Carbon Burst: will climate instability recur?—Dr. Laurie Menviel interview—Radio Ecoshock 2019-04-10
Channel: Stop Fossil Fuels
Date: 2019-05-01

The great southern ocean, reaching down to Antarctica, has absorbed up to 10% of our greenhouse gas emissions. Without that we would be much hotter already. But that ocean sink appears to be weakening. Scientists are exploring why carbon dioxide jumped 40 ppm in a few decades not so long ago, and whether that increase in warming gases could happen again.

Dr. Laurie Menviel, a researcher at the University of New South Wales in Australia, is a leading scientist with many papers.She won the 2019 Dorothy Hill Medal for her work as a ground-breaking young scientist.

In Earth’s latest glacial times, the planet’s climate went rogue, departing from the previously predictable cycles caused by our orbit and tilt. A predictable pattern of ice ages and warmer times was broken. Earth entered much longer colder ice ages, just at the time Homo sapiens emerged on this planet. The planet itself has an internal climate sensitivity that is not dependent on our position relative to the sun. We need to know how that works, because humans may be triggering that kind of process, this time toward warming.

Show by Radio Ecoshock, reposted under CC License. Episode details at https://www.ecoshock.org/2019/04/rebel-against-the-future.html

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WESTERLY WINDS BLOW UP MORE CARBON?
Around 16,000 years ago, a CO2 rise happened over mere decades, probably due to more intense westerly winds in the southern hemisphere. We're seeing a big change in southern hemisphere winds now, as the strongest winds retreat from Australia and gather closer to the South Pole.

The prime concept is the “Westerlies” in the Southern Hemisphere. Menviel: “Our study highlights the crucial role of SH [Southern Hemisphere] westerlies in driving abrupt atmospheric CO2 rise and associated global climate changes. Given the projected poleward intensification of SH westerlies over the 21st Century, and the fact that the Southern Ocean has absorbed ~10% of anthropogenic CO2 emissions, our results suggest a future reduction in CO2 sequestration in the Southern Ocean, with significant impacts on future atmospheric CO2 and climate change.

“It is crucial to document and understand the processes that led to this ice age intensification because, in the absence of changes in orbital forcing, this transition indicates an internal change in the sensitivity of the climate system.”

A NEW RECORD OF THE SOUTHERN HEMISPHERE GOING BACK 1.5 MILLION YEARS
We discuss: “Adam Hasenfratz and colleagues present a new 1.5 million-year record of temperature and salinity in the Southern Ocean. Using trace elements and oxygen isotopes locked inside the microscopic shells of foraminifera, a species of single-celled planktonic animals, Hasenfratz et al. evaluated changes in Southern Ocean circulation across the MPT.”

Most climate science comes from the Northern Hemisphere. We know a lot more about the North Atlantic than the South Atlantic. I wonder if a bias has developed that favors the Arctic as a driver of big changes, omitting important developments in Australia and the Antarctic. But now we have a detailed map of 1.5 million years in the Southern Ocean. That paper is “The residence time of Southern Ocean surface waters and the 100,000-year ice age cycle“, published March 8, 2019.

Dr Menviel studied abrupt changes that happened in the past, and not that long before humans developed agriculture and civilization. Could a poorly understood natural cycle release even more carbon dioxide on top of our enormous continuing emissions? My feeling after reading her papers: humans are playing amid giant forces that we don’t understand very well,—forces that could change our climate fairly quickly into brand new territory. Menviel writes:

“Such amplification may also occur as a result of anthropogenic emissions. The atmospheric CO2 concentration is now at its highest point since at least 800,000 years ago. The ocean has strongly mitigated this atmospheric CO2 increase, particularly in the Southern Ocean, which has absorbed ~10% of the emissions.

The observed poleward intensification of Southern Hemispheric westerly winds and increased Southern Ocean stratification, which are projected to be amplified with further greenhouse gas emissions, could weaken the Southern Ocean carbon sink and induce a nonlinear response of the oceanic circulation and continental icesheets over the coming centuries.”

In new science, just published in Nature, a team of researchers announce that Greenland’s greatest source of sea level rise, the Jakoshavn Glacier has reversed from record ice loss to a gain of ice over the past two years. Apparently this shows again the very big role of ocean temperatures modulating ice loss—another Laurie Menviel specialty.