Millennial variability, hydrological and limnological changes during MIS3-2 in Lake Petén Itzá, Guatemala.

Heinrich Stadials and Greenland Interstadials are abrupt climate variations that are observed in the Northern Hemisphere throughout Marine Isotopic Stages (MIS) 3-2. Lake Petén Itzá, northern Guatemala, is a key site for paleoclimate investigations due to its sensitivity to changes in climate forcing such as the Intertropical Convergence Zone (ITCZ) and the Atlantic Meridional Overturning Circulation (AMOC). In this study, we reconstructed the hydrology and limnology of Lake Petén Itzá during MIS3-2 based on geochemical and mineralogical evidence from the PI-2 record. The beginning of MIS3 (58-52.5 ka cal BP) is characterized by wet conditions, with high lake productivity and anoxic bottom waters that prevailed in the following period (52.5-39 ka cal BP) although with a slight decrease in runoff. During the transition of MIS3 to MIS2 (39-23 ka cal BP) the evaporation in the lake increased considerably, the contribution of aquatic organic matter decreased and bottom waters became more oxic. These conditions reversed during the Last Glacial Maximum (23-18 ka cal BP) when runoff, lake productivity and anoxic conditions in the bottom waters reached their maximum. We have updated the chronology of PI-2 and re-identified Heinrich Stadials (HS) 5-1 signals based in lithological and geochemical variations. We suggest that HS5, HS4 and HS3 were wetter than HS2 and HS1 and likely associated with the strengthening of the trade winds and an intensification of the AMOC which promoted moisture transport and precipitation in the Caribbean region and Gulf of Mexico. On the other hand, we identified 14 Greenland Interstadials (GI) as maximum values of Ca/Ti+Al+Fe. GIs were characterized by high evaporation in the lake and dry conditions. This is explained as a consequence of southern migration in the average ITCZ position.