Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Western Boundary Currents Gulf Stream & Shipping • Outstanding characteristics • Warm Gulf Stream water is clear blue – Heat & water transport – Cooler northern water is cloudier & greener – Sharp boundaries • Visible true color vs. infrared false color • Case Study: the Gulf Stream – Effects on shipping – Climate effects on Europe – Global climate effects – Climate effects on N. America – Online reading: • Philadelphia Inquirer – http://www.philly.com/mld/inquirer/news/special_packages/gulfstream/ 1 2 http://visibleearth.nasa.gov/view_rec.php?id=1453

Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Gulf Stream & Shipping Gulf Stream & Shipping • Ben Franklin first mapped current 1769 • Today satellite photos – Based on changes in surface temperature & color of Stream are used – As postmaster he noted delays in European mail • Valued in sailing races • Saved sailors time wasted fighting the current – Example: Newport - Bermuda race 2002 – Most direct route • Against the current – Winning route • Followed current

http://users.erols.com/gulfstrm/ 3 www.realcities.com/multimedia/philly/inquirer/KRT_packages/archive/slideshow/gulfgraphics/index.html 4 www.philly.com/mld/inquirer/news/special_packages/gulfstream/13415385.htm Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Gulf Stream & Shipping Gulf Stream & Climate • A cold-core ring was forming • Heat – Warm-core rings already present transport – Affects number & type of fish you can catch – Europe much warmer than N. America at same latitude • Ice-free ports • Farming 5 6 www.realcities.com/multimedia/philly/inquirer/KRT_packages/archive/slideshow/gulfgraphics/index.html Garrison Fig. 9.12 p. 208

Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Gulf Stream & Climate Gulf Stream & Climate • Heat • Climate “flip-flop?” transport – Concern that – Prevailing warmer climate westerlies could weaken or blowing over divert current the warm N. – Europe back to Atlantic Ice Age – Europe much • Happened 11k warmer than years ago N. America – Ocean 102 at same latitude 7 www.realcities.com/multimedia/philly/inquirer/KRT_packages/archive/slideshow/gulfgraphics/index.html 8 www.realcities.com/multimedia/philly/inquirer/KRT_packages/archive/slideshow/gulfgraphics/index.html Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Gulf Stream & Weather Gulf Stream & Weather • Temperature contrast • Hurricanes powered by ocean heat & moisture – Also heavy moisture content of air from tropics – Gulf storms get lift from heavy, cold air – Similar to – Shove warm, moist air aloft the way – Condensation takes over to power storms hurricanes form • Rising air • Conden- sation • “Latent heat” 9 www.realcities.com/multimedia/philly/inquirer/KRT_packages/archive/slideshow/gulfgraphics/index.html 10 www.realcities.com/multimedia/philly/inquirer/KRT_packages/archive/slideshow/gulfgraphics/index.html

Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington The Perfect Storm Eastern Boundary Currents • Famous “nor- http://en.wikipedia.org/wiki/Image:GreatBlizzardof2006.jpg • Upwelling affects physics, chemistry, & biology easters” – Supplies nutrients to the surface for production – Low pressure • Upwelling areas are generally the most biologically systems spawned productive areas in the oceans. by clash of Gulf • Green color indicates chlorophyll Stream & cold continental air – Counterclockwise flow gives winds from NE along coast • Animation 11 www.realcities.com/multimedia/philly/inquirer/KRT_packages/archive/gulfstream/part2slideshow/part2flash.html 12 Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Coastal Upwelling Coastal Upwelling • Coastal upwelling is more transient than • Strong upwelling along the coasts on the the large-scale gyre circulation. eastern sides of the ocean basins – Driven by wind & Ekman transport – Especially on a long, straight coastline – Starts and stop within a few hours or days in response to changing winds. – Appears and disappears with the changing U.S. West coast seasons in temperate zones, e.g. Pacific Northwest coast NW Africa – Fluctuations are superimposed on the large- scale mean gyre circulation Peru SW Africa

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Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Coastal Upwelling General Upwelling Principle • Weaker off Europe & W. Australia due to lack • We already looked at equatorial upwelling of long, straight coastline. • Wind blowing parallel to a coastline • Monsoons generate upwelling on Somali – Driven by wind & Ekman transport coast in late summer – Water driven away from shore – Replaced by upward movement of deep water – N. Hemisphere pictured Garrison Fig. 9.16 p. 213 15 16 Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington General Upwelling Principle Northwest Coast • Properties of upwelled deep water • High pressure off West Coast in summer – Cold, nutrient-rich, oxygen-poor – Wind from north & coastal upwelling • Chlorophyll (green-yellow-red) pictured off California – Happens any time of year when winds are from north for 1-3 days – Stops if south wind blows in summer Garrison Fig. 9.16 p. 213 17 18

Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Northwest Coast Northwest Coast • Wind (W) from the north/northwest • Low pressure off WA/OR in winter – Gives offshore Ekman transport (T) – Wind from S/SW & coastal downwelling – Upwelling, lower sea level at coast – Happens any time of year when winds are from south for 1–3 days – Stops if north wind blows in winter

19 20 Garrison Fig. 9.17 p. 214 Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Northwest coast Northwest Coast • Wind (W) from the south/southwest • Seasonal upwelling & downwelling cycle – Gives onshore Ekman transport (T) – Superimposed on long-term average geostrophic • Downwelling, higher sea level at coast current – Summer: California C. stronger, moves onshore – Winter: California C. weaker, moves offshore • Wind-driven downwelling counter-current forms

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Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Northwest coast More Ocean Asymmetry • Upwelling occurs all year off California • Pacific so large, it makes its – Average high pressure persists all year own climate • Accounts for cold ocean temp & SF fog. – Low atmospheric pressure W – Pressure, wind & upwelling weaker in winter • Indonesia & Australia – High atmospheric pressure E • S. American coast – Greater difference in SH summer (Dec.-Jan.) – An East-West convection cell on the Equator • “Walker circulation”

23 24 Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington More Ocean Asymmetry More Ocean Asymmetry • Convection • Convection cell on the Equator cell on the – Dry desert climate in eastern equatorial Pacific Equator – Wet rain forest climate in Indonesia & N. – Driven by Australia difference • Weak coriolis in ocean temperature Trade Winds – Trade winds push water High Pressure westward Low Pressure • Weak Cold upwelled

coriolis water Red = Wet, White = dry 25 Garrison Fig. 9.19 p. 215 26

Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington More Ocean Asymmetry More Ocean Asymmetry • Cold upwelled water in eastern equatorial • Low sea level in E. Pacific & along Equator Pacific & along Equator – Coastal divergence from upwelling • Surface “warm water pool” in Indonesia & N. • High sea level in W. Pacific Australia – Trade winds – Water & Earth’s warms as rotation it flows push water to west to west • Long – Western distance intensification • Weak Ekman 27 28 http://podaac-www.jpl.nasa.gov/sst/images/mcsst.gif http://oceanworld.tamu.edu/students/elnino/index.html Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Sea-Surface Elevation Sea-Surface Temperature • Continuously monitored by satellite “Jason” • Continuously monitored by satellite “AMSR-E” – Anomalies from long-term average displayed – Anomalies from long-term average displayed • An example of near- • An example of cool average conditions equatorial Pacific – May 2006 conditions – Green = average – Jan.-Feb. 2006 sea surface height – White = average – Red = high anomaly sea surface temp – Blue = low anomaly – Blue = low anomaly – Red = high anomaly

29 30 http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17291 http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17180

Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 15 © 2006 University of Washington Pacific Trade Winds Ocean Buoy Array • Continuously monitored by satellite “ADEOS” • Buoys moored along equatorial – Wind speed & direction displayed Pacific • An example of – Wind speed & direction average Pacific – Air temperature conditions – Ocean temperature – Sept. 1996 • Upper 500 meters – White = direction – Each arrow = 1 buoy

– Blue = low wind oceanworld.tamu.edu/students/elnino www.pmel.noaa.gov/tao – Red = moderate wind – Orange = high wind 31 32 http://earthobservatory.nasa.gov/Library/QuikSCAT/QuikSCAT_3.html