Monday, May 31, 2010

Sea ice volume

Arctic sea ice has an average volume of 28,600 cubic kilometres at the end of April, the freeze. It has an average volume of 14,400 at the end of September, the thaw. (note: this is the average over the satellite period, and it is likely that the averages were at least slightly higher immediately prior to this period).

Since the satellite record began, Arctic sea ice volume has declined at a rate of 340 cubic kilometres per year.

From 2002 to the start of 2010, sea ice volume declined at a rate of 800 cubic kilometres per year. At that rate, by the end of this year sea ice volume should be 7,900 cubic kilometres below the long-term average. Over the longer term, that would mean an end to summer Arctic sea ice by 2020 (more than 14,400 cubic kilometres of volume loss).

However, at present, sea ice volume is 9,500 cubic kilometres below the long-term average. If we assume that it stays there until the end of the year, we will have had three year's worth of decline in a single year.

I believe that my prediction for 2014 as the year we first get an ice-free summer is a pretty good one. It should be noted that the scientist who works most closely with the direct data (which is partly gathered from submarines from the US Navy using sonar to scan the ice from beneath) predicted an ice-free summer for 2013 way back in 2003. His name is Dr Wieslaw Maslowski.

A link to the page with my bet with Willis Eschenbach:

Friday, May 28, 2010

Rain/Inflow thus far this year

We have had close to 270 mm of rainfall this year. With what is expected over the weekend, we may top 300 mm, which is very good for this time of the year.

Inflows to dams, however, are not proceeding as well. My previous prediction that we would hit close to 23,000 megalitres from the good rainfall in April did not eventuate. We have received 22,400 megalitres as of today. We should, based again on predictions for some catch-up and for the predicted rainfall, exceed 25,000 megalitres some time in the next two weeks.

I am downgrading my prediction for total inflow for the year to 60,000 megalitres. This has been a very bad year for megalitres of inflow per millimetre of rainfall - the worst, from what I can gather, on record. But we will still receive much more inflow than last year, simply because we are having an above average rainfall year.

Monday, May 17, 2010

Arctic Ice

This is not something that I have blogged on previously, but new information has come to my attention suggesting that arctic summer sea ice may be gone even before Canberra's water. The above graph is from here:

This graph shows the daily ice volume anomaly. At present, we are heading for record low ice volume by the end of this year's northern summer.

Compare the above graph with this image:

This second graph is from here:

The second graph only uses data up until 2004. However, even given that, it is projecting the end of summer arctic sea ice by sometime this decade. The observations in the first graph not only confirm the projection based on the 2004 data but suggest that things have started to get worse. With the median projection is that summer sea ice will be gone by around 2014, it is getting more and more probable that it will disappear in the next two or three years.

For clarification, the two graphs have a different scale: 10^3 kilometres cubed for the first one and 10^4 kilometres cubed for the second one.

I should also add that personally my bet is for around 2014, even with the new data. Solar maximum will be somewhere around that time and that increases the likelihood of something bad happening.

And an interesting link on daily temperatures in the Arctic.

And the link to the historical data for sea ice area and extent used by the nsidc:

Wednesday, May 5, 2010

Current rainfall versus inflow

For the year thus far, we have had 260.8 mm of rain, above the average. The indications are that we will get around 700 mm in total this year, assuming past years are a reasonable guide.

We have had 20,704 megalitres of dam inflow thus far this year, although I would add around 2,000 megalitres to that for the rainfall that we have received in recent days. Call it 23,000. This means that I project we will get 65,260 megalitres of inflow this year, much more than last year. However, this would still equate to less than 35 per cent of average annual inflow, showing the dangerous state of our water situation.

To spell out what this means, we used to get about 180,000 megalitres of inflow per year, on average, with an average rainfall of around 630 mm per year. If the year plays out roughly as I expect, we will be getting 10 per cent more rain than that average but only around a third of the average inflow into our dams.

Something is broken in the hyrdological system. It could be the subsurface soil structure; it could be transpiration and evaporation rates; it could be that *where* the rain is falling has shifted. Is it climate change? Yes. Is it going to get worse? Yes.

Take action now, people. If we wait until mid-decade, Canberra will be facing a disastrous water situation.