Arctic sea levels dropping steadily

Sea levels in the Arctic have been falling by a little more than two millimetres a year — exactly the opposite of what is happening elsewhere.

“It’s enough to be significant. It’s remarkable that it’s the opposite sign of what we see in the rest of the world,” said researcher Remko Scharroo.

A Dutch-U.K. team made the discovery after analyzing radar altimetry data gathered by Europe’s ERS-2 satellite.

Scharroo said in an interview from his home in the U.S. that the drop in Arctic sea levels may be the result of climate change.

“It might mean that the currents are changing. It might be linked to the reasons why we see less sea ice,” Scharroo said.

Scharroo and his colleagues are eager to understand why the Arctic sea level in dropping as “everything indicates the sea level should rise.”

Generally land emerging from glaciers, such as Baffin Island or Greenland, rises, so the sea looks like it’s going down.

But what Scharroo and his team have seen is that the sea is actually dropping, too.

It’s “all contrary to whatever we expect which is what makes it so unique,” Scharroo said.

It’s puzzling because as water gets warmer and less salty, water should take more space. With glacial melt and rising temperatures, there should be more water in the Arctic,not less.

The drop in sea levels may mean that water is flowing out of the Arctic to the south.

The flow of water out of the Arctic could have an impact on the earth’s orbit, as more water settles closer to the equator.

And a lot of water around the middle could cause variations in the rotation of the Earth. Days might even lengthen “as the Earth would get more bulky in the middle” and turn on its axis more slowly.

“It’s similar to a dancer doing a pirouette — once she or he pulls her hands along her body, then she will spin faster and when she stretches out her hands she will go slower. In this case it would be the water that would have a similar effect on the Earth.”

To gather the data used in this study, the ERS-2 satellite flies around the earth and roughly over the poles. Its radar altimeter constantly throws down pulses of microwave energy at the land and sea.

The time it takes for these pulses to bounce back gives the measure of surface height.

Only data gathered over open ocean or water surfaces between cracks in the ice can be used, and this has to be corrected to take account of ocean tides, wave heights, air pressure, and atmospheric effects that might affect the signal.

Scharro said more data still has to be collected, with support from the National Oceanic and Atmospheric Association, because the satellite has only been collecting information for about 10 years.

During International Polar Year, major oceanographic expeditions are planned to bring research vessels into the polar region and gather even more information, which may tell more about why Arctic sea level is dropping.