The Catlin Arctic Survey ended safely on Wednesday, but the ice the team measured on the Arctic Ocean was so thin that this may be the last expedition of its kind ever attempted.
Scientists know from satellite images that the Arctic Ocean is a combination of first-year ice, which froze just last October and November, and multi-year ice, which has remained frozen for two winters or longer. Yet the three scientists trekking across the Arctic Ocean, measuring ice thickness and density by drilling holes through it, found first-year ice all along the way.
The average ice thickness the team measured was 1.77 meters. That thickness is similar to the height of an average adult and consistent with what is expected of first-year ice. It is also a little too thin for comfort — as navigator Ann Daniels put it, “You never know who’s going to go through.” On the open ocean, explorers have traditionally felt safer on ice that is at least two meters thick.
It may be that there was almost no second-year ice along the expedition’s route across what was supposed to be some of the thickest ice on the open ocean. Perhaps warmer water temperatures or lighter snowfall are making it difficult for second-year ice to grow thicker than first-year ice. Either way, the measurements confirm what scientists already supposed about the rapid thinning of Arctic ice since the 1970s. It’s a trend that has accelerated in the last two years, raising the prospect that the remaining Arctic ice cover could disintegrate any summer, and almost surely within five years, as soon as the weather is unusually warm or stormy.
Ice is expected to hold out longer in an area north of Greenland and Ellesmere Island, where it has a chance to stay anchored to a frozen shoreline, but as the ice gets thinner, even that depends on the wind. As soon as the wind changes direction in late summer, that ice too would scatter.
The ice melt has followed a normal pattern so far this spring, but ice melt in May mostly clears out sub-Arctic locations such as the Baltic Sea and the Sea of Okhotsk, so it isn’t a good predictor of what may happen on the Arctic Ocean during the summer months. Thin ice melts faster, and the ice on the Arctic is the thinnest we have ever seen in springtime.