Freaky Algae Bloom in North Atlantic Looks Like Dead Zone Eddy
6
July, 2015
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:
Hat
Tip to Griffin (Who was the first to spot this particular algae bloom
eddy in the MODIS shot)
No comments:
Post a Comment
Note: only a member of this blog may post a comment.