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Signs of Change
Ocean Heat
Storage and Movement

The ocean covers over
70% of Earth's surface
and holds 97% of its
water.

Its high heat capacity,
fluid motion, and
abundant life mean the
ocean plays a key role
in regulating climate.

Sunlight, wind, and convection – the buoyant rising of warm
water followed by sinking as it cools -- mix heat through the
ocean vertically.

The ocean's heat content influences sea surface temperatures
and exerts a strong influence on climate.

Tracking the ocean is key to understanding climate change.
Storage and Movement (cont’d)

The oceans are mostly
composed of warm salty
water near the surface
over cold, less salty
water in the ocean
depths. These two
regions don't mix except
in certain special areas.

The ocean currents, the
movement of the ocean
in the surface layer, are
driven mostly by the
wind.

In certain areas near the polar oceans, the colder surface water
also gets saltier due to evaporation or sea ice formation.
Storage and Movement (cont’d)

In the polar regions,
the surface water
becomes dense
enough to sink to the
ocean depths.

The pumping of
surface water into the
deep ocean forces the
deep water to move
horizontally.

The deep ocean water must find an area on the world where it can
rise back to the surface. This closes the current loop.

This process usually occurs in the equatorial ocean, mostly in the
Pacific and Indian Oceans.

This very large, slow current is called the thermohaline circulation
because it is caused by temperature and salinity (haline) variations.
Adding Heat Alters Ocean Dynamics
 As heat-trapping gases accumulate in Earth's
atmosphere, they trap more of the Sun's energy, the
ocean absorbs more heat, and its temperature rises.
 Certain gases in the atmosphere resemble glass in a
greenhouse, allowing sunlight to pass into the
"greenhouse," but blocking Earth's heat from escaping
into space.
Adding Heat Alters Ocean Dynamics (cont’d)
 The gases that contribute to the greenhouse effect
include water vapor, carbon dioxide (CO2), methane,
nitrous oxides, and chlorofluorocarbons (CFCs).
Adding Heat Alters Ocean Dynamics (cont’d)
 Added heat changes ocean dynamics, as many
currents are driven by subtle differences in
temperature (and salinity). Currents influence
climate and ecosystems.
 In addition, water expands as it warms, so as ocean
temperatures climb, sea levels also rise.
 At high latitudes, warming waters have additional
impacts: they melt sea ice and coastal ice shelves.
Adding Heat Alters Ocean Dynamics (cont’d)
 This map shows sea surface temperature. Red and
yellow depict warmer waters and blue shows colder
waters.
Adding Heat Alters Ocean Dynamics (cont’d)
 This map shows ocean salinity. The white regions
have the highest salinity and the dark regions have
the lowest.
Adding Heat Alters Ocean Dynamics (cont’d)
 This is a map of ocean density. Light blue regions
indicate the least dense waters; dark blue regions are
the most dense.
Adding Heat Alters Ocean Dynamics (cont’d)
 As water temperature warms, it also expands.
 Ocean temperatures are rising, resulting in sea level
rise.
 At high latitudes, warming waters have additional
impacts: they melt sea ice and coastal ice shelves.
Boosted Heat and Ocean Life
 Rising water temperatures and shifting currents affect
coastal and marine water quality, altering species
distribution and biological productivity.
 Seabirds like this Pigeon Guillemot, have been washing up
dead on beaches in California and Oregon.
 These dead birds are
casualties of shifts in the
California Current’s
primary productivity.
 Marine researchers
believe this marine food
shortage may be linked
to climate change.
Boosted Heat and Ocean Life
 Because heat enters the ocean at its surface, it tends
to make a warmer surface layer that is less likely to
mix with deeper, colder layers, reducing mixing in
the ocean.
Boosted Heat and Ocean Life
 Warmer seas will likely produce more coral bleaching,
hypoxia, disease, harmful algal blooms, and invasive
species. Some species or populations may shrink or
disappear unless they can relocate.
 Some species or
populations may
shrink or disappear
unless they can
relocate. In the
image below, dead
fish float alongside a
seagrass mat. A
toxic algal bloom is
the suspected cause
of the fish kill.
Behind the Numbers
 Upper-ocean heat content has increased significantly since
1955.
Behind the Numbers
 Over the latter half of the 20th century, scientists
estimate that more than 90% of the energy gained by
the biosphere as a result of human activities has
accumulated in the ocean.
 How much the ocean warms can vary greatly from
year to year despite steadily increasing greenhouse
gas concentrations over the past few decades.
 Actual year-to-year changes are influenced by events
like volcanic eruptions and recurrent oceanatmosphere patterns like El Niño.