2012年夏季挪威海和格陵兰海水文特征分析

doi:10.11867/j.issn.1001-8166.2015.03.0346

利用2012年夏季在北欧海(挪威海和格陵兰海)的水文考察数据,对调查区域内海洋水团性质和分布进行了分析,并对北欧海冷却对流的发展加深过程进行了研究。在上层,从东侧暖而咸的大西洋水跨越锋区至西侧低温低盐的格陵兰海盆上层水体,温度和盐度的变化分别可以达到8 ℃和0.4 psu。中层与深层水体的性质则相对均匀和稳定,3个海盆内从浅至深依次分布着北极中层水、海盆深层水、北极深层水以及海盆底层水。格陵兰海盆中深层水体在3 500 m深度上位温约为-0.97 ℃,相比较1970s观测到的-1.30 ℃,升温幅度超过了0.3 ℃,表明海盆深层存储的热量显著增加。在只考虑局地表面冷却的简化条件下,当前格陵兰海内部通过冷却对流混合至季节性跃层下界需要向大气释放0.9×10⁹~1.2×10⁹ J的热量,这一过程至少需要2个月的时间而不利于对流向深层的发展。大量的热量被存储于北欧海深海盆中使得北欧海已经成为北半球高纬海域的热量存储器,对当前北极气候变化的影响有待深入研究。

关键词: 北欧海, 水团分布, 北极中层水, 深层增暖, 冷却对流

Based on observations during the 5th Chinese Arctic expedition in 2012, the property and distribution of water masses were identified and the evolution of cooling convection was studied. In the upper layer, from the warm and salty Atlantic waters, which mainly lie on the east, westerly to the cold and fresh Greenland upper waters, the temperature and the salinity decreases were about 8 ℃ and 0.4 psu respectively. As for the intermediate and deep waters, water properties were more homogeneous and stable. Along with the depth deepening, there existed the Arctic Intermediate Water, the Basin Deep Water, the Arctic Deep Water and the Basin Bottom Water in all the three deep basins. In the center of the Greenland Basin, the potential temperature was about -0.97 ℃ at depth 3 500 m, which was nearly 0.3 ℃ warmer compared to the value -1.30 ℃ observed in 1970s, implying a heat increase in the deep layer. Under a simplified hypothesis only concerning the surface cooling to erode the seasonal pycnocline, now a total heat loss of about 0.9×10⁹~1.2×10⁹ J/m² was needed for the upper ocean of the Greenland Sea. This process may take at least two months and thus leaves less time for the following deepreaching convection. At present, the Nordic seas are becoming a heat reservoir on the northern hemisphere and impacts of such change on the Arctic climate are worthy of further study.

Key words: Nordic Seas, Water masses, Arctic intermediate water, Abyssal warming, Cooling convection.

中图分类号:

P731

图1 北欧海上层环流示意图 ^{[

5
]}

Fig.1 A schematic illustration of the current system in the Nordic Seas ^{[

5
]} Arrows with broken lines represent Arctic water and solid lines represent Atlantic Water

图2 北欧海地理情况以及2012中国第五次北极科学考察水文站位的分布

Fig.2 Main bathymetric features of the Nordic Seas and locations of the hydrographic stations during the fifth Chinese Arctic Research Expedition in 2012

图3 位势温度,盐度和位势密度在BB和AT断面分布（a,b）位势温度,（c,d）盐度和（e,f）位势密度在BB和AT断面上的分布;灰色区域表示数据缺测,黑色三角形表示断面上海底山脊所在位置

Fig.3 Distributions of potential temperature, salinity and potential density in section of BB and section AT (a, b)potential temperature,(c, d)salinity and (e, f)potential density in section of BB and section AT. Grey area marks the region where data is missing and the black triangles mark the location of sea ridge

图4 T-S温盐图解,所有站位的CTD数据

Fig.4 Potential temperature-salinity diagram for waters from CTD observations

图5 所有站点CTD数据在中、深层深度上的 T-S图解

Fig.5 Potential temperature-salinity diagram of waters from the intermediate to deep layers

图6 北欧海水团的温、盐和密度剖面（a）5个代表站位在上500 m的温盐剖面（只有4个）,（b）5个代表站位全深度的温盐剖面;标注的水团其颜色与其站位的颜色一致

Fig.6 The vertical potential temperature, salinity and potential density measured at the five representative stations (a) and (b) show the hydrographic profiles of the upper 500m layer and the full depth, respectively

图7 所有站点CTD数据在深层的 T-S图

Fig.7 Potential temperature-salinity diagram of deep waters for all CTD stations

表1 2012年夏季挪威海以及格陵兰海内水团性质一览

Table1 Water properties of the Norwegian sea and the Greenland sea in the summer of 2012

水团		分布深度, m （m）			位温, ℃ （℃）	盐度, psu （）	密度差异, kg/m³ （kg/m³）
北大西洋暖流水	季节性混合层	<35			8.0~11.3	35.05~35.19	26.81~27.64
	冬季混合层	60~600			2.0~7.0	35.00~35.22	27.55~27.95
	暖流回流水	60~360			1.5~6.0	34.94~35.10	27.62~27.96
格陵兰海上层水	季节性混合层			<30	5.0~6.0	34.86~35.10	27.49~27.57
	冬季混合层¹		60~1000		-0.6~0.6	34.89~34.93	28.00~28.06
	寒流回流水²			60~230	-0.3~0.3	34.88~34.90	28.00~28.05
挪威海北极中层水		650~1100			-0.3~-0.1	34.895±0.002	28.02~28.04
格陵兰海北极中层水		1100~1500			-0.69~-0.61	34.900~34.901	≈28.06
挪威海深层水		1200~2100			-0.82~-0.35	34.901±0.004	28.05~28.07
格陵兰海深层水		1600~2500			-0.91~-0.70	34.905±0.004	28.06~28.08
挪威海北极深层水		2200~2500			-0.92~-0.90	34.904~34.905	≈28.07
格陵兰海北极深层水		2600~2800			-0.93~-0.92	34.908~34.909	≈28.08
挪威海底层水		>2800			-0.98~-0.94	34.904~34.905	≈28.07
格陵兰海底层水		>3000			-0.96~-0.94	34.907~34.909	≈28.08

表1 2012年夏季挪威海以及格陵兰海内水团性质一览

Table1 Water properties of the Norwegian sea and the Greenland sea in the summer of 2012

水团		分布深度, m （m）			位温, ℃ （℃）	盐度, psu （）	密度差异, kg/m³ （kg/m³）
北大西洋暖流水	季节性混合层	<35			8.0~11.3	35.05~35.19	26.81~27.64
	冬季混合层	60~600			2.0~7.0	35.00~35.22	27.55~27.95
	暖流回流水	60~360			1.5~6.0	34.94~35.10	27.62~27.96
格陵兰海上层水	季节性混合层			<30	5.0~6.0	34.86~35.10	27.49~27.57
	冬季混合层¹		60~1000		-0.6~0.6	34.89~34.93	28.00~28.06
	寒流回流水²			60~230	-0.3~0.3	34.88~34.90	28.00~28.05
挪威海北极中层水		650~1100			-0.3~-0.1	34.895±0.002	28.02~28.04
格陵兰海北极中层水		1100~1500			-0.69~-0.61	34.900~34.901	≈28.06
挪威海深层水		1200~2100			-0.82~-0.35	34.901±0.004	28.05~28.07
格陵兰海深层水		1600~2500			-0.91~-0.70	34.905±0.004	28.06~28.08
挪威海北极深层水		2200~2500			-0.92~-0.90	34.904~34.905	≈28.07
格陵兰海北极深层水		2600~2800			-0.93~-0.92	34.908~34.909	≈28.08
挪威海底层水		>2800			-0.98~-0.94	34.904~34.905	≈28.07
格陵兰海底层水		>3000			-0.96~-0.94	34.907~34.909	≈28.08

图8 冷却对流过程的示意图红色和蓝色实线分别是BB09站所观测的海水盐度以及位势密度剖面

Fig.8 The schematic process of simplified cooling convection The salinity (red line) and potential density (blue line) are measured at station BB09

图9 冷却对流深度 h与混合层内平均温度的对应关系（实线）,以及冷却对流深度 h与混合层内水体热释放量 Q_h的对应关系（虚线）

Fig.9 Deepening of the convection depth h (solid lines) with the mixed layer cooling and the corresponding heat loss Q_h(dotted lines) needed to escape from the mixed layer

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摘要

Hydrographic Features of the Norwegian Sea and the Greenland Sea in Summer 2012