Physical and Dynamical Oceanography CLIM712 Class: 10:30am – 1:15pm, Thursday (Innovation Hall 139) Office hour: 9:30pm – 10:15pm, Thursday (Research I, 106) Bohua Huang Department of Atmospheric, Oceanic, and Earth Sciences College of Science George Mason University Center for Ocean-Land-Atmosphere Studies Phone: 301-902-1246, 703-993-6084
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Physical and Dynamical Oceanography CLIM712 Class: 10:30am – 1:15pm, Thursday (Innovation Hall 139) Office hour: 9:30pm – 10:15pm, Thursday (Research I,
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Physical and Dynamical Oceanography
CLIM712
Class: 10:30am – 1:15pm, Thursday (Innovation Hall 139)Office hour: 9:30pm – 10:15pm, Thursday (Research I, 106)
Bohua Huang
Department of Atmospheric, Oceanic, and Earth SciencesCollege of Science
More readings:• Abarbanel, H.D.I., and W.R. Young, Eds., 1987: General Circulation of the Ocean,
291pp. Springer-Verlag.• Pedlosky, J., 1996: Ocean Circulation Theory, 453pp, Springer.• Siedler,G., J. Church, and J. Gould, Eds., 2001: Ocean Circulation and Climate, 715
pp., Academic Press.• Pedlosky, J., 2003: Waves in the Ocean and Atmosphere, 260pp, Springer-Verlag.• van Aken, H.M., 2006: The Oceanic Thermohaline Circulation, An Introduction. 326pp,
Springer
Useful Online Physical Oceanography Books
• R. H. Stewart: Introduction to Physical Oceanography(http://oceanworld.tamu.edu/resources/ocng_textbook/contents.html)
• M. Tomczak: Introduction to Physical Oceanography (http://gaea.es.flinders.edu.au/~mattom/IntroOc/newstart.html)
• B. A. Warren & C. Wunsch (Ed.,): Evolution of Physical Oceanography (http://ocw.mit.edu/ans7870/resources/Wunsch/wunschtext.htm)
• M. Tomczak, & J. S. Godfrey: Regional Oceanography: an Introduction (http://gaea.es.flinders.edu.au/~mattom/regoc/index.html)
• Fluid dynamics on rotating sphere [Des 7, Dyn 6, 8, 9.1-9.4] – Coriolis force – equations of motion – geostrophy – Ekman layers
• Description of large-scale gyres [Des 7, 9, 10] – wind patterns and gyres – western and eastern boundary currents – polar currents – equatorial currents
• Barotropic dynamics of large-scale gyres [Dyn 9.5-9.14] – vorticity dynamics – gyres and western boundary currents – Sverdrup, Stommel, and Munk
[Numbers in brackets give chapters to read in Descriptive Physical Oceanography, 6th Ed.(Des), and Introductory Dynamical Oceanography, 2nd Ed.(Dyn). Lectures do not cover the entirety of all chapters assigned; students will only be responsible for material covered in lectures. For some topics, additional reading materials will be supplied with class notes]
1). A description of the temperature, salinity, and density patterns in the ocean, including their variability.
2). The three dimensional water movement (the circulation: currents and vertical movements; also, waves and tides).
3). The transfer of mass, energy, and momentum between the ocean and the atmosphere.
4). The mechanisms of these properties and processes.
Simply:• What temperature is the water?• What salinity is the water?• Where is the water going?• Why is that?
A knowledge of the circulation of the oceans; a systematic quantitative description of the character of the ocean waters and of their movements
Understanding large-scale, nearly horizontal, nearly frictionless fluid ocean behaves based on observations of the circulation and water properties
Ocean is a major component of the
earth climate system
Why is ocean important for climate?
Ocean plays important roles in maintaining the earth climate
• Ocean has large heat storage
-- Roughly, 3 meters of sea water has about the same heat capacity as the whole atmospheric column above it -- Ocean heat storage
modulates diurnal and seasonal cycles and climate variations-- Maritime climate is
generally milder than continental climate
• Ocean transfers heat and freshwater over a wide range of time and space scales
-- The earth system is not in local radiative heat balance-- The tropics gaining and the polar regions
losing heat
-- Meridional oceanic heat transport is comparable to that of the atmosphere
Sea surface temperature (SST) changes from year-to-year significantly. The SST anomalies can persist for a long time.
Fluctuations within the ocean affect the climate significantly.
The SST anomalies have serious consequences to the weather and climate
Air-sea interaction is an important source for global climate variability (e.g., ENSO)
Ocean provides the “memory” of the low frequency fluctuations
Global SST Anomaly (0C) and Anomaly Tendency (from CPC)- Negative SSTA presented in the tropical eastern and central Pacific, consistent with La Niña conditions.
- Negative PDO SST pattern presented in N. Pacific.
- Positive SSTA presented in the tropical Indian Ocean and tropical W. Pacific.
- Tripole SST anomaly pattern persisted in North Atlantic, and positive SSTA in the tropical North Atlantic has been near historical high during Mar-Jul 2010.
- SSTA continuously decreased in the central and eastern tropical Pacific, suggesting strengthening of La Niña conditions.
- SST tendency was large in N. Pacific.
- Both positive and negative SST tendency existed in the tropical Indian Ocean.
- Tripole SSTA tendency pattern suggested the persistency and slightly northward shift of the tripole SSTA pattern in North Atlantic.
Fig. G1. Sea surface temperature anomalies (top) and anomaly tendency (bottom). Data are derived from the NCEP OI SST analysis, and anomalies are departures from the 1971-2000 base period means.
Global SST Anomaly (0C) and Anomaly Tendency- Neutral SSTA persisted over the equatorial Pacific Ocean.
- A horseshoe pattern in the North Pacific intensified.
- Negative SSTA prevailed over the extratropical North Atlantic and SST in the tropical Atlantic was above normal.
- Positive SSTA was observed in mid-latitude southern oceans.
- Minor tendencies presented in the central and eastern tropical Pacific.
- The horseshoe pattern of North Pacific further intensified in Jul 2011.
- Small positive and large negative tendencies were observed in the North Atlantic.
Fig. G1. Sea surface temperature anomalies (top) and anomaly tendency (bottom). Data are derived from the NCEP OI SST analysis, and anomalies are departures from the 1971-2000 base period means.
Fig. G1. Sea surface temperature anomalies (top) and anomaly tendency (bottom). Data are derived from the NCEP OI SST analysis, and anomalies are departures from the 1981-2010 base period means.
Global SST Anomaly (0C) and Anomaly Tendency
- Positive SST anomalies presented in the central-eastern equatorial Pacific.
- Large positive SST anomalies presented in the Artic Ocean, subpolar North Atlantic, and along the Gulf Stream.
- Negative PDO-like pattern presented in North Pacific.
- Negative(positive) SST anomalies presented north of Australia (in southeast subtropical Indian Ocean).
- A weak warming tendency presented in the central-eastern equatorial Pacific.
- A strong warming tendency presented in the Artic Ocean, subpolar North Atlantic and the western-central North Pacific.
Atlantic Multi-decadal Oscillation
Figure 5.1. Time series of global annual ocean heat content (1022 J) for the 0 to 700 m layer. The black curve is updated from Levitus et al. (2005), with the shading representing the 90% confidence interval. The red and green curves are updates of the analyses by Ishii et al. (2006) and Willis et al. (2004, over 0 to 750 m) respectively, with the error bars denoting the 90% confidence interval. The black and red curves denote the deviation from the 1961 to 1990 average and the shorter green curve denotes the deviation from the average of the black curve for the period 1993 to 2003 (IPCC Report).
Global ocean circulation may be changed fundamentally by climate change
And the oceanic circulation change will feedback seriously to the earth climate.
-- T and S distribution affects phytoplankton-- Current affects the concentration and dispersion-- Mixing and upwelling are important to provide nutrients-- Phytoplankton changes the ocean color-- Phytoplankton represents the first link in the marine food web-- Phytoplankton has a major role in the global carbon cycle-- An indicator of circulation change-- Biological feedback to circulation?
ocean circulation and marine biology
As indicated by the red (warm) region off the west coast of Peru (top image), El Niño was still going strong in February 1998. Phytoplankton were growing just to the north of the equator (bright blue green region in the image second from top). By February 1999 La Niña had replaced El Niño, and the equatorial Pacific had strong phytoplankton production (bottom pair of images). Images by Robert Simmon based on data from the Distributed Active Archive Centers at the JPL and GSFC
Ocean Color and El Niño
Knowledge of ocean circulation, especially coastal processes, is helpful for environmental sciences
-- pollution
-- oil drilling
-- oil spills
-- sewage outfalls
-- industrial waste
The approach of physical oceanography research
• observations to get the basic phenomenon• applying laws of physics to explain the
features we find (hypothesis/theory)• theory leads us to find new information to
verify its predictions (more observation)• new observations test (verify, modify, or
disprove) the theory (improved theory)• general circulation models blurs the boundary
between traditional physical and dynamical branches
How do we do it?
Figure 1.1 Data, numerical models, and theory are all necessary to understand the ocean. Eventually, an understanding of the ocean-atmosphere-land system will lead to predictions of future states of the system (From Stuart 2007).
Gulf Stream: An Example
Questions:
Why does the Gulf Stream concentrate near the western boundary?
What determines its width and speed?
Why are there meanders and rings?
Any climate significance?…….
A Brief History of Oceanographic Exploration
Surface Oceanography- major approach prior to 1873
Systematic collection of phenomena observable from the deck of sailing ships (marine winds, currents, waves, temperature etc.)
Examples:Halley’s charts of the trade-winds (1685); Hadley(1735)Franklin’s map of the Gulf Stream (1769)Maury's Physical Geography for the Sea (1847)Pillsbury's measurements of the Florida Current (1885)
The 1786 version of Franklin-Folger map of the Gulf Stream
Oceanographic ExpeditionsWide range survey of surface and subsurface oceanic conditions
Program (1985-1995)World Ocean Circulation Experiment (WOCE,
1991-1996)Joint Global Ocean Flux Study (JGOFS)
World Ocean Circulation Experiment: Tracks of research ships making a one-time global survey of the oceans of the world
Some Theoretical Milestones• 1775 Laplace's published his theory of tides. • 1800 Rumford proposed a meridional circulation of the ocean with water
sinking near the poles and rising near the Equator.• 1905 Ekman published his paper on wind-driven oceanic boundary layer.• 1910-1913 Vilhelm Bjerknes published Dynamic Meteorology and
Hydrography which laid the foundation of geophysical fluid dynamics. • 1942 Publication of The Oceans by Sverdrup, Johnson, and Fleming, the
first comprehensive survey of oceanographic knowledge. • 1947-1950 Sverdrup, Stommel, and Munk publish their theories of the wind-
driven circulation of the ocean. Together the three papers lay the foundation for our understanding of the ocean's circulation.
• 1958 Stommel publishes his theory for the deep circulation of the ocean.• 1969 Kirk Bryan and Michael Cox develop the first numerical model of the