Patagonian Ice Sheet influence on southern South American climate

RIQUELME, F.; COSENTINO, N. J.; ZHU, J.; LAMBERT, F.

Roma

Congreso; XXI INQUA Congress; 2023

INQUA

The Last Glacial Maximum (LGM, between 26.5 and 19.0 ka before present) is the closest period with stable climate different from present-day conditions. Among the most striking features is a more than 5°C decrease of global temperature, ~50% less carbon dioxide atmospheric concentration than pre-industrial recent times, and a ~120 m decrease of sea level related to continental ice sheet growth. In the mid-latitudes of the Southern Hemisphere the Patagonian Ice Sheet (PIS) grew over the southern Andes. The PIS extended predominantly in a north-south orientation along ~2000 km, from 38 to 54°S, reaching a mean thickness of 1100 meters. Based on glacial records such as moraines, it is possible to infer the presence of extended glacial lobes to the east of the Andes. However, on the western side of the Andes there is little or no evidence of glacial lobes. Is this difference related to LGM climate? Some authors have hypothesized that the PIS boosted the rain shadow effect generated by the interaction of the Southern Westerly Winds (SWW), the Southern Hemisphere low-level, sub-polar jet, and Andean topography. Today, this interaction generates a variation of the precipitation rate from more than 5 m/a to the west to less than 300 mm/a to the east of the Andes. To evaluate this hypothesis, we performed a sensitivity analysis of the PIS influence on southern South American climate. For this we are running a coupled land-atmosphere model simulation using the Community Earth System Model 2 (CESM 2) with LGM boundary conditions and PIS elevation variations. Results will be presented and discussed in the session. Analyzing variations on temperature, precipitation, storm track frequency, and winds we expect to assess if PIS could have influenced glacier growth during the LGM.