Melting Fish

There is nothing the British like more than some Fish & Chips – at least for the sake of the following narrative let us believe this.

Imagine you’ve started the new year with the resolution to eat more healthily and ditch the trips to the chippy on a Friday night after work. Let’s say today is Monday. You’ve been to Waitrose (or Booths if you are from the beautiful North) and have managed to get some lovely Salmon fillets in the reduced section. You already have dinner plans for this evening so you put the fish in the freezer to keep it for another day.

Come Friday, you remember your New Year’s resolution and the fish in the freezer, so in the morning you take the fish out and leave it to defrost on the work surface.

In the evening, you arrive back home and low and behold the fish has melted….wait a second, melted? No, of course not, it has thawed. Melting would imply a phase change, i.e. solid to liquid.

Fish doesn’t melt.

Neither does permafrost!

Permafrost thaws. This is something that has popped up in the news, and every time makes me cringe. (So listen up all you science correspondents out there!) Some might say we are arguing about semantics and I say ‘Yes, that is the point!’; the true meaning of the word melting indicates a phase change from the solid to liquid phase – ice becomes water – however permafrost, although it may – and usually does – contain ice, is frozen ground (soil, rocks, organic material). These cannot melt, they thaw!

thawing permafrost core samples

Thawing permafrost core samples.

There is an excellent (and brief) paper that I would recommend to those who are interested in getting the appropriate reference on this topic:
Grosse, G., V. Romanovsky, F. E. Nelson, J. Brown, and A. G. Lewkowicz (2010), Why Permafrost Is Thawing, Not Melting, Eos Trans. AGU, 91(9), 87–87