Synthesis of Arctic Research (SOAR) in marine ecosystems of the Paciﬁc
The Paciﬁc Arctic marine ecosystem extends from the northern
Bering Sea, across the Chukchi Sea to the East Siberian and Beaufort
seas (Fig. 1). The northern Bering, Chukchi and East Siberian seas
are comprised of broad–shallow continental shelves, while the
Beaufort Sea has a narrow shelf and steep slope culminating in
the deep Canadian Basin. Sea ice covers this region for 5–7 months
of the year, typically reaching maximum and minimum areal
extent in March and September, respectively. The narrow
(85 km) and shallow (50 m) Bering Strait is the only gateway for
Paciﬁc water to enter the Arctic. Transport is primarily northward
and comprised of three water masses, the Alaska Coastal Water
(ACW), Bering Shelf Water (BSW) and Anadyr Water (AW).
Bering Strait inﬂow peaks in summer, providing a strong pulse of
comparatively fresh water, heat, nutrients and plankton to the
Chukchi–Beaufort marine ecosystem. The striking seasonality of
both sea-ice cover and transport provides foundational biophysical
conditions for ecosystem dynamics, extending from primary pro-
duction (ice algae and phytoplankton) to lower trophic (zooplank-
ton, benthic invertebrates and ﬁshes) and upper trophic (marine
birds and mammals) animals including humans.
The Paciﬁc Arctic marine food web is comprised of compara-
tively short linkages leading from primary production to humans
(Fig. 2). However, the simple linkages typical of arctic ecosystem
schematic diagrams belie the biophysical complexity underlying
these systems. Speciﬁcally, the inﬂuences of dynamic ocean pro-
cesses such as upwelling, lateral transport and eddies are not
depicted and so the ecosystem can appear static rather than typi-
ﬁed by extremes in intra and inter-annual variability.
Fortunately, the dynamic nature of arctic marine ecosystems is
becoming better known. In just the past 5 years, there have been
numerous publications describing responses of arctic marine
ecosystems to recent extreme physical changes. Of the many books
and journal articles, three volumes stand out as especially relevant
to this special issue: Wassmann (2011), which focused on impact
of rapid climate changes on marine ecosystems primarily in the
Atlantic arctic region; Kulkarni et al. (2012), which summarized
results of research conducted during the International Polar Year
in the Canadian Arctic region; and Grebmeier and Maslowski
(2014), which reviewed status and trends of the Paciﬁc Arctic mar-
ine ecosystem. Articles in each of these volumes provide context
for this issue, from the ‘discovery’ of winter production by bacteri-
oplankton and protists (e.g., Darnis et al., 2012) to projections of
novel biogeochemical cycling schemes anticipated with the loss
of sea ice (e.g., Wassmann, 2011). As in recent-past volumes, the
synthesis of information provided here contributes to an expand-
ing body of knowledge and an improved understanding of the sta-
tus and trajectories of arctic marine ecosystems.
The initiation of the Synthesis of Arctic Research (SOAR) project
coincided with the recognition that biophysical changes in the
Paciﬁc Arctic region were so extreme, compared to the recent past,
that they acquired the moniker ‘new normal’ (Jeffries et al., 2013).
Consequently, describing the biophysical properties of the ‘new’
Paciﬁc Arctic marine ecosystem was foundational to the SOAR
effort and the focus of ﬁve papers in this issue. Examining biolog-
ical responses to the new biophysical forcing then became the task
of researchers focused on the study of lower trophic level (LTL)
communities and upper trophic level (UTL) species. Two papers
provide integrated results from direct sampling of benthic and ﬁsh
communities, while three papers report on changes in LTL species
occurrence inferred by shifts in the diets of seals and marine birds.
Six papers focus on UTL species, with four presenting information
on seasonal occurrence in hotspot or core-use habitats, and two
describing variability in marine mammal body condition in the
context of decadal-scale environmental variability. Together, these
papers provide a synthetic context to focus hypotheses underpin-
ning the next-decade of research in the Paciﬁc Arctic marine
2. Biophysics of the Paciﬁc Arctic marine ecosystem
The Paciﬁc Arctic marine ecosystem is comprised of inﬂow
shelves (northern Bering and Chukchi seas) coupled to interior
shelves (East Siberian and Beaufort seas), with the contrasting
biophysics of these domains summarized in Carmack et al.
(2006). Circulation on both inﬂow and interior shelves is linked
to pan-arctic teleconnection mechanisms (e.g., Arctic Oscillation),
with interior shelves also strongly inﬂuenced by the seasonal
outﬂow of relatively warm fresh water from arctic rivers.
Evaluating ecosystem status and trends in the Paciﬁc Arctic was
the focus of a recent book, with 10 (of 12) chapters devoted to
observations and modeling of the atmosphere, ocean physics and
chemistry (Grebmeier and Maslowski, 2014). The papers in this
issue add to that body of knowledge, especially with regard to bio-
logical responses to biophysical drivers, and in this way contribute
to a more holistic understanding of the Paciﬁc Arctic marine
0079-6611/Published by Elsevier Ltd.
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Progress in Oceanography xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Progress in Oceanography
journal homepage: www.elsevier.com/locate/pocean
2.1. Physical observations and open-water projections in the ‘new
normal’ Paciﬁc Arctic
Recent observations (2003–2013) of environmental changes in
the Paciﬁc Arctic support the contention that a ‘new normal’ cli-
mate is emerging (Fig. 3;Jeffries et al., 2013; Wood et al., this
issue). The iconic indicator of this change is the dramatic summer-
time loss of sea ice (50% by area, 75% by volume), which in some
years (e.g., 2012) has resulted in nearly ice-free conditions in the
region. Speciﬁcally, satellite data from 1979 to 2012 reveal local-
ized changes in sea ice occurrence of up to 1.64 days/year in
the Canada Basin and 1.24 days/year in the Beaufort Sea, which
accelerated to 6.57 days/year (Canada Basin) and 12.84 days/
year (Beaufort Sea) during the 2000–2012 period (Frey et al., this
issue). Multiyear sea ice has almost entirely disappeared, with
inter-annual variability in ice concentration largely driven by wind
forcing in the Beaufort Sea. In the Canada Basin, differences in
annual sea ice are primarily thermally driven, while sea-ice extent
is inﬂuenced by both winds and heat on the Bering Sea shelf.
The summer atmospheric patterns inﬂuence ocean circulation,
freshwater pathways and the movement and melting of sea ice.
During the last decade, the intensiﬁcation of the Beaufort High
(Ogi and Wallace, 2012) resulted in anomalous summer winds.
These anomalous winds together with the loss of multi-year ice
were the primary factors that transformed the Chukchi and north-
ern Beaufort seas into an open water environment (Wood et al.,
this issue). In particular, the eastern Beaufort Sea appears to be
particularly susceptible to anomalous winds through their effect
on the advection of warm, fresh water from the Mackenzie River
plume. In addition, transport anomalies in the Bering Strait are
determined by competing large-scale atmospheric patterns, the
Beaufort High and Aleutian Low (Danielson et al., 2014). Notably,
changes in Bering Strait ﬂow through can impact the world climate
far beyond the Bering Strait and Arctic region (e.g., Hu et al., 2015).
Frey et al. (this issue, Fig. 13) investigate the inﬂuence of the
Paciﬁc Decadal Oscillation (PDO) and the Arctic Oscillation (AO)
on the persistence of sea ice in summer and winter. They found sig-
niﬁcant negative correlations between sea ice on the southeastern
Bering Sea shelf and the PDO in winter, as well as signiﬁcant pos-
itive correlations between the AO and sea-ice cover just south of St.
Lawrence Island. Signiﬁcant positive correlations between the PDO
and sea ice in the Canada Basin-Canadian Archipelago were found
in summer, as well as between the AO and sea ice in the Chukchi–
Beaufort seas. This novel investigation of teleconnections between
the PDO, the AO and sea-ice cover provides a critical step in under-
standing how global and regional climate patterns inﬂuence the
physics of the Paciﬁc Arctic region.
The unprecedented loss of sea ice has resulted in a tremendous
increase in open-water susceptible to rapid solar heating, with
additional heat and fresh water provided by a 50% increase in
Paciﬁc Water inﬂow at Bering Strait from 2001 to 2011
(Woodgate et al., 2012; Wood et al., this issue). The inﬂuence of
increased heat stored in the Chukchi and Beaufort seas is not well
understood. Suggestions that heat released to the atmosphere in
late autumn and winter drives aspects of mid-latitude weather
remain speculative, largely due to the short time record available
(Wood et al., this issue). Freshening of the Arctic Ocean has been
occurring at least since the 1990s (e.g., Giles et al., 2012). Several
explanations have been proposed including increased sea-ice melt,
fresher Paciﬁc Water ﬂowing through Bering Strait, changes in the
200 400 km
Fig. 1. Paciﬁc Arctic regional map depicting maximum (March) and minimum (September) sea ice extent (see Frey et al., this issue; Fig. 1) and major currents (see Wood
et al., this issue; Fig. 13).
2Preface / Progress in Oceanography xxx (2015) xxx–xxx
Fig. 2. Schematic marine food web for the Paciﬁc Arctic region.
Fig. 3. Highlights of recent biophysical changes in the Paciﬁc Arctic marine ecosystem.
Preface / Progress in Oceanography xxx (2015) xxx–xxx 3
magnitude of river discharge and the mean strengthening of the
Beaufort High. In recent years, relatively strong easterly winds have
been common due to the Arctic-wide pattern of circulation around
an intensiﬁed Beaufort High. Under these conditions fresh and
warm water fromthe Mackenzie River plume can be laterally trans-
ported far out into the Beaufort Sea (Wood et al., this issue, Fig. 17).
Wang and Overland (this issue) used twelve coupled climate
models to produce composite projections of the duration of open
water in the Chukchi and Beaufort seas, at decadal intervals from
2010 to 2050, and in 2090. For waters north of the 70°N, open-wa-
ter duration shifts from 3 to 4 months in 2010 to a projected
5 months by 2040. Projected open-water duration is about
1 month longer along the same latitudes in the Chukchi Sea com-
pared with the Beaufort Sea, with uncertainty of about ±1 month
estimated from the range of model results. All models projected
open-water duration to expand quickly over the next three dec-
ades, which will impact regional economic access and potentially
alter ecosystems. Yet the Paciﬁc Arctic region will remain covered
with thin ﬁrst-year ice from January through May into the second
half of the century, due to seasonal lack of sunlight.
2.2. Changes in primary production and ocean acidiﬁcation
The dramatic loss of sea-ice extent and volume has resulted in a
concomitant increase light penetration in the upper ocean across
the Arctic. Given the thinning and areal reduction of sea ice, a fun-
damental question arises: have these changes fostered an increase
in marine primary production? Speciﬁcally, is the Paciﬁc Arctic
region more productive than it was three decades ago? In the
Atlantic arctic, Leu et al. (2011) measured primary production
by both ice algae and phytoplankton in contrasting years
(2007–2008) of sea-ice cover in a Svalbard fjord, and concluded
that earlier ice break up corresponded with earlier onset of a
phytoplankton bloom. Similarly, Tremblay et al. (2012) report
increased primary production for 2007–2008 associated with
extreme sea-ice retreats and increased upwelling at stations
located south and east of Banks Island in the southeastern
Beaufort Sea. But, can conclusions drawn from measurements so
restricted in space and time be extrapolated to larger arctic
regions? Using satellite imagery, Arrigo and van Dijken (this
issue) investigated changes in sea ice at both regional and basin
scales from 1998 to 2012 and estimated how these changes have
impacted rates of net primary production (NPP) by phytoplankton.
They report that annual NPP increased 30% during this period, with
the largest increases on the interior shelves (including the East
Siberian and Beaufort) and smaller increases on inﬂow shelves
(including the Chukchi). Outﬂow shelves either exhibited no
change in annual NPP, or a signiﬁcant decline, perhaps indicating
that nutrients had been consumed further upstream. Increased
annual NPP was often, but not always, associated with reduced
sea-ice extent and resultant longer phytoplankton growing season.
Human activities have increased the atmospheric CO
tration by about 40% since the beginning of the industrial age
and it is estimated that the ocean has absorbed more than 25% of
the total anthropogenic emissions (Mathis et al., this issue). The
oceanic uptake of CO
triggers a series of chemical reactions in
the surface ocean that reduces pH and results in ocean acidiﬁcation
(OA). In short, OA makes seawater corrosive to calcium carbonate
minerals, which many marine organisms rely on for body struc-
tures. High-latitude oceans have naturally low carbonate concen-
trations, so are considered to be more vulnerable to the impacts
of OA because additional carbonate loss represents a much greater
proportional change to the system. In a novel study, Mathis et al.
provide a risk assessment of OA impacts to commercial and tradi-
tional ﬁsheries focused on shellﬁsh, salmon and ﬁnﬁsh. The resul-
tant index suggests that while the northern Bering Sea is at
medium risk from OA impacts to ﬁsheries, Paciﬁc Arctic waters
north of the Seward Peninsula are currently at low risk, due largely
to a lack of dependence on these food sources.
3. Lower trophic level communities: signals from direct and
The predominant conceptual model framing how marine
ecosystems in the Paciﬁc Arctic respond to reduced sea ice is based
on changes anticipated from a shift in pelagic–benthic coupling
Benthic Dominated Pelagic Dominated
Fig. 4. Generalized conceptual model depicting the inﬂuence of sea ice on pelagic–benthic coupling on Paciﬁc Arctic continental shelves.
4Preface / Progress in Oceanography xxx (2015) xxx–xxx
(Fig. 4). On the broad shelves that comprise much of the Paciﬁc
Arctic marine ecosystem, new primary production from sea-ice
algae and phytoplankton blooms falls to the sea ﬂoor to support
rich benthic communities (Grebmeier, 2012). As sea ice thins and
retreats earlier in the season, it is anticipated that earlier and larger
phytoplankton blooms will switch from a benthic-dominated to a
pelagic-dominated marine ecosystem. This shift will cascade
through the system, supporting novel communities of secondary
and tertiary consumers (zooplankton and forage ﬁshes) and upper
trophic level marine birds and mammals. Indeed, Grebmeier et al.
(2006) suggested that this type of ecosystem shift is already under-
way in the marine communities of the northern Bering Sea. The
Paciﬁc Arctic is often described as a benthic-dominated marine
ecosystem, one that does not support a large biomass or species
diversity of ﬁshes. A description of conditions that have fostered
existing benthic hotspots offers a solid foundation for assessing
future changes, while an accounting of the existing communities
of marine ﬁshes across a spectrum of habitats provides a starting
point upon which to build a long-term record.
3.1. Benthic hotspots and marine ﬁshes across a spectrum of habitats
A record of extant conditions is key to interpreting marine
ecosystem responses to the new biophysical forcing now evident
in the Paciﬁc Arctic. Such a record exists for four benthic ‘hotspot’
communities in the northern Bering and Chukchi seas (Grebmeier
et al., this issue), but not for marine ﬁshes. Long-term sampling of
benthic macrofaunal communities indicates that the benthic hot-
spots have maintained consistently high biomass for up to four
decades, due to reoccurrence of seasonally reliable moderate-to-
high water column production coupled with signiﬁcant export of
carbon from overlying waters to the sea ﬂoor. Upper trophic level
benthivores target prey aggregations in each of the hotspots.
Overall, bottom-up forcing by hydrography and food supply to
the benthos inﬂuences persistence and composition of benthic
prey, which in turn inﬂuences the upper trophic level species com-
position and seasonal occurrence. When consistently sampled in
tandem, these benthos–benthivore connections can facilitate use
of UTL species as sentinels of shifts in prey composition and
abundance (Moore et al., 2014).
Since the 2000s, there have been a host of Arctic marine ﬁsh sur-
veys in the western Beaufort and Chukchi seas, precipitated by both
scientiﬁc interest in the impacts of climate change and commercial
interest in oil and gas development (Logerwell et al., this issue).
Results from these surveys provide a novel opportunity to compare
Arctic ﬁsh communities across a spectrum of habitats, ranging from
lagoons and beaches to benthic and pelagic continental shelf
waters. A synthesis of data from these surveys revealed more sim-
ilarities than differences in habitat use between the two seas. For
example, nearshore habitat is used by all age classes of forage ﬁshes
and is also a nursery area for other species in both the Chukchi and
western Beaufort seas. Notably, some commercial species may be
expanding their range north to these waters, including chinook sal-
mon (Oncorhynchus tshawytscha), walleye pollock (Gadus
chalcogrammus) and ﬂatﬁshes (Pleuronectidae). In addition, a syn-
thesis of information on relative abundance and age of arctic cod
(Boreogadus saida) and saffron cod (Eleginus gracilis), both key prey
species in Arctic food webs, supported the development of life his-
tory and distribution models that will inform future research on
trophic dynamics in the Paciﬁc Arctic sector.
3.2. Inferences of marine ecosystem shifts from seals, seabirds and sea
Additional information regarding the impact of ‘new normal’
biophysical conditions on lower trophic level species can be
inferred from shifts in the diet and body condition of marine mam-
mals and birds. Crawford et al. (this issue) compared the diet and
condition of ringed seals (Pusa hispida) and bearded seals
(Erignathus barbatus) harvested in the Alaskan Bering and
Chukchi seas during historical (1975–1984) and recent (2003–
2012) periods. They found the proportion of ﬁsh in the diet of both
species increased in the recent reduced-ice period compared to the
historical period. In addition, ringed seals grew faster, had thicker
blubber and matured 2 years earlier. Bearded seals had thicker
blubber in the recent period, but did not manifest the other
changes reported for the ringed seals. Although a number of the
comparisons were not statistically signiﬁcant, taken together these
observations suggest greater ﬁsh availability in the Alaskan
Bering–Chukchi marine ecosystem supporting good body condi-
tion in the seals.
As in the seal paper, Divoky et al. (this issue) parsed a long-term
data set into recent (2003–2012) and historical (1975–1984) peri-
ods to compare oceanographic conditions, nestling diet and ﬂedg-
ing success at a black guillemot (Cepphus grylle mandtii) breeding
colony in the western Beaufort Sea. From 15 July to 1 September,
sea ice retreated an average of 1.8 km per day to an average dis-
tance of 95.8 km from the colony during the historical period,
while in the recent period ice retreat averaged 9.8 km per day to
an average distance of 506.9 km. Sea surface temperature near
the colony increased by 2.9 °C between the two periods. While
Arctic cod comprised over 95% of the prey provided to nestlings
in the historical period, this proportion decreased to <5% of the
nestling diet during most years in the recent period, when demer-
sal sculpin (Cottidae) comprised the majority of the diet. The shift
away from Arctic cod was associated with a ﬁve-fold increase in
the rate of nestling starvation and reductions in nestling growth
and ﬂedging mass. Conversely, annual adult survival during the
nonbreeding season (September–May), showed no signiﬁcant dif-
ference between the two periods, suggesting no change in the
availability of Arctic cod or other prey to black guillemots in their
Bering Sea wintering area.
In contrast to a reliance on pelagic prey, Lovvorn et al. (this
issue) investigated potential climate-related limits to benthic feed-
ing by sea ducks along their migration corridor in the northeastern
Chukchi Sea. King eiders (Somateria spectabilis) primarily eat clams
(bivalves) during migration and recent sampling has shown that
dense clam assemblages occur only in speciﬁc locations along the
migration corridor. Sea ice can prevent eiders from reaching these
prime feeding sites, with satellite data for April–May (2001–2013)
showing that access can vary from 0% to 100%. In a warming and
increasingly variable climate, access to benthic feeding sites may
be further eroded by the effects of winds on unconsolidated ice.
These results underscore the importance of maintaining a range
of benthic feeding areas throughout the migration corridor to
ensure prey availability to the eiders each year.
4. Upper trophic level species: marine birds and mammals as
As top predators, marine birds and mammals must adapt to
changes in their habitats resulting from physical forcing and
thereby can serve as sentinels to ecosystem shifts (Moore et al.,
2014; Moore and Gulland, 2014). Responses of upper trophic level
(UTL) species to altered habitats can be categorized as extrinsic,
including shifts in range, migratory timing (phenology), or regions
of high abundance (hotspots); or intrinsic, including changes in
diet, body condition and chemical composition (Fig. 5).
Responses are inter-related such that a shift in range, phenology
or use of hotspots will be reﬂected in changes in diet, body condi-
tion and chemistry. It is this connection that allows us to detect
ecosystem reorganization by tracking changes in the ecology and
Preface / Progress in Oceanography xxx (2015) xxx–xxx 5
physiology of UTL species. Although there have been no coordi-
nated long-term studies of UTL species in the Paciﬁc Arctic, a syn-
thesis of information from visual surveys, satellite tagging of
individuals and year-round acoustic detections provides an ecolog-
ical foundation that can provide a baseline to inform future
4.1. Seasonal occurrence, hotspot habitats and acoustic ecology
Kuletz et al. (this issue) depict spatial patterns of relative abun-
dance of seabirds and marine mammals in summer and fall,
derived from 6 years of visual surveys in the eastern Chukchi and
western Beaufort seas. Using statistical spatial analysis tools, hot-
spots for seabirds, walrus, and gray whales were identiﬁed in the
Chukchi Sea, while hotspots for bowhead whales and seals were
described near Barrow Canyon and along the Beaufort Sea shelf
and slope. Hotspots for belugas occurred in both the Chukchi and
Beaufort seas. In summer, three hotspots were shared by both sea-
birds and marine mammals in the Chukchi Sea: waters offshore
Wainwright, south of Hanna Shoal, and at the mouth of Barrow
Canyon. Only the Barrow Canyon hotspot was occupied through
the fall. Shared hotspots were characterized by strong fronts
caused by upwelling and currents, which can serve to aggregate
prey. Using a different approach, Citta et al. (this issue) provide
detailed analysis of the seasonal movements and habitat use by a
single species throughout 1 year. Locations from 54 bowhead
whales (Balaena mysticetus), obtained by satellite telemetry from
2006 to 2012, were used to identify a total of six core-use areas
in the Beaufort (3), Chukchi (1) and northern Bering (2) seas.
Taken together, the timing of use (phenology) and physical charac-
teristics (oceanography, sea ice, and winds) associated with each
area, describe a seasonal circuit by the whales through areas
thought to support elevated prey densities.
Passive acoustic sampling has become a common year-round
tool to detect calling marine mammals in arctic seas (Moore
et al., 2006; Stafford et al., 2012). Since 2007, there has been an
especially strong sampling effort associated with oil and gas explo-
ration in the northeast Chukchi and western Beaufort seas (e.g.,
Hannay et al., 2013;http://www.afsc.noaa.gov/nmml/cetacean/
chaoz.php). These recorder deployments augment a long-standing
acoustic study in the central Beaufort Sea (Blackwell et al., 2007)
and more recent deployments in the Bering Strait region (K.
Stafford, pers. comm.). Heretofore, researchers conducted each of
these studies independent of one another. Clark et al. (this issue)
presents a novel synthesis of the combined output from six
research efforts using four types of recorders and a variety of
sub-sampling and analysis schemes to describe an ‘acoustic year’
in the life of the bowhead whale. Detections of bowhead calls from
20 sites extending over 2300 km from the northern Bering Sea to
the southeast Beaufort Sea were combined over a 14-month period
(2009–2010) to describe whale occurrence across their range. The
spatial and temporal variability in sound levels within the fre-
quency band of bowhead whales was also quantiﬁed. The lowest
underwater sound levels occurred from late November until May
in the Chukchi Sea. During winter 2009–2010, singing bowhead
whales elevated broadband sound levels for roughly 38 days in
the northern Bering Sea, followed by a second month-long period
of elevated sound levels due to singing by bearded seals. High-
wind events also resulted in 2–5 day periods of elevated sound
levels, evident on multiple recorders hundreds of miles apart.
Although there were few seismic surveys during the 14-month
period, air gun sounds were detected in the Chukchi Sea in late
summer 2009, roughly 700 km away from the seismic survey
underway in the eastern Beaufort Sea.
In a second paper describing the acoustic ecology of marine
mammals in the Paciﬁc Arctic, MacIntyre et al. (this issue)
investigated bearded seal calling activity in relation to variability
in sea-ice cover. Acoustic data were analyzed from 9 recording
locations extending from the Bering to the western Beaufort Sea.
Bearded seals were vocally active nearly year-round in the
Beaufort and Chukchi seas, with peak activity occurring during
the springtime mating season. Conversely, bearded seal calling
Fig. 5. Marine birds and mammals are upper trophic level (UTL) species that reﬂect ecosystem alterations by changes in habitat use (extrinsic) and body condition (intrinsic).
Tracking both extrinsic and intrinsic responses in UTL species can reveal fundamental changes in marine ecosystems (modiﬁed from Moore et al., 2014).
6Preface / Progress in Oceanography xxx (2015) xxx–xxx
activity lasted only about 5 months in the Bering Sea, again with a
mating-season peak in the spring. In all areas, calling activity was
positively correlated with sea-ice cover (p< 0.01). These results
suggest that losses in sea ice may negatively impact bearded seals,
both by loss of haul-out habitat and by altering the phenology of
calling for bearded seals in the Paciﬁc Arctic sector.
4.2. Diet and body condition
For bowhead whales, changes associated with the new biophys-
ical conditions in the Paciﬁc Arctic may be a ‘good bump’ in a long
road. Bowhead whales can live for a century or more, with a few
whales estimated to have lived over 200 years (George et al.,
1999). The Bering–Chukchi–Beaufort (BCB) population is still
recovering in number from roughly 170 years of commercial whal-
ing, which ended around 1920, so responses by this species to
recent changes in the marine ecosystem must be interpreted in
that context. George et al. (this issue) examined the relationship
between body condition of BCB bowhead whales and inter-annual
variability in summertime environmental conditions (seasonal
sea-ice cover and wind stress) for whales harvested by Alaskan
hunters from 1989 to 2011. During this period, there was a signif-
icant increase in axillary girth (fatness) associated with the reduc-
tion in sea ice and shifts in wind stress to patterns associated with
upwelling along the slope and shelf of the Beaufort Sea.
Speciﬁcally, strong positive correlations were described between
whale girth and late-summer open water fraction in the Beaufort
Sea, and with open water and upwelling-favorable winds in areas
of the Mackenzie Delta and waters west of Banks Island.
Whether due to increased secondary productivity associated with
upwelling, or due to a longer feeding period associated with
reduced ice cover, the improved body condition of whales in the
BCB bowhead population suggest they are ﬁnding increased access
to prey in the ‘new normal’ Paciﬁc Arctic.
The utility of looking to UTL species as ecosystem sentinels is
further explored in Harwood et al. (this issue), where body condi-
tion of ﬁve predators, monitored from harvests in the Beaufort Sea
over the past 2–4 decades, indicate that all have been affected by
biophysical changes in the marine ecosystem. Improved body con-
dition is described for Arctic char (Salvelinus alpinus) and sub-adult
bowhead whales, primarily associated with the extent and persis-
tence of sea ice. Conversely, three species, which likely feed pri-
marily on arctic cod (ringed seal, beluga and black guillemot
chicks), showed declines in condition, growth and/or production
during the same period. Although the proximate causes of these
contrasting changes are unknown, they are likely mediated by an
upward trend in secondary productivity accompanied by a down-
trend in the availability of forage ﬁsh, especially Arctic cod, a key
species in arctic food webs. Notably, the reported decline in body
condition for ringed seals contrast with that reported in
Crawford et al. (this issue), but this may be due to differences in
prey availability in sub-regions of the Paciﬁc Arctic where the har-
vested seals were feeding; i.e., the eastern Beaufort Sea (Harwood
et al.) and the Bering–Chukchi (Crawford et al.). Similar contrasts
in size and body condition for polar bears (Ursus maritimus) were
recently described for animals from the Chukchi Sea (good) and
the Beaufort Sea (poor) populations (Rode et al., 2013). Indeed,
Harwood et al. (this issue) advocate the inclusion of multiple UTL
species in the sampling design of future marine ecosystem
research programs, at ecologically relevant spatial and temporal
5. Biophysics and marine ecology of the Paciﬁc Arctic region
The biophysics and marine ecology of the Paciﬁc Arctic region is
a study in contrasts, resulting from differing processes that occur
over the broad and shallow inﬂow shelves of the northern Bering
and Chukchi seas, compared to the narrow interior shelf, steep
slope and deep basin of the Beaufort Sea. Carmack and
Wassmann (2006) provide a pan-Arctic overview on the role of
shelves in guiding oceanographic processes, and promote ‘shelf
geography’ as a unifying concept with regard to linking physical
processes to food webs. Using this concept, Carmack and
Wassmann (2006) identiﬁed the Paciﬁc Arctic region as one of four
contiguous domains comprising the pan-Arctic; the other three are
the seasonal ice zone domain, the pan-Arctic marginal (shelf-break
and slope) domain and the riverine coastal domain. As described in
Wood et al. (this issue), hydrography in the Paciﬁc Arctic region is
deﬁned by Paciﬁc waters entering the Chukchi through Bering
Strait, warming as they are advected through the Chukchi Sea
and circulating at depths <200 m within the Beaufort gyre of the
Canada Basin. The entrapment of this inﬂow within the gyre
increases the volume of fresh water and intensiﬁes stratiﬁcation
with the warmer–saltier Atlantic water below.
The role of sea ice in regulating pelagic–benthic coupling (see
Fig. 4) is the foundational model regarding the structure of food
webs on the broad in-ﬂow shelves. Indeed, the biophysics and ecol-
ogy of benthic communities in the Paciﬁc Arctic is fully described
in Grebmeier et al. (this issue). However, nutrients and expatriate
zooplankton from the northern Bering Sea are also advected in
Paciﬁc water across the wide Chukchi shelf and into the Beaufort
Sea (Nelson et al., 2014), and the role of this transport is often
ignored in conceptual models of the marine ecosystems. Clearly,
advected prey are important to UTL species – one example being
the consumption of Paciﬁc species of euphausiids by bowhead
whales at Barrow and as far east as Kaktovik, Alaska in the eastern
Beaufort Sea (Lowry et al., 2004). A new conceptual model is
required to capture the complex interconnectivity between the
role of pelagic–benthic coupling and that of the strongly seasonal
transport of heat, nutrients and prey into the region.
5.1. Ecosystem conceptual models and visualization tools: the ‘Arctic
Marine Pulse’ model
The sea-ice driven pelagic–benthic coupling model has served
the science community well for nearly three decades (Grebmeier,
2012, and references therein). While the pelagic–benthic model
serves as a strong framework for depicting processes on the shal-
low shelf habitat of the northern Bering and Chukchi seas, it does
not depict the interactive processes occurring along the narrow
interior shelf, slope and deep basin of the Beaufort Sea. Carmack
and Wassmann (2006) advocate for the development of ‘‘an ecol-
ogy of advection’’ to advance ecosystem models that can support
inter-comparisons of existing and future arctic food webs.
Grebmeier et al. (2015) provide a comprehensive conceptual
model linking advective processes in the Chukchi and Beaufort.
The input function for this model is the advection north of Paciﬁc
Water (comprised of AW, BSW, ACW; see Fig. 1). The three path-
ways for this inﬂow cross the Chukchi Sea, then enter the
Beaufort Sea primarily at canyons with further advective processes,
including eddy shedding, along the slope. Freshwater inﬂow from
the Yukon and Mackenzie rivers is depicted, as is nearshore out-
ﬂow of Siberian Coastal Water (SCW) along the Russian north
coast. This conceptual advective model is an essential tool to frame
our understanding of the Paciﬁc Arctic marine ecosystem, but
remains a comparatively static representation of very dynamic
The ‘krill trap’ model, developed during a study of bowhead
whales feeding on euphausiids transported to local waters near
Barrow, provides a starting point to animate an advective model
for a portion of the Paciﬁc Arctic region (Ashjian et al., 2010).
Physical drivers of this local-area model invoke wind forcing,
Preface / Progress in Oceanography xxx (2015) xxx–xxx 7
shelf-break topography and current structure along Barrow
Canyon to explain the retention of krill along a front on the west-
ern Beaufort shelf (Okkonen et al., 2011). This dynamic model
essentially ‘‘rocks back and forth’’ between two states: upwelling
of prey and nutrients onto the narrow shelf induced by easterly
winds, and prey retention induced by relaxed or southerly winds.
This model focuses on only the western Beaufort Sea, however,
and requires expansion to serve the full Paciﬁc Arctic region.
Here we propose an Arctic Marine Pulses (AMP) conceptual
model for the Paciﬁc sector, which aims to both animate the
Grebmeier et al. (2015) advection model and link it to the pela-
gic–benthic coupling model (Fig. 6). In this way, the zooplankton
and forage ﬁsh predicted by the pelagic–benthic model with the
loss of sea ice are advected across the Chukchi and into the
Beaufort Sea by the advective model. The AMP model employs
the contiguous domain concept, described in Carmack and
Wassmann (2006), to join physical habitats by the integration of
common features such as the seasonal cycles of inﬂow at Bering
Strait, sea-ice advance and retreat, and riverine export.
Speciﬁcally, the AMP model connects four contiguous domains
(i) Paciﬁc Arctic domain – this is the ‘focal region’, comprised of
a broad–shallow inﬂow system (Chukchi) connecting to
Fig. 6. Components of the Arctic Marine Pulses (AMP) conceptual model – linking pelagic–benthic coupling and advective models to derive a seasonal model for the Paciﬁc
Arctic framed by contiguous domains.
Fig. 7. Arctic Marine Pulses (AMP) conceptual model depicting seasonal biophysical ‘pulses’ across a latitudinal gradient linking four contiguous domains: (i) summertime
peak-inﬂow of Paciﬁc Water initiates advective processes in the Paciﬁc Arctic domain; (ii) variability in the annual cycle of the seasonal ice zone domain inﬂuences pelagic–
benthic coupling on continental shelves of the northern Bering and Chukchi seas and shelf-basin exchange in the Beaufort sea; (iii) advection and upwelling dominate
processes along the Beaufort Sea shelf-break and slope in the Paciﬁc marginal domain, while (iv) the riverine and coastal domain is inﬂuenced by summertime outﬂow of
warm-fresh water from the Yukon and Mackenzie rivers.
8Preface / Progress in Oceanography xxx (2015) xxx–xxx
inner-shelf-slope-basin system (Beaufort); the strong sum-
mer-pulse of comparatively fresh water, heat, nutrients and
plankton through Bering Strait initiates the AMP model, as
it does the advection model in Grebmeier et al. (2015);
(ii) Seasonal ice zone domain – seasonal ice retreat serves to link
the AMP model to the pelagic–benthic coupling model.
Timing and pace of sea-ice retreat across the Chukchi Sea
drives pulses of organic material either to the benthos, or
toward the pelagic system; sea-ice retreat beyond the nar-
row Beaufort shelf in late summer allows the system to
respond to winds that can induce pulses of upwelling of
nutrients and prey onto the shelf;
(iii) Paciﬁc marginal domain – the Beaufort Sea shelf break and
slope is a transport pathway for nutrients and prey advected
across the Chukchi Sea; this marginal domain also provides
links to the deep basin where stores of nutrients and prey
can be upwelled by wind forcing after the sea-ice retreats;
Herald and Barrow canyons are focal points of shelf-basin
exchange (i.e., secondary pulse-points) although local winds
can reverse ﬂow;
(iv) Riverine coastal domain – the Yukon and Mackenzie river
outﬂows provide seasonal pulses of warm and fresh
water to the northern Bering and Beaufort seas, respectively.
In the Beaufort, the Mackenzie outﬂow can trap nutrients
and prey. The Mackenzie outﬂow has increased dramatically
over the past decade (Wood et al., this issue) and,
with increased seasonal run-off, the Sagavanirktok
and Colville rivers may have greater inﬂuence now than in
The AMP conceptual model could be enhanced by the applica-
tion of visualization tools to provide the capability to see a season
unfold. The ability to track water mass characteristics and to move
nutrients, prey and UTL species through the Paciﬁc Arctic in space
and time would provide a foundation for insight and aid in the
development of dynamic ecosystem models. Although not quanti-
tative, a step in this regard was taken during the production of a
short animated ﬁlm called ‘Arctic Currents: a year in the life of a
bowhead whale’ (http://www.uaf.edu/museum/exhibits/digital-
media/arctic-currents/). The ﬁlm depicts the movements of
individual whales equipped with satellite tags, in tandem with
the seasonal advection of krill through Bering Strait, across the
Chukchi Sea and along the Beaufort Sea slope. What is not por-
trayed are the pelagic–benthic ‘pulses’ of nutrients so important
to the development of benthic ‘hotspots’ and the prey of
benthivores such as eiders, walruses, bearded seals and gray
whales. Currently, visualization tools are most commonly applied
to satellite-derived data, which can only provide information on
the ‘skin’ of the ocean. Visualizing biophysical pulses in three
dimensions, parameterized by measured values where available,
could move us in the direction of predictive model capability for
the Paciﬁc Arctic marine ecosystem.
The papers in this special issue provide a range of synthesis
approaches to capture the existing conditions in the Paciﬁc
Arctic marine ecosystem. By design, the focus was on the state
of the ecosystem now, that is the biophysics of the ‘new normal’
Paciﬁc Arctic – which has emerged during this century.
Collectively the papers cover all ecosystem topics, from atmo-
spherics, sea ice and shifting hydrography, to responses by LTL
and UTL species to the new and highly variable state of the
marine ecosystem. This compendium of papers serves as a step
toward a more holistic understanding of the Paciﬁc Arctic marine
The SOAR project is not the only effort focused on an integrated
synthesis of conditions in the Paciﬁc Arctic. The seasonal and inter-
annual dynamics of the northeastern Chukchi Sea ecosystem was
the focus of intense study from 2008 to 2010, resulting in a special
volume of papers (Hopcroft and Day, 2013). A second special vol-
ume of papers describing results of sampling across the full
Chukchi Sea during the decade-long RUSALCA project is antici-
pated by the end of this year (K. Crane, pers. comm.).
Alternatively, the Paciﬁc Marine Arctic Regional Synthesis
(PacMARS) project provided an extensive review and compilation
of extant data for the Paciﬁc Arctic region, as well as detailed sug-
gestions for future research themes and focal areas (Grebmeier
et al., 2015).
All of these synthesis efforts point to the need for future
research focused on key areas and processes, including:
KEY areas – Spatial focus: Bering Strait, Hanna Shoal, Herald
Canyon, Barrow Canyon, Beaufort outer shelf and slope,
Siberian coast, Mackenzie delta and coast, the polynyas offshore
of St. Lawrence Island, Anadyr and Cape Bathurst.
KEY processes – Temporal focus: Seasonal sea ice, Bering Strait
transport, Advection of fresh water, heat, nutrients and prey
from the northern Bering Sea to the Beaufort Sea, Upwelling
and eddies along Beaufort slope, the Mackenzie Plume, Yukon
outﬂow and contributions of other rivers (e.g., Canning,
Sagavanirktok, Colville) to the Beaufort coastal system.
Visualization tools applied to an integrated model, such as the
AMP, would greatly aid the development of dynamic ecosystem
models connecting atmosphere–ocean physics with biological
responses. Because they must respond to ecosystem variability to
survive, upper trophic level species, including marine ﬁshes, birds
and mammals should be included in these models. They not only
act as sentinels to ecosystem variability, but also provide a funda-
mental link to humans – as essential food and cultural keystones
for those that live in the Arctic and as icons of the Arctic region
for those that do not.
K. Stafford, Applied Physics Laboratory, University of
Washington, Seattle, WA, USA. Email: email@example.com.
K. Crane, Ocean and Atmospheric Research, NOAA, Silver Spring,
MD, USA. Email: Kathy.Crane@noaa.gov.
The Synthesis of Arctic Research (SOAR) and was funded pri-
marily by the U.S. Department of the Interior, Bureau of Ocean
Energy Management (BOEM), Environmental Studies Program
through Interagency Agreement No. M11PG00034 with the U.S.
Department of Commerce, National Oceanic and Atmospheric
Administration (NOAA), Ofﬁce of Oceanic and Atmospheric
Research (OAR), Paciﬁc Marine Environmental Laboratory (PMEL).
The SOAR project brought together over 100 scientists and local
experts to produce a synthesis of data and observations presented
in the papers comprising this issue. While the BOEM Alaska Region
supported many of the studies upon which these papers depend,
the papers also represent contributions of data from research sup-
ported by NSF, ONR, USFWS, NSB, NPRB, ADF&G and others. The
Preface / Progress in Oceanography xxx (2015) xxx–xxx 9
SOAR project was enriched by the thoughtful and efﬁcient work of
project coordinator Lisa Shefﬁeld Guy (JISAO), while the ﬁgures in
this preface were signiﬁcantly improved by the graphic arts talent
of Karen Birchﬁeld (PMEL). We thank both Dr. Charles Monnett
(BOEM-retired) and Dr. Heather Crowley (BOEM) for their enthusi-
asm and management of the project. Finally, we sincerely thank all
of our academic, agency and arctic community colleagues who
contributed to this special issue; quite literally, we could not have
done it without you.
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Sue E. Moore
NOAA/Fisheries, 7600 Sand Point Way NE, Seattle, WA 98115, USA
⇑Tel.: +1 206 526 6889.
Phyllis J. Stabeno
NOAA/OAR, 7600 Sand Point Way NE, Seattle, WA 98115, USA
Available online xxxx
Preface / Progress in Oceanography xxx (2015) xxx–xxx 11