Factors that inflict climatic changes part 3:
Part 2 here
DISCUSSION: When thinking about the global climate and factors that affect it, many people often ponder about the more frequently covered issues which include (but are certainly not limited to): greenhouse gases, deforestation and melting of glaciers. But the Earth also contains a more complicated conveyor belt of energy which affects the state of regional climate zones all over the world and this is the Earth’s oceans. Ocean currents play a crucial role in Earth’s climate, for example, either regulating the day-to-day weather of the western United States (and other parts of North America) as well as influencing many parts of northern Europe via the consistent transport of relatively warmer water emanating from the Gulf Stream and the western Caribbean Sea. It is important to acknowledge that approximately two-thirds of the Earth is covered by water, so there is no debate at this point in scientific research that the Earth’s oceans have a substantial impact and influence on the Earth’s global climate.
Ocean currents play a crucial role in the oceanic transfer of heat energy between the two hemispheres. More specifically, they play a crucial role in helping to facilitate an effective transport of the seasonal net surplus of tropical heat and moisture from the tropical regions of the world and towards the Polar, Arctic, and Antarctic regions. Differing ocean currents are chiefly driven by varying water densities, differentiating vertical oceanic heat profiles, and the complex interactions which occur between interacting zones of freshwater and salt water of varying concentrations. Ocean currents also play a key role in helping to regulate the global climate and help reinstate balance to the uneven distribution of energy that solar radiation has on regional sea surfaces. For example, even though the Earth typically receives approximately between 1.5 and 2.5% of the Sun’s net energy output, there is often a substantial differential between net uppermost oceanic heat content in looking between the tropics and the mid-latitudes. Thus, since the Earth always seeks a state of both oceanic and atmospheric equilibrium, the oceans help to redistribute the consistent imbalances through the progression of various global ocean currents which transport such regional surpluses of oceanic heat content to other cooler oceanic waters around the world.
As shown in the image above, the global oceanic system has a plethora of ocean currents which travel in various directions and possess the role of carrying both warmer and colder water depending on the given ocean current being referenced. An example of one such ocean current is the Atlantic Meridional Overturning Circulation or AMOC. The AMOC is an ocean current which carries warm water from the Southern Hemisphere to Northern Europe. More specifically, warmer water is transported up from the Gulf Stream and into the North Atlantic Ocean before being returned towards the Central Atlantic Ocean. The water being transported to the central Atlantic is colder and denser, so it tends to sink and consequently allows warmer water to rise towards the upper layers of the ocean (a process which is scientifically referred to as upwelling). One of many primary concerns for the future with the prospects of a warming world, is the continued gradual net warming of the North Atlantic Ocean.
A pattern chiefly defined by continued gradual warming could potentially create a situation wherein water being transported to the Central Atlantic Ocean could become warmer (and consequently, somewhat less likely to sink in accordance with the overturning southward-directed deep ocean circulation). This could then result in a gradual decrease in the strength and/or magnitude of the AMOC at certain points which could lead to a compromise in the efficiency of the typical net heat transfer being accomplished between various parts of the world. In short, the continued warming of Earth’s oceans will likely trigger changes in the efficiency and magnitude of typical global heat and energy exchanges which are critical to maintain a state of global energy balance. Hence, it will be crucial to continue monitoring the state of the Earth’s oceans (and various currents therein) to see how they evolve as continued changes continued to be applied to coupled atmosphere-ocean system and what threat(s) may be consequently imposed on Earth’s global climate system.
An occurrence that often happens with warming temperatures is the melting of freshwater reserves which can often pose a threat to Earth’s global ocean circulation system. The influx of freshwater from melting glaciers and land ice can have consequences and cause the upper-most layer of the ocean to become less dense. Although colder in Polar Regions, freshwater is less dense than salty ocean water. So, paradoxically, as the planet warms, and freshwater reserves melt, regions where warm water is circulated, would likely observe a decrease in sea surface temperatures due to the weakening of various ocean currents.
Referring to the AMOC, a recent study by the United States National Academy of Sciences showed that an uneven mixture of fresh and salt water along with warming ocean temperatures could decrease the transport of water by the AMOC between 5 and 48 percent. This seems like a wide range of variability, but it is based upon 19 experiments from five models of climate scenarios. With such an example of a projected decrease in global oceanic energy transport, numerous regions around the Earth could experience corresponding changes to their regional climate due to the lack of middle to upper oceanic water mixing which is why monitoring continued changes (and fluctuations therein) in our global oceanic circulations will remain that much more important as we move deeper into the 21st century.
To learn more about the story which inspired this article, click on the following link: https://phys.org/news/2016-03-variability-major-oceanic-currents-driven.html.
To also learn more about other interesting global climate topics/issues from around the world, be sure to click here!
© 2018 Weather Forecaster Alec Kownacki and Meteorologist Jordan Rabinowitz