Since sea-ice is already in the water, its melting has little effect on sea levels.

ECONOMIST: Getting warmer

And now the Arctic's upper layers are getting less dense, for several reasons: melting Arctic glaciers, rising surface-water temperatures, increased precipitation and an absence of salt concentrations resulting from sea-ice formation.

ECONOMIST: The science

And finally, just before you head out to sea, you will pass a series of fascinating ice-making houses where huge blocks of frozen water slide down rollercoaster runners and into the waiting boats.

BBC: Bangladesh��s lesser-known charms

When snow or ice melt, they are replaced by darker melt-water pools, land or sea.

ECONOMIST: Global warming