Oceans & marine

The potential of carbon sequestration by marine based plants such as mangroves, seagrass and algae, often referred to as blue carbon, and the importance of better understanding it, has clearly been recognised (Mcleod et al. 2011). The IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (2019) concluded blue carbon can play an important role in both climate regulation and adaptation. The term algae groups together several kinds of marine photosynthetic organisms. These are often subdivided into very small microalgae like phytoplankton, and larger macroalgae like kelp and seaweed. Although there is still large uncertainty about the total amount of carbon sequestered by these marine organisms, a recent estimate by Duarte et al. (2022) indicated that all macroalgae took in as much CO2 as the Amazon rainforest.

Fisheries contribute to global CO2 emissions by the extraction of fish, disturbance of coastal and oceanic blue carbon ecosystems, and the use of fossil fuels as their main energy source. Fishing vessels are moreover a major source of short-lived climate forcers like black carbon (McKuin and Campbell 2016), which can have a major effect in Arctic and Northern regions (see Black carbon reduction).

The pH of water is lowered when it takes up atmospheric carbon. Given that the Earth’s oceans serve as a major carbon sink, there is increasing interest in the possibility to artificially increase the alkalinity of water to restore pH to previous levels, and/or increase carbon uptake potential.

Sea water has a low albedo of around 0.1 and therefore absorbs most of the incoming solar energy. Since water covers over two thirds of the Earth’s surface, changes to this albedo can potentially cause significant changes in global temperatures.

Carbon uptake in the ocean mainly occurs directly through ocean-atmosphere interaction or through weathering processes. Due to this uptake of carbon, the oceans turn more acidic overtime, and since the start of the industrial revolution oceans have become 30% more acidic. This has all sorts of effects as it, for example, impacts marine biochemistry, and prevents certain organisms from successfully growing.

Artificial upwelling (AU) is an idea to increase carbon uptake of upper ocean layers by fertilizing it with pumped-up colder nutrient-rich waters from the deep, which would encourage the biological sequestration of carbon through photosynthesis (NASEM 2022).

Hydrological systems play an important role in energy distribution in the climate system. For the Arctic and Northern region the clearest example of this is the habitability of the European Arctic thanks to the Gulf Stream. Furthermore, there are several access points to the Arctic ocean that play an important role in shaping local geophysical conditions.