Sunday, May 5, 2013

Weekend Links

  • The above shows estimates of the maximum volume of ice in the Arctic each winter (red), and the amount of it melting each summer (blue).  When the two curves meet, then the Arctic will be ice free in September.  Hard to see how it's more than a decade off.  Could even be just a couple of years off if the noise goes the wrong way.  At any rate, it's a done deal I think.  We are irrevocably committed to having melted the North Pole, and now we get to find out the consequences.
  • Australia slowing down due to (relative) slowdown in big Asian economies.
  • New nationalist party making gains in the UK.
  • Putative new motto for Silicon Valley: First Security, then innovate.  Good luck with that.
  • Interesting essay on why we tell children so many stories about animals.
  • Early wildfires bode ill for California.  Below is a NOAA map for the soil moisture anomaly across the US as of yesterday.  A lot of California has 4-7" less water in the soil profile than a normal year (1971-2000 is the base period).  That's a lot.  Given that the rainy season there is over by now, there's no way to make it up.  So likely this is going to be a rough fire year.  And a lot of the western US looks only slightly better off.


James said...

Stuart - an article on Der Spiegel echoes your concerns that "the digital revolution" is starting to "destroy jobs faster than it is creating them", and discusses some research from MIT on the issue:

TransparencyCNP said...

I've been thinking that an indicator of peak resources would be the percentage of the world economy devoted to resource extraction. Not sure what I mean by that exactly. I've found these Australian charts:

and some USA info:

Do you know of any global data that would be a good representation of resource extraction effort?

Chris Reynolds said...


My comments about that graph (sea ice volume loss during the melt season and sea ice maximum annual volume) were perhaps too obscure, I often write too much for my regular readers. First I should confirm this data is from the PIOMAS model, which in my opinion the best available proxy for sea ice volume.

There are two reasons why the convergence of those trend lines may not occur, although I am in a minority (of one?) of amateurs following sea ice in still 'clinging to' this line of reasoning.


Sea ice grows to an equilibrium thickness of the order of 2m thick, due to the insulation of ice increasing as it thickens, and the time available for thickening from open water (the ~6 months of polar darkness). As we have seen more open water at the end of the melt season in September so there has been an increase in volume production of ice. This is simply by virtue of the fact that more volume grows to thicken ice from open ocean to 2m thick, than does to thicken 1m thick ice at the end of the season to 2m thick in April. This is a negative feedback and is termed the 'thickness growth feedback.

Unlike area/extent which sees a peak in March, volume peaks in April. This is because even while the peripheral seas outside of the Arctic are losing ice, thermodynamic growth continues within the Arctic ocean itself.

I think it is possible that the red curve of maximum volume decline could level out within a few years. This would occur if thermodynamic thickening continues at current levels, but overall volume loss during the melt season fails to keep up. Which is point 2.


The melt season losses may not continue along the trend line.

The major issue is that of the transition from FYI to MYI. First Year Ice (FYI) is that which has thermodynamically grown from open water in the preceding year. It has a lower melting point due to brine inclusions, and in the Arctic this matters. Normally we in the mid latitudes think of salt as lowering the melt point of water on roads to stop freezing. However in the Arctic as the temperature rises out of the deep freeze of the Arctic night, it is the FYI which hits melting point first, and is thus more vulnerable to melting (heat) fluxes during the melt season. Another factor that aids loss of FYI is that it is flatter than MYI so holds melt ponds better, melt ponds absorb more solar radiation. Multi-year ice (MYI) grows thicker from compression and ridging, and thickens far more than 2m, it has less brine inclusion and is more mechanically robust, with a higher melting point.

I suspect that much of the increase in seasonal volume loss is due to the transition from MYI to FYI. If so there may be one-off gains in melt season volume loss occurring which will not proceed with time as my admittedly naïve extrapolation suggests.

Thus it is feasible that we could hit a point where the ice volume levels as thermodynamic growth dictates a maximum volume, and the melt season is not quite able to dispense with that volume of ice by September. In such a state a reduction of thermodynamic thickening by warming of the winter atmosphere and/or ocean would be necessary to break the impasse.

This year is particularly important and exciting because now there is so little MYI and so much FYI. What happens this year may help to throw light on the situation.

There is little in the literature that I've read which throws light upon this issue. I could name about seven other amateurs who's opinions I hold highly. However I stress that all of them disagree with the notion I have outlined in this overly long reply - citing instead the year on year volume loss as evidence of a substantial energy imbalance which will drive the system past the sort of obstacle I outline here. Our debate on this issue is suspended to all intents and purposes pending what follows in the years to come.

Sorry for not being more clear in my original post. But I'm sure you can appreciate the difficult balance between brevity and being comprehensive.

Stuart Staniford said...

Chris - no need to apologize - I just stole your graph and put my own spin on it!