Deglacial development of (sub) sea surface temperature and salinity in the subarctic northwest Pacific: Implications for upper-ocean stratification

• Published in: Paleoceanography
• Main Authors: Riethdorf, Jan-Rainer, Max, Lars, Nürnberg, Dirk, Lembke-Jene, Lester, Tiedemann, Ralf
• Format: Article in Journal/Newspaper
• Language: English
• Published: AGU (American Geophysical Union) 2013
• Subjects: Pacific; Neogloboquadrina pachyderma; Sea ice; Subarctic
• Online Access: https://oceanrep.geomar.de/id/eprint/21282/; https://oceanrep.geomar.de/id/eprint/21282/1/Riethdorf.pdf; https://doi.org/10.1002/palo.20014

Based on models and proxy data, it has been proposed that salinity-driven stratification weakened in the subarctic North Pacific during the last deglaciation, which potentially contributed to the deglacial rise in atmospheric carbon dioxide. We present high-resolution subsurface temperature (TMg/Ca) and subsurface salinity-approximating (δ18Oivc-sw) records across the last 20,000 years from the subarctic North Pacific and its marginal seas, derived from combined stable oxygen isotopes and Mg/Ca ratios of the planktonic foraminiferal species Neogloboquadrina pachyderma (sin.). Our results indicate regionally differing changes of subsurface conditions. During the Heinrich Stadial 1 and the Younger Dryas cold phases, our sites were subject to reduced thermal stratification, brine rejection due to sea-ice formation, and increased advection of low-salinity water from the Alaskan Stream. In contrast, the Bølling-Allerød warm phase was characterized by strengthened thermal stratification, stronger sea-ice melting, and influence of surface waters that were less diluted by the Alaskan Stream. From direct comparison with alkenone-based sea surface temperature estimates (SSTUk′37), we suggest deglacial thermocline changes that were closely related to changes in seasonal contrasts and stratification of the mixed layer. The modern upper-ocean conditions seem to have developed only since the early Holocene.