Bummer: Global warming allegedly makes the oceans both more salty *and* less salty

Can Geoengineering Stop Global Warming? : Discovery News

Every day seems to bring another bad piece of news about global warming. Just this month, we found out the oceans are saltier than ever and 2010 will probably be the warmest on record, so it's clear that we have a serious problem on our hands.

Flashback [Fred Pierce, New Scientist]: Arctic meltdown is a threat to humanity

There is another concern about Arctic melting: the growing amount of fresh water flowing into the Arctic Ocean. The shrinking thickness and extent of sea ice has added a huge amount of fresh water already. Meanwhile, rivers are pouring up to 10 per cent more water into the ocean than they did half a century ago. This is partly the result of rising precipitation as the air warms - warmer air can hold more moisture - and partly the result of melting permafrost, ice and snow. Yet more fresh water is coming from the melting of the Greenland ice sheet. As the Arctic warms further, these flows of fresh water will increase.

All this extra fresh water could weaken the pump that drives the thermohaline circulation, or ocean conveyor current. Its most famous element is the Gulf Stream in the North Atlantic, but the conveyor travels all the oceans. It has its beginnings in the far north of the Atlantic, off Greenland, where unusually dense water plunges to the ocean floor. The water becomes dense here partly because it cools and partly because the formation of sea ice increases salinity. As the water gets a bit warmer and a bit less salty, thanks to all the extra fresh water, the worry is that the pump could slow down.