Marine life threatened if ocean surface climates disappear

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Up to 95% of the surface climates of the 20th century’s oceans could disappear by 2100, scientists warn.

Vast swathes of ocean surface climates – defined by surface water temperature, pH, and the concentration of the mineral aragonite – could be wiped out depending on how greenhouse gas emissions evolve over time. during the first half of the 21stst century, according to a study published in Scientific reports.

The results also suggest that between 10.3% and 82% of the world’s ocean could experience surface climates that did not previously exist.

The study authors conclude that while some marine species currently keep pace with ocean climate change by dispersing into new habitats, this may no longer be possible if existing ocean climates disappear, forcing species to adapt quickly or to disappear.

Ocean currents act like a conveyor belt, carrying warm water to the poles and cold water from the poles to the tropics. Thus, ocean currents regulate the global climate, helping to counteract the uneven distribution of solar radiation reaching the planet’s surface.

Katie Lotterhos and her colleagues modeled oceanic climates on a global scale for three time periods: the start of the 19e century (1795-1834), the end of the 20e century (1965-2004) and the end of the 21stst century (2065-2104).

The team compared these modeled climates at various locations using two emission scenarios, RCP 4.5 and RCP 8.5. In these scenarios, the volume of greenhouse gases emitted during the 21st century either peaks in 2050 followed by a slower increase, or peaks in 2100 followed by a slower increase, respectively.

By their comparisons, the authors were able to show which oceanic climates of the 19e and 20e centuries can no longer be found in the 21st century (disappearance) and the climates that could emerge in the 21stst century that did not exist in the 18e and 20e centuries (new climates).

The authors showed that while oceanic climates did not change significantly between the 19e and 20e centuries, by 2100, 10 to 82% of the ocean surface could experience new climates with higher temperatures, more acidic pH, and lower saturation of aragonite, a mineral that corals and other marine organisms use for form seashells.

In the RCP 4.5 scenario, 35.6% of ocean surface climates could disappear by 2100, which increases to 95% in the RCP 8.5 scenario.

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