Introduction to Ocean Circulation - Geography 163 Wind-driven circulation of major gyres & surface currents Buoyancy-driven circulation linking the major gyres & the global conveyor belt Coastal circulations & land-ocean interactions Build from physical principles (w/out math)

Approach First principles do “work” Build descriptions from first principles Do not bludgeon students with calculus Work with available data sets

Why do we care? Climate –Global heat & water cycles –Weather & weather/climate prediction Global biogeography & biogeochemistry –Species ranges & adaptation to global change –Fossil fuel CO 2 sequestration Marine resources –Renewable (fisheries) –Non-renewable (oil, etc.)

IPCC [2007] Global Climate Change

Global Heat Transport How can it be constant?

Global Heat Transport

10 15 W = 1 Petawatt

El Niño

SST Departures ( o C) in the Tropical Pacific During the Last 4 Weeks During the last 4-weeks, equatorial SSTs were more than 1.0°C above average between 165°E and 120°W and near the western S. American coast.

Niño Region SST Departures ( o C) Recent Evolution The latest weekly SST departures are: Niño 4 1.0ºC Niño ºC Niño 3 0.7ºC Niño ºC

Recent Evolution of Equatorial Pacific SST Departures ( o C) Longitude Time Since the beginning of June 2009, SST anomalies have been at least +0.5°C across most of the equatorial Pacific. During December 2009, positive SST anomalies increased across much of the equatorial Pacific. From late December 2009 to mid- February 2010, positive SST anomalies decreased across portions of the central and east-central Pacific. Recently, positive SST anomalies have decreased over the central Pacific.

NPP & Climate NPP = Net Primary Production rate of C fixed by phytoplankton Chlorophyll is found in all plants & phytoplankton Averages are from persistently warm ocean (SST> 15C) From Behrenfeld et al. [2006]

NPP & Climate

Biogeography

Biogeographical Boundaries

Biogeography

CO 2 Sequestration It’s gotta go somewhere...

CO 2 Sequestration This is where.

Climate & Fish Pacific Decadal Oscillation Warm phase - southern Cool phase - northern We’re now in a cool phase…

Introduction to Ocean Circulation - Geography 163 Wind-driven circulation of major gyres & surface currents Buoyancy-driven circulation linking the major gyres & the global conveyor belt Coastal circulations & land-ocean interactions

Scales Ocean basins are wide & shallow –Typical scales are 10 4 km across and 5 km deep –“Spit on a basketball” Aspect ratio has important implications –Horizontal velocities are >> vertical velocities –Horizontal property changes are << vertical ones

Global Bathymetry

Hyposgraphic Curve

Wind-Driven Gyres

Global Ocean Circulation

Global Wind Climate

Conveyor Belt

Net Air-Sea Heat Flux

Atlantic Temperature eWOCE gallery –

Atlantic Salinity

Atlantic Oxygen

Atlantic Phosphate

Coastal Upwelling

July 1992 AVHRR Ch 4

Summary Importance of large-scale ocean circulation –climate, biogeochemistry, marine resources Characteristic “Types” of Ocean Circulation –Patterns of circulation can be generalized for different regions –Suggests that dynamical processes are the same –Wind-driven, Buoyancy-driven & Coastal Scales - “spit on a basketball”