Deglacial subarctic Pacific surface water hydrography and nutrient dynamics and links to North Atlantic climate variability and atmospheric CO2

• Published in: Paleoceanography
• Main Authors: Maier, E., Meheust, M., Abelmann, A., Gersonde, R., Chapligin, B., Ren, J., Stein, R., Meyer, H., Tiedemann, R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Amer Geophysical Union 2015
• Subjects: Pacific; Ice Sheet; North Atlantic; Sea ice; Subarctic
• Online Access: https://archimer.ifremer.fr/doc/00351/46254/46083.pdf; https://archimer.ifremer.fr/doc/00351/46254/46084.pdf; https://doi.org/10.1002/2014PA002763; https://archimer.ifremer.fr/doc/00351/46254/

The glacial-to-Holocene evolution of subarctic Pacific surface water stratification and silicic acid (Si) dynamics is investigated based on new combined diatom oxygen (delta O-18(diat)) and silicon (delta Si-30(diat)) isotope records, along with new biogenic opal, subsurface foraminiferal delta O-18, alkenone-based sea surface temperature, sea ice, diatom, and core logging data from the NE Pacific. Our results suggest that delta O-18(diat) values are primarily influenced by changes in freshwater discharge from the Cordilleran Ice Sheet (CIS), while corresponding delta Si-30(diat) are primarily influenced by changes in Si supply to surface waters. Our data indicate enhanced glacial to mid Heinrich Stadial 1 (HS1) NE Pacific surface water stratification, generally limiting the Si supply to surface waters. However, we suggest that an increase in Si supply during early HS1, when surface waters were still stratified, is linked to increased North Pacific Intermediate Water formation. The coincidence between fresh surface waters during HS1 and enhanced ice-rafted debris sedimentation in the North Atlantic indicates a close link between CIS and Laurentide Ice Sheet dynamics and a dominant atmospheric control on CIS deglaciation. The Bolling/Allerod (B/A) is characterized by destratification in the subarctic Pacific and an increased supply of saline, Si-rich waters to surface waters. This change toward increased convection occurred prior to the Bolling warming and is likely triggered by a switch to sea ice-free conditions during late HS1. Our results furthermore indicate a decreased efficiency of the biological pump during late HS1 and the B/A (possibly also the Younger Dryas), suggesting that the subarctic Pacific has then been a source region of atmospheric CO2.