Increased rainfall in southern Central America under glacial climate conditions

Le résumé fourni par la source

• δD of n -alkanes shows stronger rainfall in LGM than today in southern Central America. • Such northward ITCZ shift is due to an increased latitudinal SST gradient in the EEP. • PMIP4 models simulations support this ocean-atmosphere interaction during the LGM. Late Pleistocene hydroclimate variability in Central America and its associated climate forcings are poorly constrained. The region is influenced by complex ocean-atmosphere-continent interactions, and documented palaeohydrological responses, which vary by site and/or proxy specificity, are far from conclusive. We used δD of n -alkanes from a marine sediment core in the Panama Basin to infer past changes in precipitation over the last 56 kyr. Our results indicate a progressive intensification of precipitation during the last glacial period, culminating in a precipitation maximum during the Last Glacial Maximum (LGM, 23–19 kyr BP), followed by a rapid decline during the Heinrich Event 1 (H1, 18–15 kyr BP) time interval. While the regional pattern of the precipitation anomaly during the LGM is proxy and site dependent, the regional drying during H1 shows a clear north-south signature associated with the southward meridional migration of the Intertropical Convergence Zone (ITCZ). Using iTrace and PMIP4 model simulations, we show that the precipitation changes associated with the ITCZ shift are closely linked to the equatorial SST front induced by changes in the oceanic circulation. We propose that an increase in this latitudinal SST gradient could have locally pushed the ITCZ further north, bringing rainfall to southern Central America during the LGM.

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