The usually brownish-green North Atlantic has turned blue-green in recent weeks due to a combination of atmospheric conditions and it now seemingly resembles the Caribbean Sea. The uncharacteristically blue-green hue of the North Atlantic is the result of phytoplankton and has been around for at least ten days or so – but is likely to not last much longer.
Phytoplankton is a microscopic plant that lives in water and contains the pigment chlorophyll. It has been in bloom in recent days due to upwelling which is when cold water rises to the surface of the ocean. When surface level winds blow surface water away from the coast (i.e., an off-shore wind), deeper, colder water rises up and the pigment chlorophyll causes the plant to reflect blue-green wavelengths of light. Given adequate sunlight and nutrients, phytoplankton populations can explode into blooms large enough to be visible from space. On July 7, 2016, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired this natural-color image of a large phytoplankton bloom off the coast of New Jersey.
In addition to the recent off-shore winds that have contributed to the color change of the North Atlantic, dry weather also has played a role in the unusual clarity. Much of the Northeast US has been drier-than-normal causing less river flow and the lack of runoff typically means a clearer Atlantic. The chill of the North Atlantic remains; however, despite more of an appearance that resembles the Caribbean Sea. Water temperatures have been confined to the 60’s – partly the result of the rising colder waters from below.
Phytoplankton blooms are often harmless, and are an important food source for marine life. Other times, blooms can be harmful; they can deplete the water’s oxygen and suffocate marine life, and produce toxins that can be harmful to both aquatic creatures and humans.
Meteorologist Paul Dorian