Holocene temperature and water stress in the Peruvian Andes

Abstract

Global climate during the Holocene was relatively stable compared to the late Pleistocene. However, evidence from lacustrine records in South America suggests that tropical latitudes experienced significant water balance variability during the Holocene, rather than quiescence. For example, a tight coupling between insolation and carbonate delta 18O records from central Andean lakes (e.g., Lakes Jun & iacute;n, Pumacocha) suggest water balance is tied directly to South American summer monsoon (SASM) strength. However, lake carbonate delta 18O records also incorporate information about temperature and evaporation. To overcome this ambiguity, clumped and triple oxygen isotope records can provide independent constraints on temperature and evaporation. Here, we use clumped and triple oxygen isotopes to develop Holocene temperature and evaporation records from three central Andean lakes, Lakes Jun & iacute;n, Pumacocha, and Mehcocha, to build a more complete picture of regional water balance (P-E). We find that Holocene water temperatures at all three lakes were stable and slightly warmer than during the latest Pleistocene. These results are consistent with global data assimilations and records from the foothills and Amazon basin. In contrast, evaporation was highly variable and tracks SASM intensity. The hydrologic response of each lake to SASM depends greatly on the physical characteristics of the lake basin, but they all record peak evaporation in the early to mid-Holocene (11,700 to 4,200 years BP) when regional insolation was relatively low and the SASM was weak. These results corroborate other central Andean records and suggest synchronous, widespread water stress tracks insolation-paced variability in SASM strength.Lake carbonate Delta ' 17O and Delta 47 constrain lake temperature and water balance histories in ways that delta 18O records alone cannot resolve Carbonate Delta ' 17O records from three Andean lakes indicate that lake hydrology and regional water balance track insolation across the Holocene Low Delta ' 17O for reconstructed lake water indicates that greater evaporative conditions correspond to weakened early and mid-Holocene South American summer monsoon