A1261963804TeWzk

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Waters of Nares Strait in the Canadian Arctic
Archipelago E. P. Jones1, B. Rudels2, A.J.
Eert3, L.G. Anderson4 and K. Azetsu-Scott1
1Bedford Institute of Oceanography, Dartmouth,
Canada 2Finnish Institute of Marine Research,
Helsinki, Finland 3Oceanografix, Victoria,
Canada 4Department of Chemistry, Göteborg
University, Göteborg, Sweden
Kennedy Channel
Introduction Near surface waters of the Arctic
Ocean along the North American coast consist in
large part of water whose origin is the Pacific
Ocean (Jones et al., 1998), with additional
contributions from river runoff and sea ice
meltwater. Underlying this along the North
American coast is water of North Atlantic origin
that has entered the Arctic Ocean via the Barents
Sea (Jones et al., 2003 Rudels et al., 2003).
Much of these waters exit via the Canadian Arctic
Archipelago, most of whose channels are
relatively shallow, less than 120 m. Only Nares
Strait is deeper, having a sill depth of about
250 m. A first step in understanding the
freshwater budget of the Arctic Ocean is to
determine freshwater sources and trace their
pathways. We present results from expeditions in
Nares Strait in 1997 and 2001 (Figure 1).
Figure 1 Nares Strait 1997 red 2001 green
Kane Basin
Smith Sound
Approach Nutrient relationships distinguish
Pacific source water (PW) from Atlantic source
water (AW) and total alkalinity distinguishes
river runoff from the other sources (Jones et
al., 1998, 2003). We use these tracers
nitrate-phosphate relationships to distinguish
Pacific water from Atlantic water plus river
runoff and sea ice meltwater, total alkalinity to
distinguish river runoff, and these together with
salinity to obtain sea ice meltwater
concentrations determine the relative amounts of
the three sources of freshwater in Nares
Strait.  Phosphates (PO4) vs. nitrate (NO3) plots
have a linear relationship with best fit
parameters for both Pacific and Atlantic source
waters in the Arctic Ocean (Jones et al., 2003).
From limited data, we take river runoff and sea
ice meltwater to have nitrate-phosphate
relationships similar to those of Atlantic source
water. Values for total alkalinity and salinity
for Pacific and Atlantic source water and for
river runoff are shown in Table 1. Sea ice
meltwater salinity is typical of old ice, and its
total alkalinity is proportionally reduced from
that of seawater.
Table 1 Equations and Parameters
(Superscript m signifies measured values)
Figure 3 Smith Sound (Sections are viewed looking
south.)
Figure 2 Smith Sound
Results Nutrient samples were collected from
Smith Sound during the 1997 Joint Ocean Ice
Study (JOIS 97) Expedition (Figures 2, 3) and
from Smith Sound and Kennedy Channel in 2001.
The minimum channel depth in Nares Strait, 250 m,
occurs in the northern part of Kane Basin
slightly to the south of the Kennedy Channel
section. Total alkalinity samples were collected
only in 1997, thus only the Pacific, Atlantic and
net fresh water fractions can be estimated for
Kennedy Channel. Contour plots show salinity and
potential temperature.  In both Smith Sound and
Kennedy Channel, Pacific source water dominates
the upper waters (Figures 2, 3a, 4a), with
Atlantic source water being almost absent above
about 100 m. Atlantic source water dominates the
deeper waters, though the Pacific source fraction
never is less than about 0.3. In Smith Sound
(Figure 3), the river runoff fraction is high,
0.07, in the eastern part of Nares Strait. Sea
ice meltwater is clearly present, with a maximum
concentration about one-third of river runoff.
Both fractions are associated with the freshest
part of the flow, with salinities as low as 31.5.
In Kennedy Channel (Figure 4b), the maximum
freshwater fraction near the surface is about
0.08, i.e., about the same as the sum of the
river runoff and sea ice meltwater fractions in
Smith Sound. A mixing line of Pacific and
Atlantic source waters lies slightly above the
Pacific source fractions as salinities approach S
33. At lower salinities, the Pacific source
fractions are roughly constant, indicating
freshening from river runoff and sea ice
meltwater. A similar plot for Kennedy Channel
shows the same Pacific source fraction
behavior.  At higher salinities in Smith Sound
(Figure 2), the sea ice fraction is negative.
This is consistent with the Atlantic source water
flowing through Nares Strait coming mainly from
the Barents Sea branch lower halocline (Figure 5,
Rudels et al., 2003). Lower halocline water is
initially formed in the Barents Sea from
brine-enriched water produced during sea ice
formation, i.e., sea ice distilled from the
water column.
a
b
Mixing Line determined by Pacific and Atlantic
source water salinities in Table 1
Figure 5
d
c
Figure 6
The origin of Baffin Bay Bottom Water (BBBW) is
one of the smaller but intriguing oceanographic
puzzles. It has long been speculated that these
waters have an Arctic Ocean source because their
temperature and salinity are similar to those
seen in the Canada Basin and Lincoln Sea, though
waters with exactly the TS properties of BBBW
have not been observed in Nares Strait (Rudels et
al., 2003). We found that deeper waters in Nares
Strait have TS properties approaching those of
BBBW (Figure 6). What may be concluded from the
TS characteristics of Baffin Bay and the Barents
Sea branch halocline, however, is that no water
denser than the Barents Sea branch halocline
water enters the Baffin Bay from the Arctic
Ocean. If BBBW has a significant Arctic Ocean
component, it would enter Baffin Bay through a
deep channel leading from eastern Smith Sound
(Insert, Figure 6).
Figure 4 Kennedy Channel (Sections are viewed
looking south.)
Canada Basin (black) Kennedy Channel (red)
Smith Sound (blue) Baffin Bay (yellow)
a
b
References Jones, E.P., L.G. Anderson, and J.H.
Swift. 1998. Distribution of Atlantic and Pacific
waters in the upper Arctic Ocean Implications
for circulation. Geophysical Research Letters,
25, 765-768. Jones, E. P., J. H. Swift, L. G.
Anderson, M. Lipizer, G. Civitarese, K. K.
Falkner, G. Kattner, and F. McLaughlin, Tracing
Pacific water in the North Atlantic Ocean, J.
Geophys. Res., 108 (C4), 3116, doi10.1029/2001JC0
01141, 2003. Rudels, B., E. P. Jones, U.
Schauer, and P. Eriksson. 2003. Atlantic sources
of the Arctic Ocean surface and halocline waters,
submitted to Polar Research (See Session 1
Poster).   Acknowledgments This work was
partially supported by the Canada Panel on Energy
Research and Development and by the Canadian
Climate Action Fund. Photo, Icebergs at 11
O'clock by A. J. Eert