The effects of ocean chlorophyll on the mode water subduction rate in the subtropical mode water (STMW) and central mode water (CMW) in Pacific Ocean are investigated by performing two ocean-only experiments, using two different solar radiation penetration schemes, one with and one without chlorophyll effects. The biological impacts on mixed layer depth (MLD), upper ocean temperature and density are analyzed. Results show that the subduction rates of both STMW and CMW are increased with the effects of ocean chlorophyll. The increase in the subduction rate is mainly caused by the increased lateral induction term, which is related to larger MLD gradient in early spring in the chlorophyll experiment.

Declining sea-ice extent is currently amplifying climate warming in the Arctic. Instrumental records at high latitudes are too short-term to provide sufficient historical context for these trends, so paleoclimate archives are needed to better understand the functioning of the sea ice-albedo feedback. Here we use the oxygen isotope values of wood cellulose in living and sub-fossil willow shrubs (delta O-18(wc)) (Salix spp.) that have been radiocarbon-dated (C-14) to produce a multi-millennial record of climatic change on Alaska's North Slope during the Pleistocene-Holocene transition (13,500-7500 calibrated 14C years before present; 13.5-7.5 ka). We first analyzed the spatial and temporal patterns of delta O-18(wc) in living willows growing at upland sites and found that over the last 30 years delta O-18(wc) values in individual growth rings correlate with local summer temperature and inter-annual variations in summer sea-ice extent. Deglacial delta O-18(wc) values from 145 samples of subfossil willows clearly record the Allerod warm period (similar to 13.2 ka), the Younger Dryas cold period (12.9-11.7 ka), and the Holocene Thermal Maximum (11.7-9.0 ka). The magnitudes of isotopic changes over these rapid climate oscillations were similar to 4.5 parts per thousand, which is about 60% of the differences in delta O-18(wc) between those willows growing during the last glacial period and today. Modeling of isotope-precipitation relationships based on Rayleigh distillation processes suggests that during the Younger Dryas these large shifts in 6180,c values were caused by interactions between local temperature and changes in evaporative moisture sources, the latter controlled by sea ice extent in the Arctic Ocean and Bering Sea. Based on these results and on the effects that sea-ice have on climate today, we infer that ocean-derived feedbacks amplified temperature changes and enhanced precipitation in coastal regions of Arctic Alaska during warm times in the past. Today, isotope values in willows on the North Slope of Alaska are similar to those growing during the warmest times of the Pleistocene-Holocene transition, which were times of widespread permafrost thaw and striking ecological changes. (C) 2017 Elsevier Ltd. All rights reserved.

A major achievement in research supported by the Kluane Lake Research Station was the recovery, in 2001-02, of a suite of cores from the icefields of the central St. Elias Mountains, Yukon, by teams of researchers from Canada, the United States, and Japan. This project led to the development of parallel, long (10(3) - 10(4) year) ice-core records of climate and atmospheric change over an altitudinal range of more than 2 km, from the Eclipse Icefield (3017 m) to the ice-covered plateau of Mt. Logan (5340 m). These efforts built on earlier work recovering single ice cores in this region. Comparison of these records has allowed for variations in climate and atmospheric composition to be linked with changes in the vertical structure and dynamics of the North Pacific atmosphere, providing a unique perspective on these changes over the Holocene. Owing to their privileged location, cores from the St. Elias Icefields also contain a remarkably detailed record of aerosols from various sources around or across the North Pacific. In this paper we review major scientific findings from the study of St. Elias Mountain ice cores, focusing on five main themes: (1) The record of stable water isotopes (delta O-18, delta D), which has unique characteristics that differ from those of Greenland, other Arctic ice cores, and even among sites in the St. Elias; (2) the snow accumulation history; (3) the record of pollen, biomass burning aerosol, and desert dust deposition; (4) the record of long-range air pollutant deposition (sulphate and lead); and (5) the record of paleo-volcanism. Our discussion draws on studies published since 2000, but based on older ice cores from the St. Elias Mountains obtained in 1980 and 1996.