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Chapter 5 The Circulation of the Oceans. A long journey from Tahiti to Hawaii. 延伸閱讀: 冰海奇航 新新聞出版 Riddle of the Ice by Myron Arms 馴服暖化猛獸. How to observe ocean (current)?. mooring. drifter. Global Drifter Program http://www.aoml.noaa.gov/phod/dac/gdp.html.
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Chapter 5 The Circulation of the Oceans A long journey from Tahiti to Hawaii • 延伸閱讀: • 冰海奇航 新新聞出版 • Riddle of the Ice • by Myron Arms • 馴服暖化猛獸
drifter Global Drifter Program http://www.aoml.noaa.gov/phod/dac/gdp.html
60,000 Nike shoes spilled from a storm-tossed cargo ship in the northeastern Pacific in May 1990 The North Pacific gyre has been dropping off shoes around the Pacific since 1990. 1 shoe spill, May 27, 1990 2 250 recovered, March 26, 1991 3 200 recovered, May 18, 1991 4 100 recovered, January-February 1991 5 200 recovered, Nov.-Dec. 1990 6 200 recovered, February-March 1991 7 150 recovered, April 4, 1991 8 200 recovered, May 9-10, 1991 9 several recovered, January-March 1993 10 predicted, January-July 1994 From Judith Gradwohl, Smithsonian Institution (Curator/Ocean Planet) http://seawifs.gsfc.nasa.gov/OCEAN_PLANET/HTML/oceanography_currents_2.html
Surface Ocean Current: Wind-driven Current From Don ReedDepartment of Geology San Jose State University http://geosun1.sjsu.edu/~dreed/130/lab10/10.html
過去認知:海水被風吹著走,海流與風向一致!過去認知:海水被風吹著走,海流與風向一致! • 1890s: • Norwegian explorer Fidtjof Nansen試圖穿越北極海 • 船卡在海冰中長達一年 • 發現:冰與船移動的方向往風向的右側偏約20-40度 • Swedish physicist Walfrid Ekman導出數學公式解釋 • - 地球旋轉(科氏力)與 摩擦
Ekman Spiral • 透過摩擦力 • 動能下傳驅動 • 下層海水 • 科氏力使下層 • 海水往右偏 Ekman transport
Ekman transport Ekman transport 湧昇流
Downwelling: 沈降流 Upwelling: 湧昇流 From “The Blue Planet” by Skinner et al.
南美洲海岸 湧昇流
風如何驅動表面洋流? • 為何海水沒有累積在海洋兩側 • 而是累積在海洋中央? 海面高度
Geostrophic Current H L L L L L H L 平行於海面高度的 地轉流 L L L
黑潮 黑潮 掀起浪濤,顛簸氾濫, 搖撼著宇宙。 洶湧的黑潮有時把長提沖潰。 點滴的流泉有時把磬石滴穿。 - 楊華(1906-1936)「黑潮集」
甚麼因素決定海水密度? 海水成分 硫酸鹽 鎂 鈣 鉀 重碳鹽酸 溴 氯 鈉 From “The Blue Planet” by Skinner et al.
Profiles of Temperature, Salinity and Density in Mid-latitude 密度躍層 躍溫層 鹽度躍層 g鹽/Kg 溫度 鹽度 密度
Vertical Distribution of Temperature 0 0 影響溫度的因素?
Vertical Distribution of Salinity 影響鹽度的因素?
赤道太平洋 混合層 躍溫層
從熱力與動力的角度,何者讓海洋比較不穩定?從熱力與動力的角度,何者讓海洋比較不穩定? 太陽輻射 長波輻射 蒸發 大風 微風
溫鹽洋流(Thermohaline Circulation) • 深海洋流(Deep Ocean Circulation) • 由密度差驅動 • 溫度與鹽度決定密度
Formation of Antarctic Bottom Water (AABW) 南極底水的形成 http://www.geology.um.maine.edu/ges121/lectures/19-ocean-conveyor/ocean-conveyor.html
North Atlantic Deep Water(NADW) 北大西洋深水 From “The Blue Planet” by Skinner et al.
海洋輸送帶:養分、熱量、放射性物質、氟氯碳化物、…海洋輸送帶:養分、熱量、放射性物質、氟氯碳化物、… From “The Blue Planet” by Skinner et al.
Homework for Chapter 5 • Review Questions: 3, 5, 8,9, 10 • 加分題: 為何大洋環流西側洋流較強,東側較弱? • Due 23 March