Back in March, we reported on a new study that found algae blooms concentrating in ocean eddies off Africa were generating mobile dead zones threatening sea life in the Tropical Atlantic. Based on recent satellite imagery analysis, such phenomena may not just be isolated to regions off the Ivory Coast and Gibraltar. It instead appears that mobile and potentially oxygen-depleting algae blooms may also be cropping up in the far North Atlantic.

(Is the North Atlantic starting to see eddies which host ocean dead zones? The image above appears to show just such a feature. Image source: LANCE MODIS.)

Ever since mid-June, a strange feature has been visible in the satellite shot of an ocean region bracketed by Iceland, Svalbard, and the center of the Scandinavian Coastline. The area appears to include a major algae bloom which has been swept up into an ocean eddy. Measuring about 30 miles in diameter, the bloom displays visible aspects similar to its more southerly cousins. As with the mobile Tropical Atlantic Dead Zones off Africa, this swirl appears to have concentrated surface water nutrients — generating a region of more intensified microbial growth. A growth that now shows the tell-tale neon blue contrast of an algae bloom capable of tanking surface ocean oxygen levels.

High Latitude algae blooms are a prevalent occurrence during Spring and Summer as Ocean surface waters warm. And during recent years, rapidly warming waters and retreating sea ice has enabled more prolific algae blooms in northern seas. Though these waters contain more oxygen due to overall cooler temperatures, both the increased warmth and the large algae blooms generate a mechanism for loss of oxygen content in the vital surface zone.

(Strange algae bloom with characteristics similar to mobile Tropical Atlantic Dead Zones is visible as the blue dot at center frame in this July 2 LANCE MODIS satellite image.)

In addition to human forced warming of the ocean system reducing overall ocean oxygen levels, human fossil fuel burning, fertilizer runoff and deluges increasing run-off volume (due to global warming’s impact on the hydrological cycle) adds nutrients to surface waters. The nutrients come primarily in the form of nitrogen which rains down as fossil fuel fallout or is flushed in ever greater volumes down river systems as frequency of extreme rainfall events increase. As a result, the oceans are being loaded up with food for algae blooms.

A similar mechanism (usually triggered through enhanced volcanism) is thought to have lead to mass ocean die-offs in at least four of the five major mass extinction events. A mechanism which was likely most lethal when it started to enable anoxic ocean environments hosting microbes capable of producing massive volumes of hydrogen sulfide gas — which in the worst cases filled the oceans and vented into the atmosphere.

Ocean eddies further concentrate the nutrient run-off and fall-out through their churning action. So algae blooms have tended to intensify in these swirls of ocean currents. In the Tropical Atlantic, algae production in the eddies has been enough to generate large microbial die-offs and related depletion of oxygen — generating moving dead zones. If the newly identified algae blooms in these satellite photos are prolific enough to consume all the available nutrients in surface waters, they will also die off and, decaying, rob these waters of vital oxygen. Such an action could promote dead zone environments in northern waters in addition to those already documented in the Tropical Atlantic.

Links:

Ocean Dead Zones Swirl Off Africa

LANCE MODIS

Awakening the Horrors of the Ancient Hothouse — Hydrogen Sulfide in the World’s Warming Oceans

Anoxic Event

Hat Tip to Griffin (Who was the first to spot this particular algae bloom eddy in the MODIS shot)