Climate Modeling
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Climate modeling: getting it wrong again

Two recently published scientific studies demonstrate how we often err on the low side when it comes to climate modeling.  Estimates of the amount of carbon released from melting permafrost appear low by up to 100 percent. So, greenhouse gas emissions from Arctic permafrost are twice as high as previous climate modeling predicts. On another front, researchers reassessed models of carbon dioxide (CO2) uptake in the Arctic Ocean. They found that deep arctic waters take up more CO2 than previously expected, leading to accelerated ocean acidification.

Deep Arctic Waters

Joint research between the University of Bern and École normale supérieure in Paris shows that the Arctic Ocean will take up 20% more CO2 this century than previously thought. When CO2 combines with seawater, it creates carbonic acid, a reaction that increases the number of hydrogen ions in the water, thus decreasing the pH and raising the water’s acidity. 

The modeling indicates enhanced ocean acidification in the deeper waters between 200 and 1,000 meters. The Arctic ocean waters absorb CO2 from the atmosphere. But, in the Arctic, surface seawater becomes dense from high salinity and low temperatures. The denser water sinks, carrying CO2 into the deeper layers. The new work indicates that previous modeling efforts underestimated the exchange rate between the surface and deep layers, resulting in an under-prediction of deep-water acidification.

Acidity levels in marine waters affect the development of phytoplankton populations, which affects the entire food chain. Phytoplankton and algae form the lowest trophic level in the food chain. Small fish, crustaceans, and zooplankton are the next level up, and they feed on the phytoplankton. The chain continues upward with larger fish and ocean mammals eating the smaller creatures, and eventually land mammals, including humans, consuming a wide range of the ocean’s bounty. 

The phytoplankton and algae photosynthesize their food, using sunlight to build carbohydrates. Phytoplankton float around in the upper levels of the ocean, because this is where they can bask in the sun and do their photosynthesis trick. Phytoplankton live within tiny shells made out of calcium carbonate, and higher acidity degrades or destroys these shells. Without their shells, the phytoplankton die, and without the phytoplankton, the food chain collapses. This food-web collapse is one of the dangers from higher than expected ocean acidification.

Accelerated CO2 emissions from permafrost

The second miscalculation, exposed by new research at Northern Arizona University, relates to permafrost thawing in the Arctic. Using high-accuracy GPS systems, the research team spent nine years measuring widespread ground subsidence in Arctic Permafrost.

Traditionally researchers acquired measurements of permafrost thaw by inserting metal rods in the ground and measuring the thickness of the thawed zone. This method gives year-on-year measurements of total thawing. But when permafrost melts, a certain amount of ground subsidence takes place. Since the rod measurements use ground level as their reference point, they did not account for the ground subsidence.

Adding ground subsidence to existing thawing models resulted in an increase of between 37 percent and 113 percent in the amount of thawed Arctic carbon. Since the Arctic permafrost is one of the largest onshore carbon stores worldwide, the change in thawing carbon volumes is significant.

When warmed, the high ice content in permafrost soils turns to water and promotes rapid erosion and collapse of the land surface. Once unfrozen, the organic matter in the soil becomes food for bacteria. Then the bacteria rapidly consume the centuries-old organic materials and return the carbon to the atmosphere as carbon dioxide and methane.

Because the Arctic holds twice as much carbon as the atmosphere, there is the potential for massive releases of greenhouse gases from thawing permafrost. The added boost of these gases then accelerates the thawing process, so even more carbon enters the atmosphere. At some temperature related tipping point, the process becomes self-sustaining and irreversible. At that point, warming will continue until all the permafrost melts.

Proper research will always challenge our accepted views and drive us to reassess both models and their predictions. However, new projections may alarm us, even if they introduce a more accurate picture of the future.


ArcheanWeb:

A crab crisis from coastal water acidification (Source: ArcheanWeb) – https://archeanweb.com/2020/01/31/a-crab-crisis-from-coastal-water-acidification/  Also:

Ocean Acidification (Source: ArcheanWeb) – https://archeanweb.com/2019/12/24/ocean-acidification-caused-by-co2/  Also:

Acid and phytoplankton in the ocean’s food chain (Source: ArcheanWeb) – https://archeanweb.com/2020/01/28/acid-and-phytoplankton-the-oceans-food-chain/  Also:

Permafrost: A ticking carbon bomb (Source: ArcheanWeb) – https://archeanweb.com/2020/05/08/permafrost-a-ticking-carbon-bomb/  Also:


Sources:

Stocks of vulnerable carbon twice as high where permafrost subsidence is factored in (By Northern Arizona University; Phys Org) – https://phys.org/news/2020-06-stocks-vulnerable-carbon-high-permafrost.html  Also:

Arctic Ocean acidification worse than previously expected (Source: University of Bern; Science Daily) – https://www.sciencedaily.com/releases/2020/06/200617145947.htm  Also:

Emergent constraint on Arctic Ocean acidification in the twenty-first century (By Jens Terhaar, Lester Kwiatkowski, & Laurent Bopp; Nature) – https://www.nature.com/articles/s41586-020-2360-3  Also:

Feature Image: Table iceberg west of Sjuøyane (Modified) – By Andreas Weith – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=52745368

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.

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