High resolution benthic Mg/Ca temperature record of the intermediate water in the Denmark Strait across D-O stadial-interstadial cycles

Abstract

Dansgaard‐Oeschger (D‐O) climate instabilities that took place during Marine Isotope Stage 3 are connected to changes in ocean circulation patterns and sea ice cover. Here we explore in detail the configuration of the water column of the Denmark Strait during D‐O events 8–5. How the ocean currents and water masses within the Denmark Strait region responded and were connected to the North Atlantic are discussed. We investigate sediment core GS15‐198‐36CC, from the northern side of the Greenland‐Iceland Ridge, at 30‐year temporal resolution. Stable carbon and oxygen isotope reconstructions based on benthic foraminifera, together with a high‐resolution benthic foraminiferal record of Mg/Ca paleothermometry, is presented. The site was bathed by warm intermediate waters during stadials and cool but gradually warming intermediate water during interstadials. We suggest that stadial conditions in the Denmark Strait are characterized by a well‐stratified water column with a warm intermediate water mass that lies beneath a cold fresh body of water where sea ice and brine rejection work in consort to uphold the halocline conditions. Interstadial periods are not a pure replicate of modern times, but rather have two modes of operation, one similar to today, and the other incorporating a brief period of warm intermediate water and increased ventilation.