Earth & climate · the experiment
Flip the cavity
A model ice shelf, a polynya salting the sea, a cavity torn between two oceans. Four questions, from beginner to expert, on the memory of the water beneath the ice.
1 · Turn the salt up, then down
In the model, the offshore deep water is at 1 °C. The team raises the polynya's salt flux step by step, then lowers it the same way.
Beginner
What does the cavity beneath the ice do?
2 · Convert the threshold into sea ice
At 1 °C, a warm cavity turns cold when the salt flux reaches about 0.04 grams per square metre per second. By the authors' conversion, 0.005 matches the salt left by about 5 metres of new sea ice a year.
Intermediate
How much sea ice a year does that threshold correspond to?
3 · Remove the meltwater trap
The team makes the channel's walls frictionless. The gyre that held meltwater in front of the ice disappears, replaced by one large gyre that carries it off to the open ocean.
Expert
What becomes of the switch between warm and cold cavity?
4 · Spot the early sign
You watch a warm cavity in the model while the polynya's salt flux slowly rises.
Expert
Which signal heralds the switch to cold?
Cavity flipped
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