| Abstrakt: |
The loop current (LC) in the Gulf of Mexico (GoM) is part of the western North Atlantic circulation. Recording its strength and slowdown variations can help us characterize the regional climate over the Late Pleistocene. To reconstruct the sea surface and the LC intensity in the eastern GoM, we study the distribution patterns of planktonic foraminifera in the core EN‐032‐18PC, spanning the end of Marine Isotope Stage (MIS) 9 to early MIS‐4. We reconstructed a sequence of paleoceanographic events based on stable isotopes (δ18O and δ13C) of the surface dweller Globigerinoides ruber and two faunal assemblages. The first assemblage explains most of the glacial and late interglacial periods, suggesting a subtropical environment with a deep thermocline and a reduced LC due to a moderate inflow of warm Caribbean waters. The second assemblage explains the warmest interglacial substages, dominated by tropical species, a shallow thermocline, and an extended LC, driven by summer insolation. Overall, surface ocean conditions led to more ecological successions and instability during the warmest interglacial substages than during glacial periods, as supported by the stable isotope records. Besides the GoM relationship to AMOC, as a regulator of heat transport to higher latitudes, we suggest that fluctuations in the LC rely on the migration of atmospheric circulation patterns and astronomical insolation forcing. Plain Language Summary: The loop current (LP) in the Gulf of Mexico (GoM) is part of the western North Atlantic circulation. The study of LC variations can help us portray the regional climate during older periods, and of interest, as they could be similar to those we currently live in. We reconstructed past surface ocean conditions during two glacial (cold) and two interglacial (warm) episodes in the GoM. To interpret the past ocean conditions, we studied (a) ancient distribution patterns of surface dwellers' marine microfossils (planktonic foraminifera) and (b) the environmental chemical signals (called stable isotopes) left in their tests. The age of our study spans from 320 ka to 70 ka during the Late Pleistocene. Overall, two scenarios were reconstructed. The first represents subtropical surface waters, suggesting a less intense LC, a deep thermocline, and a moderate inflow of Caribbean waters. The second scenario portrays the warmer periods, which we interpret as tropical waters, an extended LC, a shallow thermocline, and a more significant entry of waters from the Caribbean. We suggest that fluctuations in the GoM primary current are based on atmospheric circulation patterns and Earth's insolation intensity changes over thousands of years. Key Points: Two faunal assemblages suggest that the surface waters of the Gulf of Mexico changed between 320 and 60 kaOne form of variation of the loop current explains most of the sequence, but a second characterizes the warmest interglacial substagesOver the Late Pleistocene, fluctuations in the loop current link to changes in the water masses of the Caribbean Sea [ABSTRACT FROM AUTHOR] |
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