The oceanic currents are not doing well. This is what two studies recently published in the Nature magazine conclude, revealing an alarming disruption of the ocean currents, especially in the Atlantic Ocean. If they were to get any slower, if not stop completely, consequences would be irreversible.
For several decades, researchers have been observing the thermohaline circulation: the circulation of oceanic currents. Today scientist are categorical and point out evidence of change: the oceanic currents hasn’t been weaker in over 1600 years.
Climate change
Studies results show that ocean circulation has been relatively stable between the 5th and the end of the 19th century, and started weakening at the beginning of the industrial era. This significant decline from around 1950 is most probably due to human activities directly impact the environment.
The weakening of these currents (known under the acronym AMOC for Atlantic meridional overturning circulation) is then the result of climate warming. The melting of polar ice releases fresh water in large quantity in the ocean. This water weakens the oceanic currents by preventing waters from becoming dense enough to circulate. This less salty water compromises the ocean circulation process between the northern and southern hemispheres.
This constant circulation of oceanic waters allows the warm waters from tropical areas of the Atlantic Ocean to flow North thanks to the Gulf Stream, thus warming up Western Europe. Once North, the waters cool down, become denser and heavier and flow back south.
This gigantic conveyor belt is set in movement by the density variations in ocean waters. This circuit flows all over Erath and regulates our climate. This is how the Gulf Stream provides Western Europe with a temperate climate. If up North the ocean water does no cool down enough, and if the salinity level lowers, the system no longer works properly. The water is no longer dense and salty enough to dive and flow back south.
Large scale consequences
The Woods Hole Oceanographic Institution, having contributed to the studies, warns: “If the system continues to weaken, it could disrupt weather patterns from the United States and Europe to the African Sahel, and cause more rapid increase in sea level on the U.S. East Coast.”
The circulation of oceanic waters is essential to marine life. Currents transport nutriments, coral larvae, fish and most of all oxygen. From an area to the other, some regions of the Atlantic Ocean can then lack these elements, thus upsetting marine ecosystems. Currents also contribute to the Oceans’ capacity to store carbon dioxide (CO2), the main responsible for climate warming. If marine currents keep weakening, the amount of carbon dioxide in the atmosphere will increase and further contribute to climate warming.
Fishing also could be impacted by the weakening of currents: the increase or decrease of temperatures, depth variations and lack of oxygen harm some fish species, quantities of plankton, whales and birds. Commercial fishing is thereby the first industry impacted by these changes.
The studies do not say whether the oceanic currents natural system is going to keep weakening. Should this be the case, more and more climatic events are to be anticipated: trajectory of storms coming from the Atlantic Ocean, intense heat and cold waves, quick sea level rising…
The conclusions of these studies are indeed concerning. The Atlantic meridional overturning circulation is the main actor in world climate regulation and thus essential to marine and land ecosystems. Climate change induced by human activities is the key suspect for these disruptions: an effort to reduce our environmental footprint is more than necessary!
