D334: Monitoring ocean crrents in the Atlantic


The D334 cruise on RRS Discovery

If you follow a straight line west from the UK across the Atlantic you’ll notice that you end up in northeastern Canada – notorious for cold, bleak winters (see map, right). Why, then, do we not get similar weather in the UK? Well, firstly because there is a large body of water – the Atlantic – directly to our west. Most of our winds flow over the water which acts to warm the air, particularly in winter. But this effect is enhanced by the fact that this water is warmer than it ought to be – thanks to a system of ocean currents known together as the Atlantic Overturning Circulation.  This system includes the well known ‘Gulf Stream’ which flows north along the eastern coast of the United States before peeling off into the north Atlantic (see diagram below).  Below the surface, colder water travels south and whole system is sometimes referred to as the Atlantic Heat Conveyor.

Right: The UK lies at the same latitude as northeastern Canada,
but escapes the harsh Canadian-style winters thanks to the Atlantic Ocean.

Above: The Atlantic Ocean Overturning Circulation brings warm surface waters into
the north Atlantic, whilst colder water below the surface returns south.

Scientists are worried that because of global warming this system of currents may slow down, or even worse (although thought to be unlikely) stop. As a result, a major system of instruments have been placed across the Atlantic Ocean to measure the strength of the circulation. You can see the location of these instruments marked on the ocean floor in the diagram to the left. Our cruise is going to recover information from the ‘Eastern Boundary’, just south of the Canary Isles, and also from the famous ‘Mid-Atlantic Ridge’ region.  This information helps us to continuously monitor the circulation and let’s us look for signs of change.

What would happen if the Atlantic Heat Conveyor switched off? Well, even though we think it is unlikely to happen in the near future, it has happened in the past, causing significant cooling in the North Atlantic region.  The last time scientists are fairly sure it happened was approximately 8 200 years ago as large amounts if ice melted at the end of the last ice age.  We can run computer models to get an idea of what might happen if the same were to happen today and these experiments suggest Britain might cool somewhere between 2-4 deg C. Not quite as dramatic as the movie ‘The Day After Tomorrow’ suggested, but enough to perhaps reduce some of predicted global warming that is likely to happen in the future.

We’re busy preparing our ship - RRS Discovery (right) - to set sail on 27 October. It’s a busy process of loading kit, computers and people onto the ship! Check back soon to meet the team, learn more about the equipment we use, the science we do and what life is like aboard a working research vessel.

The research vessel RRS Discovery in dock at Santa Cruz, Tenerife.

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