The Arctic is losing more of its older, thicker sea ice than in years past despite persistent cold weather throughout the Northern Hemisphere this winter, researchers said. Older sea ice tends to be thicker and have a lower salt content, making it more melt-resistant than new ice. In March, Arctic sea ice is usually at its largest extent and this year the area covered is almost 4 percent larger than in the last three years due to the recent cold weather. However, due to the loss of the older, thicker ice — which has continued to disappear throughout the winter — the sea-ice cover is increasingly vulnerable to melting when temperatures rise. Researchers expect this summer’s melt to mimic last year’s, which was the most extensive summertime sea-ice melt on record. Walt Meier from the National Snow and Ice Data Center said of the slightly increased area of sea ice this year, “It may look OK on the surface, but it’s like looking at a Hollywood movie set — you see the facade of a building and it looks OK, but if you look behind it, there’s no building there.”