ASLO/TOS FEBRUARY 2004 ABSTRACTS: ORAL AND POSTER-ppt or pdf available
Meeting Agenda - Thursday(PanArctic)
SS1. WESTERN ARCTIC SHELF-BASIN
INTERACTIONS (SBI) PROJECT: Chaired by TE Whitledge and JM Grebmeier
A. ORAL
THE CHUKCHI-BEAUFORT SHELF/SLOPE
BOUNDARY
Pickart, R.; Weingartner, T.; Woodgate,
R.; Aagaard, K.
The
dynamic structure of the Chukchi-Beaufort shelf and slope is determined by the
variable upstream forcing of Pacific waters through Bering Strait and over the
Chukchi shelf. Fall measurements show shelf
bottom
waters enriched in sediments, nutrients, and chlorophyll entering the upper
halocline along the
Chukchi
shelfbreak and through Barrow Canyon. Some of this outflow contributes to a
narrow, subsurface
current
setting eastward over the continental slope between 75-200 m depth, distributing
Pacific waters
around
the Canada Basin margin. Several eddies with diameters of ~15 km, vertical
extent of ~150 m,
and
core water properties identical to shelf bottom waters were found within the
upper halocline over the
slope.
These were spawned by the slope current and will presumably propagate seaward
to ventilate the
interior
Canada Basin.
THE PACIFIC INFLOW THROUGH BERING
STRAIT: 1990-2002
Aagaard, K.; Woodgate, R.; Weingartner,
T.
Nearly
continuous measurements of the northward flow of Pacific waters through Bering
Strait from 1990
onward
provide a remarkable record of the variable upstream forcing of the western
arctic shelves and of
the
Arctic Ocean halocline. Extreme warmth in the mid-1990s, accompanied by major
changes in the shelf ecosystem; large and complex salinity variations that
within a few months will be transmitted into the
Arctic
Ocean halocline; and a pronounced annual cycle in the northward flow are all
hallmarks of the
record
from Bering Strait. These and additional measurements in the Chukchi Sea
suggest that the
regional
salinity distribution and circulation in the Bering Sea are determining factors
in the variability of
the
northern shelf and of the injection of Pacific water into the Arctic Ocean.
TRANSPORT
OF PLANKTON AND PARTICLES BETWEEN THE CHUKCHI AND BEAUFORT SEAS
Ashjian,
C. J.; Gallager, S. M.; Plourde, S.
Transport
of biogenic material from Arctic shelves to the deep Arctic basin may impact
significantly the
biogeochemistry
and ecosystem structure and function of both basin and shelf ecosystems.
Plankton and
particle
abundance, vertical distribution, and association with hydrography and
circulation were described
using
a self-contained Video Plankton Recorder on two cruises (spring and summer,
2002) to the
Chuckchi
and Beaufort Seas as part of the Shelf-Basin Interactions program. The VPR was
deployed to
as
deep as 350 m along four transects across the shelf-basin interface. Nine
categories of plankton or
particles
were identified, with marine snow, copepods, diatoms, and radiolarians being
the most
common.
Concentrations of marine snow on the Chukchi Shelf appeared to be very high, as
high as
observed
in temperate regions, with much lower concentrations over the basin. Distinct
vertical patterns
associated
with hydrographic structure also were observed. Particle and plankton
concentrations were
merged
with ADCP velocity records to obtain estimates of instantaneous flux (magnitude
and direction).
Barrow
Canyon in particular is a site of high particle concentration and high flux of
material between shelf
and
basin.
SEASONAL AND SPATIAL DISTRIBUTION OF
PARTICULATE ORGANIC MATTER (POM) AND
NEW PRODUCTION IN THE CHUKCHI SEA
Bates, N. R.; Hansell, D. A.; Moran, S.
B.; Codispoti, L. A.; Swift, J.
As
part of the Western Arctic Shelf-Basin Interactions (SBI) project, the
production and fate of organic
carbon
and nitrogen from the Chukchi Sea shelf was investigated during a spring (May)
and summer
(July)
cruise in 2002. Seasonal observations of suspended particulate organic carbon
(POC) and nitrogen
(PON)
and, large particle (>53 ´m) size class, indicate that there was a large
accumulation of carbon and
nitrogen
between spring and summer in the surface mixed layer due to phytoplankton
productivity
(estimated
from dissolved inorganic carbon). Considerable organic matter appeared to be
transported
from
the shelf into the Arctic basin in an elevated POC and PON layer at the top of
the upper halocline.
Seasonal
changes in the molar C:N of the POM pool reflect a significant change in the
quality of material
being
produced and presumably exported to the sediment and from the Chukchi Sea
shelf. In spring, low
particulate
C:N ratios (<6; i.e., N rich) were observed in nitrate-replete surface
waters. By the summer,
localized
high particulate C:N ratios (>9; i.e., N-poor) were observed in
nitrate-depleted surface waters.
MOLECULAR BIOMARKERS AS TRACERS OF
ORGANIC CARBON CYCLING ALONG THE SHELFBASIN BOUNDARY OF THE WESTERN ARCTIC
OCEAN
Harvey, H. R.; Belicka, L. L.;
Macdonald, R. W.
A
suite of lipid biomarkers in particles and sediments from Arctic rivers and
shelf to basin transects in the
western
Arctic Ocean was examined and combined with radiocarbon dating to determine the
sources and
exchange
of organic carbon between the shelves and basins. Riverine particles contained
high
concentrations
of a number of terrestrial biomarkers, including beta-amyrin, friedelin, and
24-ethylcholest-5-enol. Offshore particles from the chlorophyll maximum
contained the polyunsaturated fatty acids 20:5 and 22:6, low concentrations of
24-ethylcholest-5-enol, and were modern based on 14C values. Particles from
halocline waters contained predominantly marine signatures, but ranged in age
from 300-400 years indicating the presence of an older, recalcitrant carbon pool
overlain by fresh marine material sinking from the spring bloom. Basin
sediments were, on average, greater than 6000 years old and contained low
concentrations of algal biomarkers, suggesting that marine production provides
the fuel for carbon cycling while the recalcitrant terrigenous carbon pool is
slowly recycled.
EXPORT
OF YOUNG TERRIGENOUS DOM FROM RIVERS TO THE ARCTIC OCEAN
Benner,
R.; Nelson, B.; Kaiser, K.; Amon, R.
Rivers
discharge large quantities (250 Tg C/yr) of terrigenous dissolved organic
matter (DOM) to the
oceans.
About 10% of this terrigenous DOM is discharged to the Arctic Ocean, a small
basin accounting
for
~1% of the global ocean volume. Soils in the drainage basins of Arctic rivers
are a major global C
reservoir,
and the fate of this C is of growing concern as the effects of climate change
become more
evident
in the Arctic. Herein we report natural 14C data indicating that DOM from
several Eurasian and
North
American rivers is predominantly young and largely derived from recently-fixed
C in plant litter and
upper
soil horizons. Concentrations of dissolved lignin phenols, unique organic
tracers of terrestrial plant
material,
and 14C content in DOM were strongly correlated throughout the Arctic Ocean,
indicating
terrigenous
DOM is mostly young and widely distributed in polar surface waters. It appears
the old C
stored
in terrestrial soils and peats is not currently being mobilized as DOM in
riverine discharge.
MACROBENTHIC COMMUNITIES IN THE HIGH
ARCTIC CANADA BASIN: ABUNDANCE,
BIOMASS AND TROPHIC STRUCTURE
Bluhm, B. A.; Iken, K. B.; MacDonald,
I. R.
Macro-infauna
was sampled by collecting box cores at 6 stations in the Canada Basin at
640-3250m in
Aug/Sept2002.
Total abundances ranged from 100-7650 individuals/m2 with the highest concentrations
in
Amundsen
Gulf and the lowest in the deep Canada Basin. Biomass ranged from 2-6514mg wet
weight/m2
with
the same geographical trend. Polychaetes and crustaceans were most abundant
while polychaetes
and
mollusks dominated the biomass. Visual survey of macro-epifauna revealed that
abundance of
attachment
substrata was the major factor determining community composition. Otoliths of
Boreogadus
saida
and Arctogadus glacialis were abundant at Northwind Ridge and three 14C-dated
specimens yielded
calendar
ages of 5605, 9120, and 13165yBP, respectively. 15N/14N isotopic signatures of
benthic
organisms
ranged from 10-18ë with most taxa in the 2nd and 3rd trophic level with respect
to POM
values
(average 5ë). Distinctive herbivores and 1st order predators inhabited sea ice
and upper water
column
(15N/14N: 5-12ë and 6-16ë, respectively). The findings suggest that ice,
pelagic and benthic
systems
are linked through sinking grazers and their products rather than through
direct input of algal
material
to the benthos.
REPORT
FROM A TEA TEACHER ON THE 2002 SHELF-BASIN INTERACTIONS (SBI) SUMMER
CRUISE
Carvellas,
B. A.
Through
the Teachers Experiencing Antarctica and the Arctic (TEA) program, K-12
teachers across the
United
States have taken part in scientific research in polar regions. The goals of
the TEA program
include:
immerse teachers in a research experience as a component of their continuing
professional
development,
inform teaching practices through the research experience, and bring polar
research into classrooms in engaging and innovative ways that underscore the
relevance of science to society. I will provide my perspective on the
scientific work I was involved in with Dr. Jackie Grebmeier of the University
of Tennessee during the Summer, 2002 SBI cruise (http://sbi.utk.eedu) and how
it has impacted my secondary school teaching in Essex Junction, Vermont. I will
also discuss the mechanisms I used for communicating scientific information off
the ship, including daily journals on the TEA website
(http://tea.rice.edu/tea_carvellasfrontpage.html#calendar)
and two live audio conferences held during the
40-day
cruise. Finally, I will provide information on my post-cruise presentations and
my work to
incorporate
polar science into the curriculum and the resulting impact on students from
grades 4-12 and
my
teaching colleagues.
VARIABILITY OF PHYTOPLANKTON BLOOMS IN
THE ARCTIC AND PERIPHERAL SEAS:
RELATIONSHIPS WITH SEA ICE,
TEMPERATURE, CLOUDS, AND WIND
Comiso, J. C.; Cota, G. F.
Satellite
data of ocean color, sea ice concentration, surface temperature, and clouds, as
well as
ECMWF/winds
for the period 1998 to 2002 have been compiled and analyzed to quantify
regional and
temporal
variabilities of phytoplankton blooms in the Arctic and peripheral seas and
evaluate their
relationships
with environmental variables. Large asymmetry in phytoplankton chlorophylls is
consistently
observed
in the Arctic basin with data in Eastern Arctic having about fivefold higher
concentration than
those
of the Western Arctic. Monthly-average chlorophyll concentrations also show
large seasonal and
interannual
variability with 2002 and 2001 having higher values than previous years.
Environmental
factors
that influence phytoplankton growth were examined, and results show relatively
high correlations
of
pigments with sea ice retreat and sea surface temperature (SST) during early
and late spring periods
and
an apparent preference by planktons of SSTs near 277K. The correlation with
clouds is significant in
some
areas but negligible in other areas, while the correlations with wind and its
components are
relatively
weak. Weak stratification, upwelling of nutrients, and unpredictable effect of
winds may explain
unexpected
observations.
TOWARDS
UNDERSTANDING SHELF-BASIN INTERACTIONS: SEASONAL VARIABILITY IN THE
OXYGEN
ISOTOPE COMPOSITION OF ARCTIC WATERS IN CONJUNCTION WITH OTHER
TRACERS
Cooper,
L. W.; Benner, R.; Codispoti, L. A.; Kelly, V.; McClelland, J. W.; Peterson, B.
J.; Holmes, R.;
Grebmeier,
J. M.
The
use of stable oxygen isotope variations in Arctic water masses to study
temporal mixing processes in
surface
waters is incompletely resolved because there has been only limited sampling
outside of summer.
We
report here the results of several research sampling programs that are
providing data on the isotopic
composition
of Arctic rivers (PARTNERS), shelf and deep basin regions of the Chukchi and
Beaufort Seas
(SBI),
and flow through the northern Bering Sea and Bering Strait in late winter
(Bering Strait
Environmental
Observatory). Combining these isotope ratio data with other variables,
including terrestrial
markers,
nutrients, salinity, and denitrification indicators provides new insights on
the timing and
mechanisms
of shelf-basin interaction. These findings include observations of
runoff-influenced waters
that
remain geographically separated over-winter from brine-influenced shelf and
slope waters. Apparent
source
differences in lignin contents of runoff components were also observed, as was
subsurface
ventilation
as brine-injected shelf waters flowed down Barrow Canyon. In the center of
Bering Strait an
increasing
sea ice melt signal was advected through Bering Strait in April 2003 as ice
melt commenced to
the
south.
PRIMARY
PRODUCTION IN THE WESTERN ARCTIC OCEAN
Cota,
G. F.
Primary
production was measured on four cruises in the Chukchi-Beaufort Seas over the
last decade with
spring
and summer cruises in 2002. Productivity is modest. The highest biomass and
productivity occur
in
open waters on the shelf or near the shelf-break, while low values are observed
in the largely icecovered
basin
waters or early in the spring. Phytoplankton production is highly dependent
upon biomass
and
integrated chlorophyll explains 88% of the variability in particulate organic
carbon (POC) production.
There
is additional production and release of dissolved organic carbon (DOC) which
can be ~30-40% of
POC
production. Large phytoplankton tend to dominate open water blooms, whereas in
ice-covered
areas
small cells predominate. Property distributions confirm the patterns observed,
as does ocean color
imagery
in open waters.
THE BALANCE BETWEEN AUTOTROPHY AND
HETEROTROPHY IN THE WESTERN ARCTIC
OCEAN
Cottrell, M. T.; Malmstrom, R. R.;
Kirchman, D. L.
The
balance between autotrophy and heterotrophy is a key feature of ecosystem
function that could
serve
as an indicator of environmental change, such as that suspected to be underway
in the Arctic
Ocean.
Data on microbial processes in the Arctic are sparse and few studies have
examined autotrophic
and
heterotrophic metabolism together. In order to examine the metabolic balance in
the Western Arctic
Ocean,
we measured bacterial production, community oxygen consumption and
photosynthetic oxygen
production
during the summer Western Arctic Shelf-Basin Interactions (SBI) process cruise
of 2002.
Rates
of community oxygen consumption and photosynthetic oxygen production varied
greatly over the
sampling
area, which included shelf, slope and basin environments. Low rates prevailed
with substantial
rates
of community oxygen consumption and production in only about 30% of the
samples. On average,
bacteria
seem to account for about 50% of community oxygen consumption, but this
percentage varied
greatly.
The analysis of light and dark bottle oxygen experiments suggests a dynamic
balance between
autotrophy
and heterotrophy with overall autotrophy in the SBI study area during summer.
RECORDS OF BIOGENIC FLUXES IN THE
WESTERN ARCTIC OCEAN OVER THE LAST 10,000
YEARS
Cutter, G. A.; Cutter, L. S.
In
order to understand present day changes in the oceanographic conditions of the
western Arctic Ocean
shelf,
one must consider past changes and likely processes controlling them. As part
of a
paleoceanographic
reconstruction of environmental conditions in the Chukchi Sea shelf, biogenic
tracers
were
determined in a 4 m long piston core and companion box core from 201 m depth
covering the entire
Holocene.
These parameters included organic carbon and nitrogen, sulfur, and biogenic
silica, and Cd/Ca
in
benthic forams as a tracer of nutrient inputs. Near the Pleistocene-Holocene
transition, organic C
concentrations
were quite low and C/S ratios suggest very low salinities. After this presumed
large melt
water
input, organic C and biogenic Si record large biogenic fluxes (ca. 8 ky BP).
For the next 4 ky,
biogenic
fluxes were relatively constant, suggesting stable environmental conditions in
the water column.
In
the last millennium, pulses of biogenic Si, and org. C and N indicate large
changes in productivity;
some
of these are associated with nutrient inputs (as recorded by Cd/Ca in forams).
In comparison to the
previous
9 ky, organic carbon fluxes were highest during this period. However, in the
last 300-400 y,
organic
fluxes decreased to the present. Processes likely controlling these biogenic
fluxes will be
examined.
OXYGEN CONSUMPTION, DENITRIFICATION AND
SULFATE REDUCTION IN ARCTIC
CONTINENTAL MARGIN SEDIMENTS
Devol, A. H.; Chang, B.; Christensen,
J. P.
We
have determined pore-water oxygen and nitrate profiles as well as sulfate
reduction on four SBI,
cross-margin
transects in the western Arctic (Bering-Beaufort seas). At all transects oxygen
penetration
was
less than 1 cm when the overlying water depth was less than 200 m but increased
dramatically with
increasing
water depth to 2-3 cm at 3000 m near Barrow Canyon and 10-20 cm further west.
Nitrate
penetration
depths were comparable to oxygen at shallow stations but became much greater at
deeper
stations.
Diffusive oxygen and nitrate fluxes were calculated from the profiles and
varied from 5.5 to 0.6
mMoles/m2/d
for oxygen and 0.58 to 0.17 mMoles/m2/d for nitrate. Sulfate reduction rates
varied
between
2.1 and 0.01 mMoles/m2/d per day and also decreased with increasing water
depth. Overall
carbon
oxidation rates calculated from the three electron acceptor fluxes were between
6.3 and 0.77
mMoles/m2/d.
Rates Barrow Canyon sections were similar to those along the productive U.S.
west coast
and
significantly higher than further west. Higher rates near Barrow Canyon may be
due to off-shelf
transport
of organic matter through the Canyon.
CIRCULATION
AND PROPERTY FLUXES OVER THE CHUKCHI PLATEAU - MODEL RESULTS
Dixon,
J. S.; Maslowski, W.; Okkonen, S. R.; Clement, J. L.; Walczowski, W.
Circulation
in the western Arctic Ocean and over the Chukchi Plateau is not well understood.
Mass and
property
fluxes in the region are investigated using a pan-Arctic model configured at a
1/12-degree and
45-level
grid. Results for analyses are from a 23-year integration forced with realistic
1979-2001
atmospheric
data. Velocity at three depth intervals, mean transports and fluxes are
investigated to
identify
the main current pathways and directions. Variability is determined by
comparison of results a
decade
apart. The mean velocity fields describe a cyclonic circulation pattern with
increased intensity
during
the late 1980s and early 1990s. The meander through the Chukchi Borderland Pass
is identified as
the
primary pathway for boundary flow across the Chukchi Plateau. The northern
Chukchi Plateau is
modeled
as a major region of exchanges between boundary flow and the Canada Basin
interior and it
appears
to be an area of net upward heat transport. Northward flow along the eastern
side of the
Northwind
Ridge is identified as a mechanism for freshwater advection from the Chukchi
shelves into the
interior.
ADVECTION
OF CARBON ON THE WESTERN ARCTIC SHELF: IMPLICATIONS FOR BENTHICPELAGIC COUPLING
Dunton,
K. H.; Schonberg, S. V.
This
study explores trophic linkages between the benthos and associated physical and
biological
processes
in the western Arctic. Evidence for the importance of rich Bering Sea waters on
the Arctic Shelf
is
provided by carbon and nitrogen stable isotope signatures used to trace carbon
advected onto adjacent
shelves
and as indicators of trophic links between pelagic and benthic components of
the shelf and slope.
Preliminary
del 13C measurements of POM reveal that values are 2-5 ppt lower (more
negative) in late
summer
compared to spring, especially over the shelf and basin. Based on these results
and the isotopic
values
of ice algae, we estimate that ice algal carbon potentially contributes up to
25% of the POC pool
over
the Chukchi Shelf during the spring bloom. Overall, benthic organisms become
more 13C depleted
between
the Chukchi Sea and western Beaufort, while 15N ratios remain relatively
constant. These data
support
the hypothesis that carbon advected northeastward along the Alaskan arctic
coast is assimilated
by
benthic consumers, but its relative importance begins to decline east of Point
Barrow.
MAGNITUDE AND CONTROL OF SEA-ICE ALGAL
GROWTH IN THE CHUKCHI AND BEAUFORT
SEAS IN SPRING 2002
Gradinger, R. R.; Eicken, H.
We
measured the biomass, diversity and activity of pack ice algae in the Chukchi
and Beaufort Seas in
order
to assess the impact of nutrient and light availability on algal growth.
Measurements included
estimates
of Chl a, POC, PON, stable isotopes and algal cell counts at a total of 14
stations (mainly firstyear
sea
ice). Algal pigment concentrations were in some cases extremely high, exceeding
1 g Chl a per
square
meter of sea ice at two stations. As for algal pigments, POC and PON values
increased
exponentially
towards the bottom of the ice floes with a mean C/N ratio (molar) of 16. The
d13C ratio
ranged
between -30 and -10 per mille, exhibiting a positive correlation with POC
concentration. The low
ambient
nutrient concentrations (nitrate and silicate) in the sea ice and
photosynthetic yield data
determined
via PAM fluorometry point towards nutrient limitation of ice algal growth. In
addition, new
production
and algal growth rates were estimated using exponential growth models.
Grebmeier,
J. M.; Cooper, L. W.; Codispoti, L. A.; Benner, R.
Benthic
sediment metabolism studies initiated in 2002 in the Chukchi and Beaufort seas
as part of the
Western
Arctic Shelf-Basin Interactions (SBI) global change program are investigating
the seasonal
deposition
of organic carbon and its transformation. Sediment tracers, such as plant
pigment, carbon
content,
and natural (Be-7) and artificial (Cs-137) radioisotopes are also being
measured. In the spring,
sediment
oxygen uptake (1-17 mM m-2 d-1) and nutrient flux were highest on the Chukchi
and Beaufort
shelves,
with rates decreasing from the shelf to the deep basin. Sediment respiration
rates doubled (up to
34
mM m-2 d-1) during the summer at the shelf sites, indicating tight
pelagic-benthic coupling, with rates
decreasing
with depth. Silicate and ammonium fluxes from the Chukchi and Beaufort shelf
sediments
were
high, presumably due to the influence of the nutrient-rich Pacific inflow
waters, with plumes of
nutrients
extending offshore into the Arctic Basin at halocline depths. Dissolved organic
carbon was also
released
from sediments, with implications for both lower food chain productivity as
well as carbon
sequestration
in this region.
NON-CONSERVATIVE
BEHAVIOR OF TERRIGENOUS DISSOLVED ORGANIC CARBON IN THE
WESTERN
ARCTIC OCEAN
Hansell,
D. A.; Kadko, D. C.; Bates, N. R.
DOC
was measured at the Chukchi/Beaufort Sea shelf break during the Shelf-Basin
Interaction project.
Evident
from DOC/salinity relationships was a fresh water intercept indicating low
terrigenous DOC (155
microM),
and not the commonly high values in Arctic rivers and the Eurasian Basin (600
microM). This
low
intercept results from the long residence time (~20 years) of surface waters in
the Beaufort Gyre,
allowing
significant degradation of terrigenous DOC. 228Ra/226Ra indicated the surface
gyre water had
an
age of 13 years since being over the shelf. With this age and terrigenous DOC
decrease (450 microM),
a
terrigenous DOC decay constant of 0.104 year-1 and a half life of 6.66 years
results. In contrast, in
the
Eurasian Basin, where the freshwater DOC intercept is high, surface waters have
a much shorter
residence
time. Terrigenous DOC transferred from the Eurasian shelves into the Eurasian
Basin via the
Trans
Polar Drift apparently has insufficient time to significantly degrade before
being exported out of the
Arctic
Ocean. The different ocean pathways of Arctic rivers draining North America and
Eurasia impart
different
fates for terrigenous DOC.
Kadko,
D. C.; Muench, R.
Rapid
shelf-basin exchange in the western Arctic was evaluated by use of the first
ever measurement of
the
short-lived 224Ra (3.64 d half-life) in this region. Radium-224, generated in
shelf sediment by decay
of
its parent 228Th, subsequently diffuses into the overlying water. There, the
224Ra (in excess of the
parent)
is transported to the extent that its decay-time allows thus providing a
measure of short-timescale
transport.
During the 2002 SBI program, excess 224Ra was measured over the shelf but
extended less
than
20km beyond the shelf-break. Similarly, the 228Ra/226Ra ratio dropped rapidly
across the shelfbreak.
Bering
Strait inflow is constrained by the earthÆs rotation to follow local isobaths
and does not
easily
move into deeper water. Possible mechanisms that can generate cross-shelf
currents that break
the
topographic constraint to follow isobaths, and thereby transport water (and
associated properties) off
the
shelves include meandering jets and eddies. Evidence of a jet was found during
the ICEX project in
April
2003 when excess 224Ra measured over 200 km from any shelf source corresponded
to a high
velocity
feature (measured by ADCP) within the upper 300m of the ocean.
BIOMASS,
PRODUCTION AND COMMUNITY STRUCTURE OF HETEROTROPHIC BACTERIA IN
THE
WESTERN ARCTIC
Kirchman,
D. L.; Cottrell, M. T.; Malmstrom, R. R.; Cota, G. F.
Heterotrophic
prokaryotes are often large components of biomass and carbon fluxes in many
oceans, but
they
may be less important in the Arctic Ocean because of perennially low water
temperatures. We
examined
the biomass (abundance and cell size), production, and community structure of
prokaryotic
communities
in spring and summer 2002 as part of the Western Arctic Shelf-Basin
Interactions (SBI)
project.
Bacteria appear to dominate these communities, according to results from
fluorescence in situ
hybridization
(FISH) with oligonucleotide probes; the general bacterial probe usually
recognized >75% of
total
cells. The bacterial communities were mainly composed of Cytophaga-like
bacteria and alphaproteobacteria.The alpha-proteobacterial subgroup, SAR11,
which was originally discovered in the
Sargasso
Sea, made up as much as 50% of total prokaryotic abundance. Total prokaryotic
biomass was
nearly
half of phytoplankton biomass (estimated from chlorophyll concentrations).
Bacterial production
relative
to primary production was very low (about 4%) in spring (May-June), but
increased to levels
observed
in other oceans (about 10%) in summer (July-August). Except for spring, the
activity and even
the
structure of bacterial communities are remarkably similar to other oceanic
systems.
DATA
MANAGEMENT SUPPORT TO THE WESTERN ARCTIC SHELF BASIN INTERACTIONS
(SBI)
PROJECT
Moore,
J. A.; Stossmeister, G. J.; Roberts, S. D.; Dirks, R. A.
The
UCAR Joint Office for Science Support (JOSS) provides data management support
to the SBI Project.
By
working with the investigators since the project began, we have been able to
establish useful data and
documentation
guidelines that streamline the exchange and integration of datasets among SBI
scientists.
JOSS
provides support for real-time data collection and exchange during SBI cruises
by customizing and
implementing
the SBI In-Field Data Catalog. The system is operated aboard ship and offers
real-time ship track mapping display capabilities, station event logging and
an easy way to submit
and share scientist logs and preliminary data from the cruises. Data are
relayed via satellite to an SBI 'mirrored' catalog running in Boulder, CO for
access by the larger community and public. JOSS has produced high-resolution
bathymetric maps, GIS-based cruise comparison databases and customized
satellite products to aid in project analysis and synthesis tasks. Information
on the status of SBI Phase 2 datasets will be provided. The authors will
summarize the cruises to date using the GIS MapServer tool and describe future
data management activities.
POC
EXPORT IN THE WESTERN ARCTIC OCEAN
Moran,
S. B.; Kelly, R. P.; Cota, G. F.; Smith, J. N.; Nelson, R. P.; Mulsow, S.;
Povinec, P.
The
magnitude and variability (spatial and seasonal) of POC exported from the upper
waters of the
Chukchi-Beaufort
Seas during the SBI-II 2002 field program was quantified using measurements of
Th-
234/U-238
disequilibrium and large particle (>53 ´m) POC/Th-234 ratios. Large volume
(200-1000 L)
water
samples were collected from 36 stations and 184 depths during May-June and
July-August. Results
are
characterized by: 1) enhanced particle export in the shelf and slope waters; 2)
higher particle export
in
the southeast sections near Barrow Canyon (West of Hanna Shoal), and; 3) a
marked increase in