Geoscience Reference
In-Depth Information
Fig. 5 Sea surface temperature (K) anomalies with respect to initial conditions for a HadGEM3 r1.1 and
b HadGEM1. From Hewitt et al. (
2011
). Hewitt et al. (
2011
). This work is distributed under the Creative
Commons Attribution 3.0 License
biases and poor variability are also seen in the tropical Atlantic and Indian Oceans,
affecting the simulation of monsoons in these regions, and also in the midlatitude regions
of the Atlantic and the Southern Ocean, affecting the storm tracks (e.g., Scaife et al.
2011
).
Development of ocean models with improved vertical and horizontal resolution and
physical parametrisations, in parallel with similar development of their atmospheric
counterparts, is helping to reduce SST biases and improve variability (see Sect.
2.2
). The
HadGEM2 Development Team (
2011
) showed how improvements in both the atmospheric
physical parametrisations (which resulted in improved near-surface winds across the
equatorial Pacific) and changes to the background vertical tracer diffusivity in the upper
500 m of the ocean led to improved SSTs and better simulation of ENSO in the HadGEM2
model family. Several recent climate configurations use the NEMO (Madec
2008
) ocean
model (e.g., the MetUM (Hewitt et al.
2011
), EC-Earth (Hazeleger et al.
2011
) and
CNRM-CM5.1 (Voldoire et al.
2012
)). This can also be associated with improved SSTs
(e.g., Fig.
5
).
Ocean circulations are a key part of the global water cycle. The climate of Europe is
strongly influenced by the North Atlantic ocean circulation. Variations of the strength of
the Thermohaline Circulation (THC) or the Meridional Overturning Circulation (MOC) are
in several studies implicated as a main driver for decadal and longer timescale changes for
European and Northern hemisphere climate (e.g., Mignot et al.
2007
, and references
therein). Likewise, variation in the THC is a commonly attributed mechanism for nonlinear
