Deep ocean storage of heat and CO 2 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: 2021
• Subjects: The Nordic Seas; The Fram Strait; The last glacial; Climate change; Benthic foraminiferal δ18O; Benthic foraminiferal element/Ca; Arctic; Arctic Ocean; Denmark Strait; Foraminifera*; Fram Strait; Nordic Seas; North Atlantic
• Online Access: https://risweb.st-andrews.ac.uk/portal/en/researchoutput/deep-ocean-storage-of-heat-and-co2-in-the-fram-strait-arctic-ocean-during-the-last-glacial-period(4bc85d5b-66aa-422a-9ac6-5ed3411e4f41).html; https://doi.org/10.1029/2021PA004216; https://research-repository.st-andrews.ac.uk/bitstream/10023/23685/1/Ezat_2021_PP_Deepocean_CC.pdf

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, δ 18 O, carbonate chemistry (i.e., carbonate ion concentration, [CO 3 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 modelling. 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 ~2600 m water depth during most of the late glacial period. The recirculating Atlantic layer was characterized by relatively high [CO 3 2- ] and low δ 13 C during the late glacial, and provides evidence for a Nordic Seas source to the glacial North Atlantic intermediate water flowing at 2000-3000 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 δ 13 C and qualitative [CO 3 2- ] records with results of carbon cycle box modelling suggests that the total terrestrial CO 2 release during this carbon input event was low, slow, or directly to the atmosphere.