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Andrew Xnn

Interesting that both this year and last, there was a anomalous dip in the measurement around June.

Could it be that melt ponds are more common than in the past and thus throwing off the thickness measurements?

So, rather than then -10 (1000km3), the actual anomaly is perhaps closer to -7 or 8 (1000km3).

George Phillies

If you have a very steep drop in volume, which happens at a slightly earlier date, the difference between this year and last year would have the appearance shown in the difference graph, and would as seen last year nearly disappear near the bottom of the summer. To first order the difference curve would be (dV/dt) Delta-t where V is the volume, dV/dt is the local slope of the volume vs time, and Delta-t is the displacement in the start of melting sideways on the melting curve.

Artful Dodger

Hi Neven,

One of the more interesting predictions for September minimum sea ice extent (SIE) comes from the Polar Science Center at U-Wash. On July 1st, 2011 a PIOMAS model run predicted the evolution of arctic sea ice every 3 days through to the end of September, 2011.

Since the PIOMAS is arguably the most sophisticated model for sea ice, it would be interesting to see how the model forecast from 43 days ago matches up with AMSR-E observations. So let's compare data for August 12, 2011.

  • the AMSR-E graphic was derived from the Uni-Bremen daily sea ice chart, rotated 45 degrees left, and scaled to match the PIOMAS graphic.
  • the PIOMAS graphic was extracted from the July 1 - September 30, 2011 animation published on the U-Wash site.
  • REMEMBER the AMSR-E graph data uses color to represent sea ice concentration, while in PIOMAS color represents sea ice thickness.
  • the ice edge is most critical for evaluating sea ice extent (SIE)
  • to assist visual edge-detection, I have converted both images to grey scale (and labeled them) before creating the blink animation.

Here's the animation:

A short summary of observations follows:


  • generally a remarkably good fit throughout the Arctic
  • there is substantially more sea ice in the Greenland sea now than predicted by PIOMAS on July 1st. A sign of increased advection?
  • Canadian Archipelago and Foxe Basin very good match, showing the East ice-free and some remaining ice in channels in the West.
  • SUBSTANTIAL change in position of the ice pack in the East Siberian/Chukchi seas.
  • the pack edge in this area has migrated approx. 350 km to the ESE.
  • this is a average displacement approaching 10 km/day, and contra to the normal rotation of the Beaufort Gyre.
  • still, the shape and size of the PIOMAS ice edge are well preserved, given the massive displacement.
  • the ice edge in the Laptev sea has receded North faster than PIOMAS predictions, again likely due to the prolonged influence of the Siberian High during July.
  • in the Kara sea, the ice finger pointing South out of the main pack was well-forecast by PIOMAS.
  • rounding out our brief tour of the Arctic Ocean, the Barents sea has also melted out faster than predicted by PIOMAS, with the sea ice edge being 100s of km N of schedule.

Overall, remarkable performance from PIOMAS, correctly predicting the overall pattern of progress for Arctic sea ice melt, Summer 2011 Edition.

Cheers,
Lodger

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