The science: some motivation for non-oceanographers!
What are we doing? The aim of our project is to measure the flow of fresh and cold water through Nares Strait (one of three major passages connecting the Arctic and the Atlantic through the Canadian Archipelago) as well as its variability, and to determine what sets its strength.
Why?? The relatively fresh water leaving Nares Strait and the rest of the Canadian Archipelago enters the Atlantic via the Labrador Sea. This is one of the few critical regions where surface water sinks to form deep water as part of the thermohaline overturning circulation. The amount of fresh water input into the ocean here influences the surface density, and therefore has the potential to significantly affect the strength of the thermohaline circulation and climate.
More about the thermohaline circulation
thermohaline circulation is a global circulation involving all of the
world's major ocean basins. Water sinks in the high-latitude North
Atlantic, where the strong surface cooling results in deep convection,
and then flows southwards at depth. It returns to the surface in the
Indian, Pacific and Southern Oceans, and finally flows northwards
again as a warm surface current in the Atlantic. This circulation is
responsible for transporting approximately 1 PW (10^15 Watts) of heat
northwards in the Atlantic basin, and as such has a significant impact
on climate, keeping temperatures in northern Europe far warmer than
the average for their latitude.
The thermohaline circulation
also plays a key role in the carbon cycle. Carbon dioxide is more
soluble at high latitudes where surface water temperatures are cold,
and becomes sequestered in the deep ocean when this water sinks. The
amount of carbon in the deep ocean is more than 50 times the
atmospheric carbon inventory, and is increasing at a rate of 2
Gigatons of carbon per year (approximately 30% of the anthropogenic
Recent evidence, however, suggests that the
ocean circulation has not always functioned in the same way. And
state-of-the-art numerical climate models suggest that as a result of
global warming the thermohaline circulation may weaken significantly
in the future over the course of just a few decades. Such a change
could be far more abrupt than the gradual changes associated directly
with global warming, and could have severe consequences for global
climate. Society's adaptation to change would be easier if more was
known about the mechanisms that might cause such sudden changes, and
the ways in which the ocean and atmosphere interact.
piece of the puzzle lies in understanding the influence of the polar
regions on ocean circulation. The sinking of the thermohaline
circulation occurs in very specific locations in the Labrador and
Nordic Seas where water remains for long enough to be cooled
substantially by the atmosphere, and hence becomes dense enough to
sink to great depths. However, the surface density in these critical
regions is also influenced by the outflow of fresh water from the
Arctic Ocean via Fram Strait and the Canadian Archipelago. Relatively
little is known about the amount of fresh water exchanged between the
Arctic and Atlantic, or about what governs this. Making reliable
measurements at high latitudes presents an enormous challenge to
oceanographers, and existing data is sparse.
decades the critical sinking regions, and the North Atlantic in
general, have freshened considerably. This project is part of an
intensified effort to establish the importance of fresh water outflow
from the Arctic, a thorough understanding of which is essential if we
are to predict the response of the ocean circulation to global
warming, and the resulting impact on climate.