The Gulf Stream system is located in the Atlantic and forms part of a wider network of global ocean circulation patterns. It basically works like a giant conveyer belt. The circulation starts in the tropics where high temperatures warms the water and evaporation causes an increase in salt proportion in the water. This warm and salt water, flows northeast towards the US and crosses the northern Atlantic towards Europe and Greenland. In the polar regions, the water cools, becomes less dense and sinks. This allows the north Atlantic current to send the water back down to the tropics. This stream is also known as the Gulf Stream. The Gulf Stream moves over roughly 7000 million cubic feet of water per second and influences global weather patterns (Climate Signals).
How is global warming linked to changes in the gulf stream?
The Gulf Stream is self-sustaining if the temperature and salinity gradients are large enough to allow the water to let the water sink near the poles, which allows a back flow near the tropics. This long-lasting balance is slowly shifting due to climate change (Climate Signals). Higher temperatures make ocean waters warmer and lighter, which reduces the possibility for the water to sink. Furthermore, an influx of fresh meltwater from land ice dilutes the North Atlantic’s saltiness, reducing its density. A warming of the ocean and reducing salinity both reduce the ability for the water to sink near the poles, risking the entire Gulf Stream to shut down. The process of sinking water near Greenland is also known as the Atlantic Meridional Overturning Circulation, or AMOC (Climate Signals).
Affect on the weather
The Gulf Stream brings warm and humid air along the US E coast and large parts of Europe; hence the winters are mostly mild and the summers not too hot. Furthermore, it affects the weather such as cyclogenesis (formation of low-pressure areas) and low cloud formation. Research shows that the gulf stream affects the entire troposphere. Sharp seawater temperature gradients, cause winds to convergence in parts of the Gulf Stream, resulting in narrow bands over precipitation (Minobe, S et al, 2008). The rising motion and cloud formation can extend into the upper troposphere. Locally, these mechanics can force planetary waves, affecting the weather far outside the Gulf Stream (Minobe, S et al, 2008). These mechanics help with the formation of low-pressure systems which track east of the Atlantic into western Europe. A weakening temperature gradient in the Gulf Stream could potentially lead to less low-pressure systems over the northern Atlantic and western Europe. But it is important to note that the magnitude of the anticipated weakening of the Gulf Stream undermines the predictability of the future climate in Europe (McCarthy et all., 2015).
How real
Currently we see warming conditions around the world. However, there is a place over the Atlantic where the atmosphere is cooling during the recent years. This is also known as the ‘cold blob’. The blob is the result of cold water building up near the surface of the Atlantic instead of sinking. Due to a smaller temperature and salinity gradient in the Gulf Stream, compared to the rest of the water, we already see that cold water is not able to sink as it should and therefore compiles near the surface (McCarthy et all., 2015). Hence, the cold-water pool over the northern Atlantic. The melting of land ice enhances this process as freshwater dilutes the salt ocean even further, reducing the salinity gradient even more. This disrupts the Atlantic Meridional Overturning Circulation (AMOC). Recent studies shows that the AMOC is already weakening (McCarthy et all., 2015). However, it is difficult to forecast when the AMOC will shut down, if there is no reduction in the current carbon conditions. The most recent studies show that this might already be before 2100. But it is important to note that it comes with a large uncertainty, as there is evidence that the AMOC has fluctuated in the recent past as well and recovered from weaker periods (Kalucka, 2023). But if the AMOC shuts down, it will likely cause a further reduction in the oceans capacity to take up carbon, further enhancing global warming (Kalucka, 2023).
In conclusion
There is consensus that the future AMOC will weaken as a result of climate change. However, it is still uncertain whether the AMOC will shut down completely or not, as a result of climate change. This is still an ongoing debate in research. However, a strongly weakened AMOC transports less heat to the north. This will have major consequences for our global climate, with Europe likely being the most heavily affected region. As a result, there will be a large impact on offshore operations as well.
Sources:
- Climate Signals. (z.d.). Gulf Stream system weakening. Climate Signals.
Rahmstorf, S. (2007). - A semi-empirical approach to projecting future sea-level rise. Nature, 446(7136), 200–203. https://doi.org/10.1038/nature06690.
- Minobe, S., Kuwano-Yoshida, A., Komori, N. et al. Influence of the Gulf Stream on the troposphere. Nature 452, 206–209 (2008). https://doi.org/10.1038/nature06690.
- McCarthy, G. D., Haigh, I. D., Hirschi, J. J.-M., Grist, J. P., & Smeed, D. A. (2015). Ocean impact on decadal Atlantic climate variability revealed by sea-level observations. Annual Review of Marine Science, 7, 389–413. https://doi.org/10.1146/annurev-marine-010814-015656.
- Kałucka, A. B, (2023). University of Copenhagen. Reservoir computer-based detection of AMOC tipping.
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