Deep Ocean Storage of Heat and CO2 in the Fram Strait, Arctic Ocean During the Last Glacial Period

• Published in: Paleoceanography and Paleoclimatology
• Main Authors: Ezat, Mohamed M., Rasmussen, Tine L., Hain, Mathis P., Greaves, Mervyn, Rae, James W. B., Zamelczyk, Katarzyna, Marchitto, Thomas M., Szidat, Sönke, Skinner, Luke C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union 2021
• Subjects: 540 Chemistry; Arctic; Arctic Ocean; Denmark Strait; Foraminifera*; Fram Strait; Nordic Seas; North Atlantic
• Online Access: https://boris.unibe.ch/157943/1/Ezat_Deep_ocean_storage_of_heat_and_CO2_at_Fram_Strait__Paleoocean_Paleoclim_2021_.pdf; https://boris.unibe.ch/157943/

The Fram Strait is the only deep gateway between the Arctic Ocean and the Nordic Seas and thus is a key area to study past changes in ocean circulation and the marine carbon cycle. Here, we study deep ocean temperature, δ18O, carbonate chemistry (i.e., carbonate ion concentration [CO3 2−]), and nutrient content in the Fram Strait during the late glacial (35,000–19,000 years BP) and the Holocene based on benthic foraminiferal geochemistry and carbon cycle modeling. Our results indicate a thickening of Atlantic water penetrating into the northern Nordic Seas, forming a subsurface Atlantic intermediate water layer reaching to at least ∼2,600 m water depth during most of the late glacial period. The recirculating Atlantic layer was characterized by relatively high [CO3 2−] and low δ13C during the late glacial, and provides evidence for a Nordic Seas source to the glacial North Atlantic intermediate water flowing at 2,000–3,000 m water depth, most likely via the Denmark Strait. In addition, we discuss evidence for enhanced terrestrial carbon input to the Nordic Seas at ∼23.5 ka. Comparing our δ13C and qualitative [CO3 2−] records with results of carbon cycle box modeling suggests that the total terrestrial CO2 release during this carbon input event was low, slow, or directly to the atmosphere.