27-22 ka. Part of this expansion can be explained by colder LGM temperatures, although a weakening of the westerlies at this latitude may also have contributed. No lake expansion during H1 is in evidence. The shoreline chronology of Lago Cardiel, furthest south at 49°S, was reinvestigated in detail by us, and we can confirm previous studies that show that the largest paleolake in the basin in the last 30 ka dates to 11-9 ka, totally unlike other paleolake systems along our South America transect. The lake enlargement is likely due to weakened westerlies at this time, allowing the intrusion of moisture-laden Atlantic storms into the area from the east. This is also a period of glacial retreat in the western Andes, and of warming and sea-ice retreat in the Antarctic.