Title: The
1The full idealised experiment
The diagram below shows the storm track in the
most realistic idealised experiment (including
three landmasses, the Rocky mountains, the Gulf
Stream and the North Atlantic Drift) and in a
control run performed with realistic boundary
conditions. The effects of removing some of
these components are shown in the surrounding
boxes. The colour scheme and contour lines are
constant throughout all the diagrams.
Realistic lower boundary conditions
Removing the North Atlantic Drift Changes
in surface ocean freshwater budget
Removing the North Atlantic Drift makes the storm
track stronger and more zonal, consistent with
Jacob et al (GRL, 2005). This corresponds to a
southward shift at the downstream end. This is
consistent with a southward shift of the low
level baroclinic region when the North Atlantic
Drift is removed.
Full Idealised model
This plot shows the change in surface freshwater
loss (evaporation-precipition in mm/day) when the
North Atlantic Drift is removed. Reduced loss
over eastern North Atlantic would act to suppress
the THC. However, an opposite signal at high
latitudes would strengthen the THC. The change
in loss for each of the boxes is A0.01Sv,
B-0.07Sv and C0.02Sv.
N
R
G
S
Removing the Gulf Stream
Removing South America
Colours The storm track defined by the 2-6 day
variance in the 850mb geopotential height.
Contour lines with numbers SST (in degC). Thick
lines show the modeled land masses and the 1000m
line on the Rocky mountains. Key modelling
features are highlighted (RRocky mountains,
SSouth America, GGulf Stream, NNorth Atlantic
Drift). Realistic experiment is for DJF track,
courtesy of Mariane Coutinho.
Removing the Gulf Stream along with the (North
Atlantic Drift) weakens the storm track in the
mid-North Atlantic. This is consistent with
reduced low level baroclinicity immediately
upstream of this region.
The South American continent intensifies the
storm track close to the North American east
coast. This is likely to be linked to increased
ascent over South America influencing the Hadley
cell and subtropical jet.