As predicted by chemistry, change in the Arctic Ocean is
accelerating as temperatures warm faster than the global average, as the
sea ice melts, as northern rivers run stronger and faster, delivering
more fresh water farther into the northernmost ocean, and as we continue
blasting an ever increasing quantity of greenhouse gases into the
atmosphere. The
Arctic Ocean Acidification Assessment, a new report from the Arctic Monitoring and Assessment Program (
AMAP), presents these 10 key findings:
1. Arctic marine waters are experiencing widespread and rapid ocean acidification.
In the Nordic Seas, acidification is taking place over a wide range of
ocean depths, from surface waters (faster) to deep waters (more slowly).
Seawater pH has declined ~0.02 per decade since the late 1960s in the
Iceland and Barents Seas. Other ocean acidification signals have also
been encountered in surface waters of the Bering Strait and the Canada
Basin of the central Arctic Ocean.
2. The primary driver of ocean acidification is uptake of carbon dioxide emitted to the atmosphere by human activities. The
ocean has swallowed our atmospheric carbon dioxide emissions and slowed
global warming during the past few critical decades while we dithered
in disbelief. But the cost of temporarily delaying even more warming has
been the increasing acidification of seawater. The average acidity of
surface ocean waters worldwide is now ~30% higher than at the start of
the Industrial Revolution.
3. The Arctic Ocean is especially vulnerable to ocean acidification. Arctic rivers
plus melting ice input huge (and increasing) amounts of freshwater into
the Arctic Ocean, changing the chemistry and making it less effective
at neutralizing CO2's acidifying effects. Add the fact that cold waters
slurp up more CO2 from the air. Add the fact that dramatic
decreases in Arctic summer sea-ice cover—real and projected—allow for
greater transfer of CO2 from the atmosphere into the ocean. These combined influences make Arctic waters among the world's most easily acidified.
4. Acidification is not uniform across the Arctic Ocean. Other
processes influence the pace and extent of ocean acidification. Rivers,
sea-floor sediments, and coastal erosion all supply organic material
that bacteria can convert to carbon dioxide, exacerbating ocean
acidification, especially on shallow continental shelves. Sea-ice cover,
freshwater inputs, and plant growth and decay also influence local
ocean acidification. The contributions of these processes vary
from place to place, season to season, and year to year. The result is a
complex, unevenly distributed, ever-changing mosaic of Arctic
acidification states.
5. Arctic marine ecosystems are highly likely to undergo significant change due to ocean acidification. Arctic
marine ecosystems are generally characterized by short, simple food
webs, where energy is channeled in just a few steps from small plants
and animals to large predators like seabirds and seals. The integrity of
such a simple structure depends greatly on keystone
species. Pteropods (sea butterflies) and echinoderms (sea stars,
urchins) are key food-web organisms that may be sensitive to ocean
acidification. Too few data are presently available to assess the
precise nature and extent of Arctic ecosystem vulnerability, as most
biological studies have been undertaken in other ocean regions.
Arctic-specific long-term studies are urgently needed.
6. Ocean acidification will have direct and indirect effects on arctic marine life.
Some marine organisms will respond positively to new conditions
associated with ocean acidification. Others won't. Experiments show that
a wide variety of animals grow more slowly under the acidification
levels projected for coming centuries. While some seagrasses appear to
thrive under such conditions. Birds and mammals are not likely to be
directly affected by acidification but may be indirectly affected if
their food sources decline, expand, relocate, or otherwise change in
response to ocean acidification. Ocean acidification may alter the
extent to which nutrients and essential trace elements in seawater are
available to marine organisms. Shell-building Arctic mollusks are likely
to be negatively affected by acidification, especially at early life
stages. Juvenile and adult fishes are thought likely to cope with
acidification levels projected for the next century, but fish eggs and
early larval stages may be more sensitive. In general, early life stages
are more susceptible to direct effects of ocean acidification than
later life stages.
7. Ocean acidification impacts must be assessed in the context of other changes happening in Arctic waters. Arctic
marine organisms are experiencing not only acidification but also other
large simultaneous changes: climate change, harvesting, habitat
degradation, and pollution. Ecological interactions—e.g. between
predators and prey, or among competitors—also play an important role in
shaping ocean communities. As different marine life responds to
environmental change in different ways, the mix of plants and animals in
a community will change, as will their interactions with each other. We
don't know much of anything about this yet.
8. Ocean acidification is one of several factors that may
contribute to alteration of fish species' composition in the Arctic
Ocean. Ocean acidification is likely to affect the abundance,
productivity, and distribution of marine species. But the magnitude and
direction of change are uncertain. Other processes driving Arctic change
include rising temperatures, diminishing sea ice, and freshening
surface waters.
9. Ocean acidification may affect Arctic fisheries. Few
studies have estimated the socio-economic impacts of ocean
acidification on fisheries, and most have focused largely on shellfish
and on regions outside the Arctic. The quantity, quality, and
predictability of commercially important Arctic fish stocks may be
affected by ocean acidification, but the magnitude and direction of
change are uncertain. Fish stocks may be more robust to ocean
acidification if other stresses—for example, overfishing or habitat
degradation—are minimized.
10. Ecosystem changes associated with ocean acidification may affect the livelihoods of Arctic peoples. Marine
species harvested by northern coastal communities include species
likely to be affected by acidification. Most indigenous groups harvest a
range of organisms and may be able to shift to a greater reliance on
unaffected species, but these changes would likely exert a cultural
toll. Recreational fish catches may change to different species. While
marine mammals—important to the culture, diets and livelihoods of Arctic
indigenous peoples and other Arctic residents—are unlikely to
escape changes in the Arctic Ocean food web.
Original Article
Source: motherjones.com
Author: Julia Whitty
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