STOCKHOLM +50 - OCEANS ON SIMMER

• Oceans regulate the climate by absorbing atmospheric carbon dioxide and by altering the energy budget, carbon cycle and nutrient cycle.
• Oceans reduce the worst impacts of climate change by absorbing 90% of excess global temperature rise and 25% of CO₂ emissions.
• Global warming is causing warming, acidification and deoxygenation of oceans.
• The oceans have warmed unabated since 2005, continuing the clear multi-decades trends documented by the Intergovernmental Panel on Climate Change(IPCC).
• The temperature on the ocean surface has increased by 0.88^o C from 1850-1900 to 2011-20, with 0.60^o C of the warming occurring since 1980.
• The ocean temperature is projected to increase by about 1.5 C by 2050, not only on surface waters but also in deep ocean waters.
• The major impact of ocean warming is seen over the Arctic Ocean which will likely become sea ice-free during the sea ice minimum for the first time before 2050.
• It is virtually certain that the global mean sea level 0.18-0.23m by 2050 and 0.38-0.77m by 2100.
• This rise in sea level is mainly due to thermal expansion and mass loss from glaciers and ice sheets.
• Unlike atmospheric heatwaves, MHW(Marine Heat Waves) can extend millions of square kilometres and persist for weeks to months.
• MHW can lead to severe and persistent impacts on marine ecosystems, coral bleaching, changes in phytoplankton blooms, shifts in species composition and toxic algal blooms.
• The IPCC climate change projections suggest that MHWs will become four times more frequently by 2080 compared to the 1995-2011 threshold.
• The rate of ocean uptake of atmospheric CO₂ has continued to strengthen in response to the rising atmospheric CO_2.
• The open ocean surface water pH is observed to be declining by 0.017-0.027 pH units since the 1980s.
• There is a growing consensus that the open ocean is losing oxygen, with a likely loss of 0.5-3.3% between 1970-2010 from the ocean surface to 1000m.
• The oxygen minimizing zones are expanding by 2-8%, most notable in the tropical oceans.

• The warming of oceans has serious adverse impacts. Global warming can fundamentally alter ocean biodiversity.
• It affects the marine organisms at multiple levels, impacting fisheries, and food production.
• 'The Global Assessment Report on Biodiversity and Ecosystem Services' finds that 66% of the global ocean is impacted by human pressures, with severe impacts in the declining richness and abundance of ocean biodiversity.
• There is high confidence in inferring that fisheries, catches and their composition in many regions that are already impacted.
• The erosion of ocean biodiversity and ecosystems particularly threatens the livelihoods of local communities.

• Coastal ecosystems are observed to be under stress from ocean warming and sea-level rise that are exacerbated by non-climatic pressures from human activities on the ocean and land.
• The global wetland area has declined by nearly 50% relative to the pre-industrial level.
• Warming related mangrove encroachment into subtropical salt marshes was seen in the past 50 years.
• The occurrence of algal blooms and pathogenic organisms has increased in coastal areas due to warming, deoxygenation and eutrophication with negative impacts on food provisioning, tourism, economy and human health.

• A tropical cyclone(CT) is the most important weather system, which ocean warming can influence.
• An increase in sea surface temperatures and ocean heat content could help TCs intensify quickly and travel long distances without losing appreciable energy.
• Studies have suggested that there is a 6% increase in TC exceedance probability of 50.
• The climate change projections suggest that average peak TC wind speeds & the proportion of very severe TCs will be increased with global warming.
• The average locations where TCs reach their peak wind intensity will migrate poleward as the tropics expand with warming.
• The Indian Ocean is also warming and the trend is likely to continue.
• The warm Indian Ocean can lead to more intense precipitation events over India during the monsoon, as it will help to more moisture advection.

• In view of the projected adverse impacts of warming oceans, there is a concern about the efficacy of ocean governance, highlighting the need for timely mitigation and adaptation responses.
• There are three major risks-  i) the impacts of the over-exploitation of marine resources, ii) inequitable distribution of access to and benefits from marine ecosystem services, and iii) inadequate adaptation to changing ocean conditions.
• The actions that can reduce this risk are related to the process of co-creation and implementation of improved, comprehensive and integrated ocean management and enhancement of the decision-making process.
• The 2030 Agenda for Sustainable Development, adopted by all UN member states, provides a blueprint for peace and prosperity for the planet.
• There are 17 Sustainable Development Goals(SDG) which are an urgent call for action.
• SDG 14 is to conserve and sustainably use the oceans, seas and marine resources for sustainable development.
• The UN has proclaimed a Decade of Ocean Science for Sustainable Development (2021-2030) to support efforts, and ensure ocean science can help countries to create improved conditions for sustainable development of the ocean.