Ocean Heating and Acidification

Marine heatwaves kill coral instantly

BBC 8/08/2019

Increasingly frequent marine heatwaves can lead to the almost instant death of corals, scientists working on the Great Barrier Reef have found. Scientists studying coral after a heat event discovered that extreme temperature rises decayed reefs much more rapidly than previously thought.

Rapid Coral Decay Is Associated with Marine Heatwave Mortality Events on Reefs

Current Biology 8/08/2019

Severe marine heatwaves have recently become a common feature of global ocean conditions due to a rapidly changing climate [1, 2]. These increasingly severe thermal conditions are causing an unprecedented increase in the frequency and severity of mortality events in marine ecosystems, including on coral reefs [3]. The degradation of coral reefs will result in the collapse of ecosystem services that sustain over half a billion people globally [4, 5]. Here, we show that marine heatwave events on coral reefs are biologically distinct to how coral bleaching has been understood to date, in that heatwave conditions result in an immediate heat-induced mortality of the coral colony, rapid coral skeletal dissolution, and the loss of the three-dimensional reef structure. 

Heatwaves 'cook' Great Barrier Reef corals

BBC 4/18/2018

In surveying the 3,863 individual reefs that make up the system off Australia's north-east coast, scientists found that 29% of communities were affected. In some cases up to 90% of coral died, in a process known as bleaching.

This occurs when the stress of elevated temperatures causes a breakdown of the coral's symbiotic relationship with its algae, which provide the coral with energy to survive, and give the reef its distinctive colours.

Coral reefs head for 'knock-out punch'

BBC 1/04/2018

A study of 100 reefs, published in Science Magazine, shows the interval between bleaching events in recent decades has shortened dramatically. It has gone from once every 25-30 years in the early 1980s to an average of just once every six years today.Bleaching is caused by anomalously warm water, which prompts coral polyps to eject their symbiotic algae.This drains the corals of their colour and is fatal unless conditions are reversed in a reasonably short time. But even if temperatures fall back quickly, it can still take many years for damaged reefs to fully recover.

Record Warm Water Likely Gave Kuskokwim Salmon Heart Attacks

KYUK 7/12/2019

Earlier this week, water temperatures near Bethel broke into the lower 70s, marking the highest river temperature that’s ever been recorded in early July. This spell was part of a heat wave that shot thermometers to their highest point ever in towns across Alaska.
During this time, residents along the lower Kuskokwim River from Tuntutuliak to Akiak reported dead salmon floating downstream. Salmon don’t function well past 70 degrees, and the water had pushed just above that limit.

Climate Change is Weakening an Ocean Current

Discover Magazine 4/11/2019

Both studies found that melting ice from Greenland has spilled huge quantities of freshwater into the North Atlantic, diluting the dense salinity of North Atlantic currents and weakening the AMOC by 15 percent. However, the results disagree on when the changes started.
For decades, scientists have worried that human-caused global warming could weaken this system and drastically alter weather patterns. It’s an idea best known from the scientifically and cinematically awful 2004 film The Day After Tomorrow.

Heatwaves sweeping oceans ‘like wildfires’, scientists reveal

Ocean Heat Waves The Guardian 2019

The number of heatwaves affecting the planet’s oceans has increased sharply, scientists have revealed, killing swathes of sea-life like “wildfires that take out huge areas of forest”.
The damage caused in these hotspots is also harmful for humanity, which relies on the oceans for oxygen, food, storm protection and the removal of climate-warming carbon dioxide the atmosphere, they say.