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
Increased melting in winter and spring of sea ice on the Okhotsk Sea could be partly to blame for the recent run of wet summers in the UK. That’s according to a poster at DACA-13 by James Screen of the University of Exeter, who reckons the Okhotsk Sea could be in a ‘sweet spot’ for affecting general global circulation and storm tracks because of its location relatively far south.
Screen’s simulations indicate that the reduced ice cover could set up a quasi-stationary Rossby wave train with low pressure over the North Pacific, eastern US and Europe and high pressure over the central US and Atlantic.
The cause of the recent trend for wet summers in the UK is likely to be a combination of natural variability, sea ice changes, the Atlantic Multidecadal Oscillation, and ‘other factors we are still grappling with,’ Screen said.
By Liz Kalaugher
It wasn’t until remote-sensing specialist Andreas Kääb of the University of Oslo flew over Canada’s Lawrence River and saw floating ice that he came up with an application for the time delay that occurs when satellites take stereo images to map elevation. This delay, which is otherwise an irritation, could in fact be used to measure the motion of ice over periods of just a minute or so, he realised.
By James Dacey
Advances in satellite technology are giving us fresh opportunities to monitor the Earth’s geography and track changes over time. During a recent visit to San Francisco, I got the chance to meet a few of the scientists who use such data to develop a better understanding of global processes. I met them alongside a giant screen, which was part of a NASA exhibition at the annual meeting of the American Geophysical Union.
In this first video interview, I meet NASA scientist Compton Tucker, who is interested in deforestation in the Amazon rainforest. He uses the screen to show me images of a region in north-west Brazil as captured by satellites from the Landsat Program, which has been collecting images since 1972. Tucker explains how he uses these images to identify where deforestation has increased over time and why these changes have occurred.
Tucker says that this information is useful for a number of reasons, including climate studies, because it can help to quantify the amount of carbon dioxide released as a result of deforestation. He explained that scientists collect the data and integrate them with scientific observations obtained on the ground. It was also interesting to hear about Tucker’s adventures in the jungle, particularly his experiences meeting the locals.
In this second video interview, I meet another NASA scientist, Eric Lindstrom, who uses the screen to show me an animation from NASA’s ECCO2 project. This project is designed to create an accurate model of the world’s oceans and sea-ice based on data collected by a whole fleet of satellites. He showed me how the model can identify the extent of turbulence in the oceans in the form of eddy currents.
If you enjoy these videos, then you may also be interested in one of the articles in the March issue of Physics World. It features a series of images focusing on different aspects of planet Earth, including the varying sea-surface temperatures and the elevation of the land surface. You can download a free PDF of this special earth-science issue via this link.