The oceans and sea-ice play an important part in the global climate
system. In particular, the large thermal inertia of the oceans,
and the consequent long timescales of adjustment, means an accurate
representation of ocean processes is critical for realistic climate
simulation. For many years, in the Hadley Centre and elsewhere,
the relatively coarse horizontal ocean resolution used has meant
these models have had to adjust the heat and freshwater fluxes at
the ocean surface to produce realistic simulations. In the latest
HadCM3 version of the model, a 1.25° ocean grid is used and
heat and freshwater transport processes are better represented than
before. This has been a major factor in the ability of the model
to run without the need for flux adjustments.
The ocean component of HadCM3 contains the following features:
a 1.25° x 1.25° latitude/longitude grid with 20 vertical levels,
Gent and McWilliams (1990) mixing as implemented by Visbeck et al
(1997), a hybrid Kraus Turner and K-theory mixing scheme, a simple
overflow parametrization and Levitus (1994) initial ocean temperature
and salinities. The coupled model has been run for over 1000 years
and has been extensively used in climate change simulations.
The Ocean Model Validation and Techniques Group performs two tasks.
In our validation work (which is part of the programme of the Hadley
Centre for Climate Change) we confront the climate configurations
of the ocean model with our knowledge of the real world, derived
from oceanographic observations of many kinds. The aim is to assess
how well the model is performing for key oceanic aspects of the
climate system, and to understand any important discrepancies between
the model and the observations. The ultimate aim of this understanding
is to help us develop improved climate models and so reduce uncertainty
in climate projections.
The group also co-ordinates technical developments to the Met
Office's Unified Model (UM) ocean code. This code is used by all
the ocean modelling groups in the Met Office, and some outside,
and provides a flexible modelling environment for a wide range of
deep ocean modelling applications.
Some examples of current topics of the group's work are listed
below and can be found by clicking on the following links.