Environmental Engineering Reference
In-Depth Information
(Hansen et al. 2006) with most of this added energy being absorbed by
the world's oceans (Hoegh-Gouldberg and Bruno 2010). And in addition,
to acting as the planet's heat sink, the ocean had absorbed approximately
one-third of the carbon dioxide produced by human activities. Increases
in the heat content of the ocean have driven other changes. Thermal
expansion of the oceans as well as increased meltwater and discharged
ice from terrestrial glaciers and ice sheets has increased ocean volume
and hence sea level (Rahmstorf et al. 2007). Warmer oceans also drive
more intense storm systems (Knutson et al. 2010) and other changes to
the hydrological cycle (Trenberth et al. 2007). The warming of the polar
oceans also has important ramifi cations for the stability of continental
ice sheets, such as those in Greenland and Western Antarctica, which are
sensitive to small increases in temperature (Naish et al. 2009). Marine air
and sea temperatures have risen over the northeast Atlantic in the last
25 years. The largest increase in sea surface temperatures occur in the
southern North Sea and eastern English Channel, at a rate of 0.5 and 0.8°C
per decade (Rayner et al. 2003, IPCC 2007). Changes in the West Antarctic
Peninsula are profound: mid-winter surface atmospheric temperatures have
increased by 6°C (more than fi ve times the global average) in the past 50
years (Skvarca et al. 1999, Vaughan et al. 2003). Eighty seven percent of the
Western Antarctic Peninsula glaciers are in retreat (Cook et al. 2005), the ice
season has shortened by nearly 90 days, and perennial sea ice is no longer a
feature in this environment (Martinson et al. 2008, Stammerjohn et al. 2008).
Variation in temperature also has impacts on key biological processes. The
distribution and abundance of phytoplankton communities throughout
the world, as well as their phenology and productivity, are changing in
response to warming, acidifying and stratifying oceans (Doney et al. 2009,
Polovina et al. 2008). The annual primary production of the world's oceans
has decreased by at least 6% since the early 80's, with nearly 70% of this
decline occurring at higher latitudes (Gregg et al. 2003). These changes in
the primary production of the oceans have overall profound implications
for the marine biosphere and biochemistry of the Earth (Falcowski et al.
2000). The shift in phytoplankton biomass and size has direct consequences
for grazer communities, especially Antarctic krill (
Euphausia superba
), whose
spawning behavior depends on sea ice (Quetin and Ross 2001). Because
krill form a critical trophic link between primary producers and upper-level
consumers such as whales and other species this has profound consequences
(Fraser and Hofmann 2003, Schofi eld et al. 2010).
Sea ice, coral reefs and kelp forests play a critical role in structuring
the biodiversity of polar oceans (Hoegh-Gouldberg and Bruno 2010). Many
arctic mammals face serious declines, with polar bears projected to lose 68%
of their summer habitat by 2100. Antarctic species, such as penguins and
