Frosty future for UK?
30 November 2005
The warming ocean currents that bring tropical waters past Britain's shores have slowed down by a shocking 30 per cent, say seafaring scientists. If the currents stop completely, it could be curtains for Britain's mild climate.
Antenna investigates...
This story is published in Nature on 1 December 2005.
Britain's mild winters are not the norm for our northerly location. Without the Atlantic's warming influence we'd suffer the icy conditions that Moscow and Canada endure. But the ocean's circulating currents bring tropical waters north, releasing their heat into the air and keeping temperatures toastier.
Now scientists from Southampton's National Oceanography Centre have revealed that these currents - sometimes called the Conveyor Belt by ocean experts - have slowed down by about 30 per cent since 1957.
Warm ocean currents stream past our coastline, keeping our climate mild.
Image: FreeFoto.com
Meric Srokosz, ocean-currents expert, National Oceanography Centre
Image: National Oceanography Centre
They are concerned this could signal the beginning of a complete current shutdown, exactly as some climate-change simulations have predicted. How? Ocean expert Meric Srokosz explains... |
'As warm water moves northward from the equator, it cools. Cold water is heavier than warm water, so it sinks - flowing back towards the tropics deep under the surface.
'But climate change is melting Greenland's ice sheet and causing more rain to fall in northern areas. It's this fresh water coming into the ocean that threatens to disrupt the Atlantic's warm-water Conveyor Belt.
Watch this video clip for a quick rundown of how the Atlantic Ocean's Conveyer Belt current works.
Video: NERC
'Fresh water is lighter than salty sea water, so when it mixes with the northbound currents it stops them sinking and returning south. It could put a stop to the whole system.'
Meric Srokosz, ocean-currents expert, National Oceanography Centre
Meric Srokosz, ocean-currents expert, National Oceanography Centre
How odd! The same climate change that's melting polar icecaps could bring chilly winters to northwest Europe - perhaps up to 4 degrees cooler in just 20 years if the current completely shuts off.
Image: FreeFoto.com
To record their latest measurements, the researchers voyaged all the way from the Bahamas off the coast of Florida to the Saharan coast of Africa. Their journey took nearly six weeks, with 125 stopoffs along the route to drop surveying equipment into the depths below.
The seafaring scientists' research ship, Charles Darwin.
Image: NERC
'Our main piece of kit is called a CTD system, which we lower almost to the seabed,' says ocean researcher Hannah Longworth. 'Sensors that continuously measure water temperature, saltiness and depth are attached to a large frame with 24 bottles to collect sea water.
'While the frame is lowered through the water, the sensor measurements are transmitted back to a computer on the ship. Then as we bring the frame up to the surface again, the bottles are closed one by one, giving us sea-water samples from specific depths.
Watch this video clip to see scientists launching and retrieving the CTD system Hannah describes.
Video: NERC
'These measurements tell us how fast the water is moving and in what direction at different depths. When we compared our records to those taken over the last 50 years we saw there is now less deep southward transport of cold waters from the far north Atlantic.'
Hannah Longworth, ocean researcher, National Oceanography Centre
Hannah Longworth, ocean researcher, National Oceanography Centre
Hannah takes water samples from the CTD system's bottles.
Image: National Oceanography Centre
So are we heading for the frosty future that was forecast by Hollywood flick The Day After Tomorrow? Mike Hulme from the Tyndall Centre for Climate Change Research says not.
'All the models that we use to suggest future climate scenarios for the UK already include this kind of current slowdown. These new findings don't change our projections for the next 100 years and certainly don't suggest we'll see scenes like The Day After Tomorrow. We must continue to plan for a warmer climate,' says Mike.
Mike Hulme, climate change expert, the Tyndall Centre for Climate Change Research
Image: Tyndall Centre for Climate Change Research
'We do not know whether the snapshots we studied represent a long-term trend - there are likely to be short-term fluctuations in the Conveyor Belt current. To know for sure, we need to monitor the ocean continuously. Now we've set up 22 new moorings right across the Atlantic that will do just this,' says Hannah.
Scientists launch instrument-laden buoys to monitor the ocean continuously.
Image: National Oceanography Centre