Deep temperature variability in Drake Passage
Deep temperature variability in Drake Passage
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DOI：
10.1002/2016jc012452
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发表时间：
2017-01-01
影响因子：
3.6
通讯作者：
Desbruyeres, Damien G.
中科院分区：
文献类型：
--
作者：
Firing, Yvonne L.;McDonagh, Elaine L.;Desbruyeres, Damien G.
对1993至2016年间德雷克东部航道SR1b航线21个职业的观测显示，平均气温比2000 dbar深0.53摄氏度，没有明显的趋势，但年际变化很大(标准差0.08摄氏度)。使用中性密度框架将温度变率分解为等周期位移(Heave)和等周期性质变化分量，表明深部温度年际变化的大约95%是由Heave引起的。等叶线的变化对年际变化的贡献很小，但贡献了一个显著的趋势，即每年-1.40.6摄氏度，最大的密度((N))和极锋(PF)以南的28.1。隆起分量是深度相干的，是中性密度面垂直或水平运动的结果，中性密度面围绕PF向上和向北运动，南段最密集层向下运动，亚南极锋和南极绕极洋流锋(SACCF)向下和向南运动。南极绕极流锋面位置的替代物是由重复的水文数据构造的，它与深海热含量有很强的关系，解释了76%的深海温度变化。基于卫星高度计得到的地表速度的相同锋面位置代理可以解释73%的深层温度变化。在德雷克海峡ACC锋面和深层温度变率之间的这种关系中，PF的位置起到了最大的作用，尽管该断面南半部分的大部分温度变率可以用SACCF的位置来解释。
Observations made on 21 occupations between 1993 and 2016 of GO-SHIP line SR1b in eastern Drake Passage show an average temperature of 0.53 degrees C deeper than 2000 dbar, with no significant trend, but substantial year-to-year variability (standard deviation 0.08 degrees C). Using a neutral density framework to decompose the temperature variability into isopycnal displacement (heave) and isopycnal property change components shows that approximately 95% of the year-to-year variance in deep temperature is due to heave. Changes on isopycnals make a small contribution to year-to-year variability but contribute a significant trend of -1.40.6 m degrees C per year, largest for density ((n))>28.1, south of the Polar Front (PF). The heave component is depth-coherent and results from either vertical or horizontal motions of neutral density surfaces, which trend upward and northward around the PF, downward for the densest levels in the southern section, and downward and southward in the Subantarctic Front and Southern Antarctic Circumpolar Current Front (SACCF). A proxy for the locations of the Antarctic Circumpolar Current (ACC) fronts is constructed from the repeat hydrographic data and has a strong relationship with deep ocean heat content, explaining 76% of deep temperature variance. The same frontal position proxy based on satellite altimeter-derived surface velocities explains 73% of deep temperature variance. The position of the PF plays the strongest role in this relationship between ACC fronts and deep temperature variability in Drake Passage, although much of the temperature variability in the southern half of the section can be explained by the position of the SACCF.