Sea surface temperature reconstruction for ODP Hole 178-1098B

The disintegration of ice shelves, reduced sea-ice and glacier extent, and shifting ecological zones observed around Antarctica (Cook et al., 2005, doi:10.1126/science.1104235; Stammerjohn et al., 2008, doi:10.1016/j.dsr2.2008.04.026) highlight the impact of recent atmospheric (Steig et al., 2009, doi:10.1038/nature07669) and oceanic warming (Gille, 2002, doi:10.1126/science.1065863) on the cryosphere. Observations (Cook et al., 2005, doi:10.1126/science.1104235; Stammerjohn et al., 2008, doi:10.1016/j.dsr2.2008.04.026) and models (Pollard and DeConto, 2009, doi:10.1038/nature07809) suggest that oceanic and atmospheric temperature variations at Antarctica's margins affect global cryosphere stability, ocean circulation, sea levels and carbon cycling. In particular, recent climate changes on the Antarctic Peninsula have been dramatic, yet the Holocene climate variability of this region is largely unknown, limiting our ability to evaluate ongoing changes within the context of historical variability and underlying forcing mechanisms. Here we show that surface ocean temperatures at the continental margin of the western Antarctic Peninsula cooled by 3-4 °C over the past 12,000?years, tracking the Holocene decline of local (65° S) spring insolation. Our results, based on TEX86 sea surface temperature (SST) proxy evidence from a marine sediment core, indicate the importance of regional summer duration as a driver of Antarctic seasonal sea-ice fluctuations (Huybers and Denton, 2008, doi:10.1038/ngeo311). On millennial timescales, abrupt SST fluctuations of 2-4 °C coincide with globally recognized climate variability (Mayewski et al., 2004, doi:10.1016/j.yqres.2004.07.001). Similarities between our SSTs, Southern Hemisphere westerly wind reconstructions (Moreno et al., 2010, doi:10.1130/G30962.1) and El Niño/Southern Oscillation variability (Conroy et al., 2008, doi:10.1016/j.quascirev.2008.02.015) indicate that present climate teleconnections between the tropical Pacific Ocean and the western Antarctic Peninsula (Yuan et al., 2004, doi:10.1017/S0954102004002238) strengthened late in the Holocene epoch. We conclude that during the Holocene, Southern Ocean temperatures at the western Antarctic Peninsula margin were tied to changes in the position of the westerlies, which have a critical role in global carbon cycling (Moreno et al., 2010, doi:10.1130/G30962.1; Anderson et al., 2009, doi:10.1126/science.1167441).

南极周边观测到的冰架崩解、海冰与冰川范围缩减，以及生态区带迁移（Cook等，2005，doi:10.1126/science.1104235；Stammerjohn等，2008，doi:10.1016/j.dsr2.2008.04.026），凸显了近期大气（Steig等，2009，doi:10.1038/nature07669）与海洋变暖（Gille，2002，doi:10.1126/science.1065863）对冰冻圈（cryosphere）的影响。上述观测结果（Cook等，2005，doi:10.1126/science.1104235；Stammerjohn等，2008，doi:10.1016/j.dsr2.2008.04.026）与数值模拟结果（Pollard与DeConto，2009，doi:10.1038/nature07809）表明，南极边缘的海洋与大气温度变化，会影响全球冰冻圈稳定性、海洋环流、海平面及碳循环。尤其值得关注的是，南极半岛近期的气候变化幅度极大，但该区域全新世（Holocene）的气候变异性仍基本未知，这限制了我们在历史变率与潜在驱动机制的框架下评估当前变化的能力。本研究表明，在过去12000年间，南极半岛西部大陆边缘的表层海洋温度下降了3~4℃，这一变化与当地（南纬65°）春季太阳辐射的全新世下降趋势相吻合。本研究结果基于某海洋沉积物岩芯的TEX86海表温度（SST）代用指标证据，表明区域夏季时长是南极季节性海冰波动的关键驱动因素（Huybers与Denton，2008，doi:10.1038/ngeo311）。在千年时间尺度上，2~4℃的海表温度突变波动与全球公认的气候变率事件相吻合（Mayewski等，2004，doi:10.1016/j.yqres.2004.07.001）。我们的海表温度序列、南半球西风重建结果（Moreno等，2010，doi:10.1130/G30962.1）以及厄尔尼诺-南方涛动（El Niño/Southern Oscillation）变率（Conroy等，2008，doi:10.1016/j.quascirev.2008.02.015）之间的相似性表明，当前热带太平洋与南极半岛西部之间的气候遥相关关系（Yuan等，2004，doi:10.1017/S0954102004002238）在全新世晚期得到了增强。本研究得出结论：在全新世期间，南极半岛西部边缘的南大洋温度与西风带位置的变化密切相关，而西风带在全球碳循环中发挥着关键作用（Moreno等，2010，doi:10.1130/G30962.1；Anderson等，2009，doi:10.1126/science.1167441）。