Sources of local dense shelf water near the Cape Darnley fast ice in Prydz Bay, Antarctica
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摘要: 本文采用固定冰数据集和南极象海豹获取的现场观测数据集，分析了南极达恩利角固定冰附近局地高密陆架水的变化。结果表明：首先，达恩利角固定冰存在显著季节变化，对于达恩利角冰间湖及局地高密陆架水的生成都具有重要影响。其次，达恩利角固定冰在2000−2014年期间年际变化很小，无显著增减趋势。第三，达恩利角固定冰附近局地高密陆架水有两个显著来源：（1）3−4月，达恩利角固定冰快速生成时伴随着强烈的盐析作用，进而局地生成高密陆架水；（2）5月，达恩利角固定冰达到最大范围，局地盐析作用减弱至很小，而上游在冰架水抑制作用减弱后，麦肯基湾冰间湖海域的高密陆架水生成增强，能够向西北输运至达恩利角固定冰附近。本研究初步证明达恩利角固定冰除了维持达恩利角冰间湖存在的作用外，对局地高密陆架水生成也可能有重要影响，同时指出一条重要的水团输运路径，这有助于提高对达恩利角附近冰−海相互作用的理解，对该地区开展更多观测或模拟研究是必要的。Abstract: In this paper, we analyze the variation of local dense shelf water around the Cape Darnley fast ice by using a landfast ice dataset and in-situ observation data of Antarctic elephant seals. The results show that: firstly, there are significant seasonal variations of Cape Darnley fast ice, which has a vital impact on the formation of the Cape Darnley polynya and the local dense shelf water. Secondly, the interannual variation of Cape Darnley fast ice is minimal from 2000 to 2014, with no significant trend of increasing or decreasing. Thirdly, we identify two significant sources of local dense shelf water near the Cape Darnley fast ice area: (1) dense shelf water produced by the strong brine rejection process during the rapid generation of Cape Darnley fast ice from March to April; (2) Cape Darnley fast ice reaching its maximum extent and local brine rejection being reduced to a minimum in May. After the weakening of the inhibition of ice shelf water, the formation of dense shelf water in the upstream MacKenzie Bay polynya is enhanced and transported northwest to the vicinity of the Cape Darnley fast ice. In this study, we preliminarily demonstrates that, in addition to maintaining Cape Darnley polynya, Cape Darnley fast ice probably has an important influence on the generation of local dense shelf water, and points out an important water mass transport path. These would help improve the comprehension of ice-sea interaction near Cape Darnley and point out the need for more observations or modeling studies in this area.
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Key words:
- fast ice /
- dense shelf water /
- Cape Darnley /
- Antarctic
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图 1 普里兹湾地区的地形分布及地理位置
红色细线所示区域为达恩利角冰间湖和麦肯基湾冰间湖，黑色粗线所示区域为固定冰；左下角为南极地图，其中红色框线所选区域为本文研究区域
Fig. 1 The topographic distribution and geographical location of the Prydz Bay
The red thin line shows Cape Darnley polynya and MacKenzie Bay polynya, and the black thick line shows fast ice; the map of the South Pole is in the lower left corner, in which the area selected by the red box is the research area of this paper
图 2 研究区域内MEOP-CTD数据集的时间分布
Fig. 2 Time distribution of MEOP-CTD data sets in the study area
图 3 2000年3月至2014年3月达恩利角附近区域固定冰的年平均覆盖持续时间
Fig. 3 Mean year-round fast ice coverage duration in the region around Cape Darnley from March 2000 to March 2014
图 4 2000年3月至2014年3月达恩利角附近区域固定冰的逐月平均覆盖持续时间
Fig. 4 Monthly mean fast ice coverage duration in the region around Cape Darnley from March 2000 to March 2014
图 5 2000年3月至2014年3月固定冰面积的时间序列
Fig. 5 Time series of Cape Darnley fast ice area from March 2000 to March 2014
图 6 达恩利角附近海域（66°～69°S，67°～73°E）每个剖面最深处（近于底部）的盐度平面分布
灰色细线为等深线，间隔500 m；浅蓝色线内区域为固定冰；红色框线、蓝色框线和绿色框线为下文剖面图选择区域所用
Fig. 6 Planar distribution of salinity at the deepest level (near the bottom) of each profile near Cape Darnley (66°−69°S，67°−73°E）
Gray fine solid lines are isobath lines, contour interval: 500 m; the area inside the light blue line is the fast ice; the red, blue, and green box lines are used to select the region of the section below
图 7 达恩利角附近海域1−5月和7月的盐度纬向（67.5°～68°S，对应图6中蓝色框线区域）垂直剖面分布
图中黑色方框表示达恩利角固定冰附近区域
Fig. 7 Zonal vertical profiles of salinity Cape Darnley from January to May and July (67.5°−68°S, the region corresponds to the blue box line in figure 6)
The black boxes in the figure indicate the region around the Cape Darnley fast ice
图 8 达恩利角附近海域3−10月的盐度纬向（68°～68.5°S，对应图6中绿色框线区域）垂直剖面分布
Fig. 8 Zonal vertical profiles of salinity in the sea area near Cape Darnley from March to October (68°−68.5°S, the region corresponds to the green box line in figure 6)
图 9 麦肯基湾冰间湖海域高密陆架水（盐度大于34.4）3个典型年份的月平均盐度时间序列
Fig. 9 Monthly mean salinity time series of dense shelf water (salinity is grater than 34.4) in the MacKenzie Bay polynya area
图 10 2011年达恩利角固定冰下方（67.5°～68°S）高密陆架水形成案例
2011年3−5月达恩利角固定冰面积的时间序列如图a所示；达恩利角附近盐度的纬向垂直剖面描述了3个时期分别为： b. 2011年4月1−15日；c. 2011年4月16−30日；d. 2011年5月16−30日
Fig. 10 A case of formation of dense shelf water beneath the Cape Darnley fast ice (67.5°−68°S) in 2011
The time series of Cape Darnley fast ice area from March to July 2011 are shown in figure a; zonal vertical profiles of salinity near Cape Darnley: b. April 1 to April 15, 2011; c. April 16 to April 30, 2011; d. May 16 to May 30, 2011
图 11 2011年4月16−30日达恩利角固定冰下方及其东侧高密陆架水形成案例
a. 象海豹的运动轨迹（象海豹首先从埃默里冰架前缘向西游至达恩利角固定冰下方，再向北游至67.5°S附近，最后游回普里兹湾）； b. 100 m水深处盐度平面分布情况；c. 盐度纬向垂直剖面；d. 盐度随时间的垂直剖面
Fig. 11 A case of formation of dense shelf water beneath and to the east of Cape Darnley fast ice from April 16 to April 30, 2011
a. The trajectory of the elephant seal (the elephant seal first travels westward from the Amery ice shelf front to beneath the Cape Darnley fast ice, then northward to near 67.5°S, and finally back to Prydz Bay); b. horizontal distribution of salinity at 100 m depth; c. zonal vertical profile of salinity; d. vertical profile of salinity over time
图 12 2011年5月16−30日达恩利角固定冰下方及其东侧高密陆架水案例
a. 象海豹的运动轨迹（象海豹从埃默里冰架前缘向西北游至达恩利角固定冰下方及其东侧区域）；b. 100 m水深处盐度平面分布情况；c. 盐度纬向垂直剖面；d. 盐度随时间的垂直剖面
Fig. 12 A case of formation of dense shelf water beneath and to the east of Cape Darnley fast ice from May 16 to May 30, 2011
a. The trajectory of the elephant seal (the elephant seal travels northwest from the Amery ice shelf front to the area beneath and to the east of the Cape Darnley fast ice); b. horizontal distribution of salinity at 100 m depth; c. zonal vertical profile of salinity; d. vertical profile of salinity over time
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