The gulf stream – is it drying out?

THERESA ZETTL

Back when I was student at school, I had a geography teacher in 6^th grade that would constantly warn about the gulf stream drying out. I had the same teacher for two years in preparation of my A-levels in geography, and she warned in 2007 even more than a few years before, that the gulf stream will dry out. This year, 14 years after I passed my A-levels I often think of her and her words.

What is the gulf stream?

The Gulf Stream carries warm Atlantic water from the Caribbean to Europe. That is why winters in Europe are not as cold as air masses warm up, providing a milder climate than in North America at comparable latitudes. Off Florida, for example, it travels at 32 million cubic metres of water per second, about 30 times as much as all the rivers on earth transport together. The palm trees on the British south coast would also be unthinkable without the Gulf Stream. Driven by winds, the Earth’s rotation and differences in water density, the warm water flows through the Atlantic and towards the Arctic.

How is it possible to measure, if and when the Gulf stream will dry out?

Only since 2004 has it been possible to measure the strength of the Gulf Stream system directly, via thousands of drifting buoys along its path. To determine what it looked like decades or centuries earlier, proxy data must be used. These are, for example, the water temperatures recorded since around 1870, but above all the seabed, in whose sediments the climatic past is recorded layer by layer. Even before the turn of the millennium, Professor Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research (PIK) predicted that the Gulf Stream could weaken or even dry up because of global climate change. Today, the flow is weaker than ever, but it does not behave linearly.

But what happens if the Gulf Stream really stops flowing?

According to experts, the consequences can hardly be estimated: The water level would rise, especially in North America, and the marine ecosystems would suffer from the probably decreasing oxygen content. In Europe, severe storms are expected – there has even been talk of a new ice age.

Nevertheless, more data is lacking, because reliable conclusions can only be drawn from many years of observations. Until then, researchers – any my former geography teacher – will continue to look at the Gulf Stream with a concerned eye.