You will know crushed ice in a cocktail glass. But for oceanographer filigree crushed ice is an unusual habitat in Antarctica. It occurs under meter thick ice floes and habitat for algae and myriads of small crabs and fish. But actually how powerful are these layers of water ice?Long time that there exists yet another layer of ice under the giant plaice of shelf ice around Antarctica was not known. It is also not easy to recognize, because beneath the solid ice delicate ice crystals form swimming in the icy water.
“Under the ice of Antarctica, it looks in some places like one filled with crushed ice cocktail glass with the only difference being that the crystals in the Southern Ocean. It will grow into Palm-sized millimeter-thin plates”. Describes Oceanographer Mario Haram from Alfred Wegener Institute (AWI) in Bremerhaven.
These unusual layers appear made of water and ice crystals if salt-rich water from the coastal Ocean falls. Slides under the ice shelf and at its bottom slowly melt this portrays.
That sweet melt water mixes this on the underside of the shelf ice with the salty ocean water. This water mix on the spot would freeze on the surface of the sea, because its temperature is well below the normal freezing point. The mix remains initially fluid due to high water pressure at depth.
Due to the lower density this water rises slowly at the bottom of the shelf ice. The water pressure decreases and reaches a critical water depth that tiny ice crystals formed on the spot. These grow into those delicate plates.
Habitat for small crabs and fish
But why is it important to know more about these several meters of thick layers? “…in between the plates flourish countless algae, which constitute the basis of an own ecosystem”, said Hoppmann. “They’re food for myriads of small crabs and fish which find protection from larger predators such as seals and penguins between the ice platelets.” That is why it is so important to know more about the Habitat.
Is he affected by climate change, has also long since swept North and South Pole? Is he in danger? So far researchers only when layers included drilling through the ice tanks at sea to the met. But statements about the size of this important habitat are so difficult to win.
And instruments fail. “Traditional EM instruments which determine the transitions between ice and water with only a single frequency, were unable to distinguish difficult of the sea ice or water”. With the new multi frequency method the AWI researcher can now determine first centimeter transition of sea ice to Habitats and water without to drill holes in the ice with great effort and measure the thickness with tapes.
Multi frequency device provides accurate data on the size of the ice.
“With the multiple frequency EM unit, we could determine not only the thickness of the ice in relatively precision. We could calculate even the volume of the ice from the zone by determine the amount of sea water between the plates and then have subtracted from them”, Hoppmann add.
The AWI researcher have measured the frozen Antarctic Atka Bay in the Weddell Sea with the new measuring devices in the vicinity of German Antarctic research station “Neumayer-Station III”.
The meter was in a kayak, which was drafted by a snowmobile. With the team, the researchers departed the Atka Bay sea ice for weeks. “We have found among other things that the Habitat has annually”, depicts Mario Haram.
“In June, at the beginning of the Antarctic winter, the first platelets gather under the sea ice. In the course of the winter the layer grows, until it is several meters thick in December to the end of winter and then shrink again in the course of the summer.”
Layers of crushed ice are up to ten meters thick
Solid sea ice reaches a thickness of in the section two meters in the winter. She reach water layer filled with ice crystals including average a strength of five meters, according to the researchers. There are also areas, reaching up to ten meters.
The researchers fear that climate change could have an influence on this sensitive Habitat. “One wants to understand the situation of Antarctic ice and estimate a possible impact of climate change must be considered in the future probably also the habitat” Mario Haram said.
You can currently still do not appreciate how large is the Antarctic wide importance of the habitats. But the new results give rise to hopes that its distribution and hence its role soon as be understood how this is managed at its creation.