![\"pH-Wert](\"https:\/\/earthguardian.earth\/wp-content\/uploads\/2025\/07\/PH-Werte-EN.jpg\" "\\"pH-Wert")
<\/p>\nThe ocean is currently absorbing more CO\u2082 than it naturally should. Between 1994 and 2007, the world\u2019s oceans absorbed about 31 percent of all human-caused CO\u2082 emissions. Since the Industrial Revolution, the oceans have taken up about one-third of anthropogenic CO\u2082 each year.
\nThe overload is evident in:
\nOcean acidification due to massive CO\u2082 uptake
\nDecreasing absorption capacity as temperatures rise
\nRegional reversals, where some marine areas already emit more CO\u2082 than they absorb.<\/p>\n
The world\u2019s oceans act as the largest active carbon reservoir on our planet. With about 38,000 gigatons of stored carbon, they surpass the terrestrial biosphere by 16 times and the preindustrial atmosphere by 60 times. This impressive storage capacity makes the ocean a central player in the global climate system.
\nCarbon is mainly stored in the form of dissolved inorganic carbon (DIC), which consists of three components: dissolved CO\u2082, bicarbonate, and carbonate ions. These forms of carbon are in dynamic equilibrium, influenced by the pH of seawater.<\/p>\n
Currently, the oceans absorb about 25-30% of human-caused CO\u2082 emissions, equivalent to more than 2 petagrams (2 billion tons) of carbon per year. This uptake mainly occurs through the ocean\u2019s surface layer, which varies regionally between 50 and several hundred meters thick.
\nThe exchange of CO\u2082 between atmosphere and ocean is driven by the partial pressure difference between air and water. When atmospheric CO\u2082 levels are higher than in surface water, the ocean absorbs CO\u2082. Conversely, it releases CO\u2082 when concentrations in the water are higher.<\/p>\n
The physical pump is especially efficient in regions where cold, salty water sinks, such as the North Atlantic and Southern Ocean. Dissolved CO\u2082 is transported to depth with the sinking water and remains stored there for decades to centuries. These regions are thus crucial for long-term carbon storage.
\nRecent research confirms that the Southern Ocean alone absorbs about 0.53 petagrams more carbon than it releases. This region is particularly important because cold Antarctic water rises and sinks again, enabling effective carbon transport to the deep ocean.<\/p>\n
The biological pump works through marine photosynthesis. Phytoplankton, tiny marine plants, bind CO\u2082 from seawater and convert it into organic material. These organisms contribute about 50% to global photosynthetic carbon fixation.
\nSome of this organic material sinks as \u201cmarine snow\u201d to deeper layers. These consist of dead organisms, feces, and other organic particles that sink under gravity. While much of the material is remineralized by microorganisms during sinking, a small portion reaches the sediments and is stored long-term.
\nThe biological pump sequesters about 2.8 billion tons of carbon annually, keeping it out of the atmospheric cycle for at least 50 years. The value of this ecosystem service is estimated at $545 billion per year in international waters.<\/p>\n
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The ocean\u2019s ability to absorb CO\u2082 varies greatly between regions. In cold, stormy areas like the North Atlantic and Southern Ocean, uptake is especially high, benefiting from better CO\u2082 solubility in cold water and strong mixing processes.
\nTropical upwelling areas, on the other hand, can act as CO\u2082 sources, as carbon-rich deep water reaches the surface and releases CO\u2082 to the atmosphere. These regional differences are crucial for understanding the global ocean carbon balance.
\nRecent studies also show that regional patterns can change. For example, in the subpolar North Atlantic, a weakening of CO\u2082 uptake is projected as deep water formation decreases.<\/p>\n
The Acidification Process
\nCO\u2082 uptake leads to a series of chemical reactions in seawater, forming carbonic acid and lowering the pH. This process, known as ocean acidification, is one of the most severe consequences of CO\u2082 uptake.
\nCurrent measurements show that the global average surface ocean pH has dropped from 8.11 in 1985 to 8.04 in 2024, an 18% increase in acidity. Since preindustrial times, acidity has increased by 40%.<\/p>\n
Ocean acidification is especially problematic for calcifying organisms like corals, mussels, crustaceans, and certain plankton species. These organisms have difficulty forming shells and skeletons from calcium carbonate as seawater becomes more acidic.
\nScientists use the aragonite saturation state as an indicator of the ability of organisms to form their calcareous structures. When the saturation state falls below 1, aragonite, a form of calcium carbonate, dissolves. Projections indicate that by 2100, about 61.5% of global ocean regions could fall below this critical threshold.
\nRate of Change:
\nCurrent acidification is proceeding as rapidly as at any time in at least the last 20 million years. The World Meteorological Organization (WMO) reports that the oceans are acidifying 10 times faster than in the past 300 million years. This unprecedented rate of change makes adaptation difficult for marine organisms.<\/p>\n
![\"Kalkbildende](\"https:\/\/earthguardian.earth\/wp-content\/uploads\/2025\/07\/kalkbildene-Organismen-EN.jpg\" "\\"Kalkbildende")
<\/p>\n
Temperature-Related Limitations
\nAs water temperatures rise, CO\u2082 solubility decreases, reducing the ocean\u2019s uptake capacity. Warmer water can dissolve less CO\u2082, meaning that with ongoing warming, more CO\u2082 remains in the atmosphere.
\nOcean Stratification as a Barrier:
\nIncreasing stratification of the oceans due to warming is another limitation. As the surface layer warms, it becomes less dense and mixes less with deeper, colder layers. This slows CO\u2082 transport to the depths and reduces carbon storage efficiency.
\nStudies show that stratification in the upper 200 meters of the oceans increased by about 7% between 1960 and 2018. This development could significantly impair the oceans\u2019 role as a CO\u2082 sink.<\/p>\n
Climate models predict that the ocean\u2019s capacity to absorb CO\u2082 will decrease during the 21st century. In extreme warming scenarios, CO\u2082 uptake efficiency could peak by 2100 and drop to only half by 2300.
\nThese projections are based on the formation of a surface layer with low alkalinity, which hinders CO\u2082 uptake. Extreme climate changes increase precipitation and slow ocean currents, leading to a warm freshwater layer on the surface that does not mix well with the more alkaline layers below.<\/p>\n
Marine Carbon Dioxide Removal (mCDR)
\nGiven the limits of natural CO\u2082 uptake, scientists are developing new technologies for marine carbon dioxide removal (mCDR). These ocean-based techniques aim to remove CO\u2082 from the atmosphere and store it long-term in the ocean.
\nIn January 2025, NOAA published its first comprehensive plan for ocean carbon observation. This plan aims to improve the coordination and optimization of ocean carbon observation activities and to identify key scientific questions for the next 10 years.<\/p>\n
New research has provided important insights into the role of microorganisms in the ocean carbon cycle. Scientists have identified a group of deep-sea microbes called \u201cslow copiotrophs\u201d that grow slowly but can efficiently break down hard-to-degrade organic carbon compounds.
\nThis discovery offers new insights into carbon storage mechanisms and shows that even small changes in microbial communities can have major impacts on carbon storage.<\/p>\n
The ocean plays an indispensable role in the global carbon cycle and acts as an important buffer against the effects of human CO\u2082 emissions. With its enormous storage capacity of 38,000 gigatons of carbon and the ability to absorb 25-30% of anthropogenic emissions annually, it significantly slows the pace of climate change.
\nHowever, we face critical challenges. The ocean\u2019s absorption capacity is not unlimited, and the resulting ocean acidification is a growing ecological problem. The unprecedented speed of acidification and ocean warming threaten marine ecosystems and could reduce the efficiency of natural carbon pumps.
\nCurrent research and developments in marine carbon dioxide removal offer hope for additional solutions. At the same time, new scientific findings on microbial processes and regional differences highlight the complexity of the ocean carbon system.
\nIn the future, it will be crucial to both understand and protect the oceans\u2019 natural capacities and to develop innovative technologies that can complement these natural processes. Only through a combination of drastic emission reductions and protection of marine ecosystems can we preserve the vital role of the oceans as climate regulators in the long term.<\/p>\n
<\/p>\n
Author: Francesco del Orbe<\/p>\n
Graphic: Heinrich B\u00f6ll Stiftung \/ petraboellman.de \/ CC-BY 4.0<\/em><\/p>\n","protected":false},"excerpt":{"rendered":" – Importance, Uptake, and Consequences The ocean is currently absorbing more CO\u2082 than it naturally should. Between 1994 and 2007, the world\u2019s oceans absorbed about 31 percent of all human-caused CO\u2082 emissions. Since the Industrial Revolution, the oceans have taken up about one-third of anthropogenic CO\u2082 each year. The overload is evident in: Ocean acidification…<\/p>\n","protected":false},"author":54,"featured_media":23270,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"categories":[185,605,196,603],"tags":[261,253,254,263,307,267,260,255,264,265,252,250,259,384,262,383,268,308,207,266],"class_list":["post-23269","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-climate-and-environment","category-europe-and-the-world","category-guardian-of-the-earth","category-water","tag-biodiversity","tag-carbonneutral","tag-climate-action","tag-climate-change","tag-climate-farm","tag-climate-protection","tag-co2-binding","tag-earth-guardian","tag-ecosystem","tag-farming","tag-francesco-del-orbe","tag-fresopolis","tag-healthy-soil","tag-marine-photosynthesis","tag-microclimate","tag-ocean-acidification","tag-planting","tag-regenerative-agricultura","tag-sustainability","tag-sustainable"],"acf":[],"yoast_head":"\n