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Ocean Chemistry

The ocean's chemistry is altering in several ways.

Ocean Acifidication

Ocean pH has increased by about 0.1 since the start of the Industrial Revolution, or an increase in acidity of about 30%, and it could increased by 0.2 to 0.3 by 2100 1. Uptake of carbon is the main cause of ocean acidification, or the long-term trend of falling ocean pH. Ocean acidification poses a threat to marine ecosystems.

Impacts of Ocean Acidification from CO2 emissions resulting in +2-3℃
Class of LifeSurvivalCalcificationGrowthPhotosynthesis/DevelopmentAbundance
Calcifying Algae?---?-28%-80%
Corals----32%-------47%
Coccolithophore Plankton?-23%---------
Mollusks-34%-40%-17%-25%---
Echinoderms-------10%-11%?
Crustaceans---------------
Fish??---??
Fleshy Algae??22%------
Seagrasses???---?
Diatom Plankton??17%12%---

"- - -" represents insignificant results whereas "?" represents not enough studies done. Projected impacts from ocean acidification on marine ecosystems, resulting from the carbon emissions that would cause 2-3 ℃ warming. Source: Kroeker et al. 2.

Ocean acidification has negative impacts of fisheries, the ocean as a carbon sink, and the tourism, scentific, and cultural value of biodiversity 3. Losses has been estimated to reach $1 trillion per year by 2100 under projected CO2 emissions 4.

Ocean Salinity

The ocean is becoming saltier over time, with fresh areas generally become fresher and salty areas become saltier 1. This trend is expected to have a modest warming effect on the climate 5.

Oxygen Content

The oceans' oxygen content has decreased by about 2% since 1960 6, 7, though oxygen levels have increased in some areas near river mouths due to fertilizer runoff 8. Rising temperature reduces the oceans' ability to take in oxygen, and this may be the main factor in the loss 1. Ocean patches of low oxygen may in turn drive warming by increasing emissions of nitrous oxide 1.

References

  1. United Nations "The Second World Ocean Assessment". 2021. ↩ ↩2 ↩3 ↩4

  2. Kroeker, K., Kordas, R., Crim, R., Hendriks, I., Ramajo, L., Singh, G., Duarte, C., Gattuso, J. "Impacts of ocean acidification on marine organisms: quantifying sensitivities and interaction with warming". Global Change Biology 19(6), pp. 1884-1896. February 2013. ↩

  3. Navrud, S., Seifert-Dähnn, I. "The Economics of Ocean Acidification - A Scoping Study". Fram Centre 57. January 2012. ↩

  4. Secretariat of the Convention on Biological Diversity. An Updated Synthesis of the Impacts of Ocean Acidification on Marine Biodiversity. (Eds: S. Hennige, J.M. Roberts & P. Williamson). Montreal, Technical Series No. 75, 99 pages. 2014. ↩

  5. Olson, S., Jansen, M. F., Abbot, D. S., Halevy, I., Goldblatt, C. "The Effect of Ocean Salinity on Climate and Its Implications for Earth's Habitability". Geophysical Research Letters 49(10): e2021GL095748. May 2022. ↩

  6. Schmidtko, S., Stramma, L., Visbeck, M., "Decline in global oceanic oxygen content during the past five decades". Nature 542, pp. 335–339. February 2017. ↩

  7. Ito, T., Minobe, S., Long, M. C., Deutsch, C. "Upper ocean O2 trends: 1958–2015". Geophysical Research Letters 44(9), pp. 4214-4223. April 2017. ↩

  8. Keeling, R. E., Körtzinger, A., Gruber, N. "Ocean deoxygenation in a warming world". Annual review of marine science 2: pp. 199-229. 2010. ↩