Last week, BBC news reported on a new measurement of the volume of ice in Antarctica, from the Bedmap2 project. The potential sea level equivalent of the Antarctic ice volume is 58 metres. What does this mean? The BBC article explains: “if this ice was all converted to liquid water, it would be sufficient to raise the height of the world’s oceans by 58m”.

I did my own “back of the envelope” calculation using the Bedmap2 numbers (and a few guesses and approximations), and came up with a figure of about 60 metres, close enough to convince me that the BBC explanation of “potential sea level equivalent” is correct. I suspect the actual sea rise would be slightly less, because some of the water would inundate coastal regions, making the oceans larger, not just deeper. Still, 58 metres is a lot.

Ordnance Survey cut benchmark on Bidston Lighthouse

Something about 58 metres rang a bell. Then I remembered the Ordnance Survey benchmark cut into the base of the Lighthouse, near the front door. (The first time I saw this, I mistook it for a mason’s mark. It was a surveyor who explained its significance to me.)

As I reported in an earlier post, the horizontal line at the top of the benchmark is 58.9727 metres (or thereabouts) above mean sea level at Newlyn, Cornwall. So if Antarctica melted, the sea would be lapping at the foot of the Lighthouse, and Bidston Hill would be an island.

We could buy a boat, and invest in a new dioptric lamp in case the Lighthouse is needed again. But surely it’s better to do our bit towards reducing carbon dioxide emissions, and invest instead in solar panels (assuming we can obtain planning permission and listed buildings consent).

There’s another connection between Antarctica and Bidston Hill. NERC, which used to own the Lighthouse and still owns the Observatory, is the research council that funds both the British Antarctic Survey and the National Oceanography Centre. It’s only a few months since the proposed merger of the British Antarctic Survey with the National Oceanography Centre was averted.