© Julien Holleville
Can an umbrella work underwater? The answer appears to be yes, just not for the reason many might imagine. Around the world, marine heatwaves have put coral at risk of excessive heat stress. When ocean temperatures get too hot, stressed corals can expel the microscopic algae that live in their tissues, causing them to turn white and lose their main source of food – a phenomenon known as bleaching that is occurring with alarming frequency. A group of scientists in Florida believes that underwater umbrellas could mitigate the damage………Continue reading..
Source: Euronews
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Critics:
A marine heatwave is a period of abnormally high sea surface temperatures (SST) compared to typical temperatures for a particular season and locale.[1] Marine heatwaves are caused by a variety of drivers. These include short term weather events such as fronts, intraseasonal events (30 to 90 days), annual, and decadal (10-year) modes like El Niño events, and human-caused climate change.
Such heatwaves affect marine ecosystems. For example, heatwaves can lead to events such as coral bleaching, sea star wasting disease, harmful algal blooms, and mass mortality of benthic communities. Unlike heatwaves on land, marine heatwaves can extend over vast areas, persist for weeks to months to years, and extend to subsurface levels.
Extreme bleaching events are directly linked with climate-induced phenomena that increase ocean temperature, such as El Niño-Southern Oscillation (ENSO). The warming ocean surface waters can lead to bleaching of corals which can cause serious damage and coral death. The IPCC Sixth Assessment Report in 2022 found that: “Since the early 1980s, the frequency and severity of mass coral bleaching events have increased sharply worldwide”.
Coral reefs, as well as other shelf-sea ecosystems, such as rocky shores, kelp forests, seagrasses, and mangroves, have recently undergone mass mortalities from marine heatwaves. It is expected that many coral reefs will “undergo irreversible phase shifts due to marine heatwaves with global warming levels >1.5°C”. This problem was already identified in 2007 by the Intergovernmental Panel on Climate Change (IPCC) as the greatest threat to the world’s reef systems.
The Great Barrier Reef experienced its first major bleaching event in 1998. Since then, bleaching events have increased in frequency, with three events occurring in the years 2016–2020. Bleaching is predicted to occur three times a decade on the Great Barrier Reef if warming is kept to 1.5 °C, increasing to every other year at 2 °C. With the increase of coral bleaching events worldwide.
National Geographic noted in 2017, “In the past three years, 25 reefs—which comprise three-fourths of the world’s reef systems—experienced severe bleaching events in what scientists concluded was the worst-ever sequence of bleachings to date.” In a study conducted on the Hawaiian mushroom coral Lobactis scutaria, researchers discovered that higher temperatures and elevated levels of photosynthetically active radiation (PAR) had a detrimental impact on its reproductive physiology.
The purpose of this study was to investigate the survival of reef-building corals in their natural habitat, as coral reproduction is being hindered by the effects of climate change
Major marine heatwaves affected the Great Barrier Reef in 2002, the Mediterranean Sea in 2003, the Northwest Atlantic in 2012, and the Northeast Pacific during 2013–2016. These events had drastic, long-term impacts. Scientists predict that the frequency, duration, scale (area), and intensity of marine heatwaves will increase. This is because sea surface temperatures will continue to increase with global warming.
The IPCC Sixth Assessment Report (SAR6) in 2022 stated that “marine heatwaves are more frequent […], more intense and longer […] since the 1980s, and since at least 2006 very likely attributable to anthropogenic climate change” This confirmed earlier findings in a 2019 IPCC report that “Marine heatwaves […] have doubled in frequency and have become longer lasting, more intense and more extensive (very likely).”
The 2022 report predicted that marine heatwaves will become “four times more frequent in 2081–2100 compared to 1995–2014” under the lower greenhouse gas emissions scenario, or eight times more frequent under the higher emissions scenario.
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