Thursday, September 23, 2010

Affect of Ocean Colour on Pacific Tropical Cyclones

Image by Jeff Schmaltz

In the article “Deep Blue Oceans Spawn Fewer Tropical Storms” from New Scientist Magazine, the author, Anil Ananthaswamy presents the results of a study conducted by Anand Gnanadesikan and his colleagues of the Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey titled “How ocean colour can steer Pacific tropical cyclones.” By modelling the circulating ocean currents in the North Pacific over which tropical storms form, they discovered that clearer ocean waters would result in fewer cyclones. The study explains that because ocean colour alters the absorption of sunlight, water clouded with phytoplankton will warm up closer to the surface while clear water will warm up at a deeper level. This change in sea surface temperature has a further impact on the conditions of the atmosphere (Gnanadesikan, 2010). Although both articles contain similar content, there are also some key differences to point out.

One feature to contrast between the two articles is the strength of claims within each work. In general, primary sources avoid the problem encountered with many secondary sources: each new author may distort the original study or put an entirely new spin on it. An advantage of Gnanadesikan’s study, which was published in the Geophysical Research Letters, is the reliability of the data. The author takes an objective approach and he views the study from all angles while taking into consideration that no scientific claim can truly be accepted. This is because the scientific world is always changing with new discoveries and unexpected setbacks. As a result there are many variables to take into consideration when forming a conclusion. In comparison the secondary source is more subjective; it focuses on how Ananthaswamy interpreted Gnanadesikan’s study and what he wants his audience to believe. Ananthaswamy presented an optimistic outlook that in the future there may be fewer hurricanes and typhoons affecting the American and Asian coastlines. Yet, claims made in a secondary source, such as Ananthaswamy’s, are often limited; they can never be considered as strong as those made in a primary source because of the lack of supporting data. On the other hand, Gnanadesikan’s study is backed up entirely by concise, technical evidence; the results of his study were plainly stated throughout the article without bias. Through conducting research, it is apparent that secondary sources draw information from primary sources. However, if the reader does not look into the mentioned primary source, they will have no way of knowing that what is stated in the secondary source is true. It should be noted that not all of what is stated is necessarily correct.

Through comparison, it was evident the secondary source stayed fairly consistent with the results from the primary source except in one notable area. In the primary source, Gnanadesikan describes a model where reducing the chlorophyll levels in the ocean by 50% created an atmosphere which was likely to produce 35% less tropical cyclones in the subtropical northwest Pacific. The secondary author, Ananthaswamy, used this statement to imply that 20% lower cyclone activity in the 1960s was due to chlorophyll levels which were about half of the present day values. However the original study makes it clear that although the records from the 1960s are consistent with Gnanadesikan’s model, Ananthaswamy’s statements may not apply. Gnanadesikan believes some of the change in chlorophyll levels from the 1960s to now may be attributed to differences in measurement techniques. No clear explanation exists for changing levels of ocean chlorophyll during this time period; therefore Gnanadesikan states: “It would be premature to attribute the change in cyclone activity to any such mechanism” (Gnanadesikan, 2010).

Another aspect of analysis that should be considered when comparing primary and secondary sources is the intended audience of each work and the purpose of its publication. Both publications were written with the objective of getting the reader to think and consider future possibilities based on the study. It is clear the primary source is intended for the scientific community and other researchers. It is written in a more complicated and scientific manner than the article found in New Scientist magazine and is obviously not aimed at the general public. By publishing Gnanadesikan’s work, his findings can be reported in a detailed manner thus allowing readers to understand the study and come up with conclusions on their own as opposed to being forced an opinion by the secondary sources’ author.

The secondary source compliments the original data found in the primary source. The secondary source identifies a critical area of interest in its reader that can be investigated further in the primary source. It is likely that without secondary sources, many primary sources would get little attention from the general public. The author of the secondary article did an adequate job of summarizing the data found in Gnanadesikan’s study as well as presenting the findings in a more user friendly manner. It is evident this article is intended for a different demographic of people than the primary source. However, we must remember that through this transition there is chance the author will misinterpret the results of the original study. On the positive side, secondary sources are known to provide more accessibility to research. For instance, the general public is more likely to come across research in a magazine as opposed to stumbling across the Geophysical Research Letters from which Gnanadesikan’s study was found. This lack of accessibility can be seen as a limitation to primary sources.

Through analysis of these primary and secondary sources it is clear they both have their own set of advantages and disadvantages. Neither one is superior to the other; they must be used together in order to get a broader spectrum of information and appeal to all groups of people.

Primary Source:
Gnanadesikan A., Emanuel K., Vecchi G., AndersonW., & Hallberg R. (2010). How ocean color can steer Pacific tropical cyclones. Geophysical Research Letters, 37, L18802, doi: 10.1029/2010GL044514. Retrieved from

Secondary Source:
Ananthaswamy A. New Scientist. (2010, August). Deep Blue oceans spawn fewer tropical storms. Retrieved from

Posted By: Elisha Persaud
Student Number: 0713364

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