Privileged Planet: carbon cycle under ice sheets (Introduction)

by David Turell , Saturday, August 17, 2019, 14:50 (1714 days ago) @ David Turell

Very new finding shows how carbon is sequestered under ice sheets and melt water provids nutrients to the oceans:

https://wattsupwiththat.com/2019/08/16/ice-sheets-impact-core-elements-of-the-earths-ca...

"The Earth’s carbon cycle is crucial in controlling the greenhouse gas content of our atmosphere, and ultimately our climate.

"Ice sheets which cover about 10 percent of our Earth’s land surface at present, were thought 20 years ago to be frozen wastelands, devoid of life and with supressed chemical weathering – irrelevant parts of the carbon cycle.

"Now a world-leading international team, led by Professor Jemma Wadham from the University of Bristol’ School of Geographical Sciences and Cabot Institute for the Environment, have pulled together a wealth of evidence published over the last 20 years to demonstrate that ice sheets can no longer be regarded as frozen and passive parts of Earth’s carbon cycle.

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"Professor Wadham said; “A unique set of conditions present beneath ice sheets make them important reactors in the Earth’s carbon cycle.

“'Here, grinding of rock by moving ice is high, liquid water is abundant and microbes thrive in melt zones despite inhospitable conditions – the ice sheets erode their bedrock, cold-adapted microbes process the ground rock and boost nutrient release and glacial meltwaters export this nutrient to the oceans, also stimulating the upwelling of further nutrient from depth at glacier marine margins.

“'All this nutrient supports fisheries and stimulates drawdown of carbon dioxide (CO2) from the atmosphere.”

"Co-author Professor Rob Spencer from Florida State University added: “Ice sheets are also very effective at storing vast amounts of carbon as they grow over marine sediments, soils and vegetation.

“'The Antarctic Ice Sheet alone potentially stores up to 20,000 billion tonnes of organic carbon – ten times more than that estimated for Northern Hemisphere permafrost.

“'Some of this carbon is released in meltwaters and fuels marine food webs. The carbon that is left behind in deep parts of ice sheets is converted to methane gas by microbial and/or geothermal activity, which has the potential to be stored as solid methane hydrate under low temperatures and high pressure conditions.

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"The study also takes a walk back in time to the last transition from glacial (cold) to interglacial (warm) conditions of the present day, analysing ocean cores around Antarctica for clues which might link ice sheet nutrient (iron) export via Antarctic icebergs to the changing productivity of the Southern Ocean – an important global sink for carbon.

"Co-author, Dr Jon Hawkings from Florida State University/GFZ-Potsdam, said: “One important way that the Southern Ocean takes carbon out of the atmosphere is by growth of phytoplankton in its surface waters.

“'However, these tiny ocean dwelling plants are limited by availability of iron. We have long thought that atmospheric dust was important as a supplier of iron to these waters, but we now know that icebergs host iron-rich sediments which also fertilise the ocean waters as the bergs melt.”

"Professor Karen Kohfeld, a palaeo-oceanographer and co-author from Simon Fraser University, added: “What you see in ocean cores from the sub-Antarctic is that as the climate warmed at the end of the last glacial period, iceberg sediment (and therefore, iron) supply to the sub-Antarctic Southern Ocean falls, as does marine productivity while CO2 rises.

“'While there are many possible causes for the CO2 rise, the data tantalizingly suggests that falling iron supply to the Southern Ocean via icebergs could have been a contributing factor.'”

Comment: Another evidence of the built-in systems that stabilize this planet to support life. We started as a simple rocky planet with oceans and at an ideal distance from a stable star and evolved to today's conditions. Not by chance considering all the variables that needed to be just so.