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The ocean's thermal inertia and high heat capacity is of central importance
within the global climate system: at one side the ocean regulates climate
variations by its ability to store a large amount of heat and at the other
side the ocean balances climate differences between higher and lower latitudes
by its large-scale circulation. An usefull integral parameter to determine
the large-scale circulation is the advective transport of oceanic properties
such as the transport of temperature, the heat transport, or the transport
of heat and freshwater, respectively. Simultaneously measurements of temperature
and absolute velocity are necessary to directly determine i.e. the oceanic
heat transport. Direct current measurements are only available in a few regions
of the world ocean. From hydrographic data - the measured distribution of
temperature and salinity as a function of depth - one can estimate the transports
in a quasi-direct way. But especially data sets that span the whole water
column exist temporal and spatial also only in a discret form. An exception
is there the transatlantic section between the English Channel and the Grand
Banks of Newfoundland.
Since 1993, the BSH has routinely measured the transports of heat and freshwater
in the North Atlantic Ocean across the line English Channel-Grand Banks of
Newfoundland (ca.
45°N).
The measurements were made according to the criteria of the World
Ocean Circulation Experiment (WOCE), and partly contributed
to the WOCE
hydrographic programme and since 1998 to
GOOS,
respectively. During the cruises of the German research vessels "Gauss" (BSH)
and "Meteor" (RF) and an one-time survey of the russian research vessel "Akademik
Vavilov", seven high-resolution hydrographic data sets have been obtained
so far covering the so-called WOCE/A2- or "48°N"-section. Another
transatlantic cruise is planned for 2002.
Including two historical cruises made in
1957
and
1982
and seven realisations of the WOCE/A2-section in the 90s
(1993,
1994,
1996,
1997,
1998,
1999,
2000)
a data set are presently available to determine from hydrographic observations
alone the temporal and spatial variability of the thermohaline structure
along ca. 45°N in the North Atlantic and of the large-scale circulation
- the Meridional Overturning Circulation (MOC) on
interannual and climate-relevant decadal scales.
| |
1957 |
1982 |
|
| |
 S |
 S |
|
| |
 T |
 T |
|
| 1993 |
1994 |
1996 |
1997 |
 S |
 S |
 S |
 S |
 T |
 T |
 T |
 T |
| 1998 |
1999 |
2000 |
2002? |
 S |
 S |
 S |
|
 T |
 T |
 T |
|
| Vertical distribution of potential Temperature
and Salinity along "48° N" in the North Atlantic |
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