Question

Do it yourself Ocean and climate

Answer 1

The ocean and climate change

The ocean is being disproportionately impacted by increasing carbon dioxide (CO2) and other greenhouse gas emissions () from human causes changes in water temperature, ocean acidification and , leading to changes in oceanic circulation and chemistry, rising sea levels, increased storm intensity, as well as changes in the diversity and abundance of marine of coastal and marine ecosystems threatens the physical, economic and food security of local communities, as well as resources for global change weakens the ability of the ocean and coasts to provide critical ecosystem services such as food, carbon storage, oxygen generation, as well as to support nature-based solutions to climate change sustainable management, conservation and restoration of coastal and marine ecosystems are vital to support the continued provision of ecosystem services on which people depend. A low carbon emissions trajectory is indispensable to preserve the health of the ocean

At the front line of climate change, the ocean, the coastlines and coastal communities are being disproportionately impacted by increasing carbon dioxide (CO2) and other greenhouse gas () emissions from human activities.

The ocean plays a central role in regulating the Earth’s climate. The Fifth Assessment Report published by the Intergovernmental Panel on Climate Change () in 2013 revealed that is has thus far absorbed 93% of the extra energy from the enhanced greenhouse effect, with warming now being observed at depths of 1,000 m. As a consequence, this has led to increased ocean stratification (prevention of water mixing due to different properties of water masses), changes in ocean current regimes, and expansion of depleted oxygen zones. Changes in the geographical ranges of marine species and shifts in growing seasons, as well as in the diversity and abundance of species communities are now being observed. At the same time, weather patterns are changing, with extreme events increasing in frequency.

Atmospheric warming is leading to the melting of inland glaciers and ice, causing rising sea levels with significant impacts on shorelines (coastal erosion, saltwater intrusion, habitat destruction) and coastal human settlements. The projects global mean sea level to increase by 0.40 [0.26–0.55] m for 2081–2100 compared with 1986–2005 for a low emission scenario, and by 0.63 [0.45–0.82] m for a high emission scenario. Extreme El events are predicted to increase in frequency due to rising emissions.

CO2 emissions are also making the ocean more acidic, making many marine species and ecosystems increasingly vulnerable. Ocean acidification reduces the ability of marine organisms, such as corals, plankton and shellfish, to build their shells and skeletal structures. It also exacerbates existing physiological stresses (such as impeded respiration and reproduction) and reduces growth and survival rates during the early life stag

The ocean and coasts provide critical ecosystem services such as carbon storage, oxygen generation, food and income generation.

Coastal ecosystems like mangroves, salt marshes and play a vital role in carbon storage and sequestration. Per unit of area, they sequester carbon faster and far more efficiently than terrestrial forests. When these ecosystems are degraded, lost or converted, massive amounts of CO2 – an estimated 0.15-1.02 billion tons every year – are released into the atmosphere or ocean, accounting for up to 19% of global carbon emissions from deforestation. The ecosystem services such as flood and storm protection that they provide are also lost.

The impacts of ocean warming and acidification on coastal and marine species and ecosystems are already observable. For example, the current amount of CO2 in the atmosphere is already too high