Bibliography - Whit G Anderson
- Gnanadesikan, Anand, and Whit G Anderson, February 2009: Ocean water clarity and the ocean general circulation in a coupled climate model. Journal of Physical Oceanography, 39(2), 314-332.
[ Abstract PDF ]Ocean water clarity affects the
distribution of shortwave heating in the water column. In a one-dimensional
time-mean sense, increased clarity would be expected to cool the surface and
heat subsurface depths as shortwave radiation penetrates deeper into the
water column. However, wind-driven upwelling, boundary currents, and the
seasonal cycle of mixing can bring water heated at depth back to the
surface. This warms the equator and cools the subtropics throughout the year
while reducing the amplitude of the seasonal cycle of temperature in polar
regions. This paper examines how these changes propagate through the climate
system in a coupled model with an isopycnal ocean component focusing on the
different impacts associated with removing shading from different regions.
Increasing shortwave penetration along the equator causes warming to the
south of the equator. Increasing it in the relatively clear gyres off the
equator causes the Hadley cells to strengthen and the subtropical gyres to
shift equatorward. Increasing shortwave penetration in the less clear
regions overlying the oxygen minimum zones causes the cold tongue to warm
and the Walker circulation to weaken. Increasing shortwave penetration in
the high-latitude Southern Ocean causes an increase in the formation of mode
water from subtropical water. The results suggest that more attention be
paid to the processes distributing heat below the mixed layer.
- Anderson, Whit G., Anand Gnanadesikan, and Andrew T Wittenberg, in press: Regional impacts of ocean color on tropical Pacific variability. Ocean Science. 12/08.
[ Abstract ]The role of the penetration length
scale of shortwave radiation into the surface ocean and its impact on
tropical Pacific variability is investigated with a fully coupled ocean,
atmosphere, land and ice model. Previous work has shown that removal of all
ocean color results in a system that tends strongly towards an El Niño
state. Results from a suite of surface chlorophyll perturbation experiments
show that the mean state and variability of the tropical Pacific is highly
sensitive to the concentration and distribution of ocean chlorophyll.
Setting the near-oligotrophic regions to contain optically pure water warms
the mean state and suppresses variability in the western tropical Pacific.
Doing the same above the shadow zones of the tropical Pacific also warms the
mean state but enhances the variability. It is shown that increasing
penetration can both deepen the pycnocline (which tends to damp El Niño)
while shifting the mean circulation so that the wind response to temperature
changes is altered. Depending on what region is involved this change in the
wind stress can either strengthen or weaken ENSO variability.
- Anderson, Whit G., Anand Gnanadesikan, Robert W Hallberg, John Dunne, and Bonita L Samuels, June 2007: Impact of ocean color on the maintenance of the Pacific Cold Tongue. Geophysical Research Letters, 34, L11609, doi:10.1029/2007GL030100.
[ Abstract ]The impact of the penetration length scale of shortwave radiation into the surface ocean is investigated with a fully coupled ocean, atmosphere, land and ice model. Oceanic shortwave radiation penetration is assumed to depend on the chlorophyll concentration. As chlorophyll concentrations increase the distribution of shortwave heating becomes shallower. This change in heat distribution impacts mixed-layer depth. This study shows that removing all chlorophyll from the ocean results in a system that tends strongly towards an El Niño state—suggesting that chlorophyll is implicated in maintenance of the Pacific cold tongue. The regions most responsible for this response are located off-equator and correspond to the oligotrophic gyres. Results from a suite of surface chlorophyll perturbation experiments suggest a potential positive feedback between chlorophyll concentration and a non-local coupled response in the fully coupled ocean-atmosphere system.
Direct link to page: http://www.gfdl.noaa.gov/bibliography/resultstest.php?author=1131
