NOAA/WDS Paleoclimatology - Benguela Upwelling Region Holocene and Deglacial Mg/Ca Data

Mg/Ca analyses of G. bulloides and abundances of N. pachyderma (left coiling) from Ocean Drilling Program (ODP) Leg 175 Hole 1084B in the Benguela coastal upwelling system document lower sea surface temperatures during the Last Glacial Maximum (LGM), Younger Dryas, mid-Holocene, and Little Ice Age in the southeastern Atlantic. Taking into consideration the possible effects of differential carbonate dissolution, the Mg/Ca data indicate Younger Dryas temperatures 2°-3°C cooler than those of the early Holocene and LGM temperatures 4°-5°C cooler than those of the early Holocene. The cool interval during the deglacial period at Hole 1084B matches the timing of Younger Dryas shifts in Cariaco Basin and Greenland Ice Sheet records and that of a nearby alkenone record. Comparison of mid-Holocene cooling at Hole ODP1084B with other high-resolution records of Holocene and last deglacial sea surface temperatures from the tropical Atlantic implies consistent basin-wide changes in atmospheric circulation. A brief period of 1.5°-2°C cooling between 17.8 and 17.2 ka, if related to Heinrich event 1, is consistent with a previously hypothesized tropical origin of all Heinrich climate change events.