Ninety-seven percent of climatology scientists have regarded all the human activities of the 21st century to be contributing to dangerous climate change. The rest three percent are obviously on their way for accepting this fact. However, the change is so tremendous and horrific, for example, burning of the Amazon rain forests recently, that climate change is no longer a change but rather a climate crisis or maybe even climate explosion. This crisis will definitely hugely alter one of the major oceanographic processes by the end of this century.
According to an interdisciplinary research led by a team of scientists of Northeastern University, an ensemble of climate models suggested that coastal upwelling—a process by which deep, cold, and nutrient-rich water rises to the surface—will begin earlier, end later, and increase in intensity at higher latitudes. This will result in a significant decrease in the existing latitudinal variation in coastal upwelling, which is likely to influence the geographical distribution of marine biodiversity on a global scale.
This research team comprised of Auroop Ganguly, a climate change expert at Northeastern and an associate professor in the Department of Civil and Environmental Engineering; Tarik Gouhier, an assistant professor in the Department of Marine and Environmental Sciences at Northeastern’s Marine Science Center; and Daiwei Wang, a postdoctoral researcher in Ganguly’s lab. Bruce A. Menge, a professor in the Department of Integrative Biology at Oregon State University, also collaborated on this research and co-authored the paper which recorded the entire work and the result of this research. The team published this paper online in the journal, Nature.
“It’s critically important to understand how coastal upwelling might change in a warming climate,” said co-author Auroop Ganguly. He noted that this study is the first to identify a consistent pattern of intensification and spatial homogenisation of coastal upwelling under greenhouse warming in the latest generation of climate models.“We focused on these upwelling changes that are robust and consistent across models and geographical regions because they are most likely a consequence of global climate change,” said Wang, the study’s lead author.
This work was a tremendous addition to the Northeastern’s commitment to interdisciplinary research that addresses global challenges in sustainability by bringing together two research labs whose pursuits are intertwined. The team examined four upwelling current systems found in the Atlantic and Pacific oceans. While these four systems cover less than 2 percent of the ocean’s surface, they contribute more than 20 percent of the global fish catches. Citing their analysis of climate models, the researchers projected the upwelling season would expand by several days per decade between 1950 and 2099 at high latitudes in all four systems.
In addition, the two Southern Hemisphere systems showed larger and more consistent trends than the two Northern Hemisphere systems. Still, “despite regional differences, the lengthening of the upwelling season at high latitudes in (the four systems) is a robust global response to greenhouse warming,” they wrote.
As explained by Gouhier, upwelling is an important process that drives the availability of nutrients in the marine food web. It promotes nutrient availability, which makes phytoplankton more abundant. Zooplankton then feeds off phytoplankton, and fish feed off zooplankton. Increased upwelling in higher latitudes would promote more productive fisheries and marine ecosystems. However, the researchers warned that having too many nutrients cycling through a marine ecosystem could lead to hypoxic conditions, or “dead zones,” over large swaths of the coastal ocean. These are regions where the overabundance of nutrients thrust bacteria into hyper-drive and the resulting metabolic activity causes a reduction of the concentration of oxygen in the water, which can lead to mass die-offs.
If coastal upwelling becomes stronger and more persistent at higher latitudes, as the models suggest, then there will be a reduction in the existing latitudinal variation in coastal upwelling, which may generate a concomitant reduction in marine biodiversity. In other words, the composition of marine communities at high and low latitudes will become more similar. This could put species in greater competition with each other and create more species turnover in the coastal ocean, the researchers said.
As a result, hot spots where upwelling changes are occurring should be closely monitored to ensure the stability and productivity of fisheries and coastal ecosystems.
Dibyasha Das