December 9, 2022

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weather changes.  Methane emissions from fjords.  new discovery

weather changes. Methane emissions from fjords. new discovery

The journal reports the latest findings regarding methane emissions from fjords Lakes and Oceanography Letters.

fjords They are narrow bays surrounded by steep beaches. They can press the Earth up to several hundred kilometers and have a depth of more than one kilometer. Fjords were created in ice Age – They were uprooted with blocks of ice and stones. It is relatively rare – it makes up only 0.13 percent. The surface of all oceans on Earth.

During severe storms, layers of water in oceanic fjords mix, oxygenating the water near its bottom. However, the storms themselves also increase methane emissions from the fjords into the atmosphere.

Scientists from the University of Gothenburg estimated that the total greenhouse gas emissions from the fjords are as high as that of all areas of the deep sea, which cover 84%. The world’s seas and oceans.

– It has been known for some time that many fjords have anaerobic environments closer to the sea floor, and that methane is formed in bottom sediments. Normally, only a small part of this gas reaches the atmosphere as it decomposes as it rises through oxygen-rich water near the surface. But in our research, we recorded high methane emissions when waters mixed in the fjord during storms, for example, he says. Stefano BonagliaMarine geochemist at the University of Gothenburg.

The detection and estimation of methane emissions to the atmosphere is essential for future climate modeling. Scientists have calculated that Methane emissions cause about 30% of the global warming effect. The contribution of the oceans to methane emissions is much less than the contribution of land areas. However, human activity has increased eutrophication in coastal areas, resulting in larger areas of anaerobic water on the sea floor. This is especially noticeable in the fjords – even though they only account for 0.13 percent of the total area. of the global sea surface, responsible for about half of methane emissions into the atmosphere.

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This is because the fjords deposit carbon-rich remains of marine plants and animals, as well as materials from the surrounding land carried by currents flowing into them. Because the fjords are protected from ocean currents, the water tends to stay in layers with different temperatures and different concentrations of salt and oxygen. Stefano Bonaglia explained that the layers closest to the bottom of the strait are anaerobic regions where methane is formed when matter decomposes in sediments.

Scientists from the University of Gothenburg studied by strait near Uddevalla in 2009-2021 and conducting field studies to measure methane production in the fjord. This strait is a lack of oxygen and nutrients. The Buff River flows into it, bringing with it a high percentage of nutrients from the agriculture of the region. It was evident that atmospheric methane emissions had increased during the storm-induced upheaval of the fjord. The anaerobic seafloor water is then rapidly raised to the surface, taking methane gas with it, which can then be released into the atmosphere.

Methane emissions were high, and American scientists observed the same types of events in the Canadian Straits. We estimate that emissions from all fjords worldwide are of the same magnitude – about 1 teragram (teragram) or one million tons per year – as emissions from the depths of the global oceans have been assumed in our calculations. This is because the distance from the bottom to the surface of the fjord is much shorter than in the depths of the oceans. This causes more organic matter to settle in the sediments and doesn’t have time to break down the methane on its way to the surface, Stefano Bonaglia says, adding that if climate change leads to more extreme weather events, methane emissions may increase, but only by a certain point.

“If there is a sharp increase in severe storms, methane emissions will be reduced as the anaerobic environments at the bottom of the fjords will disappear if the water is mixed frequently,” he explains.