Scientists call it the ‘deadly trio.’ If ocean acidification, oxygen loss, and overheating are not ended soon, a massive die-off of ocean life may be unstoppable.
In September 2020, Ian Angus published 3 articles in CLIMATE & CAPITALISM , an eco-socialist / ecological Marxist journal. The articles considered the elements of the deadly trio separately, but stressed the importance of understanding that they are closely related, have the same causes, and frequently reinforce each other.
We will be posting separate links to each of the 3 parts of the articles. Part 3 follows the General Introduction.
“It is impossible to overstate the importance of the ocean to life on Earth. Covering 71% of the planet’s surface, it contains 97% of the world’s surface water and is central to the great biogeochemical cycles that define the biosphere and make life possible. Marine plants generate half of the world’s breathable oxygen.
The ocean’s metabolism — the constant flows and exchanges of energy and matter that have continued for hundreds of millions of years — is a vital part of the Earth System.
Most accounts of the relationship between the ocean and climate change focus on melting ice and rising sea levels, and indeed those are critical issues. At present rates, by 2100 the combination of global glacial melting and thermal water expansion will flood coastal areas where over 630 million people live today. Well over a billion people live in areas that will be hit by storm surges made bigger and more destructive by warmer seawater. Rapid action to slash greenhouse gas emissions would be fully justified even if rising seas were the only expected result of global warming.
Devastating as sea level rise will be, however, more serious long-term damage to the Earth System is being driven by what marine ecologists describe as the “deadly trio” of ocean warming, acidification and oxygen loss – deadly because when they have occurred together in the past, mass extinctions of animal and plant life have followed. “
Ocean warming and permanent heatwaves – Part 3
“Until the 1970s, the constant flow of energy that Earth receives from the sun was offset by heat reflected back into space, so the planet’s overall energy level did not change very much over time. The amount of incoming solar energy has not changed, but rising concentrations of greenhouse gases are trapping ever more of the reflected heat, preventing it from leaving the atmosphere. Climate scientists call this Earth’s Energy Imbalance.
The excess energy is not distributed evenly through the Earth System. Although global warming is usually expressed as increased air temperatures, the ocean is actually much better at storing heat than the atmosphere — one degree of ocean warming stores over 1000 times as much heat energy as one degree of atmosphere warming — so it isn’t surprising that the ocean has taken up most of the excess solar energy. Just seven percent warms the air and land and melts snow and ice — 93 percent is absorbed by the ocean.
Since 1987 the ocean has warmed 4.5 times as fast as in the previous three decades. The Intergovernmental Panel on Climate Change (IPCC) projects that even if emissions are substantially reduced, by 2100 the ocean will heat 2 to 4 times as much as it has since 1970 — and if emissions are not cut, it will heat 5 to 7 times as much. Since 2010, the Atlantic ocean has been hotter than at any time in the past 2900 years, and the Arctic is warming two to three times as fast as the rest of the world. Summer sea ice may disappear entirely by 2035
Scientist Lijing Cheng of China’s Institute of Atmospheric Physics calculates that “The amount of heat we [humanity] have put in the world’s oceans in the past 25 years equals to 3.6 billion Hiroshima atom-bomb explosions.”
The concept of marine heatwaves is new: the term itself first appeared in 2011, in a Australian report on “a major temperature anomaly” in which “water temperatures off the south-western coast of Australia rose to unprecedented levels.”
Marine heatwaves (MHWs) are usually defined as five or more consecutive days in which sea surface temperatures are in the top ten percent of the 30-year average for the region. Using an even stricter definition — temperatures in the top one percent — the IPCC recently concluded that since 1982, marine heatwaves “have doubled in frequency and have become longer lasting, more intense and more extensive. A marine “temperature anomaly” might encompass an area as large as Canada and last over two years.
Ocean-based food webs that have sustained life for millennia have collapsed in unprecedented heat of MHWs.”
[Extracts from: TRIPLE CRISIS IN THE ANTHROPOCENE OCEAN, PART 3]
READ MORE: to better understand the impact of marine heatwaves on ocean – click this link to the whole article :