On Newsnight Now...Arctic sea ice

biffvernon · Post by **biffvernon** » 09 Sep 2012, 23:39

Ok, Ralph, a fiver says there will still be ice in winter at the North Pole in 20 years.

(I'm less certain that fivers will exist, so that may present a problem when it comes to settling the bet.)

UndercoverElephant · Post by **UndercoverElephant** » 10 Sep 2012, 12:19

RalphW wrote:I have to repeat that for ice to form on water, the water has to reach 0C (actually salt water needs to reach about -2 C), and if the water has been heated in summer to well above freezing ( eg. +10C )

But how can you be so sure that it will be heated in summer to well above freezing?

There's a big unknown here, and it is whether or not the poles will continue to warm up much faster than the rest of the planet even after most of the summer sea ice has gone. Since we don't actually know why the poles are warming much faster than we thought they would, we don't know whether this faster warming is directly connected to the fact that the ice cover is being lost. If there is a connection, then it follows that the rate of polar warming will slow down drastically after most of the ice has gone. If there isn't a connection then we might end up with sea temperatures of ten degrees.

biffvernon · Post by **biffvernon** » 10 Sep 2012, 13:48

UndercoverElephant wrote:If there is a connection, then it follows that the rate of polar warming will slow down drastically after most of the ice has gone.

I don't think so. If an ice free ocean warms more because of reduced albedo it will continue to warm more with continuing low albedo. Or conversely, if the Arctic stayed cold because of the high ice albedo bouncing the radiation away then it won't continue staying so cold when the ice is gone.

Ice melt is a factor pushing for greater polar warming.

PS_RalphW · Post by **PS_RalphW** » 10 Sep 2012, 14:14

If you plot volume ice loss with volume of ice melted each year, it is clear that the volume of ice melted each year is increasing. Net heat input into the arctic ocean is accelerating.

It takes 334J/g to melt ice to water at 0C. The specific heat capacity of water is 4.2J/gC. In other words the same heat energy needed to melt the polar ice cap would be enough to heat the same mass of water from 0C to 80C, or the top 30metres of the ocean to 10C.

Of course, it is not as simple as that, but the numbers are huge.

[edit]

This paper estimates the net increase energy at 1 W/m2 over the arctic - this is enough to heat the whole ocean by 10C to a depth of 1.5M over 20 years. Smaller than my first figure, but still significant, and doesn't include positive feedbacks.

http://bprc.osu.edu/rsl/IST/documents/Kwok.2011.PTO.pdf

Post by **clv101** » 10 Sep 2012, 15:14

RalphW wrote:One third of the winter ice has gone in the last 20 years. With feedbacks setting in, I can see the rest going in a similar time frame.

I don't think that follows.

The only reason a third of the winter ice has gone, is because a lot of the summer ice upon which it adds to has gone.

I've just drawn this chart from the PIOMAS Daily Ice Volume Data. It shows the amount of ice growth each year, generated by subtracting the year's minimum volume from the following year's maximum volume. Even if there was zero summer ice, as is likely to be the case within the decade, there's no evidence in the data that a similar 15+ thousand km3 of ice won't form during the winter. If anything the trend as been for increased winter ice formation.

Mean Mr Mustard · Post by **Mean Mr Mustard** » 10 Sep 2012, 15:53

post deleted

Post by **clv101** » 10 Sep 2012, 15:56

Yes, indeed! I'll edit the above. Thanks.

UndercoverElephant · Post by **UndercoverElephant** » 10 Sep 2012, 16:05

biffvernon wrote:
UndercoverElephant wrote:If there is a connection, then it follows that the rate of polar warming will slow down drastically after most of the ice has gone.
I don't think so. If an ice free ocean warms more because of reduced albedo it will continue to warm more with continuing low albedo. Or conversely, if the Arctic stayed cold because of the high ice albedo bouncing the radiation away then it won't continue staying so cold when the ice is gone.

Ice melt is a factor pushing for greater polar warming.

I'm still not sure about this. The whole planet is warming, but the poles are experiencing a much greater effect than anywhere else. If ice melt is an important factor explaining this, then it follows that if there is no ice melt then the difference will be diminished. In other words, the poles will still warm, but they'll stop warming so much faster than everywhere else does.

Little John · Post by **Little John** » 10 Sep 2012, 18:39

UndercoverElephant wrote:
biffvernon wrote:
UndercoverElephant wrote:If there is a connection, then it follows that the rate of polar warming will slow down drastically after most of the ice has gone.
I don't think so. If an ice free ocean warms more because of reduced albedo it will continue to warm more with continuing low albedo. Or conversely, if the Arctic stayed cold because of the high ice albedo bouncing the radiation away then it won't continue staying so cold when the ice is gone.

Ice melt is a factor pushing for greater polar warming.
I'm still not sure about this. The whole planet is warming, but the poles are experiencing a much greater effect than anywhere else. If ice melt is an important factor explaining this, then it follows that if there is no ice melt then the difference will be diminished. In other words, the poles will still warm, but they'll stop warming so much faster than everywhere else does.

If the themohaline currents shut down as a result of reduced salinity in the oceans (from the ice melt), then there would be less warm water heading to the poles. This would, in itself, reduce the rate of warming at the poles I would have thought.

Cabrone · Post by **Cabrone** » 10 Sep 2012, 22:18

Looks like this year's melt might have drawn to a close now.

This chart shows how much it's speeding up now.

Now it's time to see how quick the ice reforms over the winter.

Like 2007 this has really caught climate scientists with their pants around their ankles.

Ice free by September 2020?

If you'd have suggested that as little as 7 years ago you'd have been laughed out of court, not any more.

PS_RalphW · Post by **PS_RalphW** » 17 Sep 2012, 16:14

Now, we have to think of the entire NH as collecting heat for the Arctic. The difference in required forcing between a seasonally ice free Arctic Ocean and a year round ice free Arctic Ocean is less than the feedbacks from a seasonally ice free Arctic Ocean. That is: when we get to seasonally ice free Arctic Ocean, we are committed to year round ice free Arctic Ocean as the system comes to equlibrium over a period of 50 or 100 years.

http://profile.typepad.com/lewisaaron

This guy did work for Club of Rome, so he is at the doomer end of things, but...