More organic carbon release, but a solution proposal made at the bottom of this post
http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2331.html Hood, E., Battin, T. J., Fellman, J., O'Neel, S., & Spencer, R. G. (2015). Storage and release of organic carbon from glaciers and ice sheets. *Nature Geoscience*. Polar ice sheets and mountain glaciers, which cover roughly 11% of the Earth's land surface, store organic carbon from local and distant sources and then release it to downstream environments. Climate-driven changes to glacier runoff are expected to be larger than climate impacts on other components of the hydrological cycle, and may represent an important flux of organic carbon. A compilation of published data on dissolved organic carbon from glaciers across five continents reveals that mountain and polar glaciers represent a quantitatively important store of organic carbon. The Antarctic Ice Sheet is the repository of most of the roughly 6 petagrams (Pg) of organic carbon stored in glacier ice, but the annual release of glacier organic carbon is dominated by mountain glaciers in the case of dissolved organic carbon and the Greenland Ice Sheet in the case of particulate organic carbon. Climate change contributes to these fluxes: approximately 13% of the annual flux of glacier dissolved organic carbon is a result of glacier mass loss. These losses are expected to accelerate, leading to a cumulative loss of roughly 15 teragrams (Tg) of glacial dissolved organic carbon by 2050 due to climate change — equivalent to about half of the annual flux of dissolved organic carbon from the Amazon River. Thus, glaciers constitute a key link between terrestrial and aquatic carbon fluxes, and will be of increasing importance in land-to-ocean fluxes of organic carbon in glacierized regions. Melting glaciers set to release more organic carbon as temperatures climb - 19 Jan 2015, Robert McSweeney http://www.carbonbrief.org/blog/2015/01/melting-glaciers-set-to-release-more-organic-carbon-as-temperatures-climb/ Melting ice may affect more than sea levels, according to new research. As the earth warms, more of the carbon locked up in glaciers and ice sheets will be released into surrounding rivers and oceans. This means that, as well as pushing up sea levels, melting ice could have unknown impacts on marine life. *Carbon release to increase by half* Glaciers and ice sheets <http://www.carbonbrief.org/blog/2013/08/what-makes-ice-sheets-grow-and-shrink/> cover around 11 per cent of Earth's land surface and hold around 70 per cent of its freshwater. These giant stores of ice also hold organic carbon <http://serc.carleton.edu/microbelife/research_methods/biogeochemical/organic_carbon.html>. Carbon accumulates in new snow and ice, and is released as the glacier melts. A new study, published today in Nature Geoscience <http://dx.doi.org/10.1038/ngeo2331>, finds the release of this carbon will speed up as the Earth warms due to climate change. Around 15 million tonnes of extra organic carbon will be lost from melting glaciers over the next 35 years in the form of tiny dissolved particles, the researchers say. Ice also contains larger 'particulate' carbon, which are like bits of sediment that a river carries. This extra organic carbon is 47 per cent more than we could expect without climate change, and equivalent to around half of what the Amazon river carries each year, the researchers say. Organic carbon provides food for tiny organisms at the bottom of the food web. So the extra carbon flowing into rivers and oceans may affect the plants and animals that live around the ice sheets, the researchers say. Adding organic carbon can also affect the chemistry of water, by making it more acidic, for example. *A research first* The research is the first to estimate the total amount of organic carbon held in ice across the world. Researchers collected measurements of organic carbon concentrations from more than 300 samples of glacier and ice sheets in four continents, as the map below shows. *Scientists collected organic carbon samples across four continents. Photos show examples of a) Alaska, b) Tibet, c) Dry Valley glaciers in Antarctica, and d) the Greenland Ice Sheet. Source: Hood et al. (2015 <http://dx.doi.org/10.1038/ngeo2331>)* Worldwide, glaciers and ice sheets contain about six billion tonnes of organic carbon. But most of it is locked up in the vast Antarctic ice sheet. As the ice melts or large chunks break off, known as calving, the carbon gets released, the paper explains. Around three million tonnes of organic carbon are released from glaciers and ice sheets each year, the researchers say, with around 13 per cent caused by melting from rising global temperatures. Although the Antarctic Ice Sheet holds the majority of organic carbon in ice, it accumulates and loses ice more slowly than mountain glaciers and the Greenland ice sheet. This means the release of organic carbon is relatively small considering how much Antarctica holds, and less than half when compared to mountain glaciers. You can see this in the graph below, which shows the amount of organic carbon that ice sheets and glaciers store and release each year. *Marine food webs* The amount of carbon released from land to ocean around the Earth's poles is currently fairly limited, so more carbon flowing out from melting ice could affect the balance of marine life. As co-author, Prof Robert Spencer <http://www.eoas.fsu.edu/people/faculty/dr-robert-spencer> puts it: "It could change the whole food web. We do not know how different ecological systems will react to a new influx of carbon." Melting glaciers and ice sheets may cause more problems than rising sea levels, Spencer concludes: "The thing people have to think about is what this means for the Earth. We know we're losing glaciers, but what does that mean for marine life, fisheries, things downstream that we care about? There's a whole host of issues besides the water issue." *Are there already some remediation proposals?* Top ice layers are good thermal insulators, and natural heat transfer from the winter cold air to the liquid water under the ice is not very efficient, so the growth of the ice caps is slow and the increase of the thickness limited. The* Zhou and Flynn* strategy for Actic sea ice (Geoengineering downwelling ocean currents: a cost assessment, Clim Change, 71 (1-2) (2005), pp. 203–220) overpasses this problem, and they obtain a thicker ice cap that can last longer in spring and thus reflect more sunlight back to space. But also, during the winter manufacture of the ice by sending a seawater spay in the cold air, the latent heat of solidification (freezing) will be released in the atmosphere: cold ice is created on the ocean surface meanwhile the hot air generated, will by natural buoyancy go upper in the troposphere. So a heat transfer from the surface to a higher elevation has occurred. A similar strategy was previously described for rivers [ *http://www.theguardian.com/environment/2011/nov/15/mongolia-ice-shield-geoengineering* ] <http://www.sciencedirect.com/science/article/pii/S1364032113008460#bib53> or lakes in cold countries. It is as if a thermal bridge was created by the ice canons between warmer water and cold air to bypass the insulation caused by the first thin ice cap. Adapting some of the previous processes to slowdown glaciers melting during summer seems possible. Quite often lakes form below melting glaciers. Those lakes hidden under the snow make the risk of giving jog suddenly, releasing large quantities of water and mud. To prevent avalanches and floods in the summer, some cities upstream of these under-glacier lakes install pumping systems for emptying them as they are formed, and water is discharged into rivers. Instead, at night the water could be pumped up above the level where temperatures remain negative and with snow-cannons used to produce new fresh and clean snow with high albedo. This technique also transfers heat from the water to the air. At lower altitudes thermosyphon heat pipes, as well as other mechanisms to facilitate the sublimation of water, can also help to contain the summer glacier melting. See chapter 3.2 of free open access article* http://www.sciencedirect.com/science/article/pii/S1364032113008460 <http://www.sciencedirect.com/science/article/pii/S1364032113008460> * Renaud de_Richter -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout.
