Definition of Ocean Circulation
The concept of ocean circulation refers to the movements of water in the oceans and seas. The thickness of the surface layer of water that is moved by wind varies from 500 to 2000 meters. Surface ocean currents carry water from the poles to the tropics, where it is heated, and, afterwards, this water moves back to the poles, where it becomes cold and moves from the surface to the deep level because of its increased density.
The intensity and path of surface currents depend on wind patterns, strength, and locations (Wilson et al., 2016). The major surface ocean currents are Antarctic Circumpolar Current, Indonesian Throughflow, East Australian Current, North Equatorial Current, South Equatorial Current, North Equatorial Counter Current, and North Queensland Current (Wilson et al., 2016). Deep ocean circulation is also known as thermohaline circulation because it is caused by the different densities of water that, in its turn, are caused by the changes in temperature and salinity of the water.
The significant factors that affect the water movements are related to the wind patterns, differences in salinity and temperature of the water, and ebb and flow. Additionally, ocean circulation is strongly affected by climate change. According to Wilson et al. (2016), the intensity and path of many ocean currents will inevitably alter because of climate change. This, in turn, will negatively affect marine life (Molinos, Burrows, and Poloczanska, 2017). The reason for this destruction is that climate change alters ocean currents and, consequently, changes the habitat of marine organisms.
Ocean Circulation
The climate change and the subsequent alteration of ocean currents in the central Indo-Pacific region put in danger tropical reef ecosystems. Even though this tropical region is currently marked with the “highest levels of marine biodiversity in the world,” changes in the temperature of the environment could be detrimental for many tropical species that inhabit the Indo-Australian Archipelago (Wilson et al., 2016, p. 927). What is more, many species that used to live in the tropical region move towards poles where the temperature is lower (Wilson et al., 2016). In the temperate region, water moves in both directions: from the equator towards poles and vice versa.
Climate change in the temperate region caused the recolonization of planktonic organisms (Jaspers et al., 2018). In the subpolar region, ocean circulation is characterized by the divergence of surface water. Subpolar gyre includes Norwegian Current, North Atlantic Current, Labrador Current, and Subarctic Current, to name but a few.
Ocean Current Drive Invasion Species
As it has already been mentioned above, climate change provokes alterations in an ocean current that, in turn, affect the movement of initial inhabitants and invasion species. For example, the study conducted by Jaspers et al. (2018) reveals that ocean current connectivity propelled the “secondary spread of a marine invasive comb jelly across western Eurasia” (p. 815). At the same time, Jaspers et al. (2018) argue that the dispersal of non-native species might also be caused by other factors such as the “release of ballast water from container ships” (p. 815). Still, the importance of ocean current should not be underestimated because this was how the comb jelly Mnemiopsis leidyi moved from the Black Sea to the northern Europe area (Jaspers et al., 2018).
Wilson et al. (2016) and Molinos et al. (2017) come to similar conclusions on the relations between ocean currents, climate change, and behaviour of local organisms. Overall, it could be concluded that the critical reason for the drive of invasive species and the move of the initial inhabitants is that they try to find such an environment suitable for them and resembles the living conditions before climate change occurred.
References
GarcĂa Molinos, J., Burrows, M.T. & Poloczanska, E.S. (2017). Ocean currents modify the coupling between climate change and biogeographical shifts. Scientific Reports, 7, 1-9. Web.
Jaspers, C., Huwer, B., Antajan, E., Hosia, A., Hinrichsen, H.-H., Biastoch, A., Angel, D., Asmus, R., Augustin, C., Bagheri, S., Beggs, S. E., Balsby, T. J., Boersma, M., Bonnet, D., Christensen, J. T., Dänhardt, A., Delpy, F., Falkenhaug, T., Finenko, G., … Woźniczka, A. (2018). Ocean current connectivity propelling the secondary spread of a marine invasive comb jelly across western Eurasia. Global Ecology and Biogeography, 27(7), 814–827. Web.
Wilson, L. J., Fulton, C. J., Hogg, A. M. C., Joyce, K. E., Radford, B. T., & Fraser, C. I. (2016). Climate-driven changes to ocean circulation and their inferred impacts on marine dispersal patterns. Global Ecology and Biogeography, 25(8), 923–939. Web.