by Liz Kalaugher
The larger the area of melt ponds on Arctic sea ice in May and early June, the smaller the sea ice coverage will be the following September, Daniella Flocco of Reading University, UK, reported at the European Geosciences Union (EGU) meeting in Vienna. In fact, the relationship is strong enough to make a skilful forecast of September sea ice cover, as Flocco, Reading colleague Daniel Feltham and other team members recently published in Nature Climate Change. It seems that melt ponds reduce the albedo of the ice surface, leading to greater heat absorption and more melting.
Now the team has moved onto the next problem, Flocco explained, namely trapping of melt ponds in the autumn as ice freezes above them. The phenomenon is invisible from the air but the latent heat released as the trapped melt pond freezes delays thickening of the ice layer into the ocean below.
Ignoring trapped melt ponds could cause models to overestimate ice growth in the autumn by around 265 cubic km [figure updated from sq. km, see comments below] over two months, roughly one-quarter of the total ice growth predicted, Flocco has calculated.
From satellite images the researchers estimate that around 20% of melt ponds become trapped as the freeze begins. Ultimately their studies will help them calculate this figure, Flocco and Feltham told environmentalresearchweb at the EGU meeting. Typically ponds remain trapped for a few months under thin lids of ice, becoming increasingly salty; the team plans to investigate this further.
By Liz Kalaugher
It’s not just humans and animals who can affect plants – Earth system processes, whether caused by water, frost, snow or wind, do too. Miska Luoto of the University of Helsinki showed me some of these in action when he assessed topography and disturbance at some of the team’s independent transect sites near the fells of Korkea (High) Jehkas and Iso (Big) Jehkas, where the vegetation had already been surveyed.
By Liz Kalaugher
Last night I slept with my fleece hat pulled down over my eyes in an attempt to stave off an early wake-up call from the Sun, which rises at about 3 am after a midnight sunset. It did nothing for my hair but at least I got a lie-in.
Next on the schedule was a visit to the team’s “classic” sites – where they did their original surveys on the north face of Saana fell three years ago. So far, most of the publications resulting from this work have been about these sites. Originally the plan was to study two 8 x 20 m grid plots that first summer but by the end of the field-work the team had completed six.
By Liz Kalaugher
Sometimes I wish I had more of a head for heights. Saana’s southern slopes are steep. On Tuesday they didn’t just see the installation of temperature kit, they were also the scene for two new vegetation surveys as Peter le Roux extended a transect – a line of measurement points – begun by two other researchers.
First we headed up past some scree to around 850 m, 100 m above the two sites already measured. Here le Roux created an independent point. It’s not part of a grid plot but will help the team get an idea of how the plant-life varies across a wider area. After marking the centre with a small wire hoop in the ground and some orange forestry tape that will biodegrade in about three years, he laid out other markers 5 metres to the north, south, east and west. Each of these compass points in turn was enclosed by a 1 m x 1 m metal frame criss-crossed with cord at 10 cm intervals, like a giant empty crossword grid. Le Roux estimated the amount of each plant occurring in the letter squares to give the percentage vegetation cover overall.
by Liz Kalaugher
Sometimes research can be tough. To protect their new air temperature measurement kit from the sun, the Helsinki research group I’m following this week needed beer cans. Sixty-one of them. So the team has been diligently drinking with the sole purpose of providing test equipment.
Once the challenge was met, Jussi Mäkinen spray-painted the cans white to increase their reflectivity and transform them into white ventilated radiation shields, although he did point out that this removed any sponsorship opportunities. Stakes made from wooden fence posts got the same treatment, along with the addition of a looped cable-tie that will hold an iButton temperature logger.
Out in the field on Tuesday, on the southern slopes of Saana fell, Peter le Roux hammered in 2 or 3 fence posts near the outer edges of six of the team’s study grids, so that the top was 50 cm above the ground. He placed an iButton, which looks like a large watch battery, into the circle of the cable tie, and nailed a beer can “hat” into position. Finally, an extra coating of white paint was in order, just in case.
By Liz Kalaugher
As suspected, on Monday morning the weather took a turn for the worse and we woke to pouring rain. After stocking up on a small plastic spade for taking soil samples (steel could skew the analysis results by introducing extra iron), it was time to head out to the test sites in the valley to the north-west of Saana fell. As we climbed, we left the trees behind, pausing only to sample blueberries, juniper berries and crowberries. The height of the juniper bushes shows the depth of snow in winter, as stems sticking above the snow repeatedly freeze and thaw, and tend not to thrive.
The test sites are staked out by wooden skewers, which as it happens are sold locally under the brand Saana sticks – Saana is also a Finnish girl’s name. Each site consists of a grid 8 metres wide and 20 metres long, with a skewer pushed into the ground every metre, apart from where reindeer browsing for lichen have knocked them over.
By Liz Kalaugher
It’s not every Sunday that ends with eating pizza on a balcony in Finnish Lapland, overlooking a lake while bathed in glorious sunshine. This wasn’t what I was expecting roughly 300 km north of the Arctic circle. Indeed, it wasn’t what some of the researchers who’ve been here before were expecting either – fortunately, despite high numbers of mosquitoes earlier in the summer, they have now disappeared, and the weather, as I expect I’ll find out soon, isn’t always this good. Changeable is the name of the game.
I’ve come to Kilpisjärvi Biological Station in north-west Finland (69°N, 20°E) as part of a European Geosciences Union (EGU) science journalism fellowship to meet Miska Luoto from the University of Helsinki. Together with his eight-strong team, Luoto is studying the plants on and around Saana mountain, including information about vegetation type, soil moisture, soil temperature, soil pH, and topography.
By Liz Kalaugher
Arctic glaciers and ice caps cover an area of 402,000 square km, roughly 55% of the world’s total. But they’re punching above their weight when it comes to sea level rise – although Greenland’s ice sheet is four times larger, it contributes roughly the same amount of melted ice to the world’s oceans. That’s according to Jon Ove Hagen of the University of Oslo, Norway, speaking at the EGU meeting in Vienna.
For example from 2006-2010, around 200 Gigatonnes of ice per year melted from the Greenland ice sheet while the equivalent figure for glaciers and ice caps in the Arctic was 160 Gigatonnes. That said, there is considerable variability around the Arctic region, with some glaciers and ice caps losing mass rapidly and a few growing slightly.
As part of the ice2sea programme, Hagen and colleagues have taken continuous GPS measurements on two fast-flowing outlet glaciers of the Austfonna ice cap in northeastern Svalbard since April 2008. The data indicate that the ice is now moving between two and three times faster than four years ago.
What’s more, around 30-40% of the total ice mass loss is due to calving. Hagen said the ice cap is exhibiting unstable dynamics and the study shows the importance of monitoring calving.
By Liz Kalaugher, at the EGU General Assembly in Vienna
Spring 2011 has seen the largest-ever degree of ozone loss over the northern hemisphere, journalists at the EGU General Assembly in Vienna heard this morning.
This year about 40% of the ozone column above the Arctic has disappeared, breaking the previous record of 30%. The cause? An unusual persistence of cold temperatures in the stratosphere into March, allowing longer lifetimes for the polar stratospheric clouds that enable conversion of pollutant gases into ozone-destroying chlorine.
Arctic sea ice has become one of our bellwethers, in part because for the past 30 years we have been able to watch it expanding and retreating nearly in real time, but also because it definitely obeys the laws of physics.
Recently the extent of Arctic sea ice has decreased fairly steadily. It is also notable that 2007 was a year of record minimum extent (in September), prompting conjecture about the Arctic becoming ice-free soon, with an ice-free September perhaps as early as 2013. However 2008 did not quite match the 2007 record. This year, and the next couple of years, will show us whether 2007 was a blip or the start of something even more serious than the 30-year trend.
I still remember our geography teacher at school starting to teach us climatology by saying “The climate is the average weather”. He went on to tell us about the convention of presenting the climate as “normals”, or averages, over 30 years. One bad summer simply doesn’t add up to a climatic change. But it seems that it is human nature both to get rattled when a record is broken and to forget about the problem when the record-breaking behaviour is not repeated.
Equally, and unfortunately, it is not in human nature to worry much about systems like the climate that evolve over 30-year time scales. It is too easy to make the mistake of thinking that bad things aren’t going to happen for 30 years.
Knowing that sea ice obeys the laws of physics, we should expect replacing bright sea ice with dark open water to illustrate the idea of feedback. The less reflective the surface, the more the radiative heating, and the more the loss by melting, and the less reflective the surface … . In other words, the future of sea ice could start to look much, much worse quite suddenly. However, knowing too that we don’t know everything, we should be concerned about the inability of climate models to agree on the future of sea ice.
Sea-ice predictions come from a couple of dozen large-scale climate models. They diverge wildly over the next century. Many of them don’t even reproduce the recent evolution of sea ice, a clear indication that the modellers have development work to do. Two recent analyses show just how unsure we are about what is coming, but both also offer interesting ideas about how to cope with uncertainty as manifested in poor model performance.
Boé and colleagues point out that the models that do the best job of simulating the past 30 years are also the models that predict the earliest disappearance of sea ice. Using the A1B scenario for greenhouse-gas emissions, considered middle-of-the-road, this happens in about 2060-80 if we agree that disappearance means dropping below 10% of the 1979-2007 average in September. Boé and colleagues explain this observation in terms of the models’ accuracy in describing the proportion of the ice that was thin to begin with, and therefore more at risk of disappearing altogether.
Wang and Overland selected the best-performing models by requiring them not only to come within 20% of the September observations for 1980 to 1999, but to beat the same target for the range of extents observed during the whole year. The thinking is that a model is likely to be more trustworthy if it matches more of the firm evidence. They find, with the six models that qualify, that September sea-ice extent is most likely to drop below about 10% of the recent average in 2030-2050.
Comparing the two studies, Mat Collins prefers to put his money on the later Boé estimate than on Wang and Overland. His reasons are cogent, but I think that the crucial point is to exclude the models that obviously get the recent history of sea ice wrong, something Boé and colleagues do not do.
Our understanding of the laws of physics already gives us the message “Sooner or later”, but focusing on the models that are not obviously wrong – not the same thing as obviously right, of course – the message becomes “Sooner rather than later”.