ocn 5401 chapter 7 major ocean currents instructor: dr. george a. maul [email protected] / x 7453
TRANSCRIPT
Ocean Circulation has two components
Wind driven (surface)
Thermohaline (deep)
The Wind-Driven Circulation
Benjamin Franklin’s Map Computer Model Map
Warm currents in red; Cold currents in blue.
Global Winds
Arctic Ocean Currents
RV Fram Fridtjof Nansen
Map of the Arctic Ocean showing the routes taken during the 1893–96 Nansen's Fram expedition:RED: Fram's route eastward from Vardø to the Siberian coast, turning north at the New Siberian Islands to enter the pack ice, July – September 1893BLUE: Fram's drift in the ice from the New Siberian Islands, north and west to Spitsbergen, September 1893 – August 1896GREEN: Nansen and Johansen's march to Farthest North, 86°20'N, and their subsequent retreat to Cape Flora in Franz Josef Land. February 1895 – June 1896PURPLE: Nansen and Johansen's return to Vardø from Cape Flora, August 1896YELLOW: Fram's voyage from Spitsbergen to Tromsø, August 1896
RV Fram Expedition
Western Boundary Currents
SSH variability
Eastern Boundary Currents
coastal deserts
Benguela Current
California Current Kon Tiki
Indian Ocean Currents
sea surface temperature
SSH
Modeled SSH, March
Ocean Currents of South Africa
Southern Ocean Currents
dissolved silica
Equatorial Currents
𝑑𝑣𝑑𝑡
=−𝛼𝛻𝑝−2Ω𝑥𝑣+𝑔+𝛼𝛻⋅𝜏
Equatorially trapped currents
ζ+f= constant
El Niño SSTs
La Niña SSTs
ENSO – El Niño Southern
Oscillation
Enso String Quartet
ENSO Teleconnections
http://www.ospo.noaa.gov/Products/ocean/sst/anomaly/
Thermohaline Circulation
Transect along western Atlantic Ocean showing water masses and general circulation processes.
Water Mass Formation
North Atlantic Deep Water (NADW) when warm salty surface water from south cools and sinks to form a deep
western boundary current (DWBC).
Stommel, 1958
Deep Western Boundary Current
You’re kidding, right?
It flows to the south?
The major thermohaline circulation cells that make up the global conveyer belt are driven by exchange of heat and moisture between
the atmosphere and the ocean.
Conventional Wisdom
The Conveyor Belt - but is it correct?
“For the past several decades, oceanographers have embraced the dominant paradigm that the ocean’s meridional overturning circulation operates like a conveyor belt, transporting cold waters equatorward at depth and warm waters poleward at the surface. Within this paradigm, the conveyor, driven by changes in deepwater production at high latitudes, moves deep waters and their attendant properties continuously along western boundary currents and returns surface waters unimpeded to deepwater formation sites. A number of studies conducted over the past few years have challenged this paradigm by revealing the vital role of the ocean’s eddy and wind fields in establishing the structure and variability of the ocean’s overturning. Here, we review those studies and discuss how they have collectively changed our view of the simple conveyor-belt model.” M.S. Lozier, Science, 2010.
OCN 5401
Questions?
Chapter 7