2023-04-30 15:00:24
Listening to Francisco Navarro, glaciologist and professor at the Polytechnic University of Madrid is a true delight. Not surprisingly, he has spent a considerable part of his life investigating the different icy surfaces of the planet. His first experience was at the American Amundsen-Scott Polar Station, located at the geographic South Pole, and since then he has participated on a dozen occasions in campaigns in the Antarctic and another seven in the Arctic spread between Svalbard, a Norwegian archipelago located in the Arctic Ocean, and Greenland. As he himself says during the interview, altogether, he has spent more than two years of his life living in the most remote icy regions of our planet.
A glacier – says Francisco Navarro – is a mass of ice that forms the accumulation and compaction of the snow that falls on a place, year after year, when the amount that precipitates is greater than the amount that melts. This is how a frozen volume accumulates in which three layers can be distinguished: the most superficial is formed by the most recent snowfall; Below this is a more compact layer of snow, formed by snow that has spent more than one summer without having melted, although it still retains a quantity of air forming interconnected bubbles, and below the snow is the snow. denser ice, where the trapped air bubbles are isolated from each other, something that makes it possible to recover and analyze the composition of the atmosphere in past times.
The frozen masses of the planet are divided into two large categories: “ice sheets” and glaciers. The ice sheets are huge expanses of snow and ice that are thousands of meters thick and are accumulated in two regions: Antarctica and Greenland. The second category is made up of mountain glaciers and small ice caps, although, as Francisco Navarro comments, these small ice caps can have a surface area as large as the island of Majorca, and a thickness of a few hundred meters, however, very small compared to the 14 million square kilometers and almost 3 kilometers thick that Antarctica has or the 1.8 million square kilometers that the Greenland ice sheet occupies.
Glaciers are frozen masses that flow slowly from the highest regions and can end up on land, where the ice melts and forms a water current, or in the sea, shedding its frozen layer in the form of icebergs. There are more than 200,000 glaciers on the entire planet. For glaciologists, the stream of ice and snow that forms a glacier is a highly viscous fluid that deforms due to the effect of gravity.
There are many factors that can influence the evolution of a glacier: the geometry of the surface, the characteristics of its bed, the inclination of the terrain, the existence or not of liquid water at the bottom, the temperature, etc. Temperature is a determining factor in the behavior of a glacier because when the temperature is higher, the viscosity decreases and the speed of the ice current accelerates. Another consequence of the rise in temperature is the increase in the melting of the ice, the liquid water generated by the melting can percolate to the glacier bed and favor sliding towards lower levels. But each glacier has a different response time to the increase in surface temperature, a rise of one or two degrees in surface temperature can cause changes that in some cases are reflected immediately and in others they can occur years later. .
To study glaciers, georadar techniques are used, a device that emits radar signals from the surface of the glacier towards the bottom and captures the reflected echo when these electromagnetic waves collide with the glacier bed and the changes that take place in the signal when it crosses layers of different densities, such as snow or liquid water. Another way of studying glaciers is done with artificially generated seismic waves, because the transmission of these pressure waves is affected by the different characteristics of the layers they cross. These data are complemented by satellite measurements that constantly measure the height of the glacier surface with a synthetic aperture radar. These observations make it possible to detect changes in the amount of accumulated snow. Finally, the data collected by the different media are used to adjust theoretical models that simulate the behavior of glaciers.
Francisco Navarro, glaciologist, professor at the Polytechnic University of Madrid in the Department of Applied Mathematics to TIC from ETSI of Telecommunications where he directs the Numerical Simulation Group in Sciences and Engineering. Francisco has participated in international projects GLACIODYN y KINNVIKA, of the International Polar Year, and the SvalGlac project, of the PolarCLIMATE program of the European Science Foundation. He was Head of the Spanish Antarctic Base Juan Carlos I during the second phase of the 2006-2007 Antarctic campaign. From December 2017 to November 2021 he was President of the International Glaciological Society and has been awarded the United States of America Antarctic Service Medal.
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