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Kevin R Arrigo - One of the best experts on this subject based on the ideXlab platform.
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impacts of sea Ice Retreat thinning and melt pond proliferation on the summer phytoplankton bloom in the chukchi sea arctic ocean
Deep-sea Research Part Ii-topical Studies in Oceanography, 2014Co-Authors: Molly A Palmer, Benjamin T Saenz, Kevin R ArrigoAbstract:Abstract In 2011, a massive phytoplankton bloom was observed in the Chukchi Sea under first-year sea Ice (FYI), an environment in which primary productivity (PP) has historically been low. In this paper, we use a 1-D biological model of the Chukchi shelf ecosystem, in conjunction with in situ chemical and physiological data, to better understand the conditions that facilitated the development of such an unprecedented bloom. In addition, to assess the effects of changing Arctic environmental conditions on net PP (NPP), we perform model runs with varying sea Ice and snow thickness, timing of melt, melt ponds, and biological parameters. Results from model runs with conditions similar to 2011 indicate that first-year Ice (FYI) with at least 10% melt pond coverage transmits sufficient light to support the growth of shade-adapted Arctic phytoplankton. Increasing pond fraction by 20% enhanced peak under-Ice NPP by 26% and produced rates more comparable to those measured during the 2011 bloom, but there was no effect of further increasing pond fraction. One of the important consequences of large under-Ice blooms is that they consume a substantial fraction of surface nutrients such that NPP is greatly diminished in the marginal Ice zone (MIZ) following Ice Retreat, where NPP has historically been the highest. In contrast, in model runs with
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Evidence of under-Ice phytoplankton blooms in the Chukchi Sea from 1998 to 2012
Deep-sea Research Part Ii-topical Studies in Oceanography, 2014Co-Authors: Kate E. Lowry, Gert L. Van Dijken, Kevin R ArrigoAbstract:Abstract The discovery in 2011 of a massive phytoplankton bloom underneath first-year sea Ice in the western Arctic has prompted an investigation of the spatial and temporal distribution of under-Ice phytoplankton blooms. Here, we explore the satellite record from years 1998 to 2012 for evidence of under-Ice blooms on the Chukchi Sea shelf. Phytoplankton blooms were categorized as under-Ice blooms, probable under-Ice blooms, or marginal Ice zone blooms, depending on bloom timing in relation to the timing of Ice Retreat. Annual bloom type maps reveal that under-Ice phytoplankton blooms were present in every year of the satellite record. Averaged over all years, the combination of under-Ice blooms and probable under-Ice blooms covered a portion of the observable study area that was 2.5-fold higher than that of marginal Ice zone blooms (71.5% and 28.5%, respectively). This finding strongly contradicts the traditional view that phytoplankton in seasonally Ice-covered waters bloom only after Ice Retreat and instead indicates that blooms are initiated whenever light and nutrient availability is sufficient for photosynthesis, a condition often reached early in the season underneath first-year sea Ice on nutrient-rich continental shelves. Spatial patterns in bloom type were distinguished relative to the date of Ice Retreat, with probable under-Ice blooms dominating the nutrient-rich western Chukchi Sea and at higher latitudes where Ice Retreats later, while marginal Ice zone blooms were most common in the southern and eastern Chukchi Sea where Ice Retreats earlier. Our results suggest that under-Ice phytoplankton blooms are widespread in the Chukchi Sea and had been prevalent there for more than a decade prior to their discovery in 2011.
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sea Ice impacts on spring bloom dynamics and net primary production in the eastern bering sea
Journal of Geophysical Research, 2013Co-Authors: Zachary W Brown, Kevin R ArrigoAbstract:[1] In the Eastern Bering Sea, changes in sea Ice have been implicated in recent major upper-trophic level shifts. However, the underlying relationships between sea Ice and primary producers have not been well tested. Here, we combine data from multiple satellite platforms, reanalysis model results and biophysical moorings to explore the dynamics of spring and summer primary production in relation to sea Ice conditions. In the northern Bering Sea, sea Ice consistently Retreated in late spring, leading to Ice-edge phytoplankton blooms in cold (0–1 °C) waters. However, in the southeastern Bering Sea, sea Ice Retreat was far more irregular. Although this did not significantly alter bloom timing, late Retreat led to blooms at the Ice-edge while early Retreat led to blooms in open waters that were warmer (≤5.4 °C) and >70% more productive. Early sea Ice Retreat also led to higher productivity in summer, likely due to weaker thermal stratification. Overall, annual net primary production during warm years of early sea Ice Retreat was enhanced by 40–50% compared to years with late sea Ice Retreat in the southeastern Bering Sea. These findings suggest the potential for future sea Ice loss to enhance overall carrying capacity of the southeastern Bering Sea ecosystem. Consistently warm blooms in the future may also channel more energy flow toward the pelagic, rather than benthic, environment. To date, however, neither sea Ice extent nor the timing of its Retreat have undergone long-term changes in the Eastern Bering Sea.
George L. Hunt - One of the best experts on this subject based on the ideXlab platform.
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Variation in annual production of copepods, euphausiids, and juvenile walleye pollock in the southeastern Bering Sea
Deep-sea Research Part Ii-topical Studies in Oceanography, 2016Co-Authors: Michael F. Sigler, Phyllis J Stabeno, Jeffery M Napp, Ronald A. Heintz, Michael W. Lomas, George L. HuntAbstract:Abstract We synthesize recent research on variation in annual production of copepods (Calanus spp.), euphausiids (Thysanoessa spp.), and juvenile walleye pollock (Gadus chalcogrammus) in the southeastern Bering Sea. We reach five conclusions: 1) the timing of the spring bloom is more important than the amount of annual primary production for the transfer of primary to secondary production (i.e., timing matters); 2) summer and fall, not just spring, matter: organisms must maximize energy intake devoted to somatic growth and storage of lipids and minimize energy expenditures during each season; 3) stored lipids are important for the overwinter survival of both zooplankton and age-0 walleye pollock; 4) variation in Ice extent and timing of Ice Retreat affect the spatial distributions of phytoplankton, zooplankton, and age-0 walleye pollock; when these spatial distributions match in late-Ice-Retreat years, the annual production of copepods, euphausiids, and juvenile walleye pollock often increases (i.e., location matters); 5) if years with late Ice Retreat, which favor copepod, euphausiid, and juvenile walleye pollock production, occur in succession, top–down control increases. These conclusions help to explain annual variation in production of copepods, euphausiids and juvenile walleye pollock. Copepods and euphausiids often are more abundant in cold years with late Ice Retreat than in warm years with early Ice Retreat due to bloom timing and the availability of Ice algae during years with late Ice Retreat. As a consequence, age-0 walleye pollock consume lipid-enriched prey in cold years, better preparing them for their first winter and their overwinter survival is greater. In addition, there is a spatial match of primary production, zooplankton, and age-0 walleye pollock in cold years and a mismatch in warm years.
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timing of Ice Retreat alters seabird abundances and distributions in the southeast bering sea
Biology Letters, 2016Co-Authors: Martin Renner, Sigrid Salo, Lisa B Eisner, Patrick H Ressler, Carol Ladd, Kathy J Kuletz, Jarrod A Santora, John F Piatt, Gary S Drew, George L. HuntAbstract:Timing of spring sea-Ice Retreat shapes the southeast Bering Sea food web. We compared summer seabird densities and average bathymetry depth distributions between years with early (typically warm) and late (typically cold) Ice Retreat. Averaged over all seabird species, densities in early-Ice-Retreat-years were 10.1% (95% CI: 1.1–47.9%) of that in late-Ice-Retreat-years. In early-Ice-Retreat-years, surface-foraging species had increased numbers over the middle shelf (50–150 m) and reduced numbers over the shelf slope (200–500 m). Pursuit-diving seabirds showed a less clear trend. Euphausiids and the copepod Calanus marshallae/glacialis were 2.4 and 18.1 times less abundant in early-Ice-Retreat-years, respectively, whereas age-0 walleye pollock Gadus chalcogrammus near-surface densities were 51× higher in early-Ice-Retreat-years. Our results suggest a mechanistic understanding of how present and future changes in sea-Ice-Retreat timing may affect top predators like seabirds in the southeastern Bering Sea.
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climate change and control of the southeastern bering sea pelagic ecosystem
Deep-sea Research Part Ii-topical Studies in Oceanography, 2002Co-Authors: George L. Hunt, Phyllis J Stabeno, Gary E Walters, Elizabeth Sinclair, Richard D Brodeur, Jeffery M Napp, Nicholas A BondAbstract:We propose a new hypothesis, the Oscillating Control Hypothesis (OCH), which predicts that pelagic ecosystem function in the southeastern Bering Sea will alternate between primarily bottom-up control in cold regimes and primarily top-down control in warm regimes. The timing of spring primary production is determined predominately by the timing of Ice Retreat. Late Ice Retreat (late March or later) leads to an early, Ice-associated bloom in cold water (e.g., 1995, 1997, 1999), whereas no Ice, or early Ice Retreat before mid-March, leads to an open-water bloom in May or June in warm water (e.g., 1996, 1998, 2000). Zooplankton populations are not closely coupled to the spring bloom, but are sensitive to water temperature. In years when the spring bloom occurs in cold water, low temperatures limit the production of zooplankton, the survival of larval/juvenile fish, and their recruitment into the populations of species of large piscivorous fish, such as walleye pollock (Theragra chalcogramma), Pacific cod (Gadus macrocephalus) and arrowtooth flounder (Atheresthes stomias). When continued over decadal scales, this will lead to bottom-up limitation and a decreased biomass of piscivorous fish. Alternatively, in periods when the bloom occurs in warm water, zooplankton populations should grow rapidly, providing plentiful prey for larval and juvenile fish. Abundant zooplankton will support strong recruitment of fish and will lead to abundant predatory fish that control forage fish, including, in the case of pollock, their own juveniles. Piscivorous marine birds and pinnipeds may achieve higher production of young and survival in cold regimes, when there is less competition from large piscivorous fish for coldwater forage fish such as capelin (Mallotus villosus). Piscivorous seabirds and pinnipeds also may be expected to have high productivity in periods of transition from cold regimes to warm regimes, when young of large predatory species of fish are numerous enough to provide forage. The OCH predicts that the ability of large predatory fish populations to sustain fishing pressure will vary between warm and cold regimes. The OCH points to the importance of the timing of Ice Retreat and water temperatures during the spring bloom for the productivity of zooplankton, and the degree and direction of coupling between zooplankton and forage fish. Forage fish (e.g., juvenile pollock, capelin, Pacific herring [Clupea pallasii]) are key prey for adult pollock and other apex predators. In the southeastern Bering Sea, important changes in the biota since the mid-1970s include a marked increase
Julienne Stroeve - One of the best experts on this subject based on the ideXlab platform.
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sea Ice rain on snow and tundra reindeer nomadism in arctic russia
Biology Letters, 2016Co-Authors: Bruce C Forbes, Timo Kumpula, Nina Meschtyb, Roza Laptander, Marc Maciasfauria, Pentti Zetterberg, Mariana Verdonen, Anna Skarin, Linette N Boisvert, Julienne StroeveAbstract:Sea Ice loss is accelerating in the Barents and Kara Seas (BKS). Assessing potential linkages between sea Ice Retreat/thinning and the region's ancient and unique social–ecological systems is a pressing task. Tundra nomadism remains a vitally important livelihood for indigenous Nenets and their large reindeer herds. Warming summer air temperatures have been linked to more frequent and sustained summer high-pressure systems over West Siberia, Russia, but not to sea Ice Retreat. At the same time, autumn/winter rain-on-snow (ROS) events have become more frequent and intense. Here, we review evidence for autumn atmospheric warming and precipitation increases over Arctic coastal lands in proximity to BKS Ice loss. Two major ROS events during November 2006 and 2013 led to massive winter reindeer mortality episodes on the Yamal Peninsula. Fieldwork with migratory herders has revealed that the ecological and socio-economic impacts from the catastrophic 2013 event will unfold for years to come. The suggested link between sea Ice loss, more frequent and intense ROS events and high reindeer mortality has serious implications for the future of tundra Nenets nomadism.
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using timing of Ice Retreat to predict timing of fall freeze up in the arctic
Geophysical Research Letters, 2016Co-Authors: Julienne Stroeve, Alex D Crawford, Sharon StammerjohnAbstract:Reliable forecasts of the timing of sea Ice advance are needed in order to reduce risks associated with operating in the Arctic as well as planning of human and environmental emergencies. This study investigates the use of a simple statistical model relating the timing of Ice Retreat to the timing of Ice advance, taking advantage of the inherent predictive power supplied by the seasonal Ice-albedo feedback and ocean heat uptake. Results show that using the last Retreat date to predict the first advance date is applicable in some regions, such as Baffin Bay and the Laptev and East Siberian seas, where a predictive skill is found even after accounting for the long-term trend in both variables. Elsewhere, in the Arctic, there is some predictive skills depending on the year (e.g., Kara and Beaufort seas), but none in regions such as the Barents and Bering seas or the Sea of Okhotsk. While there is some suggestion that the relationship is strengthening over time, this may reflect that higher correlations are expected during periods when the underlying trend is strong.
R W Lindsay - One of the best experts on this subject based on the ideXlab platform.
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the 2007 bering strait oceanic heat flux and anomalous arctic sea Ice Retreat
Geophysical Research Letters, 2010Co-Authors: Rebecca A Woodgate, Thomas J Weingartner, R W LindsayAbstract:[1] To illuminate the role of Pacific Waters in the 2007 Arctic sea-Ice Retreat, we use observational data to estimate Bering Strait volume and heat transports from 1991 to 2007. In 2007, both annual mean transport and temperatures are at record-length highs. Heat fluxes increase from 2001 to a 2007 maximum, 5–6 × 1020 J/yr. This is twIce the 2001 heat flux, comparable to the annual shortwave radiative flux into the Chukchi Sea, and enough to melt 1/3rd of the 2007 seasonal Arctic sea-Ice loss. We suggest the Bering Strait inflow influences sea-Ice by providing a trigger for the onset of solar-driven melt, a conduit for oceanic heat into the Arctic, and (due to long transit times) a subsurface heat source within the Arctic in winter. The substantial interannual variability reflects temperature and transport changes, the latter (especially recently) being significantly affected by variability (> 0.2 Sv equivalent) in the Pacific-Arctic pressure-head driving the flow.
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arctic sea Ice Retreat in 2007 follows thinning trend
Journal of Climate, 2009Co-Authors: R W Lindsay, Jinlun Zhang, Michael Steele, Axel Schweiger, Harry SternAbstract:The minimum of Arctic sea Ice extent in the summer of 2007 was unprecedented in the historical record. A coupled Ice–ocean model is used to determine the state of the Ice and ocean over the past 29 yr to investigate the causes of this Ice extent minimum within a historical perspective. It is found that even though the 2007 Ice extent was strongly anomalous, the loss in total Ice mass was not. Rather, the 2007 Ice mass loss is largely consistent with a steady decrease in Ice thickness that began in 1987. Since then, the simulated mean September Ice thickness within the Arctic Ocean has declined from 3.7 to 2.6 m at a rate of 0.57 m decade 1 . Both the area coverage of thin Ice at the beginning of the melt season and the total volume of Ice lost in the summer have been steadily increasing. The combined impact of these two trends caused a large reduction in the September mean Ice concentration in the Arctic Ocean. This created conditions during the summer of 2007 that allowed persistent winds to push the remaining Ice from the Pacific side to the Atlantic side of the basin and more than usual into the Greenland Sea. This exposed large areas of open water, resulting in the record Ice extent anomaly.
Ian Eisenman - One of the best experts on this subject based on the ideXlab platform.
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faster arctic sea Ice Retreat in cmip5 than in cmip3 due to volcanoes
Journal of Climate, 2016Co-Authors: Erica Rosenblum, Ian EisenmanAbstract:AbstractThe downward trend in Arctic sea Ice extent is one of the most dramatic signals of climate change during recent decades. Comprehensive climate models have struggled to reproduce this trend, typically simulating a slower rate of sea Ice Retreat than has been observed. However, this bias has been widely noted to have decreased in models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5) compared with the previous generation of models (CMIP3). Here simulations are examined from both CMIP3 and CMIP5. It is found that simulated historical sea Ice trends are influenced by volcanic forcing, which was included in all of the CMIP5 models but in only about half of the CMIP3 models. The volcanic forcing causes temporary simulated cooling in the 1980s and 1990s, which contributes to raising the simulated 1979–2013 global-mean surface temperature trends to values substantially larger than observed. It is shown that this warming bias is accompanied by an enhanced rate of Arctic sea ic...
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factors controlling the bifurcation structure of sea Ice Retreat
Journal of Geophysical Research, 2012Co-Authors: Ian EisenmanAbstract:The contrast in surface albedo between sea Ice and open ocean suggests the possibility of an unstable climate state flanked by two separate stable climate states. Previous studies using idealized single-column models and comprehensive climate models have considered the possibility of abrupt thresholds during sea Ice Retreat associated with such multiple states, and they have produced a wide range of results. When the climate is warmed such that the summer minimum Arctic sea Ice cover reaches zero, some models smoothly transition to seasonally Ice-free conditions, others discontinuously transition to seasonally Ice-free conditions, and others discontinuously transition to annually Ice-free conditions. Among the models that simulate a continuous transition to seasonally Ice-free conditions, further warming causes some to smoothly lose the remaining wintertime-only sea Ice cover and others to discontinuously lose it. Here, we use a toy model representing the essential physics of thermodynamic sea Ice in a single column to investigate the factors controlling which of these scenarios occurs. All of the scenarios are shown to be possible in the toy model when the parameters are varied, and physical mechanisms giving rise to each scenario are investigated. We find that parameter shifts that make Ice thicker or open ocean warmer under a given climate forcing make models less prone to stable seasonally Ice-free conditions and more prone to bistability and hence bifurcations. The results are used to interpret differences in simulated sea Ice stability in comprehensive climate models.
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Consistent Changes in the Sea Ice Seasonal Cycle in Response to Global Warming
Journal of Climate, 2011Co-Authors: Ian Eisenman, David S. Battisti, Tapio Schneider, Cecilia M. BitzAbstract:The Northern Hemisphere sea Ice cover has diminished rapidly in recent years and is projected to continue to diminish in the future. The year-to-year Retreat of Northern Hemisphere sea Ice extent is faster in summer thanwinter,whichhasbeenidentifiedasoneofthemoststrikingfeaturesof satellite observations aswellasof state-of-the-art climate model projections. This is typically understood to imply that the sea Ice cover is most sensitive to climate forcing in summertime, and previous studies have explained this by calling on factors such as the surface albedo feedback. In the Southern Hemisphere, however, it is the wintertime sea Ice extent that Retreats fastest in climate model projections. Here, it is shown that the interhemispheric differences in the model projections can be attributed to differences in coastline geometry, which constrain where sea Ice can occur. After accounting for coastline geometry, it is found that the sea Ice changes simulated in both hemispheres in most climate models are consistent with sea Ice Retreat being fastest in winter in the absence of landmasses. These results demonstrate that, despite the widely differing rates of Ice Retreat among climate model projections, the seasonal structure of the sea Ice Retreat is robust among the models and is uniform in both hemispheres.
