One sea to many oceans: First of its kind study on oxygen flow and its
role in sustaining life globally

Date:
January 28, 2022
Source:
European Geosciences Union
Summary:
For the first time, scientists measure oxygen flow into the
deep ocean interior of the Labrador Sea between Canada and
Greenland. They studied how much oxygen absorbed by the sea each
winter makes it into the deep, fast-flowing currents that ultimately
transport it across the globe.



FULL STORY ==========================================================================
The Labrador Sea between Canada and Greenland is often referred to as a
'lung of the deep ocean' because it is one of only a handful of locations worldwide where oxygen from the atmosphere can enter the deepest layers
of the ocean. The ability to sustain animal life in the deep ocean
depends directly on this localized 'deep breathing'. This process is
driven by wintertime cooling at the sea surface, which makes oxygen-rich, near-surface waters denser and heavy enough to sink to depths of around
2 km in winter.


==========================================================================
In a new study published in the journal Biogeosciences, a team of
researchers from Dalhousie University in Halifax, Canada and the GEOMAR Helmholtz Centre for Ocean Research Kiel in Germany have now, for the
first time, measured the flow of oxygen into the deep ocean interior that
is carried by these deep currents. It is the oceanographic equivalent of measuring oxygen transport in our bodies through the main artery or aorta.

From one sea to many oceans Jannes Koelling, lead author of the study, explains, "We wanted to know how much of the oxygen that is breathed
in each winter actually makes it into the deep, fast-flowing currents
that transport it across the globe." The deep mixing of oxygen in the
central Labrador Sea is only a first step in the deep ocean's life support system. Deep, boundary currents then distribute the oxygen to the rest
of the Atlantic Ocean and beyond. This way, oxygen that is 'inhaled'
in the Labrador Sea can support deep ocean life off Antarctica and even
in the Pacific and Indian Oceans.

Koelling explained, "The newly inhaled oxygen was clearly noticeable
as a pulse of high oxygen concentration that passed our sensors between
March and August." Compelling insights over two years


==========================================================================
The team unravelled the connection between oxygen uptake from the
atmosphere and its onward transport into the interior using dissolved
oxygen sensors that were mounted for two years on anchored cables which
reached from the seafloor to near the surface. The sensors were deployed
at depths of about 600m, where the scientists expected water to propagate
from the deep mixing region in the centre of the Labrador Sea (the lung).

The new measurements revealed that about half of the oxygen taken up
from the atmosphere in the central Labrador Sea in winter was injected
into the deep boundary current over the following 5 months. While some
of the remaining oxygen may have been consumed locally by fish and other organisms, the bulk most likely took an alternative route out of the
deep mixing region.

Findings could impact the climate model The study and the new ability
to monitor oxygen transport becomes highly relevant, given that climate
model projections suggest an increased supply of freshwater -- from
melting glaciers and other climate-changes in the Arctic - - could
reduce the depth of wintertime mixing in the Labrador Sea in coming
decades. This would make the Labrador Sea's 'breathing' shallower and
reduce the life-supporting supply of oxygen to the deep sea.

"This is an example of how monitoring enabled by the latest ocean
technology can help us fill in knowledge gaps in this important region,"
says Dariia Atamanchuk, who leads the oxygen programme at Dalhousie.

Koelling concludes: "The circulation of the Labrador Sea is complex,
and we've only focused, so far, on the most direct export route. Some oxygen-rich water may be transported eastwards, instead of to the
southwest, and it may enter the boundary current off Greenland before
returning southwards, over a longer time- period." These other pathways,
shown as dashed lines in the map, are being investigated with further
studies, using additional oxygen sensors mounted on more moorings.

The new findings are the result of a collaboration supported by the Ocean Frontier Institute, a transatlantic research organisation that connects researchers from several major institutions in Canada, Europe and the
USA in a common focus on the climate-sensitive Northwest Atlantic Ocean.

========================================================================== Story Source: Materials provided by European_Geosciences_Union. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Jannes Koelling, Dariia Atamanchuk, Johannes Karstensen, Patricia
Handmann, Douglas W. R. Wallace. Oxygen export to the deep ocean
following Labrador Sea Water formation. Biogeosciences, 2022; 19
(2): 437 DOI: 10.5194/bg-19-437-2022 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220128161009.htm

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