Paleoceanography of the Gulf of Tehuantepec during the Medieval Warm Period

Abstract

The present study is focused on sediment core MD02–2521 in the Gulf of Tehuantepec (GT). This area, situated within the Oxygen Minimum Zone (OMZ), is rich in marine resources due to seasonal upwelling caused by the Tehuanos winds and a shallower thermocline representing an important economic sector of the region; however, has been the focus of a little number of studies. Benthic foraminifera (BF) are the target proxy to reconstruct bottom‑oxygen variability during the Medieval Warm Period (MWP), showing that this area was affected by cyclic variability of dissolved oxygen (DO) in 3 phases: higher, poorer, and oxygen-depleted shifting every ~90 years. The oxygen-depleted periods result in foraminiferal test dissolution, implying inevitable gaps of information. The MWP has been broadly identified as a warm anomaly in most parts of the globe and even compared with the current climate change to serve as analogous to predict future consequences. Opposing to the global warming stands, the Eastern Tropical North Pacific (ETNP) seems to have experienced a cooling trend. This study provides another proof that the MWP, besides that it is not a warm period everywhere, is also not homogeneous, so that quasi-centennial cycles may likely respond to solar activity and the dynamic interaction between decadal-to centennial phenomena such as the El Niño Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), and the seasonal migration of the Intertropical Convergence Zone (ITCZ).