Anand Gnanadesikan: An annotated (incomplete) bibliography of my work on Southern Ocean winds and eddies and the global circulation
1. Gnanadesikan, A., 1999, A simple model for the structure of the oceanic pycnocline, Science, 283, 2077-2079. PDF
This paper provides a theoretical underpinning for the cartoon of the overturning shown elsewhere on this site. It argues that the key driver of the overturning is how dense water is transformed into light water and how this can be controlled by Southern Ocean winds and eddies. It argues that in models with low vertical and lateral mixing, Southern Ocean winds control the global overturning circulation.
2. Gnanadesikan, A. and R.W. Hallberg, 2000, On the relationship of the Circumpolar Current to Southern Hemisphere winds in coarse-resolution ocean models, Journal of Physical Oceanography , 30, 2013-2034.PDF
This paper followed up on the ideas of (1). It argued that the principal reason for a link between Southern Ocean winds and the strength of the Antarctic Circumpolar Current was that higher winds resulted in more transformation of light to dense water, and thus a higher sea level in the Pacific and Atlantic Oceans (as in the NASA image at left).
3. Hallberg, R.W., and A. Gnanadesikan, 2001: An exploration of the role of transient eddies in determining the transport of a zonally re-entrant current, Journal of Physical Oceanography, 30 , 3312-3330. PDF
This paper considers the role of eddies in balancing changes in winds and thus in buffering the overturning using a simplified representation of the Circumpolar Current.
4. Gnanadesikan, A., R.D. Slater, N. Gruber and J.L. Sarmiento, 2002: Oceanic vertical exchange and new production: a comparison between models and observations, Deep Sea Research, Part II , 49, 363-401. PDF
This paper shows that the theory in (1) does in fact hold in ocean-only models. It is possible by varying the strength of vertical and lateral mixing to come up with models that have the same volume of light water near the surface, but differing pathways of overturning. It also demonstrates that these different solutions result in very different magnitudes of biological productivity, so that if one knew the flux of organic matter out of the mixed layer, one might be able to constrain the magnitude of deep upwelling. However, it found that satellite-based estimates of new production were insufficient to draw such constraints.
5. Gnanadesikan, A., R.D. Slater and B.L. Samuels, 2003: Sensitivity of water mass transformation to subgridscale mixing in coarse-resolution ocean models, Geophysical Research Letters , 30, 1967, doi:10.1029/2003GL018036.PDF
This paper re-examines the ability of (1) to predict watermass transformation rates in models with realistic geometry. It points out that a number of investigators have underestimated the potential impact of the Southern Ocean by not considering the whole ocean.
6. Gnanadesikan, Anand, John Dunne, Robert M Key, K Matsumoto, Jorge L Sarmiento, Richard D Slater, and P S Swathi, 2004: Oceanic ventilation and biogeochemical cycling: Understanding the physical mechanisms that produce realistic distributions of tracers and productivity, Global Biogeochemical Cycles, 18(4), GB4010,doi:10.1029/2003GB002097 PDF
This paper follows up on (4) with new models which allow for realistic deep ventilation through more careful consideration of boundary conditions and new estimates of particle export from the mixed layer. Better agreement between the models and satellite data products in found than in (4) but algorithmic uncertainties still limit using particle export as a strong constraint on upwelling pathway. Radiocarbon, however, may be a stronger constraint.
7. Gnanadesikan, A., R.D. Slater, P.S. Swathi and G.K. Vallis, 2005: The energetics of ocean heat transport, Journal of Climate, 18, 2604-2616.PDF
This paper demonstrates that in two realistic models, wind driving provides the dominant energy source for the overturning. This results in the surprising finding that the mean flow advects heat downwards to depths exceeding 2000m. Because North Atlantic Deep Water is warmer than Circumpolar Deep Water, the mean flow moves heat downwards! The only way this can work energetically is for the flow to be mechanically driven by the winds.
8. Hallberg, R.W. and A. Gnanadesikan, 2006: The role of eddies in determining the structure and response of the wind-driven Southern Hemisphere overturning: Initial results from the Modeling Eddies in the Southern Ocean Project, Journal of Physical Oceanography , 36, 2232-2252. PDF
This paper looks at how the circulation of the Southern Ocean differs at the coarse resolution associated with climate models (figure showing surface speed on left) relative to when eddies (seen as the closed circles on the right) are explicitly simulated. This follows up on (1) and (3) in examining the buffering roles of eddies. We find that the mean structure is noticeably changed, but the response to wind forcing is less sensitive to resolution.
9. Gnanadesikan, A. and 27 others,2006: GFDL's CM2 global coupled climate models- Part 2: The baseline ocean simulation, Journal of Climate , 19,675-697.PDF
This paper documents the ocean circulation in GFDL's coupled climate models developed for the IPCC Fourth Assessment Report. One of the major points of this paper is the impact of changes in winds and eddy parameterization in the solution quality of one of the leading global coupled climate models.
10. Russell, J., K.W. Dixon, A. Gnanadesikan, R.J. Stouffer, and J.R. Toggweiler, 2006: The Southern Hemisphere Westerlies in a warming world: Propping open the door to the deep ocean, Journal of Climate 19 , 6381-5390. PDF
This paper shows that the mean state of Southern Ocean winds in coupled climate models can produce noticeable changes in the uptake of heat and carbon dioxide.
11. Gnanadesikan, A., A.M. de Boer and B.K. Mignone, A simple theory of the pycnocline and overturning- revisited, Past and Future Changes of the Ocean's Meridional Overturning Circulation (A. Schmittner, J. Chiang and S. Hemming, eds.), Geophysical Monograph Series 173, 10.1029/173GM04, 19-32, 2007. PDF
This paper revisits the 1999 paper, showing that while the theory works really well in models where the geometry of the flow is well -constrained, it is not truly predictive when water mass formation regions shift, though it can still provide diagnostic guidance in interpreting the results of such simulations.
