Hrvatski
A New IUCN report shows deoxygenation in the oceans, due to climate change and nutrient pollution, which is increasingly threatening fish species.
The bulk of excess heat retained by the Earth due to greenhouse gas warming is being absorbed by the ocean. Ocean deoxygenation is occurring at all depths due to lower solubility of oxygen in warmer waters, stronger vertical stratification (steeper temperature gradient) inhibiting diffusion of oxygen from surface to deep ocean, and more sluggish deep circulation reducing oxygen supply to deep waters. Alongside this, increased nutrient inputs to the ocean through river runoff and atmospheric deposition are promoting algal blooms, increasing oxygen demand, and causing the development of hundreds of coastal hypoxic (dead) zones as well as the intensification of naturally formed low-oxygen zones.
- The global ocean oxygen inventory has decreased by ~2% over the period 1960 to 2010.
- Ocean model simulations project a further decline in the dissolved oxygen inventory of the global ocean of 1 to 7% by the year 2100, caused by a combination of a warming-induced decline in oxygen solubility and reduced ventilation of the deep ocean.
- Climate change-related longer-term oxygen trends are masked by oxygen variability on a range of different spatial and temporal scales.
- The decline in the oceanic oxygen content can affect ocean nutrient cycles and the marine habitat, with potentially detrimental consequences for ecosystems, dependent people, and coastal economies.
- Ocean oxygen loss is closely related to ocean warming and acidification caused by increasing carbon dioxide is driven by anthropogenic emissions, as well as biogeochemical consequences related to anthropogenic fertilization of the ocean; hence a combined effort investigating the different stressors will be most beneficial to understand future ocean changes.
