Is Climate Change going to cause the Gulf Stream to collapse? – If so, will it also spell the end to barbecued sardines in June?!!

Before I begin, I must say that all the usual sensible and reasonable caveats apply. I am not a Climate Change denier, I do not get paid to write any of this and, also quite important to mention, I am not a Climate scientist, nor have I ever run any climatological models. These are simply my relatively informed opinions and logical inferences… I recommend you get your own.

In Portugal, June is a month of festivities in celebration of the so called “Popular Saints”, St. Anthony, St. John and St. Peter. St. Anthony gets the 12th and the 13th days, whilst St. John gets the 23rd and 24th. As for St. Peter… I cannot remember I’m afraid…nobody really cares much for St. Peter sadly. These are no more than, as is quite common with Christian festivities, converted pagan observances – in this case on occasion of the summer solstice. They are meant to mark the longest day of the year and the beginning of the unbearably hot summer. They also mark the immense bounty of sardines that spawn throughout the seacoast… as it happens, at this time of the year, in all eastern sea basin coasts, around 30 to 40 degrees latitude north - and about 6 months later at the same latitudes in the south hemisphere.

Invariably the celebrations involve the consumption of this bounty - they say that, in Portugal, one barbecued sardine is eaten every 13 minutes during the month of June. Sardines which are in turn fed by the nutrients brought to the surface by a phenomenon called “coastal upwelling”. Long story short, the earth’s rotation and spheric shape causes the so called “Coriolis Effect”, which, together with the Global Wind System and sea currents, conspire to cause strong northerly winds parallel to the coast around this time of the year… These winds push the warm water from the surface of the sea towards south and southwest… which, in turn, pulls the cold nutrient rich water from the bottom to take its place. Any na?ve tourists, expecting the nice warm beaches of sunny Portugal (particularly in the north), will understand well the disappointment brought about by this phenomenon. Not only is the water cold, but the currents are also treacherous. Lots of salty water and seaweed though… so, still well worth the visit!!

But what does this have to do with the hypothetical collapse of the Gulf Stream and consequential peddled end of all life on earth… or at least the death of a few hundred million people. Well… both phenomena are driven, ultimately, by the same two things:

-         The earth is a sphere (apologies flat earthers, but there’s no way around that – forgive the pun);

-         The earth rotates.

The earth is a sphere and hence it is heated differentially across its surface. Therefore an “air-conditioned system” comes into place to transport excess heat from the tropics to the poles… this air-conditioned system has two elements… the Global Wind System and the ocean currents.

Simply put, the Global Wind System is caused by pressure gradients in the atmosphere due to the above-mentioned differential heating. The currents are caused by the effect of the wind friction on the sea surface, the temperature gradient caused by the by now famous differential heating of the earth, and the salinity gradient caused by differential water evaporation from the sea surface… on account of the winds not blowing with the same intensity everywhere. For this reason, the ocean currents are also called of Thermohaline Circulation (as in, it is caused by temperature and salinity differences in the oceans).

Both the Global Wind System and the Thermohaline Circulation would be very simple (moving from the equator to the poles, north and south) if the earth didn’t rotate. However, the earth does rotate, and because it rotates faster in the equator than it does in the poles, it causes an apparent force that acts on moving objects - making them deviate to the right in the north hemisphere and to the left in the south. Hence the circulatory patterns you see in the weather charts.

If it wasn’t for the presence of the masses of land…the oceans would also present these circulatory patterns… they sort of do still, but a bit distorted. They have kept, at least, the east/west sea basin divide one would expect and, for this reason, you get sardine festivals in Lisbon but not in New York (which is roughly at the same latitude). You also get sardines and anchovies seasons in the west coast of the US and the coast of Peru and Chile, but not in the coast of China, for example.

As depicted by the picture above, this circulation is global (global conveyor belt). Therefore, the Gulf Stream does not exist in isolation, it is intrinsically connected to all the other currents as, for example, the Kuroshio in Japan, the Humboldt in Chile and Peru and the Agulhas in South Africa

If I still have your attention by this point… you may be wondering by now that, just as long as the earth remains spherical and continues to rotate, there will always be a global conveyor belt in the oceans, as well as a Global Wind System in the atmosphere… so what is the fuss all about?

Well, the problem is the “haline” part of “Thermohaline”, as you will know if you have watched the greatly exaggerated movie “The day After Tomorrow”.

The global conveyor belt seems to be slowing down in the north Atlantic, due to the accelerated melting of the ice caps and consequential dumping of above normal amounts of fresh cold water in the north Atlantic every summer. This reduces the salinity differential, hence decreasing the salinity gradient “force”… and the speed of the Gulf Stream. So, this seems to be a bit of a problem… as we kind of depend greatly on this part of the air-conditioning system for our typical weather in the western world. Therefore, a lot of attention has been put into it … more than say … the Antartic Circumpolar Current and the effects of ice caps melting there.

But this is the part where we need to start thinking a bit though, and try to go beyond papers that are based on runs by models that, for example, until recently, did not even include the ice in Greenland.

Firstly - The atmospheric/oceanic system is extremely complex and difficult to model, it is also very interdependent and, if one part of the air-conditioning is not working properly, the other will have to step-up…as the energy is still there, and it is still roughly the same. Some scientists say this is already happening and this is why we are seeing higher frequency of bigger storms…bigger storms, faster winds…faster winds > more evaporation from the ocean…more evaporation…higher salinity… and, after a while, we are roughly back to where we started.

Secondly - This has happened before, not once, but a number of times. Earth has experienced multiple ice ages and multiple melting of the ice caps before. Or indeed this has been happening since the last ice age – and the Gulf Stream is still here. If you think that the difference is that, now, it is happening too fast… than let’s look at the last ice age more closely. New evidence from ice cores drilled in Greenland (of all places) seem to indicate that the last ice age ended in a dramatic change…in a period of only 3 to 4 years. This was about 12 000 years ago after a period called the “Younger Dryas”, that many anthropologists and archaeologists think ushered in the Neolithic revolution – the dawn of civilization.

I don’t intend to be cavalier about this issue and do think this is something the scientific community should pay attention to, but in a dispassionate, scientific and rigorous way. They should leave behind the click bite paper tittles and the doomsday scenarios based on fallible simplistic models. Most of them do not have the appeal of a Dennis Quaid or a Jake Gyllenhaal, or their talent for drama, and this is unlikely to win them any Nobel prizes. In the meantime, they are doing the world a disservice.

I would prefer to see papers and model runs that focus on the amount of time that it will take for the air-conditioning system to reach a new state of equilibrium, and what that new state of equilibrium will look like…so that we can better prepare for what is coming.

Underneath the waters of the North Sea… you can find archaeological sites where Paleolithic tribes used to make their living. The Dogger bank was a mountain and the Thames river used to be a tributary of the Rhine. Our Paleolithic ancestors managed to escape the rising waters of the North Sea, I would assume we can also manage, even if we must temporarily limit our sardine consumption to protect stocks.