Detrimental Impacts of Rising Sea Temperatures Build Up
By ROGER WARBURTON/ecoRI News contributor
January sea surface
temperatures off the coast of southern New England have risen significantly
since 1980. (Roger Warburton/ecoRI News)
Living in Rhode Island,
we are aware how the ocean rules our weather. What is less well known is that
climate change is fundamentally altering the waters off our coast.
The image above shows
how the January temperature of the ocean off the coast of southern New England
has changed since 1980. For example, vast areas of dark blue — representing
temperatures around 41-43 degrees Fahrenheit — have shrunk and are now a
lighter blue, representing temperatures around 43-45 degrees.
The effects of a
temperature rise in the ocean are significantly different from a temperature
rise over land. We experience this difference when we walk across a sandy beach
on a hot day. Exposed to the same sunlight, the sand burns our feet while the
ocean warms gradually to the perfect temperature for a summer swim.
Rhode Island’s climate
is moderated because the ocean takes longer than the land to heat up over the
summer and longer to cool down during the fall.
The global impact of this effect is shown in the image below, which shows that, over recent decades, the continents have warmed much more rapidly than the oceans. The Earth’s land areas were 1.4 degrees Celsius (2.5 degrees Fahrenheit) warmer than the 20th-century average, while the oceans were 0.8 degrees Celsius (1.4 degrees Fahrenheit) warmer.
Unfortunately, the
ocean’s smaller temperature rise isn’t good news, because the oceans can store
more than four times as much heat as the land.
Even though ocean temperatures have risen less than the land’s, it’s becoming clear that the impacts of climate
change depend on a complex interaction between dry land and the warming ocean.
Ships and buoys have
been recording sea surface temperatures for more than a century. International
cooperation and sharing of data between nations has created a global database
of sea surface temperatures going back to the middle of the 19th century.
In addition, modern
satellites remotely measure many ocean characteristics over the entire extent
of the Earth’s oceans. The data are now so accurate
that it’s possible to detect the small temperature rise from ships’ propellers
as they traverse the oceans.
The warming of both the
land and the oceans is caused by rising levels of atmospheric carbon dioxide.
When CO2 dissolves in the ocean, it forms carbonic acid, which in turn, breaks
into hydrogen and bicarbonate ions. Clams, mussels, crabs, corals, and other
sea life rely on those carbonate ions to grow their shells.
In 2015, Mark Gibson,
deputy chief of marine fisheries at the Rhode Island Department of
Environmental Management, noted that ocean
acidification is a “significant threat” to local fisheries.
In fact, a study published in 2015
found that the Ocean State’s shellfish populations are among the most
vulnerable in the United States to the impacts of acidification.
In polar regions like
Alaska, the ocean water is relatively cold and can take up more CO2 than warmer
tropical waters. As a result, polar waters are generally acidifying faster than
those in other latitudes.
The water in warmer
regions can’t hold as much CO2 and are releasing it into the atmosphere.
Therefore, the acidification from carbon dioxide is damaging the oceans in both
polar and equatorial regions.
Warming oceans are also
changing the winds that whip up the ocean, resulting in upwells from deep
waters that are nutrient-rich but also more acidic.
Normally, this infusion
of nutrient-rich, cool, and acidic waters into the upper layers is beneficial
to coastal ecosystems. But in regions with acidifying waters, the infusion of
cooler deep waters amplifies the existing acidification.
In the tropics, rising temperatures
are slowing down winds and reducing the exchange of carbon between deep waters
and surface waters. As a result, tropical waters are becoming increasingly
stratified and more saturated with carbon dioxide. Lower layers then have less
oxygen, a process known as deoxygenation.
Warming ocean
temperatures have also caused a rapid increase of toxic algal blooms. Toxic
algae produce domoic acid, a dangerous neurotoxin, that builds up in the bodies
of shellfish and poses a risk to human health.
In coastal areas, like
Rhode Island, temperature changes can favor one organism over another, causing
populations of one species of bacteria, algae, or fish to thrive and others to
decline.
The sum of all these
impacts is damaging to the Rhode Island economy. The state’s shellfish
populations are already among the most vulnerable in the United States to the
impacts of a warmer ocean.
Roger Warburton, Ph.D.,
is a Newport resident. He can be reached at rdh.warburton@gmail.com.
Figure 1 was generated
using data from the Copernicus Climate Change and Atmosphere Monitoring
Services (2020). The ERA5
dataset is produced by the European Space Agency SST Climate Change Initiative
based on global daily sea surface temperature data from the Group for High
Resolution Sea Surface Temperature and made available by the Copernicus Climate
Data Store.
Figure 2 was generated
using data from NOAA’s National Centers for Environmental information, Climate at a
Glance: Global Time Series.
