On Aug 5 this month a news alert emerged from London that all is perilously unwell with North Atlantic waters. Two science writers lost no time to put out reports, Sarah Kaplan from Washington Post (WP) as a Breaking News and Jessica Corbett with her version in Science Daily. This writer wrote an initial muted response to Kaplan in WP’s Comments. The study by Niklas Boers of the Potsdam Institute of the Free University of Berlin and Exeter University, U.K. appeared on August 5, 2021, in Nature Climate Change, 2021 DOI: 10.1038/s41558-021-01097-4 with the title “ Observation-based early-warning signals for a collapse of the Atlantic Meridional Overturning Circulation”(AMOC). Nowhere was it mentioned, that a forerunner detailed study on this was published on 16 June 2021, by an expert group of Katinka Bellomo, Michela Angeloni, Susanna Corti & Jost von Hardenberg in another publication of the same journal Nature, called Nature Communications volume 12, Article number: 3659 (2021) with the title – “Future climate change shaped by inter-model differences in Atlantic meridional overturning circulation response.”
Based on that study and other available data now, may I be permitted to reset the perception on this issue with few nuances?
The acronym AMOC is a newcomer to world public knowledge, including for this writer. But geophysicists would say, the phenomenon was existent the past 40 k years. Only, we weren’t aware of it till it got too critical for our survival most recently. The matter is technically far more complex than what the science writers reported even as they did a great job in informing us.
Let’s face the actual data. Taken from the Aug 5 eight-page article of Niklas Boers we are given to understand that the AMOC is a major ocean current system conveying warm surface waters to North Atlantic from South having a strong and a weak mode. More succinctly, “A collapse from the currently attained strong to the weak mode would have severe impacts on the global climate system and further multi-stable Earth system components”. The so-called fingerprints of AMOC imply “a gradual weakening during the last decades”. Due to estimate uncertainty a reliable early-warning indicator was tooled and applied incorporating sea-surface temperature and salinity data of the Atlantic Ocean basin. While in the past there was stability, now emerges a “critical transition” devolving to instability.
The previous forewarning study by other experts Bellomo et.al on 16 June, 2021 says more.
“ In climate model simulations of future climate change, the Atlantic Meridional Overturning Circulation (AMOC) is projected to decline. However, the impacts of this decline, relative to other changes, remain to be identified. Here we address this problem by analyzing 30 idealized abrupt-4xCO2 climate model simulations. We find that in models with larger AMOC decline, there is a minimum warming in the North Atlantic, a southward displacement of the Inter-tropical Convergence Zone, and a poleward shift of the mid-latitude jet. The changes in the models with smaller AMOC decline are drastically different: there is a relatively larger warming in the North Atlantic, the precipitation response exhibits a wet-get-wetter, dry-get-drier pattern, and there are smaller displacements of the mid-latitude jet. Our study indicates that the AMOC is a major source of inter-model uncertainty, and continued observational efforts are needed to constrain the AMOC response in future climate change.”
Additionally it informs us that AMOC is “a large system of ocean currents, and plays a crucial role in the earth’s climate by regulating the global transport of heat, carbon, and freshwater. “Annually as much as ~0.5 PW of heat is carried across the equator into the North Atlantic by the AMOC, which is believed to be responsible for making the northern hemisphere approximately 1 °C warmer than the southern hemisphere, and for shifting the zonal average of the Inter-Tropical Convergence Zone (ITCZ) north of the equator at about 5°N, thus influencing global rainfall and atmospheric circulation patterns.”
Thus, they underline that AMOC is central to Our Earth’s climate, and one “tipping” element (threshold point since 2004) of Planet Earth’s climate fate. They also point out that abrupt changes in the AMOC assumedly caused glacial-interglacial transitions. AMOC amplifies these transitions. Simulations further show “an AMOC shutdown causes cooling of the northern hemisphere by several degrees, increased sea ice in the North Atlantic and Nordic Sea, and a southward shift of the ITCZ. Even smaller AMOC declines have been shown to cause widespread impacts.”
The human “anthropogenic contribution” these experts say is the reduction of AMOC via greenhouse gas generated. The decline caused sea water density decrease in Sub-Polar North Atlantic (SPNA), and is associated with a reduced warming in the SPNA sea surface temperature (SST) “ the North Atlantic warming hole (NAWH)
There seems a “paradoxical” function of NAWH as according to simulation study, it helps the AMOC through cooling to counteract this millennium’s warming over the North Atlantic. Atmospheric Processes also add to the formation of the NAWH. Experts opine, ocean circulation defines the onset and development of the NAWH. More studies are still awaited. Currently, one interesting result is, “ a decline in the AMOC has a cooling effect on Europe, but not so much on North America”, very true if one considers recent heatwaves and wild fires on U.S.-Canadian West Coast.
Global Realities Not To Miss
1) The NASA picture in Jessica Corbett’s story indicates ocean currents as also winds above ocean waters are never unidirectional. Multi-directional, they hover over oceans in circular waves and loops, moving forward further in loops and circles unpredictably.
2) Not many events can mono-causally be explained. For e.g. Greenland ice can melt under the warmer southern stream flowing to North Atlantic, as much by the heatwave that has currently struck the entire Arctic rim. But where from is this heatwave, what is its origin? Thus, many events are interconnected that we may or may not be able to explain to one-hundred percent scientific satisfaction today. But the fact is they are happening.
3) The major oceans are glued, The Atlantic, the Indian and the Pacific Oceans are openly interconnected that the warmth increase will spread around the Globe, although initially they are or may seem regionalised. That’s one demonstration how climate change affects the entire Globe.
4) The huge Arctic-Greenland ice melts have diluted the sea-water salinity, which also means reduced mineral absorption in-take for those salinity-sensitive fauna (mostly fish) that may disappear or their collective species growth significantly hampered with marine ecological ‘Misbalance’ (thrown out of balance and very onerous to correct unlike ‘Imbalance’).
5) The worst of it all is the calamitous truth experts confirm that the North Atlantic Ocean temperature has moved up approximately by 1 pc Celsius, significant enough, if one considers the maximum U.N. experts-set threshold of ≤1.5 deg Celsius as bearable upper limit for human and biological life to continue without serious risk worldwide for our Globe. The latest U.N. report on climate just released yesterday shows that we have already reached the 1.1 dig Celsius increase
6) The latest U.N. Report on Climate Change (released Aug 9, 2021) confirms an overall sea level rise. The rise trend as observed between 2008 -2016, currently stands at 3.7 millimetres, but will remain at a pre-determined statistical rise around 2 to 3 metres per year functional on assumed planet temperature rise of 1.5 deg Celsius. However, if it kicks up to a 5 deg Celsius rise we are doomed to an apocalyptic sea rise of 22 metres, enough to submerge a vast number of coastal cities on our planet. These warnings are dead serious.
Acknowledgedly, the General Root Cause is Global Warming which in turn is caused primarily by increased GH gases and CO2 emissions from advanced industrial countries (includes China with world’s largest consumer population and second largest economy) plus extra X-Sun flare ejections that possibly evaporate more water of the oceans generating more massive clouds bringing in floods and displacements of rains in many regions of Earth, more geo-thermic energy emerging from seabed possibly due to our Earth turning more on its axis. The general heat produced and the upward drift of the increased Atlantic warm water along with atmospheric warmth increased in the Poles (especially the North Pole of late) have in turn melted the Arctic and Greenland ice in huge quantities raising the Atlantic water to erosion scales on North-American sea coasts eventually to submerge coastal towns. Nobody can stop this surface movement of warm water from South Atlantic to the North.
Climatologists and atmospheric scientists are still studying the details. The inter-dependent parameters studied under global warming are, ocean currents, atmospheric currents, precipitation, sea surface temperatures, geomagnetic pulls connected to climate changes and so forth. Frankly, we don’t have to wait that long for their conclusions to arrive to do what we humans are obligated to do on our part.
Specifically, we the governing and the governed can impossibly deny – we have no control over the Sun, or on Earth’s geothermic energy or on Earth’s increased spin on its axis as we move around a hot-flaring gaseous planet The Sun. However, what we all can do is to tell our governments as public, because we vote for them, to invest and innovate immensely to develop pollution-free industrial production as a top priority, engaging the best of our brains, instead of promoting an obscene / rancorous greed for multi-billion dollar profit swell of a fractional super-rich (multi-billionaires), who own or govern the Big Industries that create the pollution and the only ones to profit at the cost of humanity’s mortality. After all it is our collective survival as human beings as a species and biological life as a whole that are at stake.
We have produced finally vaccines against an ominous devil the Covid-19 / its cohort variants that beleaguered us for nearly 2 years destroying tragically 4.27 million valuable human lives. This is the largest number of humans who died mono-causally in a short time ever since the World War II ended. We can also achieve a similar win in de-poisoning and saving our atmosphere and nature, so that we can at all live. Yes, we can. America and the rich nations should open the way with their resources, while the helpless poor cannot. Don’t wait for flood or sea erosion to reach your bedrooms! Time to act and not for blimp talk!
George Chakko, former U.N. correspondent, now retiree in Austria.