Icy calculation in polar latitudes

Permeability of sea ice follows the universal transport equation

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The polar sea ice melts. How fast, that depends, among other things, on how much salt water flows in and through the floating seep water. A mathematician has now calculated this and found that the seawater follows a universal transport equation and that this may also apply to ice on other worlds, such as the icy Jupiter's moon Europe.

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The sea ice of the polar latitudes is one of the most important indicators of climate change: its thinning and the defrosting of large areas show the effects of global warming most clearly. At the same time, however, it is also a crucial regulator of warming, because the presence of the highly reflective surfaces reduces the heat absorption and thus the heating of the polar oceans. The floating ice sheets, however, are far less massive and impenetrable than it seems: the ice is criss-crossed by millions of the finest pores and channels through which salt-enriched seawater flows. These leach channels and adjacent ice surfaces provide a valuable habitat for a variety of microbial communities. The algae and bacteria in turn form a basis for the marine food webs.

Sea ice follows universal equation

Both for the physical ice behavior and for its role as a habitat, the permeability of the sea ice for the brine is therefore crucial. But so far, this property was hardly explored. Now published in the journal Geophysical Research Letters, Ken Golden, a professor of mathematics at the University of Utah, has now calculated the behavior of water in the caustic channels. On the basis of laboratory measurements, field studies and mathematical models, as well as micro-images of the pore structure of the ice, he came to the conclusion that the sea ice follows the so-called universal transport equation.

"These formulas show a universality. This means that the end result does not depend on the details of the model or system, but only on the dimension of the system, "says the researcher. "While large classes of abstract models obey this principle, real materials often do not. Therefore, it is surprising that a complex real material such as sea ice actually obeys these formulas. "Display

And yet another surprising consequence is this: "This means that nearly the same formulas that describe how water flows through the sedimentary rocks of the earth's crust can also be applied to saltwater in the sea ice leaching channels, although this is a very different microstructure than the rock, "explains Golden. Ultimately, it could also follow that ice on other planets, such as the ice moon Europa, also follows this law.

Albedo and melt more predictable in the future

"One of the most important aspects of polar sea ice is the role it plays in Earth's albedo, " explains Golden. "It's about whether the Earth absorbs or reflects the incoming sunlight. White sea ice reflecting absorbing open ocean. In late spring meltwater pools on the ice surface affect the albedo of the pack ice. The drainage of these ponds is also controlled by the permeability of the ice. "

"Now that we have a much better understanding of how the permeability of sea ice is affected by environmental conditions, such as temperature and salinity, our findings can help to more realistically represent ice in global climate models, " said Golden, "This helps us to make the predictions for the global climate and the effects of warming more accurate."

The results can also help better assess the reactions of polar ecosystems to climate change. "The biological processes in the polar regions are dependent on the salt water flow through the sea ice, " said Golden. ReichenThe rich food webs of the polar seas are based on algae and bacteria that live in the ice and whose nutrient uptake is regulated by the lye canals.

(University of Utah, 11.09.2007 - NPO)