Humans as a species behave in interesting ways. We respond to events such as a terrorist attack, a flooding or a wildfire with some sort of intellectual answer – not always the right response but that’s a different story. On the other hand, dramatic events that affect our world as a whole and which are long lasting seem too big to fathom.
One such event is the ocean circulation of the Atlantic Ocean, which includes the Gulf Stream, has probably lost stability over the past century and could now be facing a crucial tipping point. The news should have sent shockwaves through the world – but it didn’t.
Niklas Boers, a climate researcher of the Potsdam Institute for Climate Impact Research (PIK) came to conclude this. He published his findings in the Journal, Nature Climate Change .
Hurricane Maria to the southeast of Puerto Rico. Source Wikimedia Commons
Why is this important and what does it mean?
The Gulf Stream is considered the long-distance heater of Europe, as it brings heat as far as the British Isles and off the coast of Norway. The Gulf Stream, in turn, is part of the larger Atlantic Meridional Overturning Circulation (AMOC). This carries warm and salty water northward at the ocean surface, while cold and low-salinity water flows back at depth. Based on evidence from Earth’s history, researchers suspect that the circulatory system can, in principle, switch between two different operating states: a strong circular motion, as currently observed, and a much weaker one.
Because the AMOC system redistributes large amounts of heat, it affects weather worldwide. A sudden change from the strong to the weak state would therefore have serious consequences: Europe would possibly cool, while hurricanes would increase over the Atlantic.
A number of factors are probably responsible for the approach to the tipping point. The increased input of freshwater originating from the melting of the Greenland ice masses is a main factor while, in addition, precipitation and input from rivers into the ocean have also increased as a result of climate change. Fresh water is lighter than salt water and therefore tends to remain at the surface instead of sinking into the depths. This process is slowing down the normal ocean circulation.
Boers traced the telltale signs of change in ocean circulation, such as saltwater content and ocean temperature, back over 150 years. His analysis shows that the AMOC system transitioned from relatively stable conditions to a point near a critical threshold over the last century.
And the boas?
We saw in the recent past glimpses of what hurricane intensification means for the West Indies. Hurricane Maria devastated the northeastern West Indies in September 2017, particularly Dominica (Category 5), Saint Croix, US Virgin Islands and Puerto Rico (Category 4) were affected. It is regarded as the worst natural disaster in recorded history to affect those islands. Considering the above mentioned study, we need to prepare for more of this.
But even if some islands are unaffected by hurricanes, and aside from big tangible impacts, even a small change in weather, which might not be considered as dramatic in human terms, might have a huge impact on the boas. The food source of the boas might be affected and most probably the ability to reproduce will be strongly affected, since reproductive stimuli to which the boas evolved are altered and the chances of proper thermoregulation for gravid females might decline.
We have but one chance to improve the likelihood of survival for the West Indian Boas – captive breeding through willing institutions and the Invisible Ark.
Addendum
On August 9th the IPCC published it’s Sixth Assessment Report .
Key findings:
Global surface temperature was 1.09C higher in the last decade (2011-2020) than in the last pre industrialisation half century (1850-1900).
The past five years have been the hottest on record since 1850
The recent rate of sea level rise has nearly tripled compared with 1901-1971
Human influence is “very likely” (90%) the main driver of the global retreat of glaciers since the 1990s and the decrease in Arctic sea-ice
It is virtually certain that hot extremes including heatwaves have become more frequent and more intense since the 1950s, while cold events have become less frequent and less severe
Masson-Delmotte, V., P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud, et al. 2021. “IPCC, 2021: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change.” Cambridge Univ. Press. https://www.ipcc.ch/assessment-report/ar6/.
Boers, Niklas. 2021. “Observation-Based Early-Warning Signals for a Collapse of the Atlantic Meridional Overturning Circulation.” Nature Climate Change 11 (8): 680–88. https://doi.org/10.1038/s41558-021-01097-4.
