chapter 5 the circulation of the oceans

Chapter 5

The Circulation of the Oceans

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

A long journey fromTahiti to Hawaii

How to observe ocean (current)?

mooring

drifter Global Drifter Program http://www.aoml.noaa.gov/phod/dac/gdp.html

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

60,000 Nike shoes spilled from a storm-tossed cargo ship in the northeastern Pacific in May 199060,000 Nike shoes spilled from a storm-tossed cargo ship in the northeastern Pacific in May 1990

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 Reed Department of Geology San Jose State Universityhttp://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！

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 SpiralEkman 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

湧昇流

Ekman transport

Ekman transport

Downwelling: 沈降流Upwelling: 湧昇流

From “The Blue Planet” by Skinner et al.

南美洲海岸

湧昇流

Surface Ocean Current: Wind-driven Current風生（成）洋流

•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

Convergence in the Center of a Convergence in the Center of a Subtropical Gyre Subtropical Gyre （環流圈）（環流圈）

Convergence vs. DivergenceConvergence vs. Divergence

X X

Geostrophic CurrentGeostrophic Current

H

L

L

L

L

L

L

L

L

L

H

平行於海面高度的地轉流

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」

（墨西哥）灣流 （ Gulf Stream)

洋流與海溫分佈

甚麼因素決定海水密度？甚麼因素決定海水密度？

氯鈉

硫酸鹽鎂

鈣鉀

溴重碳鹽酸

海水成分

From “The Blue Planet” by Skinner et al.

Profiles of Temperature, Salinity Profiles of Temperature, Salinity and Density in Mid-latitudeand Density in Mid-latitude

溫度 鹽度 密度

躍溫層 鹽度躍層 密度躍層

g 鹽 /Kg

Vertical Distribution of TemperatureVertical Distribution of Temperature

0

0

影響溫度的因素？

Vertical Distribution of SalinityVertical Distribution of Salinity

影響鹽度的因素？

躍溫層混合層

赤道太平洋

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

The Weddel Sea: The Weddel Sea: An Ice-making FactoryAn Ice-making Factory

南極地形高度南極地形高度

Formation of Antarctic Bottom Formation of Antarctic Bottom Water (AABW) Water (AABW) 南極底水的形成南極底水的形成

http://www.geology.um.maine.edu/ges121/lectures/19-ocean-conveyor/ocean-conveyor.html

Polynya Polynya 無冰區無冰區

North Atlantic Deep WaterNorth Atlantic Deep Water(NADW) (NADW) 北大西洋深水北大西洋深水

From “The Blue Planet” by Skinner et al.

Flow Pattern of NADW and AABWFlow Pattern of NADW and AABW

Ages of Water MassesAges of Water Masses

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.

Achilles (Heel)

Ocean ColorOcean Color

Spread of Mediterranean SeaSpread of Mediterranean Sea Water Water

Poleward Heat TransportPoleward Heat Transport

Homework for Chapter 5

1.Review Questions: 3, 5, 8, 9, 102.加分題 : 為何大洋環流西側洋流較強，東側較弱？

Due 23 March

VorticityVorticity

VorticityVorticity

Asymmetric Subtropical GyreAsymmetric Subtropical Gyre

Plankton Blooms, Capricorn Channel

大箭頭區：底水生成區，人造大箭頭區：底水生成區，人造 CO2CO2 儲存區儲存區

Mean annual net airMean annual net air--sea COsea CO22 fluxfluxfor year 1995for year 1995

Takahashi et al. 2002

海氣的二氧化碳通量

海洋酸化 海洋酸化 ((ocean acidification)ocean acidification)

格寧蘭地形格寧蘭地形

陸地與海底地形陸地與海底地形

From “The Blue Planet” by Skinner et al.