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Climate change projections

To plan effective climate change adaptation we need a good understanding how marine ecosystems may change in response to current and future climate change. The UK's National Oceanography Centre (NOC) are therefore providing leading-edge projections of ocean physics, biogeochemistry and ecosystems at high resolution. Key ocean characteristics are projected up to 2099, based on the 'business as usual' greenhouse gas emission scenario (RCP8.5).[1]

The Internation Panel for Climate Change (IPCC) have developed 40 scenarios for how human activities may contribute to future climate change. These make different assumptions about future levels of greenhouse gas pollution, land-use and other forces that drive global warming. The Representative Concentration Pathways (RCPs) are based on some of these scenarios and designed to make it easier to create climate change projections. The RCPs are consistent sets of greenhouse gas projections that lead to specific changes in the Earth's energy budget - the balance between incoming and outgoing radiation.

RCP8.5 is 'business as usual' - the pathway we are heading down if only limited action is taken to reduce greenhouse gas emissions, deforestation, etc. It assumes that populations continue to rise fast, that incomes will grow slowly, and that technological change and improvements to energy use will also be slow. In the long term this leads to high energy demand and high greenhouse gas emissions, leading to an imbalance in Earth's energy budget of 8.5 W m-2

The NOC ocean projections will underpin the effort to identify marine resources likely to be affected by climate change and contribute to the development of effective adaptation strategies.

Surface currents

The animation (right) shows surface current speeds as simulated by the global ocean circulation model NEMO. The more intense white colours indicate faster speeds. The animation shows the complex dynamics of the ocean currents affecting marine ecosystems around Madagascar: South Equatorial Current, East Madagascar Current, Mozambique Current and the vigorous eddies of the Mozambique Channel.

Ocean currents redistribute heat, nutrients and living organisms around the globe. Surface currents can move tropical heat to temperate zones, and upwelling currents bring nutrients that drive ocean primary production.

Many fish and other marine species rely on ocean currents to transport their eggs and larvae from spawning grounds to the locations they will inhabit as adults. Changes to the speed or direction of some currents may therefore affect recruitment to commercial and artisanal fisheries, with potential impact on coastal communities.

View in higher resolution
(1080x1080 pixels, 12 MB, animation opens in a new window).

Sea surface temperature

Ocean Temperature is one of the key stressors of marine ecosystems. Rising temperatures brought on by climate change will negatively impact a range of marine organisms living close to their thermal tolerances. Marine heatwaves affect corals and the many organisms that use coral reefs as habitat. If the high temperatures persist for prolonged periods of time, the corals experience bleaching, which weakens and eventually kills the coral. Such coral bleaching events are becoming more frequent and intense as the oceans warm and marine heatwaves increase in frequency, duration and intensity.

The animation on the right shows projection of sea surface temperature (SST) around Madagascar as simulated by the global ocean circulation NEMO under the 'business as usual' climate scenario (RCP8.5). Future SST up to 2099 (right panel) are compared to present values (decade 2000-09 on the left panel). The Madagascar region is a marine hotspot where mean annual temperatures are currently increasing faster than the global average.

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(1920x1080 pixels, 13 MB, animation opens in a new window).

Ocean acidification

Much of the carbon dioxide that enters the atmosphere dissolves in the ocean, altering the chemistry of the seawater and causing ocean acidification. While impacts of ocean acidification are still uncertain, many organisms are undoubtedly vulnerable. Decreased ocean pH may lead to corals becoming increasingly rare on reef systems. The result will be less diverse reef communities and a slow-down in the building of carbonate reef structures.

The animation on the right shows projection of future pH patterns as simulated by the NEMO global ocean circulation model under the RCP8.5 climate scenario. Future values (right panel) are compared to present values (left panel).

View in higher resolution
(1920x1080 pixels, 13 MB, animation opens in a new window).

Primary Production

Primary production by microscopic algae (phytoplankton) represents the total amount of energy – stored in organic carbon – available to the local ecosystems. Changes to the total amount of production can have profound impacts up the entire food chain and affect the success of fisheries and aquaculture. Highly productive regions, such as the Benguela upwelling system, support some of the world's richest fisheries. In other areas, for example the Mozambique Channel, production is lower.

The animation on the right shows a projection of total primary production (TPP) for the region around Madagascar as simulated by the NEMO-MEDUSA bio-physical model under the the RCP8.5 climate scenario. Primary production around Madagascar shows little response to the climate change.

View in higher resolution
(1920x1080 pixels, 13 MB, animation opens in a new window).