Climate Dynamics

EPS 231 (Spring 2005)

Instructor: Eli Tziperman,

Day, time & location: Tue, Thu 11:30-1; Room: Maxwell-Dvorkin G135. Additional optional class time (to be used instead of canceled lectures, will be announced here and in class if actually used): Fri 13:00-14:40, Maxwell-Dvorkin G135.

Outline Detailed Syllabus Bibliography Requirements

Announcements Last updated: May 19, 2005.

The exam will be on Monday, May 23 2005, 10:00. You can come pick it up from my office then, and return it to me 24 hours later. If you have any conflicts please let me know, and we can schedule individual times that are 1-2 days before or after this date.
Feel free to write or call me with any questions:
Eli Tziperman; eli AT eps.harvard.edu
* Office hours: call/ write.

Matlab code: THC_3box.m, elnino_delay_model_1994.m, THC_winton_1993.m, circle_map.m,

Homework: HW-ENSO-1, HW-ENSO-2, HW-ENSO-3, HW-ENSO-4, HW-THC-1, HW-THC-2, HW-THC-3, HW-GLACIAL-1, HW-GLACIAL-2

Some of the homework require the manipulation of data. You can find sample relevant data and programs to read and plot it here,

Outline

Climate variability phenomena and mechanisms. From El Nino (3-7 years), thermohaline circulation variability (decadal to centennial), Dansgaard-Oeschger events (millennial), Heinrich events (10kyr) and to glacial-interglacial variability (100 kyr). In each case, we will discuss physical mechanisms and demonstrate them with a hierarchical modeling approach, from toy models to GCMs. Needed background in nonlinear dynamics will be covered. Students are expected to be familiar with basic GFD, planetary waves, etc.

Detailed syllabus

A detailed outline of the lectures, and a complete list of reference materials used in each lecture is available here.

  1. Outline and motivation.
  2. ENSO: main reference is (Cessi et al., 2001); additional supporting material may be found here.
    1. Phenomenology: basics: Gill atmosphere; reduced gravity models, equatorial ocean waves (Dijkstra, 2000), (Gill, 1982).
    2. Coupled ocean-atmosphere dynamics, demonstrated via the Cane-Zebiak model
    3. Delayed oscillator
    4. ENSO regimes: fast SST, fast wave, mixed; recharge oscillator:
    5. Irregularity: chaos
    6. Irregularity: stochastic forcing, non normal dynamics, optimal initial conditions and stochastic optimals
    7. Westerly wind bursts
    8. Locking to seasonal cycle
    9. Atmospheric teleconnections
  3. Thermohaline circulation; main reference is (Dijkstra, 2000); additional supporting material may be found here.
    1. Phenomenology, mixed boundary conditions, Stommel model
    2. Advective and convective feedbacks; flip flop and loop oscillations.
    3. Stability, bifurcations and multiple equilibria
    4. Stochastic forcing; linear vs nonlinear; non normal dynamics, noise induced transitions between steady states
    5. Thermohaline flushes (``deep decoupling'' relaxation oscillations)
    6. Zonally averaged models and closures to 2d models.
    7. Atmospheric feedbacks
  4. D/O and Heinrich events: supporting material may be found here.
    1. DO:THC flushes vs sea ice changes;
    2. Heinrich events: binge-purge oscillator, climatic effects, synchronous collapses
  5. Glacial cycles: supporting material may be found here.
    1. Phenomenology
    2. Milankovitch forcing
    3. Energy balance atmosphere
    4. Ice sheets: mass balance, geometry, parabolic profile.
    5. Glaciology basics: Glenn's law, basic solutions equilibrium profiles of ice sheets and ice shelves.
    6. Simple models of glacial cycles
    7. Phase locking to Milankovitch forcing

Requirements

Prerequisites: basic geophysical fluid dynamics.

Homework will be given throughout the course. The best 80% of the homework will constitute 50% of the final grade. The final exam will constitute the remaining 50%.

Links

Bibliography

Cessi, P., Pierrehumbert, R., and Tziperman, E. (2001).
Lectures on enso, the thermohaline circulation, glacial cycles and climate basics.
In Balmforth, N. J., editor, Conceptual Models of the Climate. Woods Hole Oceanographic Institution, http://gfd.whoi.edu/proceedings/2001/PDFvol2001.html.

Dijkstra, H. A. (2000).
Nonlinear physical oceanography.
Kluwer Academic Publishers.

Gill, A. E. (1982).
Atmosphere-Ocean Dynamics.
Academic Press, Inc, San Diego, CA, 662pp.