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

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 (T-Mg/Ca) and subsurface salinity-approximating (delta O-18(ivc-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 Bolling-Allerod 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. Citation: Riethdorf, J.-R., L. Max, D. Nurnberg, L. Lembke-Jene, and R. Tiedemann (2013), Deglacial development of (sub) sea surface temperature and salinity in the subarctic northwest Pacific: Implications for upper-ocean stratification, Paleoceanography, 28, 91-104, doi:10.1002/palo.20014.