Polar Oceans’ Influence on the Tropics
18.06.2010 - Water & Oceans, Bi-polar
Research conducted by an international team of scientists and recently published in the journal Science demonstrates a close link between the changes in the subpolar climate and the development of the modern tropical Pacific climate approximately 2 million years ago. The researchers studied the Northern Pacific and Southern Atlantic sea-surface temperatures from the Pliocene Era (3.65 million years ago) to the present day. The data they obtained undelines the fundamental role played by both polar oceans in the evolution of the tropical climate.
The cooling and expansion of both oceans between 1.8 and 1.2 million years ago resulted in an increased temperature difference between the equator and the poles. This helped create the modern day ‘cold tongue’ in east tropical Pacific. Created by the ocean’s thermocline, the cold tongue brings cold, deep waters to the surface. During the warmer climate of the Pliocene, the cold tongue was much smaller, creating a situation more like the ‘El Niño’ events that hit the Pacific every three to five years.
Dr Erin McClymont of Newcastle University mentiond that the team’s results “show that the polar region oceansp lay a key role in the global climate, and that one outcome of a rise in global temperature could be an increase in the depth of the thermocline and contraction of the cold tongue in the eastern Pacific.” She also explained that as “the high latitudes are currently experiencing the largest climate changes…this could impact on tropical climates” similar to what happened in the Pliocene.
The researchers drilled sediment cores in the ocean to measure the composition of alkenones - highly resistant organic compounds produced by phytoplankton, which researchers use as ‘biomarkers’ to reconstruct past temperatures of the ocean surface.
