The September 2012 record low in Arctic sea-ice extent was big news, but a missing piece of the puzzle was lurking below the ocean’s surface. What volume of ice floats on Arctic waters? And how does that compare to previous summers? These are difficult but important questions, because how much ice actually remains suggests how vulnerable the ice pack will be to more warming.
It is relatively easy to determine the surface area of ice in the Arctic. But getting volume and thus measuring depth takes more specialized equipment. We had such a satellite until 2008.
Now there is anew satellite, up since 2010, that can provide the data we need.
In the interim, a computer model was created to fit the data we had based on the surface measurements we could make, along with submarine soundings and other data.
This model extends back to before any satellite data and was used to fill in the numbers while we had no satellite up there.
So, how’d the model do predicting ice volumes while we had no satellite data?
Actually pretty good, if actually slightly underestimating what was happening. The model predicted that total ice volume has dropped between 75 and 80% since 1979.
The new data suggest that the higher value is correct – 80%.
So, a climate model was carried forward for several years without the needed satellite data to confirm it. When we get satellite data back, it is right where the model suggested.
Looks like a validated model and one worth looking at when we talk about the Arctic. It is not just the surface area – which has declined about 50%. It is the volume, down 80%.