Variability of Subantarctic Mode Water and Antarctic Intermediate Water in the Drake Passage during the Late-Twentieth and Early-Twenty-First Centuries
Variability of Subantarctic Mode Water and Antarctic Intermediate Water in the Drake Passage during the Late-Twentieth and Early-Twenty-First Centuries
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DOI：
10.1175/2009jcli2621.1
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发表时间：
2009-07-01
影响因子：
4.9
通讯作者：
King, Brian A.
中科院分区：
文献类型：
--
作者：
Garabato, Alberto C. Naveira;Jullion, Loic;King, Brian A.
利用1969 - 2005年德雷克海峡24条断面的测量数据，建立了德雷克海峡亚南极模式水（SAMW）和南极中层水（AAIW）的物理和地球化学性质的时间序列。这两个水团都经历了年际到年代际的时间尺度上的重大变化。SAMW是由冬季在德雷克海峡及其以西的南极绕极流（ACC）向赤道一侧的翻转形成的。它的年际变化主要是由冬季海气湍流热通量和净蒸发的变化由厄尔尼诺-南方涛动（ENSO）调制驱动。尽管它们在空间上很接近，但德雷克海峡的AAIW与SAMW的来源非常不同，因为它是由来自别林斯高晋海的冬季水向北俯冲而通风的。在AAIW的变化主要是被迫在冬季水属性的变化，导致冬季海-气湍流热通量和春季海冰融化的波动，这两者都与主要ENSO驱动的南极半岛以西的季风强度的变化。SAMW和AAIW形成的普遍模式的一个突出的例外发生在1998年，当强风强迫与ENSO和南部环形模式（SAM）之间的建设性干扰触发了SAMW通风和AAIW生产的1-2年的关闭Ekman主导模式的过渡。SAMW在1970年代变暖（近似0.3摄氏度）和盐化（近似0.04），并在1990年至2005年期间经历了相反的趋势，当时观察到有记录以来最冷和最新鲜的SAMW。相比之下，20世纪70年代至21世纪世纪，农业、工业和水资源净增长（增长幅度约为0.05）。虽然SAMW的反向变化主要是由与年代际太平洋振荡相关的区域海气湍流热通量和降水的类似30年振荡所强迫的，但来自南部的南极表面沃茨的Ekman供应的增强也有显著贡献，AAIW的淡化与近几十年来南极半岛西部发生的极端气候变化有关。在那里，一个清新的冬季水通风AAIW带来了降水的增加和冬季海冰边缘的退缩，这似乎是被迫的年代际趋势的SAM和区域的正反馈的空气-海冰耦合的气候系统。总而言之，这些发现突出了南半球气候变率的主要模式在推动德雷克海峡地区和更广泛的南大西洋SAMW和AAIW演变中的作用，并表明这些模式可能对近几十年来这些沃茨经历的半球尺度变化做出了重大贡献。
A time series of the physical and biogeochemical properties of Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) in the Drake Passage between 1969 and 2005 is constructed using 24 transects of measurements across the passage. Both water masses have experienced substantial variability on interannual to interdecadal time scales. SAMW is formed by winter overturning on the equatorward flank of the Antarctic Circumpolar Current (ACC) in and to the west of the Drake Passage. Its interannual variability is primarily driven by variations in wintertime air-sea turbulent heat fluxes and net evaporation modulated by the El Nino-Southern Oscillation (ENSO). Despite their spatial proximity, the AAIW in the Drake Passage has a very different source than that of the SAMW because it is ventilated by the northward subduction of Winter Water originating in the Bellingshausen Sea. Changes in AAIW are mainly forced by variability in Winter Water properties resulting from fluctuations in wintertime air-sea turbulent heat fluxes and spring sea ice melting, both of which are linked to predominantly ENSO-driven variations in the intensity of meridional winds to the west of the Antarctic Peninsula. A prominent exception to the prevalent modes of SAMW and AAIW formation occurred in 1998, when strong wind forcing associated with constructive interference between ENSO and the southern annular mode (SAM) triggered a transitory shift to an Ekman-dominated mode of SAMW ventilation and a 1-2-yr shutdown of AAIW production.The interdecadal evolutions of SAMW and AAIW in the Drake Passage are distinct and driven by different processes. SAMWwarmed (by similar to 0.3 degrees C) and salinified (by similar to 0.04) during the 1970s and experienced the reverse trends between 1990 and 2005, when the coldest and freshest SAMW on record was observed. In contrast, AAIW underwent a net freshening (by similar to 0.05) between the 1970s and the twenty-first century. Although the reversing changes in SAMW were chiefly forced by a similar to 30-yr oscillation in regional air-sea turbulent heat fluxes and precipitation associated with the interdecadal Pacific oscillation, with a SAM-driven intensification of the Ekman supply of Antarctic surface waters from the south contributing significantly too, the freshening of AAIW was linked to the extreme climate change that occurred to the west of the Antarctic Peninsula in recent decades. There, a freshening of the Winter Water ventilating AAIW was brought about by increased precipitation and a retreat of the winter sea ice edge, which were seemingly forced by an interdecadal trend in the SAM and regional positive feedbacks in the air-sea ice coupled climate system. All in all, these findings highlight the role of the major modes of Southern Hemisphere climate variability in driving the evolution of SAMW and AAIW in the Drake Passage region and the wider South Atlantic and suggest that these modes may have contributed significantly to the hemispheric-scale changes undergone by those waters in recent decades.