Landscape Characterization of Arctic Ecosystems Using Data Mining Algorithms and Large Geospatial Datasets

NASA Astrophysics Data System (ADS)

Langford, Z. L.; Kumar, J.; Hoffman, F. M.

2015-12-01

Observations indicate that over the past several decades, landscape processes in the Arctic have been changing or intensifying. A dynamic Arctic landscape has the potential to alter ecosystems across a broad range of scales. Accurate characterization is useful to understand the properties and organization of the landscape, optimal sampling network design, measurement and process upscaling and to establish a landscape-based framework for multi-scale modeling of ecosystem processes. This study seeks to delineate the landscape at Seward Peninsula of Alaska into ecoregions using large volumes (terabytes) of high spatial resolution satellite remote-sensing data. Defining high-resolution ecoregion boundaries is difficult because many ecosystem processes in Arctic ecosystems occur at small local to regional scales, which are often resolved in by coarse resolution satellites (e.g., MODIS). We seek to use data-fusion techniques and data analytics algorithms applied to Phased Array type L-band Synthetic Aperture Radar (PALSAR), Interferometric Synthetic Aperture Radar (IFSAR), Satellite for Observation of Earth (SPOT), WorldView-2, WorldView-3, and QuickBird-2 to develop high-resolution (˜5m) ecoregion maps for multiple time periods. Traditional analysis methods and algorithms are insufficient for analyzing and synthesizing such large geospatial data sets, and those algorithms rarely scale out onto large distributed- memory parallel computer systems. We seek to develop computationally efficient algorithms and techniques using high-performance computing for characterization of Arctic landscapes. We will apply a variety of data analytics algorithms, such as cluster analysis, complex object-based image analysis (COBIA), and neural networks. We also propose to use representativeness analysis within the Seward Peninsula domain to determine optimal sampling locations for fine-scale measurements. This methodology should provide an initial framework for analyzing dynamic landscape

The Northern Bering Sea: An Arctic Ecosystem in Change

NASA Astrophysics Data System (ADS)

Grebmeier, J. M.; Cooper, L. W.

2004-12-01

Arctic systems can be rich and diverse habitats for marine life in spite of the extreme cold environment. Benthic faunal populations and associated biogeochemical cycling processes are influenced by sea-ice extent, seawater hydrography (nutrients, salinity, temperature, currents), and water column production. Benthic organisms on the Arctic shelves and margins are long-term integrators of overlying water column processes. Because these organisms have adapted to living at cold extremes, it is reasonable to expect that these communities will be among the most susceptible to climate warming. Recent observations show that Arctic sea ice in the North American Arctic is melting and retreating northward earlier in the season and the timing of these events can have dramatic impacts on the biological system. Changes in overlying primary production, pelagic-benthic coupling, and benthic production and community structure can have cascading effects to higher trophic levels, particularly benthic feeders such as walruses, gray whales, and diving seaducks. Recent indicators of contemporary Arctic change in the northern Bering Sea include seawater warming and reduction in ice extent that coincide with our time-series studies of benthic clam population declines in the shallow northern Bering shelf in the 1990's. In addition, declines in benthic amphipod populations have also likely influenced the movement of feeding gray whales to areas north of Bering Strait during this same time period. Finally a potential consequence of seawater warming and reduced ice extent in the northern Bering Sea could be the northward movement of bottom feeding fish currently in the southern Bering Sea that prey on benthic fauna. This would increase the feeding pressure on the benthic prey base and enhance competition for this food source for benthic-feeding marine mammals and seabirds. This presentation will outline recent biological changes observed in the northern Bering Sea ecosystem as documented in

Transitions in Arctic ecosystems: Ecological implications of a changing hydrological regime

NASA Astrophysics Data System (ADS)

Wrona, Frederick J.; Johansson, Margareta; Culp, Joseph M.; Jenkins, Alan; Mârd, Johanna; Myers-Smith, Isla H.; Prowse, Terry D.; Vincent, Warwick F.; Wookey, Philip A.

2016-03-01

Numerous international scientific assessments and related articles have, during the last decade, described the observed and potential impacts of climate change as well as other related environmental stressors on Arctic ecosystems. There is increasing recognition that observed and projected changes in freshwater sources, fluxes, and storage will have profound implications for the physical, biogeochemical, biological, and ecological processes and properties of Arctic terrestrial and freshwater ecosystems. However, a significant level of uncertainty remains in relation to forecasting the impacts of an intensified hydrological regime and related cryospheric change on ecosystem structure and function. As the terrestrial and freshwater ecology component of the Arctic Freshwater Synthesis, we review these uncertainties and recommend enhanced coordinated circumpolar research and monitoring efforts to improve quantification and prediction of how an altered hydrological regime influences local, regional, and circumpolar-level responses in terrestrial and freshwater systems. Specifically, we evaluate (i) changes in ecosystem productivity; (ii) alterations in ecosystem-level biogeochemical cycling and chemical transport; (iii) altered landscapes, successional trajectories, and creation of new habitats; (iv) altered seasonality and phenological mismatches; and (v) gains or losses of species and associated trophic interactions. We emphasize the need for developing a process-based understanding of interecosystem interactions, along with improved predictive models. We recommend enhanced use of the catchment scale as an integrated unit of study, thereby more explicitly considering the physical, chemical, and ecological processes and fluxes across a full freshwater continuum in a geographic region and spatial range of hydroecological units (e.g., stream-pond-lake-river-near shore marine environments).

Symptoms of change in multi-scale observations of arctic ecosystem carbon cycling

NASA Astrophysics Data System (ADS)

Stoy, P. C.; Williams, M. D.; Hartley, I. P.; Street, L.; Hill, T. C.; Prieto-Blanco, A.; Wayolle, A.; Disney, M.; Evans, J.; Fletcher, B.; Poyatos, R.; Wookey, P.; Merbold, L.; Wade, T. J.; Moncrieff, J.

2009-12-01

Arctic ecosystems are responding rapidly to observed climate change. Quantifying the magnitude of these changes, and their implications for the climate system, requires observations of their current structure and function, as well as extrapolation and modelling (i.e. ‘upscaling’) across time and space. Here, we describe the major results of the International Polar Year (IPY) ABACUS project, a multi-scale investigation across arctic Fennoscandia that couples plant and soil process studies, isotope analyses, flux and micrometeorological measurements, process modelling, and aircraft and satellite observations to improve predictions of the response of the arctic terrestrial biosphere to global change. We begin with a synthesis of eddy covariance observations from the global FLUXNET database. We demonstrate that a simple model parameterized using pan-arctic chamber measurements explains over 80% of the variance of half-hourly CO2 fluxes during the growing season across most arctic and montane tundra ecosystems given accurate measurements of leaf area index (LAI), which agrees with the recently proposed ‘functional convergence’ paradigm for tundra vegetation. The ability of MODIS to deliver accurate LAI estimates is briefly discussed and an adjusted algorithm is presented and validated using direct observations. We argue for an Information Theory-based framework for upscaling in Earth science by conceptualizing multi-scale research as a transfer of information across scales. We then demonstrate how error in upscaled arctic C flux estimates can be reduced to less than 4% from their high-resolution counterpart by formally preserving the information content of high spatial and spectral resolution aircraft and satellite imagery. Jaynes’ classic Maximum Entropy (MaxEnt) principle is employed to incorporate logical, biological and physical constraints to reduce error in downscaled flux estimates. Errors are further reduced by assimilating flux, biological and remote

Light-stress avoidance mechanisms in a Sphagnum-dominated wet coastal Arctic tundra ecosystem in Alaska.

PubMed

Zona, D; Oechel, Walter C; Richards, James H; Hastings, Steven; Kopetz, Irene; Ikawa, Hiroki; Oberbauer, Steven

2011-03-01

The Arctic experiences a high-radiation environment in the summer with 24-hour daylight for more than two months. Damage to plants and ecosystem metabolism can be muted by overcast conditions common in much of the Arctic. However, with climate change, extreme dry years and clearer skies could lead to the risk of increased photoxidation and photoinhibition in Arctic primary producers. Mosses, which often exceed the NPP of vascular plants in Arctic areas, are often understudied. As a result, the effect of specific environmental factors, including light, on these growth forms is poorly understood. Here, we investigated net ecosystem exchange (NEE) at the ecosystem scale, net Sphagnum CO2 exchange (NSE), and photoinhibition to better understand the impact of light on carbon exchange from a moss-dominated coastal tundra ecosystem during the summer season 2006. Sphagnum photosynthesis showed photoinhibition early in the season coupled with low ecosystem NEE. However, later in the season, Sphagnum maintained a significant CO2 uptake, probably for the development of subsurface moss layers protected from strong radiation. We suggest that the compact canopy structure of Sphagnum reduces light penetration to the subsurface layers of the moss mat and thereby protects the active photosynthetic tissues from damage. This stress avoidance mechanism allowed Sphagnum to constitute a significant percentage (up to 60%) of the ecosystem net daytime CO2 uptake at the end of the growing season despite the high levels of radiation experienced.

Changing snow cover in tundra ecosystems tips the Arctic carbon balance

NASA Astrophysics Data System (ADS)

Zona, D.; Hufkens, K.; Gioli, B.; Kalhori, A. A. M.; Oechel, W. C.

2014-12-01

The Arctic environment has witnessed important changes due to global warming, resulting in increased surface air temperatures and rain events which both exacerbate snow cover deterioration (Semmens et al, 2013; Rennert et al, 2009; White et al, 2007; Min et al, 2008; Sharp et al, 2013; Schaeffer et al, 2013). Snow cover duration is declining by almost 20% per decade, a far higher rate than model estimates (Derksen and Brown, 2012). Concomitant with increasing temperatures and decreasing snow cover duration, the length of the arctic growing season is reported to have increased by 1.1 - 4.9 days per decade since 1951 (Menzel et al, 2006), and, plant productivity and CO2 uptake from arctic vegetation are strongly influenced by changes in growing season length (Myneni et al., 1997; Schaefer et al., 2005; Euskirchen et al., 2006). Based on more than a decade of eddy flux measurements in Arctic tundra ecosystems across the North slope of Alaska, and remotely sensed snow cover data, we show that earlier snow melt in the spring increase C uptake while an extended snow free period in autumn is associated with a higher C loss. Here we present the impacts of changes in snow cover dynamics between spring and autumn in arctic tundra ecosystems on the carbon dynamics and net C balance of the Alaskan Arctic. ReferencesDerksen, C., Brown R. (2012) Geophys. Res. Lett., doi:10.1029/2012GL053387 Euskirchen, E.S., et al. (2006) Glob. Change Biol., 12, 731-750. Menzel, A., et al. 2006. Glob. Change Biol., 12, 1969-1976. Min SK, Zhang X, Zweirs F (2008) Science 320: 518-520. Rennert K J, Roe G, Putkonen J and Bitz C M (2009) J. Clim. 22 2302-15. Schaefer, K., Denning A.S., Leonard O. (2005) Global Biogeochem. Cycles, 19, GB3017. Schaeffer, S. M., Sharp, E., Schimel, J. P. & Welker, J. M. (2013). Soil- plant N processes in a High Arctic ecosystem, NW Greenland are altered by long-term experimental warming and higher rainfall. Glob. Change Biol., 11, 3529-39. doi: 10.1111/gcb.12318

Arctic mosses govern below-ground environment and ecosystem processes.

PubMed

Gornall, J L; Jónsdóttir, I S; Woodin, S J; Van der Wal, R

2007-10-01

Mosses dominate many northern ecosystems and their presence is integral to soil thermal and hydrological regimes which, in turn, dictate important ecological processes. Drivers, such as climate change and increasing herbivore pressure, affect the moss layer thus, assessment of the functional role of mosses in determining soil characteristics is essential. Field manipulations conducted in high arctic Spitsbergen (78 degrees N), creating shallow (3 cm), intermediate (6 cm) and deep (12 cm) moss layers over the soil surface, had an immediate impact on soil temperature in terms of both average temperatures and amplitude of fluctuations. In soil under deep moss, temperature was substantially lower and organic layer thaw occurred 4 weeks later than in other treatment plots; the growing season for vascular plants was thereby reduced by 40%. Soil moisture was also reduced under deep moss, reflecting the influence of local heterogeneity in moss depth, over and above the landscape-scale topographic control of soil moisture. Data from field and laboratory experiments show that moss-mediated effects on the soil environment influenced microbial biomass and activity, resulting in warmer and wetter soil under thinner moss layers containing more plant-available nitrogen. In arctic ecosystems, which are limited by soil temperature, growing season length and nutrient availability, spatial and temporal variation in the depth of the moss layer has significant repercussions for ecosystem function. Evidence from our mesic tundra site shows that any disturbance causing reduction in the depth of the moss layer will alleviate temperature and moisture constraints and therefore profoundly influence a wide range of ecosystem processes, including nutrient cycling and energy transfer.

Arctic foxes as ecosystem engineers: increased soil nutrients lead to increased plant productivity on fox dens

NASA Astrophysics Data System (ADS)

Gharajehdaghipour, Tazarve; Roth, James D.; Fafard, Paul M.; Markham, John H.

2016-04-01

Top predators can provide fundamental ecosystem services such as nutrient cycling, and their impact can be even greater in environments with low nutrients and productivity, such as Arctic tundra. We estimated the effects of Arctic fox (Vulpes lagopus) denning on soil nutrient dynamics and vegetation production near Churchill, Manitoba in June and August 2014. Soils from fox dens contained higher nutrient levels in June (71% more inorganic nitrogen, 1195% more extractable phosphorous) and in August (242% more inorganic nitrogen, 191% more extractable phosphorous) than adjacent control sites. Inorganic nitrogen levels decreased from June to August on both dens and controls, whereas extractable phosphorous increased. Pup production the previous year, which should enhance nutrient deposition (from urine, feces, and decomposing prey), did not affect soil nutrient concentrations, suggesting the impact of Arctic foxes persists >1 year. Dens supported 2.8 times greater vegetation biomass in August, but δ15N values in sea lyme grass (Leymus mollis) were unaffected by denning. By concentrating nutrients on dens Arctic foxes enhance nutrient cycling as an ecosystem service and thus engineer Arctic ecosystems on local scales. The enhanced productivity in patches on the landscape could subsequently affect plant diversity and the dispersion of herbivores on the tundra.

Arctic foxes as ecosystem engineers: increased soil nutrients lead to increased plant productivity on fox dens

PubMed Central

Gharajehdaghipour, Tazarve; Roth, James D.; Fafard, Paul M.; Markham, John H.

2016-01-01

Top predators can provide fundamental ecosystem services such as nutrient cycling, and their impact can be even greater in environments with low nutrients and productivity, such as Arctic tundra. We estimated the effects of Arctic fox (Vulpes lagopus) denning on soil nutrient dynamics and vegetation production near Churchill, Manitoba in June and August 2014. Soils from fox dens contained higher nutrient levels in June (71% more inorganic nitrogen, 1195% more extractable phosphorous) and in August (242% more inorganic nitrogen, 191% more extractable phosphorous) than adjacent control sites. Inorganic nitrogen levels decreased from June to August on both dens and controls, whereas extractable phosphorous increased. Pup production the previous year, which should enhance nutrient deposition (from urine, feces, and decomposing prey), did not affect soil nutrient concentrations, suggesting the impact of Arctic foxes persists >1 year. Dens supported 2.8 times greater vegetation biomass in August, but δ15N values in sea lyme grass (Leymus mollis) were unaffected by denning. By concentrating nutrients on dens Arctic foxes enhance nutrient cycling as an ecosystem service and thus engineer Arctic ecosystems on local scales. The enhanced productivity in patches on the landscape could subsequently affect plant diversity and the dispersion of herbivores on the tundra. PMID:27045973

Arctic foxes as ecosystem engineers: increased soil nutrients lead to increased plant productivity on fox dens.

PubMed

Gharajehdaghipour, Tazarve; Roth, James D; Fafard, Paul M; Markham, John H

2016-04-05

Top predators can provide fundamental ecosystem services such as nutrient cycling, and their impact can be even greater in environments with low nutrients and productivity, such as Arctic tundra. We estimated the effects of Arctic fox (Vulpes lagopus) denning on soil nutrient dynamics and vegetation production near Churchill, Manitoba in June and August 2014. Soils from fox dens contained higher nutrient levels in June (71% more inorganic nitrogen, 1195% more extractable phosphorous) and in August (242% more inorganic nitrogen, 191% more extractable phosphorous) than adjacent control sites. Inorganic nitrogen levels decreased from June to August on both dens and controls, whereas extractable phosphorous increased. Pup production the previous year, which should enhance nutrient deposition (from urine, feces, and decomposing prey), did not affect soil nutrient concentrations, suggesting the impact of Arctic foxes persists >1 year. Dens supported 2.8 times greater vegetation biomass in August, but δ(15)N values in sea lyme grass (Leymus mollis) were unaffected by denning. By concentrating nutrients on dens Arctic foxes enhance nutrient cycling as an ecosystem service and thus engineer Arctic ecosystems on local scales. The enhanced productivity in patches on the landscape could subsequently affect plant diversity and the dispersion of herbivores on the tundra.

Rough-legged buzzards, Arctic foxes and red foxes in a tundra ecosystem without rodents.

PubMed

Pokrovsky, Ivan; Ehrich, Dorothée; Ims, Rolf A; Kondratyev, Alexander V; Kruckenberg, Helmut; Kulikova, Olga; Mihnevich, Julia; Pokrovskaya, Liya; Shienok, Alexander

2015-01-01

Small rodents with multi-annual population cycles strongly influence the dynamics of food webs, and in particular predator-prey interactions, across most of the tundra biome. Rodents are however absent from some arctic islands, and studies on performance of arctic predators under such circumstances may be very instructive since rodent cycles have been predicted to collapse in a warming Arctic. Here we document for the first time how three normally rodent-dependent predator species-rough-legged buzzard, arctic fox and red fox - perform in a low-arctic ecosystem with no rodents. During six years (in 2006-2008 and 2011-2013) we studied diet and breeding performance of these predators in the rodent-free Kolguev Island in Arctic Russia. The rough-legged buzzards, previously known to be a small rodent specialist, have only during the last two decades become established on Kolguev Island. The buzzards successfully breed on the island at stable low density, but with high productivity based on goslings and willow ptarmigan as their main prey - altogether representing a novel ecological situation for this species. Breeding density of arctic fox varied from year to year, but with stable productivity based on mainly geese as prey. The density dynamic of the arctic fox appeared to be correlated with the date of spring arrival of the geese. Red foxes breed regularly on the island but in very low numbers that appear to have been unchanged over a long period - a situation that resemble what has been recently documented from Arctic America. Our study suggests that the three predators found breeding on Kolguev Island possess capacities for shifting to changing circumstances in low-arctic ecosystem as long as other small - medium sized terrestrial herbivores are present in good numbers.

Rough-Legged Buzzards, Arctic Foxes and Red Foxes in a Tundra Ecosystem without Rodents

PubMed Central

Pokrovsky, Ivan; Ehrich, Dorothée; Ims, Rolf A.; Kondratyev, Alexander V.; Kruckenberg, Helmut; Kulikova, Olga; Mihnevich, Julia; Pokrovskaya, Liya; Shienok, Alexander

2015-01-01

Small rodents with multi-annual population cycles strongly influence the dynamics of food webs, and in particular predator-prey interactions, across most of the tundra biome. Rodents are however absent from some arctic islands, and studies on performance of arctic predators under such circumstances may be very instructive since rodent cycles have been predicted to collapse in a warming Arctic. Here we document for the first time how three normally rodent-dependent predator species—rough-legged buzzard, arctic fox and red fox – perform in a low-arctic ecosystem with no rodents. During six years (in 2006-2008 and 2011-2013) we studied diet and breeding performance of these predators in the rodent-free Kolguev Island in Arctic Russia. The rough-legged buzzards, previously known to be a small rodent specialist, have only during the last two decades become established on Kolguev Island. The buzzards successfully breed on the island at stable low density, but with high productivity based on goslings and willow ptarmigan as their main prey – altogether representing a novel ecological situation for this species. Breeding density of arctic fox varied from year to year, but with stable productivity based on mainly geese as prey. The density dynamic of the arctic fox appeared to be correlated with the date of spring arrival of the geese. Red foxes breed regularly on the island but in very low numbers that appear to have been unchanged over a long period – a situation that resemble what has been recently documented from Arctic America. Our study suggests that the three predators found breeding on Kolguev Island possess capacities for shifting to changing circumstances in low-arctic ecosystem as long as other small - medium sized terrestrial herbivores are present in good numbers. PMID:25692786

A new way to study the changing Arctic ecosystem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hubbard, Susan

2011-09-12

Berkeley Lab scientists Susan Hubbard and Margaret Torn discuss the proposed Next Generation Ecosystem Experiment, which is designed to answer one of the most urgent questions facing researchers today: How will a changing climate impact the Arctic, and how will this in turn impact the planet's climate? More info: http://newscenter.lbl.gov/feature-stories/2011/09/14/alaska-climate-change/

A new way to study the changing Arctic ecosystem

ScienceCinema

Hubbard, Susan

2017-12-09

Berkeley Lab scientists Susan Hubbard and Margaret Torn discuss the proposed Next Generation Ecosystem Experiment, which is designed to answer one of the most urgent questions facing researchers today: How will a changing climate impact the Arctic, and how will this in turn impact the planet's climate? More info: http://newscenter.lbl.gov/feature-stories/2011/09/14/alaska-climate-change/

Arctic ecosystem functional zones: identification and quantification using an above and below ground monitoring strategy

NASA Astrophysics Data System (ADS)

Hubbard, Susan S.; Ajo-Franklin, Jonathan B.; Dafflon, Baptiste; Dou, Shan; Kneafsey, Tim J.; Peterson, John E.; Tas, Neslihan; Torn, Margaret S.; Phuong Tran, Anh; Ulrich, Craig; Wainwright, Haruko; Wu, Yuxin; Wullschleger, Stan

2015-04-01

Although accurate prediction of ecosystem feedbacks to climate requires characterization of the properties that influence terrestrial carbon cycling, performing such characterization is challenging due to the disparity of scales involved. This is particularly true in vulnerable Arctic ecosystems, where microbial activities leading to the production of greenhouse gasses are a function of small-scale hydrological, geochemical, and thermal conditions influenced by geomorphology and seasonal dynamics. As part of the DOE Next-Generation Ecosystem Experiment (NGEE-Arctic), we are advancing two approaches to improve the characterization of complex Arctic ecosystems, with an initial application to an ice-wedge polygon dominated tundra site near Barrow, AK, USA. The first advance focuses on developing a new strategy to jointly monitor above- and below- ground properties critical for carbon cycling in the tundra. The strategy includes co-characterization of properties within the three critical ecosystem compartments: land surface (vegetation, water inundation, snow thickness, and geomorphology); active layer (peat thickness, soil moisture, soil texture, hydraulic conductivity, soil temperature, and geochemistry); and permafrost (mineral soil and ice content, nature, and distribution). Using a nested sampling strategy, a wide range of measurements have been collected at the study site over the past three years, including: above-ground imagery (LiDAR, visible, near infrared, NDVI) from various platforms, surface geophysical datasets (electrical, electromagnetic, ground penetrating radar, seismic), and point measurements (such as CO2 and methane fluxes, soil properties, microbial community composition). A subset of the coincident datasets is autonomously collected daily. Laboratory experiments and new inversion approaches are used to improve interpretation of the field geophysical datasets in terms of ecosystem properties. The new strategy has significantly advanced our ability

Ecosystem Metabolism and Air-Water Fluxes of Greenhouse Gases in High Arctic Wetland Ponds

NASA Astrophysics Data System (ADS)

Lehnherr, I.; Venkiteswaran, J.; St. Louis, V. L.; Emmerton, C.; Schiff, S. L.

2012-12-01

Freshwater lakes and wetlands can be very productive systems on the Arctic landscape compared to terrestrial tundra ecosystems and provide valuable resources to many organisms, including waterfowl, fish and humans. Rates of ecosystem productivity dictate how much energy flows through food webs, impacting the abundance of higher-level organisms (e.g., fish), as well as the net carbon balance, which determines whether a particular ecosystem is a source or sink of carbon. Climate change is predicted to result in warmer temperatures, increased precipitation and permafrost melting in the Arctic and is already altering northern ecosystems at unprecedented rates; however, it is not known how freshwater systems are responding to these changes. To predict how freshwater systems will respond to complex environmental changes, it is necessary to understand the key processes, such as primary production and ecosystem respiration, that are driving these systems. We sampled wetland ponds (n=8) and lakes (n=2) on northern Ellesmere Island (81° N, Nunavut, Canada) during the open water season for a suite of biogeochemical parameters, including concentrations of dissolved gases (O2, CO2, CH4, N2O) as well as stable-isotope ratios of dissolved inorganic carbon (δ13C-DIC), dissolved oxygen (δ18O-DO), and water (δ18O-H2O). We will present rates of primary production and ecosystem respiration, modeled from the concentration and stable isotope ratios of DIC and DO, as well as air-water gas exchange of greenhouse gases in these high Arctic ponds and lakes. Preliminary results demonstrate that ecosystem metabolism in these ponds was high enough to result in significant deviations in the isotope ratios of DIC and DO from atmospheric equilibrium conditions. In other words ecosystem rates of primary production and respiration were faster than gas exchange even in these small, shallow, well-mixed ponds. Furthermore, primary production was elevated enough at all sites except Lake Hazen, a

A gradient of nutrient enrichment reveals nonlinear impacts of fertilization on Arctic plant diversity and ecosystem function.

PubMed

Prager, Case M; Naeem, Shahid; Boelman, Natalie T; Eitel, Jan U H; Greaves, Heather E; Heskel, Mary A; Magney, Troy S; Menge, Duncan N L; Vierling, Lee A; Griffin, Kevin L

2017-04-01

Rapid environmental change at high latitudes is predicted to greatly alter the diversity, structure, and function of plant communities, resulting in changes in the pools and fluxes of nutrients. In Arctic tundra, increased nitrogen (N) and phosphorus (P) availability accompanying warming is known to impact plant diversity and ecosystem function; however, to date, most studies examining Arctic nutrient enrichment focus on the impact of relatively large (>25x estimated naturally occurring N enrichment) doses of nutrients on plant community composition and net primary productivity. To understand the impacts of Arctic nutrient enrichment, we examined plant community composition and the capacity for ecosystem function (net ecosystem exchange, ecosystem respiration, and gross primary production) across a gradient of experimental N and P addition expected to more closely approximate warming-induced fertilization. In addition, we compared our measured ecosystem CO 2 flux data to a widely used Arctic ecosystem exchange model to investigate the ability to predict the capacity for CO 2 exchange with nutrient addition. We observed declines in abundance-weighted plant diversity at low levels of nutrient enrichment, but species richness and the capacity for ecosystem carbon uptake did not change until the highest level of fertilization. When we compared our measured data to the model, we found that the model explained roughly 30%-50% of the variance in the observed data, depending on the flux variable, and the relationship weakened at high levels of enrichment. Our results suggest that while a relatively small amount of nutrient enrichment impacts plant diversity, only relatively large levels of fertilization-over an order of magnitude or more than warming-induced rates-significantly alter the capacity for tundra CO 2 exchange. Overall, our findings highlight the value of measuring and modeling the impacts of a nutrient enrichment gradient, as warming-related nutrient

Delayed responses of an Arctic ecosystem to an extremely dry summer: impacts on net ecosystem exchange and vegetation functioning

NASA Astrophysics Data System (ADS)

Zona, D.; Lipson, D. A.; Richards, J. H.; Phoenix, G. K.; Liljedahl, A. K.; Ueyama, M.; Sturtevant, C. S.; Oechel, W. C.

2013-12-01

The importance and mode of action of extreme events on the global carbon budget are inadequately understood. This includes the differential impact of extreme events on various ecosystem components, lag effects, recovery times, and compensatory processes. Summer 2007 in Barrow, Arctic Alaska, experienced unusually high air temperatures (fifth warmest over a 65 yr period) and record low precipitation (lowest over a 65 yr period). These abnormal conditions resulted in strongly reduced net Sphagnum CO2 uptake, but no effect neither on vascular plant development nor on net ecosystem exchange (NEE) from this arctic tundra ecosystem. Gross primary production (GPP) and ecosystem respiration (Reco) were both generally greater during most of this extreme summer. Cumulative ecosystem C uptake in 2007 was similar to the previous summers, showing the capacity of the ecosystem to compensate in its net ecosystem exchange (NEE) despite the impact on other functions and structure such as substantial necrosis of the Sphagnum layer. Surprisingly, the lowest ecosystem C uptake (2005-2009) was observed during the 2008 summer, i.e the year directly following the extremely summer. In 2008, cumulative C uptake was ∼70% lower than prior years. This reduction cannot solely be attributed to mosses, which typically contribute with ∼40% - of the entire ecosystem C uptake. The minimum summer cumulative C uptake in 2008 suggests that the entire ecosystem experienced difficulty readjusting to more typical weather after experiencing exceptionally warm and dry conditions. Importantly, the return to a substantial cumulative C uptake occurred two summers after the extreme event, which suggest a high resilience of this tundra ecosystem. Overall, these results show a highly complex response of the C uptake and its sub-components to atypically dry conditions. The impact of multiple extreme events still awaits further investigation.

Herbivory Network: An international, collaborative effort to study herbivory in Arctic and alpine ecosystems

NASA Astrophysics Data System (ADS)

Barrio, I. C.; Hik, D. S.; Jónsdóttir, I. S.; Bueno, C. G.; Mörsdorf, M. A.; Ravolainen, V. T.

2016-09-01

Plant-herbivore interactions are central to the functioning of tundra ecosystems, but their outcomes vary over space and time. Accurate forecasting of ecosystem responses to ongoing environmental changes requires a better understanding of the processes responsible for this heterogeneity. To effectively address this complexity at a global scale, coordinated research efforts, including multi-site comparisons within and across disciplines, are needed. The Herbivory Network was established as a forum for researchers from Arctic and alpine regions to collaboratively investigate the multifunctional role of herbivores in these changing ecosystems. One of the priorities is to integrate sites, methodologies, and metrics used in previous work, to develop a set of common protocols and design long-term geographically-balanced, coordinated experiments. The implementation of these collaborative research efforts will also improve our understanding of traditional human-managed systems that encompass significant portions of the sub-Arctic and alpine areas worldwide. A deeper understanding of the role of herbivory in these systems under ongoing environmental changes will guide appropriate adaptive strategies to preserve their natural values and related ecosystem services.

Relationships between ecosystem metabolism, benthic macroinvertebrate densities, and environmental variables in a sub-arctic Alaskan river

USGS Publications Warehouse

Benson, Emily R.; Wipfli, Mark S.; Clapcott, Joanne E.; Hughes, Nicholas F.

2013-01-01

Relationships between environmental variables, ecosystem metabolism, and benthos are not well understood in sub-arctic ecosystems. The goal of this study was to investigate environmental drivers of river ecosystem metabolism and macroinvertebrate density in a sub-arctic river. We estimated primary production and respiration rates, sampled benthic macroinvertebrates, and monitored light intensity, discharge rate, and nutrient concentrations in the Chena River, interior Alaska, over two summers. We employed Random Forests models to identify predictor variables for metabolism rates and benthic macroinvertebrate density and biomass, and calculated Spearman correlations between in-stream nutrient levels and metabolism rates. Models indicated that discharge and length of time between high water events were the most important factors measured for predicting metabolism rates. Discharge was the most important variable for predicting benthic macroinvertebrate density and biomass. Primary production rate peaked at intermediate discharge, respiration rate was lowest at the greatest time since last high water event, and benthic macroinvertebrate density was lowest at high discharge rates. The ratio of dissolved inorganic nitrogen to soluble reactive phosphorus ranged from 27:1 to 172:1. We found that discharge plays a key role in regulating stream ecosystem metabolism, but that low phosphorous levels also likely limit primary production in this sub-arctic stream.

Arctic Alpine Ecosystems and People in a Changing Environment

NASA Astrophysics Data System (ADS)

Körner, Christian

2007-04-01

Jon Borre Orbaek, Roland Kallenborn, Ingunn Tombre, Else Nost Hegseth, Stig Falk-Petersen, and Alf Hakon Hoel, Editors Springer, 434 pp.; ISBN: 978-3-540-48512-4; 2007; $199 Because of my own interest in this topic, Arctic Alpine Ecosystems and People in a Changing Environment immediately caught my attention. However, upon opening the book and reviewing the contents, I felt somewhat misguided by the title (as most potential buyers would be), given the actual topics addressed.

Sources of inorganic and monomethyl mercury to high and sub Arctic marine ecosystems

NASA Astrophysics Data System (ADS)

Kirk, Jane Liza

Monomethyl mercury (MMHg), a toxic and bioaccumulative form of Hg, is present in some Canadian high and sub Arctic marine mammals at concentrations high enough to pose health risks to Northern peoples using these animals as food. To quantify potentially large sources of Hg to Arctic marine ecosystems, we examined several aspects of Hg cycling in the Canadian Arctic Archipelago (CAA) and Hudson Bay. Firstly, we quantified net Hg inputs to Hudson Bay from atmospheric Hg depletion events (AMDEs). During AMDEs, gaseous elemental Hg(0) (GEM), which is present in the Arctic atmosphere at global background concentrations, is oxidized to inorganic Hg(II) species that deposit to snowpacks. By simultaneously monitoring Hg in the atmosphere and in snowpacks of western Hudson Bay, we demonstrated that most of the Hg(II) deposited during AMDEs is rapidly (photo)reduced and emitted to the atmosphere. Secondly, we examined Hg speciation in marine waters of the CAA and Hudson Bay. We found high concentrations of MMHg and dimethyl Hg (DMHg; a toxic, gaseous form of Hg) in deep marine waters, where they are likely produced from Hg(II). Arctic marine waters were also found to be a substantial source of DMHg and GEM to the atmosphere. Thirdly, we quantified Hg exports to Hudson Bay from two major rivers, the Nelson and the Churchill, which have been altered for hydroelectric power production. When landscapes are inundated during river diversion or reservoir creation, microbial production of MMHg is stimulated in flooded soils. Newly produced MMHg can then be exported to downstream waterbodies. We found that annual inputs of total Hg (THg; includes both Hg(II) and MMHg) to Hudson Bay from combined Nelson and Churchill River discharge were comparable to inputs from AMDEs. MMHg inputs from river discharge are, however, ˜13 times greater than those from annual snowmelt of Hudson Bay snowpacks. Finally, although combined river and AMDE Hg inputs may account for a large portion of the THg

Peak season carbon exchange shifts from a sink to a source following 50+ years of herbivore exclusion in an Arctic tundra ecosystem

DOE PAGES

Lara, Mark J.; Johnson, David R.; Andresen, Christian; ...

2016-08-27

To date, the majority of our knowledge regarding the impacts of herbivory on arctic ecosystem function has been restricted to short-term (<5 years) exclusion or manipulation experiments. Here, our understanding of long-term responses of sustained herbivory and/or herbivore exclusion on arctic tundra ecosystem function is severely limited.

Peak season carbon exchange shifts from a sink to a source following 50+ years of herbivore exclusion in an Arctic tundra ecosystem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lara, Mark J.; Johnson, David R.; Andresen, Christian

To date, the majority of our knowledge regarding the impacts of herbivory on arctic ecosystem function has been restricted to short-term (<5 years) exclusion or manipulation experiments. Here, our understanding of long-term responses of sustained herbivory and/or herbivore exclusion on arctic tundra ecosystem function is severely limited.

Photodemethylation of Methylmercury in Eastern Canadian Arctic Thaw Pond and Lake Ecosystems.

PubMed

Girard, Catherine; Leclerc, Maxime; Amyot, Marc

2016-04-05

Permafrost thaw ponds of the warming Eastern Canadian Arctic are major landscape constituents and often display high levels of methylmercury (MeHg). We examined photodegradation potentials in high-dissolved organic matter (DOC) thaw ponds on Bylot Island (BYL) and a low-DOC oligotrophic lake on Cornwallis Island (Char Lake). In BYL, the ambient MeHg photodemethylation (PD) rate over 48 h of solar exposure was 6.1 × 10(-3) m(2) E(-1), and the rate in MeHg amended samples was 9.3 × 10(-3) m(2) E(-1). In contrast, in low-DOC Char Lake, PD was only observed in the first 12 h, which suggests that PD may not be an important loss process in polar desert lakes. Thioglycolic acid addition slowed PD, while glutathione and chlorides did not impact northern PD rates. During an ecosystem-wide experiment conducted in a covered BYL pond, there was neither net MeHg increase in the dark nor loss attributable to PD following re-exposure to sunlight. We propose that high-DOC Arctic thaw ponds are more prone to MeHg PD than nearby oligotrophic lakes, likely through photoproduction of reactive species rather than via thiol complexation. However, at the ecosystem level, these ponds, which are widespread through the Arctic, remain likely sources of MeHg for neighboring systems.

Global change and ecosystem connectivity: How geese link fields of central Europe to eutrophication of Arctic freshwaters.

PubMed

Hessen, Dag O; Tombre, Ingunn M; van Geest, Gerben; Alfsnes, Kristian

2017-02-01

Migratory connectivity by birds may mutually affect different ecosystems over large distances. Populations of geese overwintering in southern areas while breeding in high-latitude ecosystems have increased strongly over the past decades. The increase is likely due to positive feedbacks caused by climate change at both wintering, stopover sites and breeding grounds, land-use practices at the overwintering grounds and protection from hunting. Here we show how increasing goose populations in temperate regions, and increased breeding success in the Arctic, entail a positive feedback with strong impacts on Arctic freshwater ecosystems in the form of eutrophication. This may again strongly affect community composition and productivity of the ponds, due to increased nutrient loadings or birds serving as vectors for new species.

Endoparasites in the feces of arctic foxes in a terrestrial ecosystem in Canada

PubMed Central

Elmore, Stacey A.; Lalonde, Laura F.; Samelius, Gustaf; Alisauskas, Ray T.; Gajadhar, Alvin A.; Jenkins, Emily J.

2013-01-01

The parasites of arctic foxes in the central Canadian Arctic have not been well described. Canada’s central Arctic is undergoing dramatic environmental change, which is predicted to cause shifts in parasite and wildlife species distributions, and trophic interactions, requiring that baselines be established to monitor future alterations. This study used conventional, immunological, and molecular fecal analysis techniques to survey the current gastrointestinal endoparasite fauna currently present in arctic foxes in central Nunavut, Canada. Ninety-five arctic fox fecal samples were collected from the terrestrial Karrak Lake ecosystem within the Queen Maud Gulf Migratory Bird Sanctuary. Samples were examined by fecal flotation to detect helminths and protozoa, immunofluorescent assay (IFA) to detect Cryptosporidium and Giardia, and quantitative PCR with melt-curve analysis (qPCR-MCA) to detect coccidia. Positive qPCR-MCA products were sequenced and analyzed phylogenetically. Arctic foxes from Karrak Lake were routinely shedding eggs from Toxascaris leonina (63%). Taeniid (15%), Capillarid (1%), and hookworm eggs (2%), Sarcocystis sp. sporocysts 3%), and Eimeria sp. (6%), and Cystoisospora sp. (5%) oocysts were present at a lower prevalence on fecal flotation. Cryptosporidium sp. (9%) and Giardia sp. (16%) were detected by IFA. PCR analysis detected Sarcocystis (15%), Cystoisospora (5%), Eimeria sp., and either Neospora sp. or Hammondia sp. (1%). Through molecular techniques and phylogenetic analysis, we identified two distinct lineages of Sarcocystis sp. present in arctic foxes, which probably derived from cervid and avian intermediate hosts. Additionally, we detected previously undescribed genotypes of Cystoisospora. Our survey of gastrointestinal endoparasites in arctic foxes from the central Canadian Arctic provides a unique record against which future comparisons can be made. PMID:24533320

Hematology of southern Beaufort Sea polar bears (2005-2007): biomarker for an Arctic ecosystem health sentinel.

PubMed

Kirk, Cassandra M; Amstrup, Steven; Swor, Rhonda; Holcomb, Darce; O'Hara, Todd M

2010-09-01

Declines in sea-ice habitats have resulted in declining stature, productivity, and survival of polar bears in some regions. With continuing sea-ice declines, negative population effects are projected to expand throughout the polar bear's range. Precise causes of diminished polar bear life history performance are unknown, however, climate and sea-ice condition change are expected to adversely impact polar bear (Ursus maritimus) health and population dynamics. As apex predators in the Arctic, polar bears integrate the status of lower trophic levels and are therefore sentinels of ecosystem health. Arctic residents feed at the apex of the ecosystem, thus polar bears can serve as indicators of human health in the Arctic. Despite their value as indicators of ecosystem welfare, population-level health data for U.S. polar bears are lacking. We present hematological reference ranges for southern Beaufort Sea polar bears. Hematological parameters in southern Beaufort Sea polar bears varied by age, geographic location, and reproductive status. Total leukocytes, lymphocytes, monocytes, eosinophils, and serum immunoglobulin G were significantly greater in males than females. These measures were greater in nonlactating females ages ≥5, than lactating adult females ages ≥5, suggesting that females encumbered by young may be less resilient to new immune system challenges that may accompany ongoing climate change. Hematological values established here provide a necessary baseline for anticipated changes in health as arctic temperatures warm and sea-ice declines accelerate. Data suggest that females with dependent young may be most vulnerable to these changes and should therefore be a targeted cohort for monitoring in this sentinel.

Responses of CO2 Fluxes to Arctic Browning Events in a Range of High Latitude, Shrub-Dominated Ecosystems

NASA Astrophysics Data System (ADS)

Phoenix, G. K.; Treharne, R.; Emberson, L.; Tømmervik, H. A.; Bjerke, J. W.

2017-12-01

Climatic and biotic extreme events can result in considerable damage to arctic vegetation, often at landscape and larger scale. These acute events therefore contribute to the browning observed in some arctic regions. It is of considerable concern, therefore, that such extreme events are increasing in frequency as part of climate change. However, despite the increasing importance of browning events, and the considerable impact they can have on ecosystems, to date there is little understanding of their impacts on ecosystem carbon fluxes. To address this, the impacts of a number of different, commonly occurring, extreme events and their subsequent browning (vegetation damage) on key ecosystem CO2 fluxes were assessed during the growing season at a range of event damaged sites of shrub dominated vegetation. Sites were located from the boreal to High Arctic (64˚N-79˚N) and had been previously been damaged by events of frost-drought, extreme winter warming, ground icing and caterpillar (Epirrita autumnata) outbreaks. Plot-level CO2 fluxes of Ecosystem Exchange (NEE), Gross Primary Productivity (GPP) and Ecosystem Respiration (Reco) were assessed using vegetation chambers. At a sub-set of sites, NDVI (greenness) in flux plots was also assessed by hand-held proximal sensor, allowing the relationship between NDVI of damage plots to CO2 flux to be calculated. Despite the contrasting sites and drivers, damage had consistent, major impacts on all fluxes. All sites showed reductions in GPP and NEE with increasing damage, despite efflux from Reco also declining with damage. When scaled to site-level, reductions of up to 81% of NEE, 51% of GPP and 37% of Reco were observed. In the plot-level NDVI-flux relationship, NDVI was shown to explain up to 91% of variation in GPP, and therefore supports the use of NDVI for estimating changes in ecosystem CO2 flux at larger scales in regions where browning has been driven by extreme events. This work is the first attempt to quantify the

Monitoring ecosystem dynamics in an Arctic tundra ecosystem using hyperspectral reflectance and a robotic tram system

NASA Astrophysics Data System (ADS)

Goswami, Santonu

Global change, which includes climate change and the impacts of human disturbance, is altering the provision and sustainability of ecosystem goods and services. These changes have the capacity to initiate cascading affects and complex feedbacks through physical, biological and human subsystems and interactions between them. Understanding the future state of the earth system requires improved knowledge of ecosystem dynamics and long term observations of how these are being impacted by global change. Improving remote sensing methods is essential for such advancement because satellite remote sensing is the only means by which landscape to continental-scale change can be observed. The Arctic appears to be impacted by climate change more than any other region on Earth. Arctic terrestrial ecosystems comprise only 6% of the land surface area on Earth yet contain an estimated 25% of global soil organic carbon, most of which is stored in permafrost. If projected increases in plant productivity do not offset forecast losses of soil carbon to the atmosphere as greenhouse gases, regional to global greenhouse warming could be enhanced. Soil moisture is an important control of land-atmosphere carbon exchange in arctic terrestrial ecosystems. However, few studies to date have examined using remote sensing, or developed remote sensing methods for observing the complex interplay between soil moisture and plant phenology and productivity in arctic landscapes. This study was motivated by this knowledge gap and addressed the following questions as a contribution to a large scale, multi investigator flooding and draining experiment funded by the National Science Foundation near Barrow, Alaska (71°17'01" N, 156°35'48" W): (1) How can optical remote sensing be used to monitor the surface hydrology of arctic landscapes? (2) What are the spatio-temporal dynamics of land-surface phenology (NDVI) in the study area and do hydrological treatment has any effect on inter-annual patterns? (3

Net ecosystem exchange of CO2 and CH4 in the high arctic (81°N) during the growing season

NASA Astrophysics Data System (ADS)

Barker, J. D.; St. Louis, V. L.; Graydon, J. A.; Lehnherr, I.

2009-12-01

The role of high arctic ecosystems in the global carbon budget has attracted scientific interest because a) arctic terrestrial ecosystems currently store significant amounts of organic carbon in permafrost and poorly drained tundra soils, and b) the arctic climate system is changing rapidly in response to global warming. The role of the high arctic terrestrial ecosystem as either a source or sink of atmospheric CO2 is unknown, although it is generally assumed that it will become a source of CO2 to the atmosphere as climate change continues to warm the region and previously sequestered organic matter in soils is mineralized as the active layer develops. We will present data on the net ecosystem exchange (NEE) of CO2 from high arctic tundra near Lake Hazen, Quittinirpaaq National Park (81°N) during the 2008 and 2009 growing seasons, collected using an eddy covariance flux tower. This is the first report of NEE from such a northerly latitude. We will also present data on the exchange of CH4 with tundra soils collected using static chambers. The tundra at Lake Hazen was a continuous CO2 sink during the growing season, and is carbon neutral during snow cover conditions in early spring. The CO2 flux correlated strongly with PAR and soil temperature. Despite active layer development at the site during our observation period (11 cm in 2008, 37 cm in 2009), no evidence of a corresponding CO2 pulse to the atmosphere was detected. Soil respiration rates, separately measured using a LiCOR 6400, indicated a correlation between soil respiration and plant cover corresponded. The strong correlation between NEE and vegetation parameters suggests that as vegetation cover increases in the high arctic in response to climate warming, the tundra at Lake Hazen may continue to function as a carbon sink despite continued active layer development. Dry tundra soils always consumed CH4 at our site, suggesting that parts of the high Arctic are actually sinks for this strong greenhouse gas.

Marine Arctic Ecosystem Study (MARES): Pilot Project - Marine Mammal Tagging and Tracking

DTIC Science & Technology

2015-09-30

project . NOPP is an innovative collaboration of federal agencies that support ocean research partnerships among academia, government, industry, and...1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Marine Arctic Ecosystem Study (MARES): Pilot Project ...Francis.Wiese@stantec.com Award Number: N0001415IP00085 LONG-TERM GOALS The overarching goal of the MARES project is to understand the

Hematology of southern Beaufort Sea polar bears (2005-2007): Biomarker for an arctic ecosystem health sentinel

USGS Publications Warehouse

Kirk, Cassandra M.; Amstrup, Steven C.; Swor, Rhonda; Holcomb, Darce; O'Hara, T. M.

2010-01-01

Declines in sea-ice habitats have resulted in declining stature, productivity, and survival of polar bears in some regions. With continuing sea-ice declines, negative population effects are projected to expand throughout the polar bear's range. Precise causes of diminished polar bear life history performance are unknown, however, climate and sea-ice condition change are expected to adversely impact polar bear (Ursus maritimus) health and population dynamics. As apex predators in the Arctic, polar bears integrate the status of lower trophic levels and are therefore sentinels of ecosystem health. Arctic residents feed at the apex of the ecosystem, thus polar bears can serve as indicators of human health in the Arctic. Despite their value as indicators of ecosystem welfare, population-level health data for U.S. polar bears are lacking. We present hematological reference ranges for southern Beaufort Sea polar bears. Hematological parameters in southern Beaufort Sea polar bears varied by age, geographic location, and reproductive status. Total leukocytes, lymphocytes, monocytes, eosinophils, and serum immunoglobulin G were significantly greater in males than females. These measures were greater in nonlactating females ages ???5, than lactating adult females ages ???5, suggesting that females encumbered by young may be less resilient to new immune system challenges that may accompany ongoing climate change. Hematological values established here provide a necessary baseline for anticipated changes in health as arctic temperatures warm and sea-ice declines accelerate. Data suggest that females with dependent young may be most vulnerable to these changes and should therefore be a targeted cohort for monitoring in this sentinel. ?? 2010 International Association for Ecology and Health.

Conceptual data modeling of wildlife response indicators to ecosystem change in the Arctic

USGS Publications Warehouse

Walworth, Dennis; Pearce, John M.

2015-08-06

Large research studies are often challenged to effectively expose and document the types of information being collected and the reasons for data collection across what are often a diverse cadre of investigators of differing disciplines. We applied concepts from the field of information or data modeling to the U.S. Geological Survey (USGS) Changing Arctic Ecosystems (CAE) initiative to prototype an application of information modeling. The USGS CAE initiative is collecting information from marine and terrestrial environments in Alaska to identify and understand the links between rapid physical changes in the Arctic and response of wildlife populations to these ecosystem changes. An associated need is to understand how data collection strategies are informing the overall science initiative and facilitating communication of those strategies to a wide audience. We explored the use of conceptual data modeling to provide a method by which to document, describe, and visually communicate both enterprise and study level data; provide a simple means to analyze commonalities and differences in data acquisition strategies between studies; and provide a tool for discussing those strategies among researchers and managers.

Effects of long-term nutrient additions on Arctic tundra, stream, and lake ecosystems: beyond NPP.

PubMed

Gough, Laura; Bettez, Neil D; Slavik, Karie A; Bowden, William B; Giblin, Anne E; Kling, George W; Laundre, James A; Shaver, Gaius R

2016-11-01

Primary producers form the base of food webs but also affect other ecosystem characteristics, such as habitat structure, light availability, and microclimate. Here, we examine changes caused by 5-30+ years of nutrient addition and resulting increases in net primary productivity (NPP) in tundra, streams, and lakes in northern Alaska. The Arctic provides an important opportunity to examine how ecosystems characterized by low diversity and low productivity respond to release from nutrient limitation. We review how responses of algae and plants affect light availability, perennial biotic structures available for consumers, oxygen levels, and temperature. Sometimes, responses were similar across all three ecosystems; e.g., increased NPP significantly reduced light to the substrate following fertilization. Perennial biotic structures increased in tundra and streams but not in lakes, and provided important new habitat niches for consumers as well as other producers. Oxygen and temperature responses also differed. Life history traits (e.g., longevity) of the primary producers along with the fate of detritus drove the responses and recovery. As global change persists and nutrients become more available in the Arctic and elsewhere, incorporating these factors as response variables will enable better prediction of ecosystem changes and feedbacks in this biome and others.

Coordinating for Arctic Conservation: Implementing Integrated Arctic Biodiversity Monitoring, Data Management and Reporting

NASA Astrophysics Data System (ADS)

Gill, M.; Svoboda, M.

2012-12-01

Arctic ecosystems and the biodiversity they support are experiencing growing pressure from various stressors (e.g. development, climate change, contaminants, etc.) while established research and monitoring programs remain largely uncoordinated, lacking the ability to effectively monitor, understand and report on biodiversity trends at the circumpolar scale. The maintenance of healthy arctic ecosystems is a global imperative as the Arctic plays a critical role in the Earth's physical, chemical and biological balance. A coordinated and comprehensive effort for monitoring arctic ecosystems is needed to facilitate effective and timely conservation and adaptation actions. The Arctic's size and complexity represents a significant challenge towards detecting and attributing important biodiversity trends. This demands a scaled, pan-arctic, ecosystem-based approach that not only identifies trends in biodiversity, but also identifies underlying causes. It is critical that this information be made available to generate effective strategies for adapting to changes now taking place in the Arctic—a process that ultimately depends on rigorous, integrated, and efficient monitoring programs that have the power to detect change within a "management" time frame. To meet these challenges and in response to the Arctic Climate Impact Assessment's recommendation to expand and enhance arctic biodiversity monitoring, the Conservation of Arctic Flora and Fauna (CAFF) Working Group of the Arctic Council launched the Circumpolar Biodiversity Monitoring Program (CBMP). The CBMP is led by Environment Canada on behalf of Canada and the Arctic Council. The CBMP is working with over 60 global partners to expand, integrate and enhance existing arctic biodiversity research and monitoring efforts to facilitate more rapid detection, communication and response to significant trends and pressures. Towards this end, the CBMP has established three Expert Monitoring Groups representing major Arctic

Enhancing a Socio-technical Data Ecosystem for Societally Relevant, Sustained Arctic Observing

NASA Astrophysics Data System (ADS)

Pulsifer, P. L.

2017-12-01

In recent years, much has been learned about the state of data and related systems for the Arctic region, however work remains to be done to achieve an envisioned integrated and well-defined pan-Arctic observing and data network. The envisioned comprehensive network will enables access to high quality data, expertise and information in support of scientific understanding, stakeholder needs, and agency operations. In this paper we argue that priorities for establishing such a network are in the areas of better understanding the current system, machine-enhanced data discovery and mediation, and the human aspects of community building. The author has engaged extensively in international, Canadian and U.S.-based data coordination and system design efforts. This includes a series of meetings, workshops, systems design activities, and publications. The results of these efforts have been analyzed and a synthesis of these analyses are presented here. Analysis reveals that there are a large number of polar data resources interacting in a complex network that functions as a data ecosystem. Understanding this ecosystem is critical and required to guide design. Given the size and complexity of the network, achieving broad data discovery and access and meaningful data integration will require advanced techniques including machine learning, semantic mediation, and the use of highly connected virtual research environments. To achieve the aforementioned goal will require a community of engaged researchers, technologists, and stakeholders to establish requirements and the social and organizational context needed for effective approaches. The results imply that: i) an effective governance mechanism must be established that includes "bottom up" and "top down" control; ii) the established governance mechanism must include effective networking of actors in the system; iii) funders must adopt a long-term, sustainable infrastructure approach to systems development; iv) best practices

Decrease of lichens in Arctic ecosystems: the role of wildfire, caribou, reindeer, competition and climate in north-western Alaska

Treesearch

Kyle Joly; Randi R. Jandt; David R. Klein

2009-01-01

We review and present a synthesis of the existing research dealing with changing Arctic tundra ecosystems, in relation to caribou and reindeer winter ranges. Whereas pan-Arctic studies have documented the effects on tundra vegetation from simulated climate change, we draw upon recent long-term regional studies in Alaska that have documented the actual, on-the-ground...

Mercury in Arctic Marine Ecosystems: Sources, Pathways, and Exposure

PubMed Central

Kirk, Jane L.; Lehnherr, Igor; Andersson, Maria; Braune, Birgit M.; Chan, Laurie; Dastoor, Ashu P.; Durnford, Dorothy; Gleason, Amber L.; Loseto, Lisa L.; Steffen, Alexandra; St. Louis, Vincent L.

2014-01-01

Mercury in the Arctic is an important environmental and human health issue. The reliance of Northern Peoples on traditional foods, such as marine mammals, for subsistence means that they are particularly at risk from mercury exposure. The cycling of mercury in Arctic marine systems is reviewed here, with emphasis placed on the key sources, pathways and processes which regulate mercury levels in marine food webs and ultimately the exposure of human populations to this contaminant. While many knowledge gaps exist limiting our ability to make strong conclusions, it appears that the long range transport of mercury from Asian emissions is an important source of atmospheric Hg to the Arctic and that mercury methylation resulting in monomethylmercury production (an organic form of mercury which is both toxic and bioaccumulated) in Arctic marine waters is the principal source of mercury incorporated into food webs. Mercury concentrations in biological organisms have increased since the onset of the industrial age and are controlled by a combination of abiotic factors (e.g., monomethylmercury supply), food web dynamics and structure, and animal behavior (e.g., habitat selection and feeding behavior). Finally, although some Northern Peoples have high mercury concentrations of mercury in their blood and hair, harvesting and consuming traditional foods has many nutritional, social, cultural and physical health benefits which must be considered in risk management and communication. PMID:23102902

Linking ecosystem characteristics to final ecosystem services for public policy

PubMed Central

Wong, Christina P; Jiang, Bo; Kinzig, Ann P; Lee, Kai N; Ouyang, Zhiyun

2015-01-01

Governments worldwide are recognising ecosystem services as an approach to address sustainability challenges. Decision-makers need credible and legitimate measurements of ecosystem services to evaluate decisions for trade-offs to make wise choices. Managers lack these measurements because of a data gap linking ecosystem characteristics to final ecosystem services. The dominant method to address the data gap is benefit transfer using ecological data from one location to estimate ecosystem services at other locations with similar land cover. However, benefit transfer is only valid once the data gap is adequately resolved. Disciplinary frames separating ecology from economics and policy have resulted in confusion on concepts and methods preventing progress on the data gap. In this study, we present a 10-step approach to unify concepts, methods and data from the disparate disciplines to offer guidance on overcoming the data gap. We suggest: (1) estimate ecosystem characteristics using biophysical models, (2) identify final ecosystem services using endpoints and (3) connect them using ecological production functions to quantify biophysical trade-offs. The guidance is strategic for public policy because analysts need to be: (1) realistic when setting priorities, (2) attentive to timelines to acquire relevant data, given resources and (3) responsive to the needs of decision-makers. PMID:25394857

The resilience and functional role of moss in boreal and arctic ecosystems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Turetsky, Merritt; Bond-Lamberty, Benjamin; Euskirchen, Eugenie S.

2012-08-24

Mosses in boreal and arctic ecosystems are ubiquitous components of plant communities, represent an important component of plant diversity, and strongly influence the cycling of water, nutrients, energy and carbon. Here we use a literature review and synthesis as well as model simulations to explore the role of moss in ecological stability and resilience. Our literature review of moss community responses to disturbance showed all possible responses (increases, decreases, no change) within most disturbance categories in boreal and arctic regions. Our modeling simulations suggest that loss of moss within northern plant communities will reduce soil carbon accumulation primarily by influencingmore » decomposition rates and soil nitrogen availability. While two models (HPM and STM-TEM) showed a significant effect of moss removal, results from the Biome-BGC and DVM-TEM models suggest that northern, moss-rich ecosystems would need to experience extreme perturbation before mosses were eliminated. We highlight a number of issues that have not been adequately explored in moss communities, such as functional redundancy and singularity, relationships between response and effect traits, phenotypical plasticity in traits, and whether the effects of moss on ecosystem processes scale with local abundance. We also suggest that as more models explore issues related to ecological resilience, issues related to both parameter and conceptual uncertainty should be addressed: are the models more limited by uncertainty in the parameterization of the processes included or by what is not represented in the model at all? It seems clear from our review that mosses need to be incorporated into models as one or more plant functional types, but more empirical work is needed to determine how to best aggregate species.« less

Linking ecosystem characteristics to final ecosystem services for public policy.

PubMed

Wong, Christina P; Jiang, Bo; Kinzig, Ann P; Lee, Kai N; Ouyang, Zhiyun

2015-01-01

Governments worldwide are recognising ecosystem services as an approach to address sustainability challenges. Decision-makers need credible and legitimate measurements of ecosystem services to evaluate decisions for trade-offs to make wise choices. Managers lack these measurements because of a data gap linking ecosystem characteristics to final ecosystem services. The dominant method to address the data gap is benefit transfer using ecological data from one location to estimate ecosystem services at other locations with similar land cover. However, benefit transfer is only valid once the data gap is adequately resolved. Disciplinary frames separating ecology from economics and policy have resulted in confusion on concepts and methods preventing progress on the data gap. In this study, we present a 10-step approach to unify concepts, methods and data from the disparate disciplines to offer guidance on overcoming the data gap. We suggest: (1) estimate ecosystem characteristics using biophysical models, (2) identify final ecosystem services using endpoints and (3) connect them using ecological production functions to quantify biophysical trade-offs. The guidance is strategic for public policy because analysts need to be: (1) realistic when setting priorities, (2) attentive to timelines to acquire relevant data, given resources and (3) responsive to the needs of decision-makers. © 2014 The Authors. Ecology Letters published by John Wiley & Sons Ltd and CNRS.

Shifting the Arctic Carbon Balance: Effects of a Long-Term Fertilization Experiment and Anomalously Warm Temperatures on Net Ecosystem Exchange in the Alaskan Tundra

NASA Astrophysics Data System (ADS)

Ludwig, S.; Natali, S.; Rastetter, E. B.; Shaver, G. R.; Graham, L. M.; Jastrow, J. D.

2017-12-01

The arctic is warming at an accelerated rate relative to the globe. Among the predicted consequences of warming temperatures in the arctic are increased gross primary productivity (GPP), ecosystem respiration (ER), and nutrient availability. The net effect of these changes on the carbon (C) cycle and resulting C balance and feedback to climate change remain unclear. Historically the Arctic has been a C sink, but evidence from recent years suggests some regions in the Arctic are becoming C sources. To predict the role of the Arctic in global C cycling, the mechanisms affecting arctic C balances need to be better resolved. We measured net ecosystem exchange (NEE) in a long-term, multi-level, fertilization experiment at Toolik Lake, AK during an anomalously warm summer. We modeled NEE, ER, and GPP using a Bayesian network model. The best-fit model included Q10 temperature functions and linear fertilization functions for both ER and GPP. ER was more strongly affected by temperature and GPP was driven more by fertilization level. As a result, fertilization increased the C sink capacity, but only at moderate and low temperatures. At high temperatures (>28 °C) the NEE modeled for the highest level of fertilization was not significantly different from zero. In contrast, at ambient nutrient levels modeled NEE was significantly below zero (net uptake) until 35 °C, when it becomes neutral. Regardless of the level of fertilization, NEE never decreased with warming. Temperature in low ranges (5-15°C) had no net effect on NEE, whereas NEE began to increase exponentially with temperature after a threshold of 15°C until becoming a net source to the atmosphere at 37°C. Our results indicate that the C sink strength of tundra ecosystems can be increased with small increases in nutrient availability, but that large increase in nutrient availability can switch tundra ecosystems into C sources under warm conditions. Warming temperatures in tundra ecosystems will only decrease C

Small birds, big effects: the little auk (Alle alle) transforms high Arctic ecosystems

PubMed Central

Johansen, Kasper L.; Mosbech, Anders; Landkildehus, Frank; Jeppesen, Erik; Davidson, Thomas A.

2017-01-01

In some arctic areas, marine-derived nutrients (MDN) resulting from fish migrations fuel freshwater and terrestrial ecosystems, increasing primary production and biodiversity. Less is known, however, about the role of seabird-MDN in shaping ecosystems. Here, we examine how the most abundant seabird in the North Atlantic, the little auk (Alle alle), alters freshwater and terrestrial ecosystems around the North Water Polynya (NOW) in Greenland. We compare stable isotope ratios (δ15N and δ13C) of freshwater and terrestrial biota, terrestrial vegetation indices and physical–chemical properties, productivity and community structure of fresh waters in catchments with and without little auk colonies. The presence of colonies profoundly alters freshwater and terrestrial ecosystems by providing nutrients and massively enhancing primary production. Based on elevated δ15N in MDN, we estimate that MDN fuels more than 85% of terrestrial and aquatic biomass in bird influenced systems. Furthermore, by using different proxies of bird impact (colony distance, algal δ15N) it is possible to identify a gradient in ecosystem response to increasing bird impact. Little auk impact acidifies the freshwater systems, reducing taxonomic richness of macroinvertebrates and truncating food webs. These results demonstrate that the little auk acts as an ecosystem engineer, transforming ecosystems across a vast region of Northwest Greenland. PMID:28202811

Arctic Messages: Arctic Research in the Vocabulary of Poets and Artists

NASA Astrophysics Data System (ADS)

Samsel, F.

2017-12-01

Arctic Messages is a series of prints created by a multidisciplinary team designed to build understanding and encourage dialogue about the changing Arctic ecosystems and the impacts on global weather patterns. Our team comprised of Arctic researchers, a poet, a visual artist, photographers and visualization experts set out to blend the vocabularies of our disciplines in order to provide entry into the content for diverse audiences. Arctic Messages is one facet of our broader efforts experimenting with mediums of communication able to provide entry to those of us outside scientific of fields. We believe that the scientific understanding of change presented through the languages art will speak to our humanity as well as our intellect. The prints combine poetry, painting, visualization, and photographs, drawn from the Arctic field studies of the Next Generation Ecosystem Experiments research team at Los Alamos National Laboratory. The artistic team interviewed the scientists, read their papers and poured over their field blogs. The content and concepts are designed to portray the wonder of nature, the complexity of the science and the dedication of the researchers. Smith brings to life the intertwined connection between the research efforts, the ecosystems and the scientist's experience. Breathtaking photography of the research site is accompanied by Samsel's drawings and paintings of the ecosystem relationships and geological formations. Together they provide entry to the variety and wonder of life on the Arctic tundra and that resting quietly in the permafrost below. Our team has experimented with many means of presentation from complex interactive systems to quiet individual works. Here we are presenting a series of prints, each one based on a single thread of the research or the scientist's experience but containing intertwined relationships similar to the ecosystems they represent. Earlier interactive systems, while engaging, were not tuned to those seeking

Seabird guano is an efficient conveyer of persistent organic pollutants (POPs) to Arctic lake ecosystems.

PubMed

Evenset, A; Carroll, J; Christensen, G N; Kallenborn, R; Gregor, D; Gabrielsen, G W

2007-02-15

Migratory seabirds have been linked to localized "hotspots" of contamination in remote Arctic lakes. One of these lakes is Lake Ellasjøen on Bjørnøya in the Barents Sea. Here we provide quantitative evidence demonstrating that even relatively small populations of certain seabird species can lead to major impacts for ecosystems. In the present example, seabird guano accounts for approximately 14% of the contaminant inventory of the Lake Ellasjøen catchment area, approximately 80% of the contaminant inventory of the lake itself, and is approximately thirty times more efficient as a contaminant transport pathway compared to atmospheric long-range transport. We have further shown that this biological transport mechanism is an important contaminant exposure route for ecosystems, responsible for POPs levels in freshwater fish that are an order of magnitude higher than those in Arctic top predators. Given the worldwide presence of seabird colonies in coastal marine areas where resources are also harvested by humans, this biological transport pathway may be a greater source of dietary contamination than is currently recognized with consequent risks for human health.

The Changing Seasonality of Tundra Nutrient Cycling: Implications for Arctic Ecosystem Function

NASA Astrophysics Data System (ADS)

Weintraub, M. N.; Steltzer, H.; Sullivan, P.; Schimel, J.; Wallenstein, M. D.; Darrouzet-Nardi, A.; Segal, A. D.

2011-12-01

Arctic soils contain large stores of carbon (C) and may act as a significant CO2 source with warming. However, the key to understanding tundra soil processes is nitrogen (N), as both plant growth and decomposition are N limited. However, current models of tundra ecosystems assume that while N limits plant growth, C limits decomposition. In addition, N availability is strongly seasonal with relatively high concentrations early in the growing season followed by a pronounced crash. We need to understand the controls on this seasonality to predict responses to climate change, but there are multiple questions that need answers: 1) What causes the seasonality in N? 2) Does microbial activity switch seasonally between C and N limitation? 3) How will a lengthening of the growing season alter overall ecosystem C and N dynamics, as a result of differential extension of the periods before and after the nutrient crash? We hypothesized that microbial activity is C limited early in the growing season, when N availability is higher and root exudate C is unavailable, and that microbial activity becomes N limited in response to plant N uptake and immobilization stimulated by root C. To address these questions we are conducting an accelerated snow-melt X warming field experiment in an Alaskan moist acidic arctic tundra community, and following plant and soil dynamics. Changes in the timing of C and N interactions in the different treatments will enable us to develop an enhanced mechanistic understanding of why the nutrient crash occurs and what the implications are for a lengthening of the arctic growing season. In 2010 we successfully accelerated snowmelt by 4 days. Both earlier snowmelt and warming accelerated early season plant life history events, with a few exceptions. However, responses to the combined treatment could not always be predicted from single factor effects. End of season life history events occurred later in response to the treatments, again with a few exceptions

Coupled cryoconite ecosystem structure-function relationships are revealed by comparing bacterial communities in alpine and Arctic glaciers.

PubMed

Edwards, Arwyn; Mur, Luis A J; Girdwood, Susan E; Anesio, Alexandre M; Stibal, Marek; Rassner, Sara M E; Hell, Katherina; Pachebat, Justin A; Post, Barbara; Bussell, Jennifer S; Cameron, Simon J S; Griffith, Gareth Wyn; Hodson, Andrew J; Sattler, Birgit

2014-08-01

Cryoconite holes are known as foci of microbial diversity and activity on polar glacier surfaces, but are virtually unexplored microbial habitats in alpine regions. In addition, whether cryoconite community structure reflects ecosystem functionality is poorly understood. Terminal restriction fragment length polymorphism and Fourier transform infrared metabolite fingerprinting of cryoconite from glaciers in Austria, Greenland and Svalbard demonstrated cryoconite bacterial communities are closely correlated with cognate metabolite fingerprints. The influence of bacterial-associated fatty acids and polysaccharides was inferred, underlining the importance of bacterial community structure in the properties of cryoconite. Thus, combined application of T-RFLP and FT-IR metabolite fingerprinting promises high throughput, and hence, rapid assessment of community structure-function relationships. Pyrosequencing revealed Proteobacteria were particularly abundant, with Cyanobacteria likely acting as ecosystem engineers in both alpine and Arctic cryoconite communities. However, despite these generalities, significant differences in bacterial community structures, compositions and metabolomes are found between alpine and Arctic cryoconite habitats, reflecting the impact of local and regional conditions on the challenges of thriving in glacial ecosystems. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

[Nitrogen bio-cycle in the alpine tundra ecosystem of Changbai Mountain and its comparison with arctic tundra].

PubMed

Wei, Jing; Zhao, Jing-zhu; Deng, Hong-bing; Wu, Gang; Hao, Ying-jie; Shang, Wen-yan

2005-03-01

The nitrogen bio-cycle was discussed in the alpine tundra ecosystem of Changbai Mountain through compartment model. The alpine tundra of Changbai Mountain was compared with Arctic tundra by the common ratio of genus and species in this paper. It was found that the 89.3% of genus and 58.6% of species was the common between Changbai alpine tundra and Arctic tundra while 95.5% of lichen genus and 58.7% lichen species, 82.1% of moss genus and 76.3% of moss species, 93.1% of vascular bundle genus and 40.5% of vascular bundle species were the common, respectively, which made vegetation type or community to be similar between Changbai alpine tundra and Arctic tundra. The total storage of nitrogen was 65220.6 t in the vegetation-plant system of Changbai Mountain, of which soil pool amounted to 99.3%. The nitrogen storage of each compartment was as follows: the vegetation pool, litterfall pool and soil pool were 237.4 t, 145.3 t and 64837.9 t respectively. The transferable amounts of nitrogen were 131.7 t x a(-1), 58 t/a and 73.7 t x a(-1) in the aboveground plant, belowground root system and litterfall of alpine tundra ecosystem of Changbai Mountain.

Small birds, big effects: the little auk (Alle alle) transforms high Arctic ecosystems.

PubMed

González-Bergonzoni, Ivan; Johansen, Kasper L; Mosbech, Anders; Landkildehus, Frank; Jeppesen, Erik; Davidson, Thomas A

2017-02-22

In some arctic areas, marine-derived nutrients (MDN) resulting from fish migrations fuel freshwater and terrestrial ecosystems, increasing primary production and biodiversity. Less is known, however, about the role of seabird-MDN in shaping ecosystems. Here, we examine how the most abundant seabird in the North Atlantic, the little auk ( Alle alle ), alters freshwater and terrestrial ecosystems around the North Water Polynya (NOW) in Greenland. We compare stable isotope ratios ( δ 15 N and δ 13 C) of freshwater and terrestrial biota, terrestrial vegetation indices and physical-chemical properties, productivity and community structure of fresh waters in catchments with and without little auk colonies. The presence of colonies profoundly alters freshwater and terrestrial ecosystems by providing nutrients and massively enhancing primary production. Based on elevated δ 15 N in MDN, we estimate that MDN fuels more than 85% of terrestrial and aquatic biomass in bird influenced systems. Furthermore, by using different proxies of bird impact (colony distance, algal δ 15 N) it is possible to identify a gradient in ecosystem response to increasing bird impact. Little auk impact acidifies the freshwater systems, reducing taxonomic richness of macroinvertebrates and truncating food webs. These results demonstrate that the little auk acts as an ecosystem engineer, transforming ecosystems across a vast region of Northwest Greenland. © 2017 The Author(s).

Application of Terrestrial Ecosystem Monitoring under the CAFF Circumpolar Biodiversity Monitoring Program: Designing and Implementing Terrestrial Monitoring to Establish the Canadian High Arctic Research Station as a Flagship Arctic Environmental Monitoring Site

NASA Astrophysics Data System (ADS)

McLennan, D.; Kehler, D.

2016-12-01

The Canadian High Arctic Research Station (CHARS) is scheduled for completion in July 2017 and is the northern science component of Polar Knowledge Canada (POLAR). A mandated goal for POLAR is to establish the adjacent Experimental and Reference Area (ERA) as an Arctic Flagship monitoring site that will track change in Arctic terrestrial, freshwater and marine ecosystems. Situated in the community of Cambridge Bay, CHARS provides the opportunity to draw on the Indigenous Knowledge of local residents to help design and conduct the monitoring, and to operate 12 months a year. Monitoring at CHARS will be linked to networks nationally and internationally, and is being designed so that change in key indicators can be understood in terms of drivers and processes, modeled and scaled up regionally, and used to predict important changes in critical indicators. As a partner in the Circumpolar Biodiversity Monitoring Program (CBMP), the monitoring design for terrestrial ecosystems follows approaches outlined by the CBMP Terrestrial Expert Monitoring Group, who have listed key monitoring questions and identified a list of important Focal Ecosystem Components (FECs). To link drivers to FECs we are proposing a multi-scaled approach: 1) an Intensive Monitoring Area to establish replicated monitoring plots that track change in snow depth and condition, active layer depth, soil temperature, soil moisture, and soil solution chemistry that are spatially and temporally linked to changes in microbiological activity, CO2/CH4 net ecosystem flux, vegetation relative frequency, species composition, growth and foliar nutrient concentration, arthropod abundance, lemming abundance and health, and shorebird/songbird abundance and productivity. 2) These intensive observations are supported by watershed scale measures that will monitor, during the growing season, lemming winter nest abundance, songbird, shorebird and waterfowl staging and nesting, and other observations; in the winter we will

How well does your model capture the terrestrial ecosystem dynamics of the Arctic-Boreal Region?

NASA Astrophysics Data System (ADS)

Stofferahn, E.; Fisher, J. B.; Hayes, D. J.; Huntzinger, D. N.; Schwalm, C.

2016-12-01

The Arctic-Boreal Region (ABR) is a major source of uncertainties for terrestrial biosphere model (TBM) simulations. These uncertainties are precipitated by a lack of observational data from the region, affecting the parameterizations of cold environment processes in the models. Addressing these uncertainties requires a coordinated effort of data collection and integration of the following key indicators of the ABR ecosystem: disturbance, flora / fauna and related ecosystem function, carbon pools and biogeochemistry, permafrost, and hydrology. We are developing a model-data integration framework for NASA's Arctic Boreal Vulnerability Experiment (ABoVE), wherein data collection for the key ABoVE indicators is driven by matching observations and model outputs to the ABoVE indicators. The data are used as reference datasets for a benchmarking system which evaluates TBM performance with respect to ABR processes. The benchmarking system utilizes performance metrics to identify intra-model and inter-model strengths and weaknesses, which in turn provides guidance to model development teams for reducing uncertainties in TBM simulations of the ABR. The system is directly connected to the International Land Model Benchmarking (ILaMB) system, as an ABR-focused application.

Ecosystem and human health assessment to define environmental management strategies: The case of long-term human impacts on an Arctic lake.

PubMed

Moiseenko, T I; Voinov, A A; Megorsky, V V; Gashkina, N A; Kudriavtseva, L P; Vandish, O I; Sharov, A N; Sharova, Yu; Koroleva, I N

2006-10-01

There are rich deposits of mineral and fossil natural resources in the Arctic, which make this region very attractive for extracting industries. Their operations have immediate and vast consequences for ecological systems, which are particularly vulnerable in this region. We are developing a management strategy for Arctic watersheds impacted by industrial production. The case study is Lake Imandra watershed (Murmansk oblast, Russia) that has exceptionally high levels of economic development and large numbers of people living there. We track the impacts of toxic pollution on ecosystem health and then--human health. Three periods are identified: (a) natural, pre-industrial state; (b) disturbed, under rapid economic development; and (c) partial recovery, during recent economic meltdown. The ecosystem is shown to transform into a qualitatively new state, which is still different from the original natural state, even after toxic loadings have substantially decreased. Fish disease where analyzed to produce and integral evaluation of ecosystem health. Accumulation of heavy metals in fish is correlated with etiology of many diseases. Dose-effect relationships are between integral water quality indices and ecosystem health indicators clearly demonstrates that existing water quality standards adopted in Russia are inadequate for Arctic regions. Health was also poor for people drinking water from the Lake. Transport of heavy metals from drinking water, into human organs, and their effect on liver and kidney diseases shows the close connection between ecosystem and human health. A management system is outlined that is based on feedback from indices of ecosystem and human health and control over economic production and/or the amount of toxic loading produced. We argue that prospects for implementation of such a system are quite bleak at this time, and that more likely we will see a continued depopulation of these Northern regions.

Disentangling trophic relationships in a High Arctic tundra ecosystem through food web modeling.

PubMed

Legagneux, P; Gauthier, G; Berteaux, D; Bêty, J; Cadieux, M C; Bilodeau, F; Bolduc, E; McKinnon, L; Tarroux, A; Therrien, J F; Morissette, L; Krebs, C J

2012-07-01

Determining the manner in which food webs will respond to environmental changes is difficult because the relative importance of top-down vs. bottom-up forces in controlling ecosystems is still debated. This is especially true in the Arctic tundra where, despite relatively simple food webs, it is still unclear which forces dominate in this ecosystem. Our primary goal was to assess the extent to which a tundra food web was dominated by plant-herbivore or predator-prey interactions. Based on a 17-year (1993-2009) study of terrestrial wildlife on Bylot Island, Nunavut, Canada, we developed trophic mass balance models to address this question. Snow Geese were the dominant herbivores in this ecosystem, followed by two sympatric lemming species (brown and collared lemmings). Arctic foxes, weasels, and several species of birds of prey were the dominant predators. Results of our trophic models encompassing 19 functional groups showed that <10% of the annual primary production was consumed by herbivores in most years despite the presence of a large Snow Goose colony, but that 20-100% of the annual herbivore production was consumed by predators. The impact of herbivores on vegetation has also weakened over time, probably due to an increase in primary production. The impact of predators was highest on lemmings, intermediate on passerines, and lowest on geese and shorebirds, but it varied with lemming abundance. Predation of collared lemmings exceeded production in most years and may explain why this species remained at low density. In contrast, the predation rate on brown lemmings varied with prey density and may have contributed to the high-amplitude, periodic fluctuations in the abundance of this species. Our analysis provided little evidence that herbivores are limited by primary production on Bylot Island. In contrast, we measured strong predator-prey interactions, which supports the hypothesis that this food web is primarily controlled by top-down forces. The presence of

Fall season atypically warm weather event leads to substantial CH4 loss in Arctic ecosystems?

NASA Astrophysics Data System (ADS)

Zona, Donatella; Moreaux, Virginie; Liljedahl, Anna; Losacco, Salvatore; Murphy, Patrick; Oechel, Walter

2014-05-01

In the last century (during 1875-2008) high-latitudes are warming at a rate of 1.360C century-1, almost 2 times faster than the Northern Hemisphere trend (Bekryaev et al., 2010). This warming has been more intense outside of the summer season, with anomalies of 1.09, 1.59, 1.730C in the fall, winter, and spring season respectively (Bekryaev et al., 2010). This substantial temperature anomalies have the potential to increase the emission of greenhouse gas (CO2 and CH4) fluxes from arctic tundra ecosystems. In particular, CH4 emissions, which are primarily controlled by temperature (in addition to water table), can steeply increase with warming. Despite the potential relevance of CH4 emissions, very few measurements have been performed outside of the growing season across the entire Arctic, due to logistic constrains. Importantly, no flux measurements achieved a temporal and spatial data coverage sufficient to estimate with confidence an annual CH4 emissions from tundra ecosystem in Alaska, and its sensitivity to warming. Fall 2013 was unusually warm in central and northern Alaska. Following a relatively warm summer with dramatically above-average rainfall, the October mean monthly temperatures was the 4th and top warmest in Barrow (1949-2013) and Ivotuk (1998-2013), respectively. As we just upgraded several eddy covariance towers to measure CO2 and CH4 fluxes year-round, the atypical weather conditions of fall 2013 represented a unique chance for testing the sensitivity of CH4 loss to these atypically warm temperatures. All our sites across a latitudinal gradient (from the northern site, Barrow, to the southern site, Ivotuk), presented substantial CH4 loss in the fall. Importantly, in two of these sites (Barrow, Ivotuk) where the fall weather was substantially warmer than the long term trend, fall CH4 emission represented between 44-63% of the June-November cumulative emission. Surprisingly, in the southernmost site (Ivotuk), when the temperature anomaly was the

Ecosystem dynamics of the Pacific-influenced Northern Bering and Chukchi Seas in the Amerasian Arctic

NASA Astrophysics Data System (ADS)

Grebmeier, Jacqueline M.; Cooper, Lee W.; Feder, Howard M.; Sirenko, Boris I.

2006-10-01

The shallow continental shelves and slope of the Amerasian Arctic are strongly influenced by nutrient-rich Pacific waters advected over the shelves from the northern Bering Sea into the Arctic Ocean. These high-latitude shelf systems are highly productive both as the ice melts and during the open-water period. The duration and extent of seasonal sea ice, seawater temperature and water mass structure are critical controls on water column production, organic carbon cycling and pelagic-benthic coupling. Short food chains and shallow depths are characteristic of high productivity areas in this region, so changes in lower trophic levels can impact higher trophic organisms rapidly, including pelagic- and benthic-feeding marine mammals and seabirds. Subsistence harvesting of many of these animals is locally important for human consumption. The vulnerability of the ecosystem to environmental change is thought to be high, particularly as sea ice extent declines and seawater warms. In this review, we focus on ecosystem dynamics in the northern Bering and Chukchi Seas, with a more limited discussion of the adjoining Pacific-influenced eastern section of the East Siberian Sea and the western section of the Beaufort Sea. Both primary and secondary production are enhanced in specific regions that we discuss here, with the northern Bering and Chukchi Seas sustaining some of the highest water column production and benthic faunal soft-bottom biomass in the world ocean. In addition, these organic carbon-rich Pacific waters are periodically advected into low productivity regions of the nearshore northern Bering, Chukchi and Beaufort Seas off Alaska and sometimes into the East Siberian Sea, all of which have lower productivity on an annual basis. Thus, these near shore areas are intimately tied to nutrients and advected particulate organic carbon from the Pacific influenced Bering Shelf-Anadyr water. Given the short food chains and dependence of many apex predators on sea ice, recent

Arctic tipping points in an Earth system perspective.

PubMed

Wassmann, Paul; Lenton, Timothy M

2012-02-01

We provide an introduction to the volume The Arctic in the Earth System perspective: the role of tipping points. The terms tipping point and tipping element are described and their role in current science, general debates, and the Arctic are elucidated. From a wider perspective, the volume focuses upon the role of humans in the Arctic component of the Earth system and in particular the envelope for human existence, the Arctic ecosystems. The Arctic climate tipping elements, the tipping elements in Arctic ecosystems and societies, and the challenges of governance and anticipation are illuminated through short summaries of eight publications that derive from the Arctic Frontiers conference in 2011 and the EU FP7 project Arctic Tipping Points. Then some ideas based upon resilience thinking are developed to show how wise system management could ease pressures on Arctic systems in order to keep them away from tipping points.

Determining Regional Arctic Tundra Carbon Exchange: A Bottom-Up Approach

NASA Technical Reports Server (NTRS)

Huemmrich, Fred

2006-01-01

This viewgraph presentation reviews the carbon atmospheric exchange with Arctic tundra. In the Arctic the ecosystem has been a net carbon sink. The project investigates the question of how might climate warming effect high latitude ecosystems and the Earth ecosystems and how to measure the changes.

Effect of Freeze-Thaw Cycles on Soil Nitrogen Reactive Transport in a Polygonal Arctic Tundra Ecosystem at Barrow AK Using 3-D Coupled ALM-PFLOTRAN

NASA Astrophysics Data System (ADS)

Yuan, F.; Wang, G.; Painter, S. L.; Tang, G.; Xu, X.; Kumar, J.; Bisht, G.; Hammond, G. E.; Mills, R. T.; Thornton, P. E.; Wullschleger, S. D.

2017-12-01

In Arctic tundra ecosystem soil freezing-thawing is one of dominant physical processes through which biogeochemical (e.g., carbon and nitrogen) cycles are tightly coupled. Besides hydraulic transport, freezing-thawing can cause pore water movement and aqueous species gradients, which are additional mechanisms for soil nitrogen (N) reactive-transport in Tundra ecosystem. In this study, we have fully coupled an in-development ESM(i.e., Advanced Climate Model for Energy, ACME)'s Land Model (ALM) aboveground processes with a state-of-the-art massively parallel 3-D subsurface thermal-hydrology and reactive transport code, PFLOTRAN. The resulting coupled ALM-PFLOTRAN model is a Land Surface Model (LSM) capable of resolving 3-D soil thermal-hydrological-biogeochemical cycles. This specific version of PFLOTRAN has incorporated CLM-CN Converging Trophic Cascade (CTC) model and a full and simple but robust soil N cycle. It includes absorption-desorption for soil NH4+ and gas dissolving-degasing process as well. It also implements thermal-hydrology mode codes with three newly-modified freezing-thawing algorithms which can greatly improve computing performance in regarding to numerical stiffness at freezing-point. Here we tested the model in fully 3-D coupled mode at the Next Generation Ecosystem Experiment-Arctic (NGEE-Arctic) field intensive study site at the Barrow Environmental Observatory (BEO), AK. The simulations show that: (1) synchronous coupling of soil thermal-hydrology and biogeochemistry in 3-D can greatly impact ecosystem dynamics across polygonal tundra landscape; and (2) freezing-thawing cycles can add more complexity to the system, resulting in greater mobility of soil N vertically and laterally, depending upon local micro-topography. As a preliminary experiment, the model is also implemented for Pan-Arctic region in 1-D column mode (i.e. no lateral connection), showing significant differences compared to stand-alone ALM. The developed ALM-PFLOTRAN coupling

Advanced Ecosystem Mapping Techniques for Large Arctic Study Domains Using Calibrated High-Resolution Imagery

NASA Astrophysics Data System (ADS)

Macander, M. J.; Frost, G. V., Jr.

2015-12-01

Regional-scale mapping of vegetation and other ecosystem properties has traditionally relied on medium-resolution remote sensing such as Landsat (30 m) and MODIS (250 m). Yet, the burgeoning availability of high-resolution (<=2 m) imagery and ongoing advances in computing power and analysis tools raises the prospect of performing ecosystem mapping at fine spatial scales over large study domains. Here we demonstrate cutting-edge mapping approaches over a ~35,000 km² study area on Alaska's North Slope using calibrated and atmospherically-corrected mosaics of high-resolution WorldView-2 and GeoEye-1 imagery: (1) an a priori spectral approach incorporating the Satellite Imagery Automatic Mapper (SIAM) algorithms; (2) image segmentation techniques; and (3) texture metrics. The SIAM spectral approach classifies radiometrically-calibrated imagery to general vegetation density categories and non-vegetated classes. The SIAM classes were developed globally and their applicability in arctic tundra environments has not been previously evaluated. Image segmentation, or object-based image analysis, automatically partitions high-resolution imagery into homogeneous image regions that can then be analyzed based on spectral, textural, and contextual information. We applied eCognition software to delineate waterbodies and vegetation classes, in combination with other techniques. Texture metrics were evaluated to determine the feasibility of using high-resolution imagery to algorithmically characterize periglacial surface forms (e.g., ice-wedge polygons), which are an important physical characteristic of permafrost-dominated regions but which cannot be distinguished by medium-resolution remote sensing. These advanced mapping techniques provide products which can provide essential information supporting a broad range of ecosystem science and land-use planning applications in northern Alaska and elsewhere in the circumpolar Arctic.

The Arctic Marine Pulses Model: Linking Contiguous Domains in the Pacific Arctic Region

NASA Astrophysics Data System (ADS)

Moore, S. E.; Stabeno, P. J.

2016-02-01

The Pacific Arctic marine ecosystem extends from the northern Bering Sea, across the Chukchi and into the East Siberian and Beaufort seas. Food webs in this domain are short, a simplicity that belies the biophysical complexity underlying trophic linkages from primary production to humans. Existing biophysical models, such as pelagic-benthic coupling and advective processes, provide frameworks for connecting certain aspects of the marine food web, but do not offer a full accounting of events that occur seasonally across the Pacific Arctic. In the course of the Synthesis of Arctic Research (SOAR) project, a holistic Arctic Marine Pulses (AMP) model was developed that depicts seasonal biophysical `pulses' across a latitudinal gradient, and linking four previously-described contiguous domains, including the: (i) Pacific-Arctic domain = the focal region; (ii) seasonal ice zone domain; (iii) Pacific marginal domain; and (iv) riverine coastal domain. The AMP model provides a spatial-temporal framework to guide research on dynamic ecosystem processes during this period of rapid biophysical changes in the Pacific Arctic. Some of the processes included in the model, such as pelagic-benthic coupling in the Northern Bering and Chukchi seas, and advection and upwelling along the Beaufort shelf, are already the focus of sampling via the Distributed Biological Observatory (DBO) and other research programs. Other aspects such as biological processes associated with the seasonal ice zone and trophic responses to riverine outflow have received less attention. The AMP model could be enhanced by the application of visualization tools to provide a means to watch a season unfold in space and time. The capability to track sea ice dynamics and water masses and to move nutrients, prey and upper-trophic predators in space and time would provide a strong foundation for the development of predictive human-inclusive ecosystem models for the Pacific Arctic.

Seasonal dynamics of bacterial biomass and production in a coastal arctic ecosystem: Franklin Bay, western Canadian Arctic

NASA Astrophysics Data System (ADS)

Garneau, Marie-Ã. Ve; Roy, SéBastien; Lovejoy, Connie; Gratton, Yves; Vincent, Warwick F.

2008-07-01

The Canadian Arctic Shelf Exchange Study (CASES) included the overwintering deployment of a research platform in Franklin Bay (70°N, 126°W) and provided a unique seasonal record of bacterial dynamics in a coastal region of the Arctic Ocean. Our objectives were (1) to relate seasonal bacterial abundance (BA) and production (BP) to physico-chemical characteristics and (2) to quantify the annual bacterial carbon flux. BA was estimated by epifluorescence microscopy and BP was estimated from 3H-leucine and 3H-thymidine assays. Mean BA values for the water column ranged from 1.0 (December) to 6.8 × 105 cells mL-1 (July). Integral BP varied from 1 (February) to 80 mg C m-2 d-1 (July). During winter-spring, BP was uncorrelated with chlorophyll a (Chl a), but these variables were significantly correlated during summer-autumn (rs = 0.68, p < 0.001, N = 38), suggesting that BP was subject to bottom-up control by carbon supply. Integrated BP data showed three distinct periods: fall-winter, late winter-late spring, and summer. A baseline level of BB and BP was maintained throughout late winter-late spring despite the persistent cold and darkness, with irregular fluctuations that may be related to hydrodynamic events. During this period, BP rates were correlated with colored dissolved organic matter (CDOM) but not Chl a (rs BP.CDOM∣Chl a = 0.20, p < 0.05, N = 176). Annual BP was estimated as 6 g C m-2 a-1, implying a total BP of 4.8 × 1010 g C a-1 for the Franklin Bay region. These results show that bacterial processes continue throughout all seasons and make a large contribution to the total biological carbon flux in this coastal arctic ecosystem.

Effects of Conversion from Boreal Forest to Arctic Steppe on Soil Communities and Ecosystem Carbon Pools

NASA Astrophysics Data System (ADS)

Han, P. D.; Natali, S.; Schade, J. D.; Zimov, N.; Zimov, S. A.

2014-12-01

The end of the Pleistocene marked the extinction of a great variety of arctic megafauna, which, in part, led to the conversion of arctic grasslands to modern Siberian larch forest. This shift may have increased the vulnerability of permafrost to thawing because of changes driven by the vegetation shift; the higher albedo of grassland and low insulation of snow trampled by animals may have decreased soil temperatures and reduced ground thaw in the grassland ecosystem, resulting in protection of organic carbon in thawed soil and permafrost. To test these hypothesized impacts of arctic megafauna, we examined an experimental reintroduction of large mammals in northeast Siberia, initiated in 1988. Pleistocene Park now contains 23 horses, three musk ox, one bison, and several moose in addition to the native fauna. The park is 16 square km with a smaller enclosure (< 1 km) where animals spend most of their time and our study was focused. We measured carbon-pools in forested sites (where scat surveys showed low animal use), and grassy sites (which showed higher use), within the park boundaries. We also measured thaw depth and documented the soil invertebrate communities in each ecosystem. There was a substantial difference in number of invertebrates per kg of organic soil between the forest (600 ± 250) and grassland (300 ± 250), though these differences were not statistically significant they suggest faster nutrient turnover in the forest or a greater proportion of decomposition by invertebrates than other decomposers. While thaw depth was deeper in the grassland (60 ± 4 cm) than in the forest (40 ± 6 cm), we did not detect differences in organic layer depth or percent organic matter between grassland and forest. However, soil in the grassland had higher bulk density, and higher carbon stocks in the organic and mineral soil layers. Although deeper thaw depth in the grassland suggests that more carbon is available to microbial decomposers, ongoing temperature monitoring

Vole abundance and reindeer carcasses determine breeding activity of Arctic foxes in low Arctic Yamal, Russia.

PubMed

Ehrich, Dorothee; Cerezo, Maite; Rodnikova, Anna Y; Sokolova, Natalya A; Fuglei, Eva; Shtro, Victor G; Sokolov, Aleksandr A

2017-09-16

High latitude ecosystems are at present changing rapidly under the influence of climate warming, and specialized Arctic species at the southern margin of the Arctic may be particularly affected. The Arctic fox (Vulpes lagopus), a small mammalian predator endemic to northern tundra areas, is able to exploit different resources in the context of varying tundra ecosystems. Although generally widespread, it is critically endangered in subarctic Fennoscandia, where a fading out of the characteristic lemming cycles and competition with abundant red foxes have been identified as main threats. We studied an Arctic fox population at the Erkuta Tundra Monitoring site in low Arctic Yamal (Russia) during 10 years in order to determine which resources support the breeding activity in this population. In the study area, lemmings have been rare during the last 15 years and red foxes are nearly absent, creating an interesting contrast to the situation in Fennoscandia. Arctic fox was breeding in nine of the 10 years of the study. The number of active dens was on average 2.6 (range 0-6) per 100 km 2 and increased with small rodent abundance. It was also higher after winters with many reindeer carcasses, which occurred when mortality was unusually high due to icy pastures following rain-on-snow events. Average litter size was 5.2 (SD = 2.1). Scat dissection suggested that small rodents (mostly Microtus spp.) were the most important prey category. Prey remains observed at dens show that birds, notably waterfowl, were also an important resource in summer. The Arctic fox in southern Yamal, which is part of a species-rich low Arctic food web, seems at present able to cope with a state shift of the small rodent community from high amplitude cyclicity with lemming dominated peaks, to a vole community with low amplitude fluctuations. The estimated breeding parameters characterized the population as intermediate between the lemming fox and the coastal fox ecotype. Only continued

Nitrogen accumulation and partitioning in a High Arctic tundra ecosystem from extreme atmospheric N deposition events.

PubMed

Choudhary, Sonal; Blaud, Aimeric; Osborn, A Mark; Press, Malcolm C; Phoenix, Gareth K

2016-06-01

Arctic ecosystems are threatened by pollution from recently detected extreme atmospheric nitrogen (N) deposition events in which up to 90% of the annual N deposition can occur in just a few days. We undertook the first assessment of the fate of N from extreme deposition in High Arctic tundra and are presenting the results from the whole ecosystem (15)N labelling experiment. In 2010, we simulated N depositions at rates of 0, 0.04, 0.4 and 1.2 g Nm(-2)yr(-1), applied as (15)NH4(15)NO3 in Svalbard (79(°)N), during the summer. Separate applications of (15)NO3(-) and (15)NH4(+) were also made to determine the importance of N form in their retention. More than 95% of the total (15)N applied was recovered after one growing season (~90% after two), demonstrating a considerable capacity of Arctic tundra to retain N from these deposition events. Important sinks for the deposited N, regardless of its application rate or form, were non-vascular plants>vascular plants>organic soil>litter>mineral soil, suggesting that non-vascular plants could be the primary component of this ecosystem to undergo measurable changes due to N enrichment from extreme deposition events. Substantial retention of N by soil microbial biomass (70% and 39% of (15)N in organic and mineral horizon, respectively) during the initial partitioning demonstrated their capacity to act as effective buffers for N leaching. Between the two N forms, vascular plants (Salix polaris) in particular showed difference in their N recovery, incorporating four times greater (15)NO3(-) than (15)NH4(+), suggesting deposition rich in nitrate will impact them more. Overall, these findings show that despite the deposition rates being extreme in statistical terms, biologically they do not exceed the capacity of tundra to sequester pollutant N during the growing season. Therefore, current and future extreme events may represent a major source of eutrophication. Crown Copyright © 2016. Published by Elsevier B.V. All rights reserved.

Modelling the process-based controls of long term CO2 exchange in High Arctic heath ecosystems

NASA Astrophysics Data System (ADS)

Zhang, W.; Jansson, P. E.; Elberling, B.

2016-12-01

Frozen organic carbon (C) stored in northern permafrost soils may become vulnerable due to the rapid warming of the Arctic. The loss of C as greenhouse gases may imply a critical warming potential, resulting in positive feedbacks to global climate change. However, how permafrost ecosystems C dynamics is associated with changes in hydrothermal conditions (e.g. extent and duration of snow, soil water content and active layer depth) and changes in the responses of ecosystem biogeochemistry to climate (e.g. carbon assimilation of the entire growing season, falling rates of plants' litter, and turnover rates of different soil carbon pools) is still unclear and needs to be distinguished from site to site. Here, we use a process-oriented model (CoupModel) that couples heat and mass transfer within the high resolution soil-plant-atmosphere profile to simulate the high Arctic Cassiope tetragona Heath ecosystems in Northeast Greenland. The 15 years of net ecosystem exchange (NEE) flux (2000-2014) measured during the growing season indicate that the ecosystems may be at a transition from a C sink to a C source. We calibrated the model with the NEE flux transformed from hourly data to daily, yearly and total cumulative data to identify ensembles of parameters that best described the various patterns in the observed C fluxes. Only the ensembles of yearly and total cumulative transformation described reasonably well for seasonal variability, inter-annual variability and long term trends of measurements. The correlations between parameters and simulation performance described the relative importance of physical or biological parameters that contributes to the short- and long-term variation of C flux from biogeochemical processes of such ecosystems. The estimated C budget including internal fluxes and redistribution between various pools showed that the ecosystem functioned as a C source in the first-half period and a week C sink in the second-half period. The respiration outside

Arctic Browning: vegetation damage and implications for carbon balance.

NASA Astrophysics Data System (ADS)

Treharne, Rachael; Bjerke, Jarle; Emberson, Lisa; Tømmervik, Hans; Phoenix, Gareth

2016-04-01

'Arctic browning' is the loss of biomass and canopy in Arctic ecosystems. This process is often driven by climatic and biological extreme events - notably extreme winter warm periods, winter frost-drought and severe outbreaks of defoliating insects. Evidence suggests that browning is becoming increasingly frequent and severe at the pan-arctic scale, a view supported by observations from more intensely observed regions, with major and unprecedented vegetation damage reported at landscape (>1000km2) and regional (Nordic Arctic Region) scales in recent years. Critically, the damage caused by these extreme events is in direct opposition to 'Arctic greening', the well-established increase in productivity and shrub abundance observed at high latitudes in response to long-term warming. This opposition creates uncertainty as to future anticipated vegetation change in the Arctic, with implications for Arctic carbon balance. As high latitude ecosystems store around twice as much carbon as the atmosphere, and vegetation impacts are key to determining rates of loss or gain of ecosystem carbon stocks, Arctic browning has the potential to influence the role of these ecosystems in global climate. There is therefore a clear need for a quantitative understanding of the impacts of browning events on key ecosystem carbon fluxes. To address this, field sites were chosen in central and northern Norway and in Svalbard, in areas known to have been affected by either climatic extremes or insect outbreak and subsequent browning in the past four years. Sites were chosen along a latitudinal gradient to capture both conditions already causing vegetation browning throughout the Norwegian Arctic, and conditions currently common at lower latitudes which are likely to become more damaging further North as climate change progresses. At each site the response of Net Ecosystem CO2 Exchange to light was measured using a LiCor LI6400 Portable Photosynthesis system and a custom vegetation chamber with

Divergent patterns of experimental and model derived variables of tundra ecosystem carbon exchange in response to arctic warming

NASA Astrophysics Data System (ADS)

Schaedel, C.; Koven, C.; Celis, G.; Hutchings, J.; Lawrence, D. M.; Mauritz, M.; Pegoraro, E.; Salmon, V. G.; Taylor, M.; Wieder, W. R.; Schuur, E.

2017-12-01

Warming over the Arctic in the last decades has been twice as high as for the rest of the globe and has exposed large amounts of organic carbon to microbial decomposition in permafrost ecosystems. Continued warming and associated changes in soil moisture conditions not only lead to enhanced microbial decomposition from permafrost soil but also enhanced plant carbon uptake. Both processes impact the overall contribution of permafrost carbon dynamics to the global carbon cycle, yet field and modeling studies show large uncertainties in regard to both uptake and release mechanisms. Here, we compare variables associated with ecosystem carbon exchange (GPP: gross primary production; Reco: ecosystem respiration; and NEE: net ecosystem exchange) from eight years of experimental soil warming in moist acidic tundra with the same variables derived from an experimental model (Community Land Model version 4.5: CLM4.5) that simulates the same degree of arctic warming. While soil temperatures and thaw depths exhibited comparable increases with warming between field and model variables, carbon exchange related parameters showed divergent patterns. In the field non-linear responses to experimentally induced permafrost thaw were observed in GPP, Reco, and NEE. Indirect effects of continued soil warming and thaw created changes in soil moisture conditions causing ground surface subsidence and suppressing ecosystem carbon exchange over time. In contrast, the model predicted linear increases in GPP, Reco, and NEE with every year of warming turning the ecosystem into a net annual carbon sink. The field experiment revealed the importance of hydrology in carbon flux responses to permafrost thaw, a complexity that the model may fail to predict. Further parameterization of variables that drive GPP, Reco, and NEE in the model will help to inform and refine future model development.

Atmosphere-Ice-Ocean-Ecosystem Processes in a Thinner Arctic Sea Ice Regime: The Norwegian Young Sea ICE (N-ICE2015) Expedition

NASA Astrophysics Data System (ADS)

Granskog, Mats A.; Fer, Ilker; Rinke, Annette; Steen, Harald

2018-03-01

Arctic sea ice has been in rapid decline the last decade and the Norwegian young sea ICE (N-ICE2015) expedition sought to investigate key processes in a thin Arctic sea ice regime, with emphasis on atmosphere-snow-ice-ocean dynamics and sea ice associated ecosystem. The main findings from a half-year long campaign are collected into this special section spanning the Journal of Geophysical Research: Atmospheres, Journal of Geophysical Research: Oceans, and Journal of Geophysical Research: Biogeosciences and provide a basis for a better understanding of processes in a thin sea ice regime in the high Arctic. All data from the campaign are made freely available to the research community.

Climate change and Arctic ecosystems: 2. Modeling, paleodata-model comparisons, and future projections

USGS Publications Warehouse

Kaplan, J.O.; Bigelow, N.H.; Prentice, I.C.; Harrison, S.P.; Bartlein, P.J.; Christensen, T.R.; Cramer, W.; Matveyeva, N.V.; McGuire, A.D.; Murray, D.F.; Razzhivin, V.Y.; Smith, B.; Walker, D.A.; Anderson, P.M.; Andreev, A.A.; Brubaker, L.B.; Edwards, M.E.; Lozhkin, A.V.

2003-01-01

Large variations in the composition, structure, and function of Arctic ecosystems are determined by climatic gradients, especially of growing-season warmth, soil moisture, and snow cover. A unified circumpolar classification recognizing five types of tundra was developed. The geographic distributions of vegetation types north of 55??N, including the position of the forest limit and the distributions of the tundra types, could be predicted from climatology using a small set of plant functional types embedded in the biogeochemistry-biogeography model BIOME4. Several palaeoclimate simulations for the last glacial maximum (LGM) and mid-Holocene were used to explore the possibility of simulating past vegetation patterns, which are independently known based on pollen data. The broad outlines of observed changes in vegetation were captured. LGM simulations showed the major reduction of forest, the great extension of graminoid and forb tundra, and the restriction of low- and high-shrub tundra (although not all models produced sufficiently dry conditions to mimic the full observed change). Mid-Holocene simulations reproduced the contrast between northward forest extension in western and central Siberia and stability of the forest limit in Beringia. Projection of the effect of a continued exponential increase in atmospheric CO2 concentration, based on a transient ocean-atmosphere simulation including sulfate aerosol effects, suggests a potential for larger changes in Arctic ecosystems during the 21st century than have occurred between mid-Holocene and present. Simulated physiological effects of the CO2 increase (to > 700 ppm) at high latitudes were slight compared with the effects of the change in climate.

Simulating carbon and water fluxes at Arctic and boreal ecosystems in Alaska by optimizing the modified BIOME-BGC with eddy covariance data

NASA Astrophysics Data System (ADS)

Ueyama, M.; Kondo, M.; Ichii, K.; Iwata, H.; Euskirchen, E. S.; Zona, D.; Rocha, A. V.; Harazono, Y.; Nakai, T.; Oechel, W. C.

2013-12-01

To better predict carbon and water cycles in Arctic ecosystems, we modified a process-based ecosystem model, BIOME-BGC, by introducing new processes: change in active layer depth on permafrost and phenology of tundra vegetation. The modified BIOME-BGC was optimized using an optimization method. The model was constrained using gross primary productivity (GPP) and net ecosystem exchange (NEE) at 23 eddy covariance sites in Alaska, and vegetation/soil carbon from a literature survey. The model was used to simulate regional carbon and water fluxes of Alaska from 1900 to 2011. Simulated regional fluxes were validated with upscaled GPP, ecosystem respiration (RE), and NEE based on two methods: (1) a machine learning technique and (2) a top-down model. Our initial simulation suggests that the original BIOME-BGC with default ecophysiological parameters substantially underestimated GPP and RE for tundra and overestimated those fluxes for boreal forests. We will discuss how optimization using the eddy covariance data impacts the historical simulation by comparing the new version of the model with simulated results from the original BIOME-BGC with default ecophysiological parameters. This suggests that the incorporation of the active layer depth and plant phenology processes is important to include when simulating carbon and water fluxes in Arctic ecosystems.

Experiences in multiyear combined state-parameter estimation with an ecosystem model of the North Atlantic and Arctic Oceans using the Ensemble Kalman Filter

NASA Astrophysics Data System (ADS)

Simon, Ehouarn; Samuelsen, Annette; Bertino, Laurent; Mouysset, Sandrine

2015-12-01

A sequence of one-year combined state-parameter estimation experiments has been conducted in a North Atlantic and Arctic Ocean configuration of the coupled physical-biogeochemical model HYCOM-NORWECOM over the period 2007-2010. The aim is to evaluate the ability of an ensemble-based data assimilation method to calibrate ecosystem model parameters in a pre-operational setting, namely the production of the MyOcean pilot reanalysis of the Arctic biology. For that purpose, four biological parameters (two phyto- and two zooplankton mortality rates) are estimated by assimilating weekly data such as, satellite-derived Sea Surface Temperature, along-track Sea Level Anomalies, ice concentrations and chlorophyll-a concentrations with an Ensemble Kalman Filter. The set of optimized parameters locally exhibits seasonal variations suggesting that time-dependent parameters should be used in ocean ecosystem models. A clustering analysis of the optimized parameters is performed in order to identify consistent ecosystem regions. In the north part of the domain, where the ecosystem model is the most reliable, most of them can be associated with Longhurst provinces and new provinces emerge in the Arctic Ocean. However, the clusters do not coincide anymore with the Longhurst provinces in the Tropics due to large model errors. Regarding the ecosystem state variables, the assimilation of satellite-derived chlorophyll concentration leads to significant reduction of the RMS errors in the observed variables during the first year, i.e. 2008, compared to a free run simulation. However, local filter divergences of the parameter component occur in 2009 and result in an increase in the RMS error at the time of the spring bloom.

Fire and ecosystem change in the Arctic across the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Denis, Elizabeth H.; Pedentchouk, Nikolai; Schouten, Stefan; Pagani, Mark; Freeman, Katherine H.

2017-06-01

Fire has been an important component of ecosystems on a range of spatial and temporal scales. Fire can affect vegetation distribution, the carbon cycle, and climate. The relationship between climate and fire is complex, in large part because of a key role of vegetation type. Here, we evaluate regional scale fire-climate relationships during a past global warming event, the Paleocene-Eocene Thermal Maximum (PETM), in order to understand how vegetation influenced the links between climate and fire occurrence in the Arctic region. To document concurrent changes in climate, vegetation, and fire occurrence, we evaluated biomarkers, including polycyclic aromatic hydrocarbons (PAHs), terpenoids, and alkanes, from the PETM interval at a marine depositional site (IODP site 302, the Lomonosov Ridge) in the Arctic Ocean. Biomarker, fossil, and isotope evidence from site 302 indicates that terrestrial vegetation changed during the PETM. The abundance of the C29n-alkanes, pollen, and the ratio of leaf-wax n-alkanes relative to diterpenoids all indicate that proportional contributions from angiosperm vegetation increased relative to that from gymnosperms. These changes accompanied increased moisture transport to the Arctic and higher temperatures, as recorded by previously published proxy records. We find that PAH abundances were elevated relative to total plant biomarkers throughout the PETM, and suggest that fire occurrence increased relative to plant productivity. The fact that fire frequency or prevalence may have increased during wetter Arctic conditions suggests that changes in fire occurrence were not a simple function of aridity, as is commonly conceived. Instead, we suggest that the climate-driven ecological shift to angiosperm-dominated vegetation was what led to increased fire occurrence. Potential increases in terrestrial plant biomass that arose from warm, wet, and high CO2 conditions were possibly attenuated by biomass burning associated with compositional changes

USING LAKE SEDIMENT MERCURY FLUX RATIOS TO EVALUATE THE REGIONAL AND CONTINENTAL DIMENSIONS OF MERCURY DEPOSITION IN ARCTIC AND BOREAL ECOSYSTEMS

EPA Science Inventory

Anthropogenically elevated Hg deposition in arctic and subarctic ecosystems is potentially a serious environmental problem, particularly in northern Europe and North America. To determine the magnitude of this concern, it is necessary to make an evaluation over a broad spatial sc...

Reviews and Syntheses: Effects of permafrost thaw on arctic aquatic ecosystems

NASA Astrophysics Data System (ADS)

Vonk, J. E.; Tank, S. E.; Bowden, W. B.; Laurion, I.; Vincent, W. F.; Alekseychik, P.; Amyot, M.; Billet, M. F.; Canário, J.; Cory, R. M.; Deshpande, B. N.; Helbig, M.; Jammet, M.; Karlsson, J.; Larouche, J.; MacMillan, G.; Rautio, M.; Anthony, K. M. Walter; Wickland, K. P.

2015-07-01

The Arctic is a water-rich region, with freshwater systems covering 16 % of the northern permafrost landscape. The thawing of this permafrost creates new freshwater ecosystems, while at the same time modifying the existing lakes, streams, and rivers that are impacted by thaw. Here, we describe the current state of knowledge regarding how permafrost thaw affects lentic and lotic systems, exploring the effects of both thermokarst (thawing and collapse of ice-rich permafrost) and deepening of the active layer (the surface soil layer that thaws and refreezes each year). Within thermokarst, we further differentiate between the effects of thermokarst in lowland areas, vs. that on hillslopes. For almost all of the processes that we explore, the effects of thaw vary regionally, and between lake and stream systems. Much of this regional variation is caused by differences in ground ice content, topography, soil type, and permafrost coverage. Together, these modifying variables determine the degree to which permafrost thaw manifests as thermokarst, whether thermokarst leads to slumping or the formation of thermokarst lakes, and the manner in which constituent delivery to freshwater systems is altered by thaw. Differences in thaw-enabled constituent delivery can be considerable, with these modifying variables determining, for example, the balance between delivery of particulate vs. dissolved constituents, and inorganic vs. organic materials. Changes in the composition of thaw-impacted waters, coupled with changes in lake morphology, can strongly affect the physical and optical properties of thermokarst lakes. The ecology of thaw-impacted systems is also likely to change, with thaw-impacted lakes and streams having unique microbiological communities, and showing differences in respiration, primary production, and food web structure that are largely driven by differences in sediment, dissolved organic matter and nutrient delivery. The degree to which thaw enables the delivery of

Reviews and syntheses: Effects of permafrost thaw on Arctic aquatic ecosystems

NASA Astrophysics Data System (ADS)

Vonk, J. E.; Tank, S. E.; Bowden, W. B.; Laurion, I.; Vincent, W. F.; Alekseychik, P.; Amyot, M.; Billet, M. F.; Canário, J.; Cory, R. M.; Deshpande, B. N.; Helbig, M.; Jammet, M.; Karlsson, J.; Larouche, J.; MacMillan, G.; Rautio, M.; Anthony, K. M. Walter; Wickland, K. P.

2015-12-01

The Arctic is a water-rich region, with freshwater systems covering about 16 % of the northern permafrost landscape. Permafrost thaw creates new freshwater ecosystems, while at the same time modifying the existing lakes, streams, and rivers that are impacted by thaw. Here, we describe the current state of knowledge regarding how permafrost thaw affects lentic (still) and lotic (moving) systems, exploring the effects of both thermokarst (thawing and collapse of ice-rich permafrost) and deepening of the active layer (the surface soil layer that thaws and refreezes each year). Within thermokarst, we further differentiate between the effects of thermokarst in lowland areas vs. that on hillslopes. For almost all of the processes that we explore, the effects of thaw vary regionally, and between lake and stream systems. Much of this regional variation is caused by differences in ground ice content, topography, soil type, and permafrost coverage. Together, these modifying factors determine (i) the degree to which permafrost thaw manifests as thermokarst, (ii) whether thermokarst leads to slumping or the formation of thermokarst lakes, and (iii) the manner in which constituent delivery to freshwater systems is altered by thaw. Differences in thaw-enabled constituent delivery can be considerable, with these modifying factors determining, for example, the balance between delivery of particulate vs. dissolved constituents, and inorganic vs. organic materials. Changes in the composition of thaw-impacted waters, coupled with changes in lake morphology, can strongly affect the physical and optical properties of thermokarst lakes. The ecology of thaw-impacted lakes and streams is also likely to change; these systems have unique microbiological communities, and show differences in respiration, primary production, and food web structure that are largely driven by differences in sediment, dissolved organic matter, and nutrient delivery. The degree to which thaw enables the delivery

Ecological dynamics across the Arctic associated with recent climate change.

PubMed

Post, Eric; Forchhammer, Mads C; Bret-Harte, M Syndonia; Callaghan, Terry V; Christensen, Torben R; Elberling, Bo; Fox, Anthony D; Gilg, Olivier; Hik, David S; Høye, Toke T; Ims, Rolf A; Jeppesen, Erik; Klein, David R; Madsen, Jesper; McGuire, A David; Rysgaard, Søren; Schindler, Daniel E; Stirling, Ian; Tamstorf, Mikkel P; Tyler, Nicholas J C; van der Wal, Rene; Welker, Jeffrey; Wookey, Philip A; Schmidt, Niels Martin; Aastrup, Peter

2009-09-11

At the close of the Fourth International Polar Year, we take stock of the ecological consequences of recent climate change in the Arctic, focusing on effects at population, community, and ecosystem scales. Despite the buffering effect of landscape heterogeneity, Arctic ecosystems and the trophic relationships that structure them have been severely perturbed. These rapid changes may be a bellwether of changes to come at lower latitudes and have the potential to affect ecosystem services related to natural resources, food production, climate regulation, and cultural integrity. We highlight areas of ecological research that deserve priority as the Arctic continues to warm.

CARVE: The Carbon in Arctic Reservoirs Vulnerability Experiment

NASA Technical Reports Server (NTRS)

Miller, Charles E.; Dinardo, Steven J.

2012-01-01

The Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) is a NASA Earth Ventures (EV-1) investigation designed to quantify correlations between atmospheric and surface state variables for the Alaskan terrestrial ecosystems through intensive seasonal aircraft campaigns, ground-based observations, and analysis sustained over a 5-year mission. CARVE bridges critical gaps in our knowledge and understanding of Arctic ecosystems, linkages between the Arctic hydrologic and terrestrial carbon cycles, and the feedbacks from fires and thawing permafrost. CARVE's objectives are to: (1) Directly test hypotheses attributing the mobilization of vulnerable Arctic carbon reservoirs to climate warming; (2) Deliver the first direct measurements and detailed maps of CO2 and CH4 sources on regional scales in the Alaskan Arctic; and (3) Demonstrate new remote sensing and modeling capabilities to quantify feedbacks between carbon fluxes and carbon cycle-climate processes in the Arctic (Figure 1). We describe the investigation design and results from 2011 test flights in Alaska.

The western arctic linkage experiment (WALE): overview and synthesis

Treesearch

A.D. McGuire; J. Walsh; J.S. Kimball; J.S. Clein; S.E. Euskirdhen; S. Drobot; U.C. Herzfeld; J. Maslanik; R.B. Lammers; M.A. Rawlins; C.J. Vorosmarty; T.S. Rupp; W. Wu; M. Calef

2008-01-01

The primary goal of the Western Arctic Linkage Experiment (WALE) was to better understand uncertainties of simulated hydrologic and ecosystem dynamics of the western Arctic in the context of 1) uncertainties in the data available to drive the models and 2) different approaches to simulating regional hydrology and ecosystem dynamics. Analyses of datasets on climate...

The Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE): Examining the complex Arctic biological-climatologic-hydrologic system

NASA Astrophysics Data System (ADS)

McDonald, K. C.; Podest, E.; Miller, C. E.; Dinardo, S. J.

2012-12-01

Fundamental aspects of the complex Arctic biological-climatologic-hydrologic system remain poorly quantified. As a result, significant uncertainties exist in the carbon budget of the Arctic ecosystem. NASA's Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) is a currently-operational Earth Venture 1 (EV-1) mission that is examining correlations between atmospheric and surface state variables for the Alaskan terrestrial ecosystems. CARVE is conducted through a series of intensive seasonal aircraft campaigns, ground-based observations, and analysis sustained over a 5-year mission timeframe. CARVE employs a C-23 Sherpa aircraft to fly an innovative airborne remote sensing payload. This payload includes an L-band radiometer/radar system and a nadir-viewing spectrometer to deliver simultaneous measurements of land surface state variables that control gas emissions (i.e., soil moisture and inundation, freeze/thaw state, surface temperature) and total atmospheric columns of carbon dioxide, methane, and carbon monoxide. The aircraft payload also includes a gas analyzer that links greenhouse gas measurements directly to World Meteorological Organization standards and provide vertical profile information. CARVE measurement campaigns are scheduled regularly throughout the growing season each year to capture the seasonal variability in Arctic system carbon fluxes associated with the spring thaw, the summer drawdown, and the fall refreeze. Continuous ground-based measurements provide temporal and regional context as well as calibration for CARVE airborne measurements. CARVE bridges critical gaps in our knowledge and understanding of Arctic ecosystems, linkages between the Arctic hydrologic and terrestrial carbon cycles, and the feedbacks from fires and thawing permafrost. Ultimately, CARVE will provide an integrated set of data that will provide unprecedented experimental insights into Arctic carbon cycling. Portions of this work were carried out at the Jet

Warming increases methylmercury production in an Arctic soil

DOE PAGES

Yang, Ziming; Fang, Wei; Lu, Xia; ...

2016-04-29

The rapid temperature rise in Arctic permafrost concerns not only the degradation of stored soil organic carbon (SOC) and climate feedback, but also the production and bioaccumulation of methylmercury (MeHg) that may endanger humans, as well as wildlife in terrestrial, aquatic, and marine ecosystems. Decomposition of SOC provides an energy source for microbial methylation, although little is known how rapid permafrost thaw affects Hg methylation and how SOC degradation is coupled to MeHg biosynthesis. We describe rates of MeHg production in Arctic soils from an 8-month warming microcosm experiment under anoxic conditions. MeHg production increased >10 fold in both organic-more » and the mineral-rich soil layers at a warmer temperature (8 C) compared to a sub-zero temperature ( 2 C). MeHg production was positively correlated to methane and ferrous ion concentrations, suggesting that Hg methylation is coupled with methanogenesis and iron reduction. Labile SOC, such as reducing sugars and alcohol, were particularly effective in fueling the initial rapid biosynthesis of MeHg. In freshly amended Hg we found that there was more bioavailable than existing Hg in the mineral soil. Finally, the data indicate that climate warming and permafrost thaw could greatly enhance MeHg production, thereby impacting Arctic aquatic and marine ecosystems through biomagnification in the food web.« less

Chamber and Diffusive Based Carbon Flux Measurements in an Alaskan Arctic Ecosystem

NASA Astrophysics Data System (ADS)

Wilkman, E.; Oechel, W. C.; Zona, D.

2013-12-01

Eric Wilkman, Walter Oechel, Donatella Zona Comprising an area of more than 7 x 106 km2 and containing over 11% of the world's organic matter pool, Arctic terrestrial ecosystems are vitally important components of the global carbon cycle, yet their structure and functioning are sensitive to subtle changes in climate and many of these functional changes can have large effects on the atmosphere and future climate regimes (Callaghan & Maxwell 1995, Chapin et al. 2002). Historically these northern ecosystems have acted as strong C sinks, sequestering large stores of atmospheric C due to photosynthetic dominance in the short summer season and low rates of decomposition throughout the rest of the year as a consequence of cold, nutrient poor, and generally water-logged conditions. Currently, much of this previously stored carbon is at risk of loss to the atmosphere due to accelerated soil organic matter decomposition in warmer future climates (Grogan & Chapin 2000). Although there have been numerous studies on Arctic carbon dynamics, much of the previous soil flux work has been done at limited time intervals, due to both the harshness of the environment and labor and time constraints. Therefore, in June of 2013 an Ultraportable Greenhouse Gas Analyzer (UGGA - Los Gatos Research Inc.) was deployed in concert with the LI-8100A Automated Soil Flux System (LI-COR Biosciences) in Barrow, AK to gather high temporal frequency soil CO2 and CH4 fluxes from a wet sedge tundra ecosystem. An additional UGGA in combination with diffusive probes, installed in the same location, provides year-round soil and snow CO2 and CH4 concentrations. When used in combination with the recently purchased AlphaGUARD portable radon monitor (Saphymo GmbH), continuous soil and snow diffusivities and fluxes of CO2 and CH4 can be calculated (Lehmann & Lehmann 2000). Of particular note, measuring soil gas concentration over a diffusive gradient in this way allows one to separate both net production and

Improving coordination and integration of observations of Arctic change

NASA Astrophysics Data System (ADS)

Perovich, Donald; Payne, John; Eicken, Hajo

2012-10-01

U.S. Arctic Observing Coordination Workshop;Anchorage, Alaska, 20-22 March 2012 The Arctic is undergoing tremendous changes. Permafrost is thawing, ice sheets are melting, and sea ice is thinning and retreating. These changes are impacting ecosystems and human activities. Observing, understanding, and responding to these changes are the central themes of the U.S. Interagency Study of Environmental Arctic Change (SEARCH, http://www.arcus.org/search/index.php). SEARCH brings together academic and government agency scientists and stakeholders to prioritize, plan, conduct, and synthesize research focused on Arctic environmental change. The U.S. Arctic Observing Coordination Workshop (http://www.arcus.org/search/meetings/2012/coordination-workshop/) focused on two key themes for cross-disciplinary and cross-agency collaboration: (1) understanding and predicting sea ice changes and their consequences for ecosystems, human activities, and climate and (2) determining consequences of loss and warming of shallow permafrost on Arctic and global systems.

Ecological dynamics across the Arctic associated with recent climate change

Treesearch

Eric Post; Mads C. Forchhammer; M. Syndonia Bret-Harte; Terry V. Callaghan; Torben R. Christensen; Bo Elberling; Anthony D. Fox; Olivier Gilg; David S. Hik; Toke T. Høye; Rolf A. Ims; Erik Jeppesen; David R. Klein; Jesper Madsen; A. David McGuire; Søren Rysgaard; Daniel E. Schindler; Ian Stirling; Mikkel P. Tamstorf; Nicholas J.C. Tyler; Rene van der Wal; Jeffrey Welker; Philip A. Wookey; Niels Martin Schmidt; Peter Aastrup

2009-01-01

At the close of the Fourth International Polar Year, we take stock of the ecological consequences of recent climate change in the Arctic, focusing on effects at population, community, and ecosystem scales. Despite the buffering effect of landscape heterogeneity, Arctic ecosystems and the trophic relationships that structure them have been severely perturbed. These...

Exploratory Hydrocarbon Drilling Impacts to Arctic Lake Ecosystems

PubMed Central

Thienpont, Joshua R.; Kokelj, Steven V.; Korosi, Jennifer B.; Cheng, Elisa S.; Desjardins, Cyndy; Kimpe, Linda E.; Blais, Jules M.; Pisaric, Michael FJ.; Smol, John P.

2013-01-01

potential for these industrial wastes to impact sensitive Arctic ecosystems. PMID:24223170

Exploratory hydrocarbon drilling impacts to Arctic lake ecosystems.

PubMed

Thienpont, Joshua R; Kokelj, Steven V; Korosi, Jennifer B; Cheng, Elisa S; Desjardins, Cyndy; Kimpe, Linda E; Blais, Jules M; Pisaric, Michael F J; Smol, John P

2013-01-01

potential for these industrial wastes to impact sensitive Arctic ecosystems.

Tipping points in the arctic: eyeballing or statistical significance?

PubMed

Carstensen, Jacob; Weydmann, Agata

2012-02-01

Arctic ecosystems have experienced and are projected to experience continued large increases in temperature and declines in sea ice cover. It has been hypothesized that small changes in ecosystem drivers can fundamentally alter ecosystem functioning, and that this might be particularly pronounced for Arctic ecosystems. We present a suite of simple statistical analyses to identify changes in the statistical properties of data, emphasizing that changes in the standard error should be considered in addition to changes in mean properties. The methods are exemplified using sea ice extent, and suggest that the loss rate of sea ice accelerated by factor of ~5 in 1996, as reported in other studies, but increases in random fluctuations, as an early warning signal, were observed already in 1990. We recommend to employ the proposed methods more systematically for analyzing tipping points to document effects of climate change in the Arctic.

Climate Change in the North American Arctic: A One Health Perspective.

PubMed

Dudley, Joseph P; Hoberg, Eric P; Jenkins, Emily J; Parkinson, Alan J

2015-12-01

Climate change is expected to increase the prevalence of acute and chronic diseases among human and animal populations within the Arctic and subarctic latitudes of North America. Warmer temperatures are expected to increase disease risks from food-borne pathogens, water-borne diseases, and vector-borne zoonoses in human and animal populations of Arctic landscapes. Existing high levels of mercury and persistent organic pollutant chemicals circulating within terrestrial and aquatic ecosystems in Arctic latitudes are a major concern for the reproductive health of humans and other mammals, and climate warming will accelerate the mobilization and biological amplification of toxic environmental contaminants. The adverse health impacts of Arctic warming will be especially important for wildlife populations and indigenous peoples dependent upon subsistence food resources from wild plants and animals. Additional research is needed to identify and monitor changes in the prevalence of zoonotic pathogens in humans, domestic dogs, and wildlife species of critical subsistence, cultural, and economic importance to Arctic peoples. The long-term effects of climate warming in the Arctic cannot be adequately predicted or mitigated without a comprehensive understanding of the interactive and synergistic effects between environmental contaminants and pathogens in the health of wildlife and human communities in Arctic ecosystems. The complexity and magnitude of the documented impacts of climate change on Arctic ecosystems, and the intimacy of connections between their human and wildlife communities, makes this region an appropriate area for development of One Health approaches to identify and mitigate the effects of climate warming at the community, ecosystem, and landscape scales.

Amplified Arctic warming by phytoplankton under greenhouse warming.

PubMed

Park, Jong-Yeon; Kug, Jong-Seong; Bader, Jürgen; Rolph, Rebecca; Kwon, Minho

2015-05-12

Phytoplankton have attracted increasing attention in climate science due to their impacts on climate systems. A new generation of climate models can now provide estimates of future climate change, considering the biological feedbacks through the development of the coupled physical-ecosystem model. Here we present the geophysical impact of phytoplankton, which is often overlooked in future climate projections. A suite of future warming experiments using a fully coupled ocean-atmosphere model that interacts with a marine ecosystem model reveals that the future phytoplankton change influenced by greenhouse warming can amplify Arctic surface warming considerably. The warming-induced sea ice melting and the corresponding increase in shortwave radiation penetrating into the ocean both result in a longer phytoplankton growing season in the Arctic. In turn, the increase in Arctic phytoplankton warms the ocean surface layer through direct biological heating, triggering additional positive feedbacks in the Arctic, and consequently intensifying the Arctic warming further. Our results establish the presence of marine phytoplankton as an important potential driver of the future Arctic climate changes.

Amplified Arctic warming by phytoplankton under greenhouse warming

PubMed Central

Park, Jong-Yeon; Kug, Jong-Seong; Bader, Jürgen; Rolph, Rebecca; Kwon, Minho

2015-01-01

Phytoplankton have attracted increasing attention in climate science due to their impacts on climate systems. A new generation of climate models can now provide estimates of future climate change, considering the biological feedbacks through the development of the coupled physical–ecosystem model. Here we present the geophysical impact of phytoplankton, which is often overlooked in future climate projections. A suite of future warming experiments using a fully coupled ocean−atmosphere model that interacts with a marine ecosystem model reveals that the future phytoplankton change influenced by greenhouse warming can amplify Arctic surface warming considerably. The warming-induced sea ice melting and the corresponding increase in shortwave radiation penetrating into the ocean both result in a longer phytoplankton growing season in the Arctic. In turn, the increase in Arctic phytoplankton warms the ocean surface layer through direct biological heating, triggering additional positive feedbacks in the Arctic, and consequently intensifying the Arctic warming further. Our results establish the presence of marine phytoplankton as an important potential driver of the future Arctic climate changes. PMID:25902494

Black-legged kittiwakes as messengers of Atlantification in the Arctic.

PubMed

Vihtakari, Mikko; Welcker, Jorg; Moe, Børge; Chastel, Olivier; Tartu, Sabrina; Hop, Haakon; Bech, Claus; Descamps, Sébastien; Gabrielsen, Geir Wing

2018-01-19

Climate warming is rapidly altering marine ecosystems towards a more temperate state on the European side of the Arctic. However, this "Atlantification" has rarely been confirmed, as long-term datasets on Arctic marine organisms are scarce. We present a 19-year time series (1982-2016) of diet samples from black-legged kittiwakes as an indicator of the changes in a high Arctic marine ecosystem (Kongsfjorden, Svalbard). Our results highlight a shift from Arctic prey dominance until 2006 to a more mixed diet with high contribution of Atlantic fishes. Capelin, an Atlantic species, dominated the diet composition in 2007, marking a shift in the food web. The occurrence of polar cod, a key Arctic fish species, positively correlated with sea ice index, whereas Atlantic species demonstrated the opposite correlation indicating that the diet shift was likely connected with recent climate warming. Kittiwakes, which gather available fish and zooplankton near the sea surface to feed their chicks, can act as messengers of ecosystem change. Changes in their diet reveal that the Kongsfjord system has drifted in an Atlantic direction over the last decade.

Remote sensing of vegetation and land-cover change in Arctic Tundra Ecosystems

USGS Publications Warehouse

Stow, Douglas A.; Hope, Allen; McGuire, David; Verbyla, David; Gamon, John A.; Huemmrich, Fred; Houston, Stan; Racine, Charles H.; Sturm, Matthew; Tape, Ken D.; Hinzman, Larry D.; Yoshikawa, Kenji; Tweedie, Craig E.; Noyle, Brian; Silapaswan, Cherie; Douglas, David C.; Griffith, Brad; Jia, Gensuo; Howard E. Epstein,; Walker, Donald A.; Daeschner, Scott; Petersen, Aaron; Zhou, Liming; Myneni, Ranga B.

2004-01-01

The objective of this paper is to review research conducted over the past decade on the application of multi-temporal remote sensing for monitoring changes of Arctic tundra lands. Emphasis is placed on results from the National Science Foundation Land–Air–Ice Interactions (LAII) program and on optical remote sensing techniques. Case studies demonstrate that ground-level sensors on stationary or moving track platforms and wide-swath imaging sensors on polar orbiting satellites are particularly useful for capturing optical remote sensing data at sufficient frequency to study tundra vegetation dynamics and changes for the cloud prone Arctic. Less frequent imaging with high spatial resolution instruments on aircraft and lower orbiting satellites enable more detailed analyses of land cover change and calibration/validation of coarser resolution observations.The strongest signals of ecosystem change detected thus far appear to correspond to expansion of tundra shrubs and changes in the amount and extent of thaw lakes and ponds. Changes in shrub cover and extent have been documented by modern repeat imaging that matches archived historical aerial photography. NOAA Advanced Very High Resolution Radiometer (AVHRR) time series provide a 20-year record for determining changes in greenness that relates to photosynthetic activity, net primary production, and growing season length. The strong contrast between land materials and surface waters enables changes in lake and pond extent to be readily measured and monitored.

Organic N cycling in Arctic ecosystems: Quantifying root uptake kinetics and temporal variability of soil amino acids.

NASA Astrophysics Data System (ADS)

Homyak, P. M.; Iverson, S. L.; Slessarev, E.; Marchus, K.; Schimel, J.

2017-12-01

Arctic ecosystems are undergoing shifts in plant community composition with increased warming. How these changes may alter ecosystem function is not well constrained, owing in part to uncertainties on how plant-soil feedbacks influence nutrient cycling. For nitrogen (N), in particular, understanding how these feedbacks may alter cycling rates is challenging because i) Arctic plants take up organic N (i.e., amino acids; AA) when inorganic N is limiting, yet ii) it has never been quantified, for any plant species growing in the wild, how much of its N demand is actually met by taking up AA. To advance fundamental understanding of plant-soil feedbacks as the Arctic warms, we are integrating field measurements of AA availability in N-limited tussock tundra (E. vaginatum) and a comparably less N-limited birch shrub tundra (Betula nana and Salix spp.) with a root uptake model. We used soil microdialysis to determine available AA concentrations in the soil solution and potential rates of AA diffusion and mass flow to roots at the Toolik Field Station in Alaska. These measurements are being combined with AA root uptake kinetic experiments using E. vaginatum to establish actual AA root uptake rates. We found that in the early growing season (June), total AA concentrations in the soil solution averaged 104 µg N L-1 and were similar to NH4+ across sites. In the late growing season (August), AA were the dominant form of N averaging 75 µg N L-1 while NH4+ decreased to 13 µg N L-1. In the early growing season AA diffusion rates in the soil averaged 200 ng N cm-2 s-1 and declined to 150 ng N cm-2 s-1 in the late growing season. Lysine, serine, and arginine were the most abundant AA and differences in the N status of sites did not affect total AA concentrations. Amino acids made up at least half of the N diffusing through the soil solution, suggesting they can subsidize the N demand of arctic plants. Ongoing field experiments at Toolik will be used to constrain actual AA root

Arctic-COLORS (Coastal Land Ocean Interactions in the Arctic) - a NASA field campaign scoping study to examine land-ocean interactions in the Arctic

NASA Astrophysics Data System (ADS)

Hernes, P.; Tzortziou, M.; Salisbury, J.; Mannino, A.; Matrai, P.; Friedrichs, M. A.; Del Castillo, C. E.

2014-12-01

The Arctic region is warming faster than anywhere else on the planet, triggering rapid social and economic changes and impacting both terrestrial and marine ecosystems. Yet our understanding of critical processes and interactions along the Arctic land-ocean interface is limited. Arctic-COLORS is a Field Campaign Scoping Study funded by NASA's Ocean Biology and Biogeochemistry Program that aims to improve understanding and prediction of land-ocean interactions in a rapidly changing Arctic coastal zone, and assess vulnerability, response, feedbacks and resilience of coastal ecosystems, communities and natural resources to current and future pressures. Specific science objectives include: - Quantify lateral fluxes to the arctic inner shelf from (i) rivers and (ii) the outer shelf/basin that affect biology, biodiversity, biogeochemistry (i.e. organic matter, nutrients, suspended sediment), and the processing rates of these constituents in coastal waters. - Evaluate the impact of the thawing of Arctic permafrost within the river basins on coastal biology, biodiversity and biogeochemistry, including various rates of community production and the role these may play in the health of regional economies. - Assess the impact of changing Arctic landfast ice and coastal sea ice dynamics. - Establish a baseline for comparison to future change, and use state-of-the-art models to assess impacts of environmental change on coastal biology, biodiversity and biogeochemistry. A key component of Arctic-COLORS will be the integration of satellite and field observations with coupled physical-biogeochemical models for predicting impacts of future pressures on Arctic, coastal ocean, biological processes and biogeochemical cycles. Through interagency and international collaborations, and through the organization of dedicated workshops, town hall meetings and presentations at international conferences, the scoping study engages the broader scientific community and invites participation of

Biogeochemistry and nitrogen cycling in an Arctic, volcanic ecosystem

NASA Astrophysics Data System (ADS)

Fogel, M. L.; Benning, L.; Conrad, P. G.; Eigenbrode, J.; Starke, V.

2007-12-01

As part of a study on Mars Analogue environments, the biogeochemistry of Sverrefjellet Volcano, Bocfjorden, Svalbard, was conducted and compared to surrounding glacial, thermal spring, and sedimentary environments. An understanding of how nitrogen might be distributed in a landscape that had extinct or very cold adapted, slow- growing extant organisms should be useful for detecting unknown life forms. From high elevations (900 m) to the base of the volcano (sea level), soil and rock ammonium concentrations were uniformly low, typically less than 1- 3 micrograms per gm of rock or soil. In weathered volcanic soils, reduced nitrogen concentrations were higher, and oxidized nitrogen concentrations lower. The opposite was found in a weathered Devonian sedimentary soil. Plants and lichens growing on volcanic soils have an unusually wide range in N isotopic compositions from -5 to +12‰, a range rarely measured in temperate ecosystems. Nitrogen contents and isotopic compositions of volcanic soils and rocks were strongly influenced by the presence or absence of terrestrial herbivores or marine avifauna with higher concentrations of N and elevated N isotopic compositions occurring as patches in areas immediately influenced by reindeer, Arctic fox ( Alopex lagopus), and marine birds. Because of the extreme conditions in this area, ephemeral deposition of herbivore feces results in a direct and immediate N pulses into the ecosystem. The lateral extent and distribution of marine- derived nitrogen was measured on a landscape scale surrounding an active fox den. Nitrogen was tracked from the bones of marine birds to soil to vegetation. Because of extreme cold, slow biological rates and nitrogen cycling, a mosaic of N patterns develops on the landscape scale.

Status and trends in Arctic biodiversity - Synthesis: implications for conservation

USDA-ARS?s Scientific Manuscript database

Arctic biodiversity – the multitude of species and ecosystems in the land north of the tree line together with the Arctic Ocean and adjacent seas – is an irreplaceable cultural, aesthetic, scientific, ecological, economic and spiritual asset. For Arctic peoples, biodiversity has been the very basis ...

Improving the Characterization of Arctic Coastline Ecosystem Change near Utqiagvik, Alaska Utilizing Multiyear Terrestrial Laser Scanning

NASA Astrophysics Data System (ADS)

Escarzaga, S. M.; Cody, R. P.; Vargas, S. A., Jr.; Fuson, T.; Hodge, B. E.; Tweedie, C. E.

2017-12-01

The Arctic Ocean comprises the largest coastline on Earth and is undergoing environmental change on a level disproportionate to those in lower-latitudes. In the US Arctic, coastal erosion rates along the North Slope of Alaska show that they are among highest in the nation at an average rate of 1.4 meters per year. Despite their importance to biogeochemical cycling, Native village infrastructure and providing pristine species habitat, Arctic coastlines and near shore environments are relatively understudied due to logistical challenges of conducting fieldwork in these locations. This study expands on past efforts which showed dGPS foot surveys work well at describing planar erosion on less complex permafrost bluff types like those seen on the higher-energy coasts east of Utqiagvik, Alaska along the Beaufort Sea where the main mechanism of erosion happens by block failure caused by wave action. However, coastal bluffs along the Chukchi Sea to the west are more complex and variable in terms of form and mechanisms of erosion. Here, where wide beaches tend to buffer wave action, thermal erosion and permafrost slumping produce slower erosion rates. Terrestrial Laser Scanning (TLS) has been applied across a multitude of terrain types, including coastlines spanning various ecosystems. Additionally, this approach allows 3D modeling of fine scale geomorphological features which can facilitate modeling of erosion rates in these areas. This study utilizes a six year time series of TLS on a section of coastal permafrost bluff along the Chukchi Sea south of Utqiagvik. The aim of the work presented is to better understand spatio-temporal trends of coastal bluff face erosion, bluff top subsidence and how these landscape microtopographic changes are coupled to ecosystem changes and land cover types. Preliminary analysis suggests a high rate of stability of the bluff face over the TLS record with most of the detectable permafrost subsidence happening closer to the coastal bluff edge.

Practical Strategies for Integrating Final Ecosystem Goods and ...

EPA Pesticide Factsheets

The concept of Final Ecosystem Goods and Services (FEGS) explicitly connects ecosystem services to the people that benefit from them. This report presents a number of practical strategies for incorporating FEGS, and more broadly ecosystem services, into the decision-making process. Whether a decision process is in early or late stages, or whether a process includes informal or formal decision analysis, there are multiple points where ecosystem services concepts can be integrated. This report uses Structured Decision Making (SDM) as an organizing framework to illustrate the role ecosystem services can play in a values-focused decision-process, including: • Clarifying the decision context: Ecosystem services can help clarify the potential impacts of an issue on natural resources together with their spatial and temporal extent based on supply and delivery of those services, and help identify beneficiaries for inclusion as stakeholders in the deliberative process. • Defining objectives and performance measures: Ecosystem services may directly represent stakeholder objectives, or may be means toward achieving other objectives. • Creating alternatives: Ecosystem services can bring to light creative alternatives for achieving other social, economic, health, or general well-being objectives. • Estimating consequences: Ecosystem services assessments can implement ecological production functions (EPFs) and ecological benefits functions (EBFs) to link decision alt

Soil Carbon Inputs and Ecosystem Respiration: a Field Priming Experiment in Arctic Coastal Tundra

NASA Astrophysics Data System (ADS)

Vaughn, L. S.; Zhu, B.; Bimueller, C.; Curtis, J. B.; Chafe, O.; Bill, M.; Abramoff, R. Z.; Torn, M. S.

2016-12-01

In Arctic ecosystems, climate change is expected to influence soil carbon stocks through changes in both plant carbon inputs and organic matter decomposition. This study addresses the potential for a priming effect, an interaction between these changes in which root-derived carbon inputs alter SOM decomposition rates via microbial biomass increases, co-metabolism of substrates, induced nitrogen limitation, or other possible mechanisms. The priming effect has been observed in numerous laboratory and greenhouse experiments, and is increasingly included in ecosystem models. Few studies, however, have evaluated the priming effect with in situ field manipulations. In a two-year field experiment in Barrow, Alaska, we tested for a priming effect under natural environmental variability. In September 2014 and August 2015, we added 6.1g of 13C-labeled glucose to 25cm diameter mesocosms, 15cm below the soil surface in the mineral soil layer. Over the following month, we quantified effects on the rate and temperature sensitivity of native (non-glucose) ecosystem respiration and GPP. Following the 2014 treatment, soil samples were collected at 1 and 3 weeks for microbial biomass carbon and 13C/12C analysis, and ion exchange membranes were buried for one week to assess nitrate and ammonium availability. In contrast with many laboratory incubation studies using soils from a broad range of ecosystems, we observed no significant priming effect. In spite of a clear signal of 13C-glucose decomposition in respired CO2 and microbial biomass, we detected no treatment effect on background ecosystem respiration or total microbial biomass carbon. Our findings suggest that glucose taken up by microbes was not used for production of additional SOM-decomposing enzymes, possibly due to stoichiometric limitations on enzyme production. To best inform models representing complex and dynamic ecosystems, this study calls for further research relating theory, laboratory findings, and field

USGS Arctic Science Strategy

USGS Publications Warehouse

Shasby, Mark; Smith, Durelle

2015-07-17

The United States is one of eight Arctic nations responsible for the stewardship of a polar region undergoing dramatic environmental, social, and economic changes. Although warming and cooling cycles have occurred over millennia in the Arctic region, the current warming trend is unlike anything recorded previously and is affecting the region faster than any other place on Earth, bringing dramatic reductions in sea ice extent, altered weather, and thawing permafrost. Implications of these changes include rapid coastal erosion threatening villages and critical infrastructure, potentially significant effects on subsistence activities and cultural resources, changes to wildlife habitat, increased greenhouse-gas emissions from thawing permafrost, threat of invasive species, and opening of the Arctic Ocean to oil and gas exploration and increased shipping. The Arctic science portfolio of the U.S. Geological Survey (USGS) and its response to climate-related changes focuses on landscapescale ecosystem and natural resource issues and provides scientific underpinning for understanding the physical processes that shape the Arctic. The science conducted by the USGS informs the Nation's resource management policies and improves the stewardship of the Arctic Region.

Ice Shelf Microbial Ecosystems in the High Arctic and Implications for Life on Snowball Earth

NASA Astrophysics Data System (ADS)

Vincent, W. F.; Gibson, J. A. E.; Pienitz, R.; Villeneuve, V.; Broady, P. A.; Hamilton, P. B.; Howard-Williams, C.

The Ward Hunt Ice Shelf (83°N, 74°W) is the largest remaining section of thick (>10m) landfast sea ice along the northern coastline of Ellesmere Island, Canada. Extensive meltwater lakes and streams occur on the surface of the ice and are colonized by photosynthetic microbial mat communities. This High Arctic cryo-ecosystem is similar in several of its physical, biological and geochemical features to the McMurdo Ice Shelf in Antarctica. The ice-mats in both polar regions are dominated by filamentous cyanobacteria but also contain diatoms, chlorophytes, flagellates, ciliates, nematodes, tardigrades and rotifers. The luxuriant Ward Hunt consortia also contain high concentrations (107-108cm-2) of viruses and heterotrophic bacteria. During periods of extensive ice cover, such as glaciations during the Proterozoic, cryotolerant mats of the type now found in these polar ice shelf ecosystems would have provided refugia for the survival, growth and evolution of a variety of organisms, including multicellular eukaryotes.

Mammalian herbivores confer resilience of Arctic shrub-dominated ecosystems to changing climate.

PubMed

Kaarlejärvi, Elina; Hoset, Katrine S; Olofsson, Johan

2015-09-01

Climate change is resulting in a rapid expansion of shrubs in the Arctic. This expansion has been shown to be reinforced by positive feedbacks, and it could thus set the ecosystem on a trajectory toward an alternate, more productive regime. Herbivores, on the other hand, are known to counteract the effects of simultaneous climate warming on shrub biomass. However, little is known about the impact of herbivores on resilience of these ecosystems, that is, the capacity of a system to absorb disturbance and still remain in the same regime, retaining the same function, structure, and feedbacks. Here, we investigated how herbivores affect resilience of shrub-dominated systems to warming by studying the change of shrub biomass after a cessation of long-term experimental warming in a forest-tundra ecotone. As predicted, warming increased the biomass of shrubs, and in the absence of herbivores, shrub biomass in tundra continued to increase 4 years after cessation of the artificial warming, indicating that positive effects of warming on plant growth may persist even over a subsequent colder period. Herbivores contributed to the resilience of these systems by returning them back to the original low-biomass regime in both forest and tundra habitats. These results support the prediction that higher shrub biomass triggers positive feedbacks on soil processes and microclimate, which enable maintaining the rapid shrub growth even in colder climates. Furthermore, the results show that in our system, herbivores facilitate the resilience of shrub-dominated ecosystems to climate warming. © 2015 John Wiley & Sons Ltd.

Arctic and boreal ecosystems of western North America as components of the climate system

USGS Publications Warehouse

Chapin, F. S.; McGuire, A.D.; Randerson, J.; Pielke, R.; Baldocchi, D.; Hobbie, S.E.; Roulet, Nigel; Eugster, W.; Kasischke, E.; Rastetter, E.B.; Zimov, S.A.; Running, S.W.

2000-01-01

Synthesis of results from several Arctic and boreal research programmes provides evidence for the strong role of high-latitude ecosystems in the climate system. Average surface air temperature has increased 0.3??C per decade during the twentieth century in the western North American Arctic and boreal forest zones. Precipitation has also increased, but changes in soil moisture are uncertain. Disturbance rates have increased in the boreal forest; for example, there has been a doubling of the area burned in North America in the past 20 years. The disturbance regime in tundra may not have changed. Tundra has a 3-6-fold higher winter albedo than boreal forest, but summer albedo and energy partitioning differ more strongly among ecosystems within either tundra or boreal forest than between these two biomes. This indicates a need to improve our understanding of vegetation dynamics within, as well as between, biomes. If regional surface warming were to continue, changes in albedo and energy absorption would likely act as a positive feedback to regional warming due to earlier melting of snow and, over the long term, the northward movement of treeline. Surface drying and a change in dominance from mosses to vascular plants would also enhance sensible heat flux and regional warming in tundra. In the boreal forest of western North America, deciduous forests have twice the albedo of conifer forests in both winter and summer, 50-80% higher evapotranspiration, and therefore only 30-50% of the sensible heat flux of conifers in summer. Therefore, a warming-induced increase in fire frequency that increased the proportion of deciduous forests in the landscape, would act as a negative feedback to regional warming. Changes in thermokarst and the aerial extent of wetlands, lakes, and ponds would alter high-latitude methane flux. There is currently a wide discrepancy among estimates of the size and direction of CO2 flux between high-latitude ecosystems and the atmosphere. These

The initiation and development of small peat-forming ecosystems adjacent to lakes in the north central Canadian low arctic during the Holocene

NASA Astrophysics Data System (ADS)

Camill, Philip; Umbanhowar, Charles E.; Geiss, Christoph; Edlund, Mark B.; Hobbs, Will O.; Dupont, Allison; Doyle-Capitman, Catherine; Ramos, Matthew

2017-07-01

Small peat-forming ecosystems in arctic landscapes may play a significant role in the regional biogeochemistry of high-latitude systems, yet they are understudied compared to arctic uplands and other major peat-forming regions of the North. We present a new data set of 25 radiocarbon-dated permafrost peat cores sampled around eight low arctic lake sites in northern Manitoba (Canada) to examine the timing of peat initiation and controls on peat accumulation throughout the Holocene. We used macrofossils and charcoal to characterize changes in the plant community and fire, and we explored potential impacts of these local factors, as well as regional climatic change, on rates of C accumulation and C stocks. Peat initiation was variable across and within sites, suggesting the influence of local topography, but 56% of the cores initiated after 3000 B.P. Most cores initiated and remained as drier bog hummock communities, with few vegetation transitions in this landscape. C accumulation was relatively slow and did not appear to be correlated with Holocene-scale climatic variability, but C stocks in this landscape were substantial (mean = 45.4 kg C m-2), potentially accounting for 13.2 Pg C in the Taiga Shield ecozone. To the extent that small peat-forming systems are underrepresented in peatland mapping, soil organic carbon (SOC) stocks may be underestimated in arctic regions. Mean fire severity appeared to be negatively correlated with C accumulation rates. Initiation and accumulation of soil C may respond to both regional and local factors, and substantial lowland soil C stocks have the potential for biogeochemical impacts on adjacent aquatic ecosystems.

SEARCH: Study of Environmental Arctic Change--A System-scale, Cross-disciplinary, Long-term Arctic Research Program

NASA Astrophysics Data System (ADS)

Wiggins, H. V.; Schlosser, P.; Loring, A. J.; Warnick, W. K.; Committee, S. S.

2008-12-01

The Study of Environmental Arctic Change (SEARCH) is a multi-agency effort to observe, understand, and guide responses to changes in the arctic system. Interrelated environmental changes in the Arctic are affecting ecosystems and living resources and are impacting local and global communities and economic activities. Under the SEARCH program, guided by the Science Steering Committee (SSC), the Interagency Program Management Committee (IPMC), and the Observing, Understanding, and Responding to Change panels, scientists with a variety of expertise--atmosphere, ocean and sea ice, hydrology and cryosphere, terrestrial ecosystems, human dimensions, and paleoclimatology--work together to achieve goals of the program. Over 150 projects and activities contribute to SEARCH implementation. The Observing Change component is underway through National Science Foundation's (NSF) Arctic Observing Network (AON), NOAA-sponsored atmospheric and sea ice observations, and other relevant national and international efforts, including the EU- sponsored Developing Arctic Modelling and Observing Capabilities for Long-term Environmental Studies (DAMOCLES) Program. The Understanding Change component of SEARCH consists of modeling and analysis efforts, with strong linkages to relevant programs such as NSF's Arctic System Synthesis (ARCSS) Program. The Responding to Change element is driven by stakeholder research and applications addressing social and economic concerns. As a national program under the International Study of Arctic Change (ISAC), SEARCH is also working to expand international connections in an effort to better understand the global arctic system. SEARCH is sponsored by eight (8) U.S. agencies, including: the National Science Foundation (NSF), the National Oceanic and Atmospheric Administration (NOAA), the National Aeronautics and Space Administration (NASA), the Department of Defense (DOD), the Department of Energy (DOE), the Department of the Interior (DOI), the Smithsonian

Design and Development of a Spectral Library for Different Vegetation and Landcover Types for Arctic, Antarctic and Chihuahua Desert Ecosystem

NASA Astrophysics Data System (ADS)

Matharasi, K.; Goswami, S.; Gamon, J.; Vargas, S.; Marin, R.; Lin, D.; Tweedie, C. E.

2008-12-01

All objects on the Earth's surface absorb and reflect portions of the electromagnetic spectrum. Depending on the composition of the material, every material has its characteristic spectral profile. The characteristic spectral profile for vegetation is often used to study how vegetation patterns at large spatial scales affect ecosystem structure and function. Analysis of spectroscopic data from the laboratory, and from various other platforms like aircraft or spacecraft, requires a knowledge base that consists of different characteristic spectral profiles for known different materials. This study reports on establishment of an online and searchable spectral library for a range of plant species and landcover types in the Arctic, Anatarctic and Chihuahuan desert ecosystems. Field data were collected from Arctic Alaska, the Antarctic Peninsula and the Chihuahuan desert in the visible to near infrared (IR) range using a handheld portable spectrometer. The data have been archived in a database created using postgre sql with have been made publicly available on a plone web-interface. This poster describes the data collected in more detail and offers instruction to users who wish to make use of this free online resource.

Spatial and temporal variation of an ice-adapted predator's feeding ecology in a changing Arctic marine ecosystem.

PubMed

Yurkowski, David J; Ferguson, Steven H; Semeniuk, Christina A D; Brown, Tanya M; Muir, Derek C G; Fisk, Aaron T

2016-03-01

Spatial and temporal variation can confound interpretations of relationships within and between species in terms of diet composition, niche size, and trophic position (TP). The cause of dietary variation within species is commonly an ontogenetic niche shift, which is a key dynamic influencing community structure. We quantified spatial and temporal variations in ringed seal (Pusa hispida) diet, niche size, and TP during ontogeny across the Arctic-a rapidly changing ecosystem. Stable carbon and nitrogen isotope analysis was performed on 558 liver and 630 muscle samples from ringed seals and on likely prey species from five locations ranging from the High to the Low Arctic. A modest ontogenetic diet shift occurred, with adult ringed seals consuming more forage fish (approximately 80 versus 60 %) and having a higher TP than subadults, which generally decreased with latitude. However, the degree of shift varied spatially, with adults in the High Arctic presenting a more restricted niche size and consuming more Arctic cod (Boreogadus saida) than subadults (87 versus 44 %) and adults at the lowest latitude (29 %). The TPs of adult and subadult ringed seals generally decreased with latitude (4.7-3.3), which was mainly driven by greater complexity in trophic structure within the zooplankton communities. Adult isotopic niche size increased over time, likely due to the recent circumpolar increases in subarctic forage fish distribution and abundance. Given the spatial and temporal variability in ringed seal foraging ecology, ringed seals exhibit dietary plasticity as a species, suggesting adaptability in terms of their diet to climate change.

Net Ecosystem Exchange of CO2 with Rapidly Changing High Arctic Landscapes

NASA Astrophysics Data System (ADS)

Emmerton, C. A.

2015-12-01

High Arctic landscapes are expansive and changing rapidly. However our understanding of their functional responses and potential to mitigate or enhance anthropogenic climate change is limited by few measurements. We collected eddy covariance measurements to quantify the net ecosystem exchange (NEE) of CO2 with polar semidesert and meadow wetland landscapes at the highest-latitude location measured to date (82°N). We coupled these rare data with ground and satellite vegetation production measurements (Normalized Difference Vegetation Index; NDVI) to evaluate the effectiveness of upscaling local to regional NEE. During the growing season, the dry polar semidesert landscape was a near zero sink of atmospheric CO2 (NEE: -0.3±13.5 g C m-2). A nearby meadow wetland accumulated over two magnitudes more carbon (NEE: -79.3±20.0 g C m-2) than the polar semidesert landscape, and was similar to meadow wetland NEE at much more southern latitudes. Polar semidesert NEE was most influenced by moisture, with wetter surface soils resulting in greater soil respiration and CO2 emissions. At the meadow wetland, soil heating enhanced plant growth, which in turn increased CO2 uptake. Our upscaling assessment found that polar semidesert NDVI measured on site was low (mean: 0.120-0.157) and similar to satellite measurements (mean: 0.155-0.163). However, weak plant growth resulted in poor satellite NDVI-NEE relationships and created challenges for remotely-detecting changes in the cycling of carbon on the polar semidesert landscape. The meadow wetland appeared more suitable to assess plant production and NEE via remote-sensing, however high Arctic wetland extent is constrained by topography to small areas that may be difficult to resolve with large satellite pixels. We predict that until summer precipitation and humidity increases substantially, climate-related changes of dry high Arctic landscapes may be restricted by poor soil moisture retention, and therefore have some inertia against

NGEE Arctic Webcam Photographs, Barrow Environmental Observatory, Barrow, Alaska

DOE Data Explorer

Bob Busey; Larry Hinzman

2012-04-01

The NGEE Arctic Webcam (PTZ Camera) captures two views of seasonal transitions from its generally south-facing position on a tower located at the Barrow Environmental Observatory near Barrow, Alaska. Images are captured every 30 minutes. Historical images are available for download. The camera is operated by the U.S. DOE sponsored Next Generation Ecosystem Experiments - Arctic (NGEE Arctic) project.

Pan-Arctic observations in GRENE Arctic Climate Change Research Project and its successor

NASA Astrophysics Data System (ADS)

Yamanouchi, Takashi

2016-04-01

We started a Japanese initiative - "Arctic Climate Change Research Project" - within the framework of the Green Network of Excellence (GRENE) Program, funded by the Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT), in 2011. This Project targeted understanding and forecasting "Rapid Change of the Arctic Climate System and its Global Influences." Four strategic research targets are set by the Ministry: 1. Understanding the mechanism of warming amplification in the Arctic; 2. Understanding the Arctic climate system for global climate and future change; 3. Evaluation of the impacts of Arctic change on the weather and climate in Japan, marine ecosystems and fisheries; 4. Projection of sea ice distribution and Arctic sea routes. Through a network of universities and institutions in Japan, this 5-year Project involves more than 300 scientists from 39 institutions and universities. The National Institute of Polar Research (NIPR) works as the core institute and The Japan Agency for Marine- Earth Science and Technology (JAMSTEC) joins as the supporting institute. There are 7 bottom up research themes approved: the atmosphere, terrestrial ecosystems, cryosphere, greenhouse gases, marine ecology and fisheries, sea ice and Arctic sea routes and climate modeling, among 22 applications. The Project will realize multi-disciplinal study of the Arctic region and connect to the projection of future Arctic and global climatic change by modeling. The project has been running since the beginning of 2011 and in those 5 years pan-Arctic observations have been carried out in many locations, such as Svalbard, Russian Siberia, Alaska, Canada, Greenland and the Arctic Ocean. In particular, 95 GHz cloud profiling radar in high precision was established at Ny-Ålesund, Svalbard, and intensive atmospheric observations were carried out in 2014 and 2015. In addition, the Arctic Ocean cruises by R/V "Mirai" (belonging to JAMSTEC) and other icebreakers belonging to other

Arctic Sea Ice

NASA Image and Video Library

2017-12-08

On July 12, 2011, crew from the U.S. Coast Guard Cutter Healy retrieved a canister dropped by parachute from a C-130, which brought supplies for some mid-mission fixes. The ICESCAPE mission, or "Impacts of Climate on Ecosystems and Chemistry of the Arctic Pacific Environment," is NASA's two-year shipborne investigation to study how changing conditions in the Arctic affect the ocean's chemistry and ecosystems. The bulk of the research takes place in the Beaufort and Chukchi seas in summer 2010 and 2011. Credit: NASA/Kathryn Hansen For updates on the five-week ICESCAPE voyage, visit the mission blog at: go.usa.gov/WwU NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Carbon cycling in high-latitude ecosystems

NASA Technical Reports Server (NTRS)

Townsend, Alan; Frolking, Stephen; Holland, Elizabeth

1992-01-01

The carbon-rich soils and peatlands of high-latitude ecosystems could substantially influence atmospheric concentrations of CO2 and CH4 in a changing climate. Currently, cold, often waterlogged conditions retard decomposition, and release of carbon back to the atmosphere may be further slowed by physical protection of organic matter in permafrost. As a result, many northern ecosystems accumulate carbon over time (Billings et al., 1982; Poole and Miller, 1982), and although such rates of accumulation are low, thousands of years of development have left Arctic ecosystems with an extremely high soil carbon content; Schlesinger's (1984) average value of 20.4 kg C/m(sup 2) leads to a global estimate of 163 x 10(exp 15) g C. All GCM simulations of a doubled CO2 climate predict the greatest warming to occur in the polar regions (Dickinson, 1986; Mitchell, 1989). Given the extensive northern carbon pools and the strong sensitivity of decomposition processes to temperature, even a slight warming of the soil could dramatically alter the carbon balance of Arctic ecosystems. If warming accelerates rates of decomposition more than rates of primary production, a sizeable additional accumulation of CO2 in the atmosphere could occur. Furthermore, CH4 produced in anaerobic soils and peatlands of the Arctic already composes a good percentage of the global efflux (Cicerone and Oremlund, 1988); if northern soils become warmer and wetter as a whole, CH4 emissions could dramatically rise. A robust understanding of the primary controls of carbon fluxes in Arctic ecosystems is critical. As a framework for a systematic examination of these controls, we discussed a conceptual model of regional-scale Arctic carbon turnover, including CH4 production, and based upon the Century soil organic matter model.

Carbon cycle uncertainty in the Alaskan Arctic

NASA Astrophysics Data System (ADS)

Fisher, J. B.; Sikka, M.; Oechel, W. C.; Huntzinger, D. N.; Melton, J. R.; Koven, C. D.; Ahlström, A.; Arain, A. M.; Baker, I.; Chen, J. M.; Ciais, P.; Davidson, C.; Dietze, M.; El-Masri, B.; Hayes, D.; Huntingford, C.; Jain, A.; Levy, P. E.; Lomas, M. R.; Poulter, B.; Price, D.; Sahoo, A. K.; Schaefer, K.; Tian, H.; Tomelleri, E.; Verbeeck, H.; Viovy, N.; Wania, R.; Zeng, N.; Miller, C. E.

2014-02-01

Climate change is leading to a disproportionately large warming in the high northern latitudes, but the magnitude and sign of the future carbon balance of the Arctic are highly uncertain. Using 40 terrestrial biosphere models for Alaska, we provide a baseline of terrestrial carbon cycle structural and parametric uncertainty, defined as the multi-model standard deviation (σ) against the mean (x\\bar) for each quantity. Mean annual uncertainty (σ/x\\bar) was largest for net ecosystem exchange (NEE) (-0.01± 0.19 kg C m-2 yr-1), then net primary production (NPP) (0.14 ± 0.33 kg C m-2 yr-1), autotrophic respiration (Ra) (0.09 ± 0.20 kg C m-2 yr-1), gross primary production (GPP) (0.22 ± 0.50 kg C m-2 yr-1), ecosystem respiration (Re) (0.23 ± 0.38 kg C m-2 yr-1), CH4 flux (2.52 ± 4.02 g CH4 m-2 yr-1), heterotrophic respiration (Rh) (0.14 ± 0.20 kg C m-2 yr-1), and soil carbon (14.0± 9.2 kg C m-2). The spatial patterns in regional carbon stocks and fluxes varied widely with some models showing NEE for Alaska as a strong carbon sink, others as a strong carbon source, while still others as carbon neutral. Additionally, a feedback (i.e., sensitivity) analysis was conducted of 20th century NEE to CO2 fertilization (β) and climate (γ), which showed that uncertainty in γ was 2x larger than that of β, with neither indicating that the Alaskan Arctic is shifting towards a certain net carbon sink or source. Finally, AmeriFlux data are used at two sites in the Alaskan Arctic to evaluate the regional patterns; observed seasonal NEE was captured within multi-model uncertainty. This assessment of carbon cycle uncertainties may be used as a baseline for the improvement of experimental and modeling activities, as well as a reference for future trajectories in carbon cycling with climate change in the Alaskan Arctic.

Arctic Research Plan: FY2017-2021

USGS Publications Warehouse

Starkweather, Sandy; Jeffries, Martin O; Stephenson, Simon; Anderson, Rebecca D.; Jones, Benjamin M.; Loehman, Rachel A.; von Biela, Vanessa R.

2016-01-01

The United States is an Arctic nation—Americans depend on the Arctic for biodiversity and climate regulation and for natural resources. America’s Arctic—Alaska—is at the forefront of rapid climate, environmental, and socio-economic changes that are testing the resilience and sustainability of communities and ecosystems. Research to increase fundamental understanding of these changes is needed to inform sound, science-based decision- and policy-making and to develop appropriate solutions for Alaska and the Arctic region as a whole. Created by an Act of Congress in 1984, and since 2010 a subcommittee of the National Science and Technology Council (NSTC) in the Executive Office of the President, the Interagency Arctic Research Policy Committee (IARPC) plays a critical role in advancing scientific knowledge and understanding of the changing Arctic and its impacts far beyond the boundaries of the Arctic. Comprising 14 Federal agencies, offices, and departments, IARPC is responsible for the implementation of a 5-year Arctic Research Plan in consultation with the U.S. Arctic Research Commission, the Governor of the State of Alaska, residents of the Arctic, the private sector, and public interest groups.

Toward Process-resolving Synthesis and Prediction of Arctic Climate Change Using the Regional Arctic System Model

NASA Astrophysics Data System (ADS)

Maslowski, W.

2017-12-01

The Regional Arctic System Model (RASM) has been developed to better understand the operation of Arctic System at process scale and to improve prediction of its change at a spectrum of time scales. RASM is a pan-Arctic, fully coupled ice-ocean-atmosphere-land model with marine biogeochemistry extension to the ocean and sea ice models. The main goal of our research is to advance a system-level understanding of critical processes and feedbacks in the Arctic and their links with the Earth System. The secondary, an equally important objective, is to identify model needs for new or additional observations to better understand such processes and to help constrain models. Finally, RASM has been used to produce sea ice forecasts for September 2016 and 2017, in contribution to the Sea Ice Outlook of the Sea Ice Prediction Network. Future RASM forecasts, are likely to include increased resolution for model components and ecosystem predictions. Such research is in direct support of the US environmental assessment and prediction needs, including those of the U.S. Navy, Department of Defense, and the recent IARPC Arctic Research Plan 2017-2021. In addition to an overview of RASM technical details, selected model results are presented from a hierarchy of climate models together with available observations in the region to better understand potential oceanic contributions to polar amplification. RASM simulations are analyzed to evaluate model skill in representing seasonal climatology as well as interannual and multi-decadal climate variability and predictions. Selected physical processes and resulting feedbacks are discussed to emphasize the need for fully coupled climate model simulations, high model resolution and sensitivity of simulated sea ice states to scale dependent model parameterizations controlling ice dynamics, thermodynamics and coupling with the atmosphere and ocean.

Molecular analyses reveal high species diversity of trematodes in a sub-Arctic lake

USGS Publications Warehouse

Soldánová, Miroslava; Georgieva, Simona; Roháčováa, Jana; Knudsen, Rune; Kuhn, Jesper A.; Henriksen, Eirik H.; Siwertsson, Anna; Shaw, Jenny C.; Kuris, Armand M.; Amundsen, Per-Arne; Scholz, Tomáš; Lafferty, Kevin D.; Kostadinova, Aneta

2017-01-01

To identify trematode diversity and life-cycles in the sub-Arctic Lake Takvatn, Norway, we characterised 120 trematode isolates from mollusc first intermediate hosts, metacercariae from second intermediate host fishes and invertebrates, and adults from fish and invertebrate definitive hosts, using molecular techniques. Phylogenies based on nuclear and/or mtDNA revealed high species richness (24 species or species-level genetic lineages), and uncovered trematode diversity (16 putative new species) from five families typical in lake ecosystems (Allocreadiidae, Diplostomidae, Plagiorchiidae, Schistosomatidae and Strigeidae). Sampling potential invertebrate hosts allowed matching of sequence data for different stages, thus achieving molecular elucidation of trematode life-cycles and exploration of host-parasite interactions. Phylogenetic analyses also helped identify three major mollusc intermediate hosts (Radix balthica, Pisidium casertanum and Sphaerium sp.) in the lake. Our findings increase the known trematode diversity at the sub-Arctic Lake Takvatn, showing that digenean diversity is high in this otherwise depauperate sub-Arctic freshwater ecosystem, and indicating that sub-Arctic and Arctic ecosystems may be characterised by unique trematode assemblages.

Omics in the Arctic: Genome-enabled Contributions to Carbon Cycle Research in High-Latitude Ecosystems (JGI Seventh Annual User Meeting 2012: Genomics of Energy and Environment)

ScienceCinema

Wullschleger, Stan

2018-02-13

Stan Wullschleger of Oak Ridge National Laboratory on "Omics in the Arctic: Genome-enabled Contributions to Carbon Cycle Research in High-Latitude Ecosystems" on March 22, 2012 at the 7th Annual Genomics of Energy & Environment Meeting in Walnut Creek, California.

Are hotspots always hotspots? The relationship between diversity, resource and ecosystem functions in the Arctic.

PubMed

Link, Heike; Piepenburg, Dieter; Archambault, Philippe

2013-01-01

The diversity-ecosystem function relationship is an important topic in ecology but has not received much attention in Arctic environments, and has rarely been tested for its stability in time. We studied the temporal variability of benthic ecosystem functioning at hotspots (sites with high benthic boundary fluxes) and coldspots (sites with lower fluxes) across two years in the Canadian Arctic. Benthic remineralisation function was measured as fluxes of oxygen, silicic acid, phosphate, nitrate and nitrite at the sediment-water interface. In addition we determined sediment pigment concentration and taxonomic and functional macrobenthic diversity. To separate temporal from spatial variability, we sampled the same nine sites from the Mackenzie Shelf to Baffin Bay during the same season (summer or fall) in 2008 and 2009. We observed that temporal variability of benthic remineralisation function at hotspots is higher than at coldspots and that taxonomic and functional macrobenthic diversity did not change significantly between years. Temporal variability of food availability (i.e., sediment surface pigment concentration) seemed higher at coldspot than at hotspot areas. Sediment chlorophyll a (Chl a) concentration, taxonomic richness, total abundance, water depth and abundance of the largest gallery-burrowing polychaete Lumbrineristetraura together explained 42% of the total variation in fluxes. Food supply proxies (i.e., sediment Chl a and depth) split hot- from coldspot stations and explained variation on the axis of temporal variability, and macrofaunal community parameters explained variation mostly along the axis separating eastern from western sites with hot- or coldspot regimes. We conclude that variability in benthic remineralisation function, food supply and diversity will react to climate change on different time scales, and that their interactive effects may hide the detection of progressive change, particularly at hotspots. Time-series of benthic functions and

The future of Arctic benthos: Expansion, invasion, and biodiversity

NASA Astrophysics Data System (ADS)

Renaud, Paul E.; Sejr, Mikael K.; Bluhm, Bodil A.; Sirenko, Boris; Ellingsen, Ingrid H.

2015-12-01

One of the logical predictions for a future Arctic characterized by warmer waters and reduced sea-ice is that new taxa will expand or invade Arctic seafloor habitats. Specific predictions regarding where this will occur and which taxa are most likely to become established or excluded are lacking, however. We synthesize recent studies and conduct new analyses in the context of climate forecasts and a paleontological perspective to make concrete predictions as to relevant mechanisms, regions, and functional traits contributing to future biodiversity changes. Historically, a warmer Arctic is more readily invaded or transited by boreal taxa than it is during cold periods. Oceanography of an ice-free Arctic Ocean, combined with life-history traits of invading taxa and availability of suitable habitat, determine expansion success. It is difficult to generalize as to which taxonomic groups or locations are likely to experience expansion, however, since species-specific, and perhaps population-specific autecologies, will determine success or failure. Several examples of expansion into the Arctic have been noted, and along with the results from the relatively few Arctic biological time-series suggest inflow shelves (Barents and Chukchi Seas), as well as West Greenland and the western Kara Sea, are most likely locations for expansion. Apparent temperature thresholds were identified for characteristic Arctic and boreal benthic fauna suggesting strong potential for range constrictions of Arctic, and expansions of boreal, fauna in the near future. Increasing human activities in the region could speed introductions of boreal fauna and reduce the value of a planktonic dispersal stage. Finally, shelf regions are likely to experience a greater impact, and also one with greater potential consequences, than the deep Arctic basin. Future research strategies should focus on monitoring as well as compiling basic physiological and life-history information of Arctic and boreal taxa, and

Anthropogenic impacts on habitat structure and species richness in the west Siberian Arctic

Treesearch

Olga Khitun; Olga Rebristaya

2002-01-01

Intensive technogenous invasion in the West Siberian Arctic during the last two decades in connection with gas and oil exploration, along with the constant growth of domestic reindeer herds, has caused dramatic changes in arctic ecosystems. Loss of biodiversity on the species level has not yet been documented in the region on a whole, but changes in ecosystems in...

Collaborative Proposal: Improving Decadal Prediction of Arctic Climate Variability and Change Using a Regional Arctic System Model (RASM)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maslowski, Wieslaw

This project aims to develop, apply and evaluate a regional Arctic System model (RASM) for enhanced decadal predictions. Its overarching goal is to advance understanding of the past and present states of arctic climate and to facilitate improvements in seasonal to decadal predictions. In particular, it will focus on variability and long-term change of energy and freshwater flows through the arctic climate system. The project will also address modes of natural climate variability as well as extreme and rapid climate change in a region of the Earth that is: (i) a key indicator of the state of global climate throughmore » polar amplification and (ii) which is undergoing environmental transitions not seen in instrumental records. RASM will readily allow the addition of other earth system components, such as ecosystem or biochemistry models, thus allowing it to facilitate studies of climate impacts (e.g., droughts and fires) and of ecosystem adaptations to these impacts. As such, RASM is expected to become a foundation for more complete Arctic System models and part of a model hierarchy important for improving climate modeling and predictions.« less

Effects of Disturbances on Vegetation Composition and Permafrost Thaw in Boreal Forests and Tundra Ecosystems of the Siberian Arctic

NASA Astrophysics Data System (ADS)

Ramos, E.; Alexander, H. D.; Natali, S.

2014-12-01

In Arctic ecosystems, climate-driven changes to the thermal regime of permafrost soils have the potential to create surface disturbances that influence vegetation dynamics and underlying soil properties. Disturbance-mediated changes in vegetation are important because vegetation and the accumulation of soil organic matter drive ecosystem carbon (C) dynamics and contribute to the insulation of soils and protection of permafrost from thaw. We examined the effect of two disturbance types—thermokarsts and frost boils—to determine disturbance effects on the vegetation community and soil properties in northeast Siberia. In summer 2014, we measured vegetation cover, soil moisture, soil temperature, and thaw depth in two thermokarst sites within boreal forests, two frost boil sites in tundra, and in adjacent undisturbed sites within both ecosystems. Both thermokarst and frost boils resulted in decreased vegetation cover and greater exposure of mineral soils (10-40% bare soils vs. 0% in undisturbed), and consequently, 2-3 times higher soil temperature and deeper thaw depth. Compared to undisturbed areas, soil moisture was 3-4 times higher in thermokarst areas but 1.2-2 times lower in frost boil areas, which reflected differences in microtopography between these two disturbance types. In both thermokarst and frost boil disturbed areas, deciduous and evergreen shrubs covered only 5 and 10%, respectively, compared to approximately 10 and 20%, respectively, in undisturbed areas. In general, graminoids were substantially more abundant (2-20 times) in disturbed areas than in those undisturbed. These results highlight important linkages between disturbances, vegetation communities, and permafrost soils, and contribute to our understanding of how changes in arctic vegetation dynamics as direct and/or indirect consequences of climate change have the potential to impact permafrost C pools.

Hanna Shoal: An integrative study of a High Arctic marine ecosystem in the Chukchi Sea

NASA Astrophysics Data System (ADS)

Dunton, Kenneth H.; Grebmeier, Jacqueline M.; Trefry, John H.

2017-10-01

This second special issue on the ecosystem under the COMIDA (Chukchi Sea Offshore Monitoring in the Drilling Area) Project focuses on the productive region around Hanna Shoal, the northernmost shoal on the Chukchi shelf. Our first issue (Dunton et al., 2014) emphasized the chemical and biological characteristics of the northeastern Chukchi Sea benthos. This effort expands our studies on the unique physical oceanography of Hanna Shoal, which lies at the interface between northward flowing Pacific Water and the Arctic Ocean, to include its influence on zooplankton dynamics and higher trophic level biota. Between both studies, conducted over a 5-year period (2009-2013) and four summer cruises, COMIDA scientists from seven institutions occupied some 85 stations (Fig. 1).

Freshwater and its role in the Arctic Marine System: Sources, disposition, storage, export, and physical and biogeochemical consequences in the Arctic and global oceans

NASA Astrophysics Data System (ADS)

Carmack, E. C.; Yamamoto-Kawai, M.; Haine, T. W. N.; Bacon, S.; Bluhm, B. A.; Lique, C.; Melling, H.; Polyakov, I. V.; Straneo, F.; Timmermans, M.-L.; Williams, W. J.

2016-03-01

The Arctic Ocean is a fundamental node in the global hydrological cycle and the ocean's thermohaline circulation. We here assess the system's key functions and processes: (1) the delivery of fresh and low-salinity waters to the Arctic Ocean by river inflow, net precipitation, distillation during the freeze/thaw cycle, and Pacific Ocean inflows; (2) the disposition (e.g., sources, pathways, and storage) of freshwater components within the Arctic Ocean; and (3) the release and export of freshwater components into the bordering convective domains of the North Atlantic. We then examine physical, chemical, or biological processes which are influenced or constrained by the local quantities and geochemical qualities of freshwater; these include stratification and vertical mixing, ocean heat flux, nutrient supply, primary production, ocean acidification, and biogeochemical cycling. Internal to the Arctic the joint effects of sea ice decline and hydrological cycle intensification have strengthened coupling between the ocean and the atmosphere (e.g., wind and ice drift stresses, solar radiation, and heat and moisture exchange), the bordering drainage basins (e.g., river discharge, sediment transport, and erosion), and terrestrial ecosystems (e.g., Arctic greening, dissolved and particulate carbon loading, and altered phenology of biotic components). External to the Arctic freshwater export acts as both a constraint to and a necessary ingredient for deep convection in the bordering subarctic gyres and thus affects the global thermohaline circulation. Geochemical fingerprints attained within the Arctic Ocean are likewise exported into the neighboring subarctic systems and beyond. Finally, we discuss observed and modeled functions and changes in this system on seasonal, annual, and decadal time scales and discuss mechanisms that link the marine system to atmospheric, terrestrial, and cryospheric systems.

Temperature response of respiration across heterogeneous microtopography in the Arctic tundra, Utqiaġvik, Alaska

NASA Astrophysics Data System (ADS)

Wilkman, E.; Zona, D.; Tang, Y.; Gioli, B.; Lipson, D.; Oechel, W. C.

2017-12-01

The response of ecosystem respiration to warming in the Arctic is not well constrained, partly due to the presence of ice-wedge polygons in continuous permafrost areas. These formations lead to substantial variation in vegetation, soil moisture, water table, and active layer depth over the meter scale that can drive respiratory carbon loss. Accurate calculations of in-situ temperature sensitivities (Q10) are vital for the prediction of future Arctic emissions, and while the eddy covariance technique has commonly been used to determine the diurnal and season patterns of net ecosystem exchange (NEE) of CO2, the lack of suitable dark periods in the Arctic summer has limited our ability to estimate and interpret ecosystem respiration. To therefore improve our understanding of and define controls on ecosystem respiration, we directly compared CO2 fluxes measured from automated chambers across the main local polygonised landscape forms (high and low centers, polygon rims, and polygon troughs) to estimates from an adjacent eddy covariance tower. Low-centered polygons and polygon troughs had the greatest cumulative respiration rates, and ecosystem type appeared to be the most important explanatory variable for these rates. Despite the difference in absolute respiration rates, Q10 was surprisingly similar across all microtopographic features, despite contrasting water levels and vegetation types. Conversely, Q10 varied temporally, with higher values during the early and late summer and lower values during the peak growing season. Finally, good agreement was found between chamber and tower based Q10 estimates during the peak growing season. Overall, this study suggests that it is possible to simplify estimates of the temperature sensitivity of respiration across heterogeneous landscapes, but that seasonal changes in Q10 should be incorporated into current and future model simulations.

A New Perspective on Changing Arctic Marine Ecosystems: Panarchy Adaptive Cycles in Pan-Arctic Spatial and Temporal Scales

NASA Astrophysics Data System (ADS)

Wiese, F. K.; Huntington, H. P.; Carmack, E.; Wassmann, P. F. J.; Leu, E. S.; Gradinger, R.

2016-02-01

Changes in the physical/biological interactions in the Arctic are occurring across a variety of spatial and temporal scales and may be mitigated or strengthened based on varying rates of evolutionary adaptation. A novel way to view these interactions and their social relevance is through the systems theory perspective of "Panarchy" proposed by Gunderson and Holling. Panarchy is an interdisciplinary approach in which structures, scales and linkages of complex-adaptive systems, including those of nature (e.g. ocean), humans (e.g. economics), and combined social-ecological systems (e.g. institutions that govern natural resource use), are mapped across multiple space and time scales in continual and interactive adaptive cycles of growth, accumulation, restructuring and renewal. In complex-adaptive systems the dynamics at a given scale are generally dominated by a small number of key internal variables that are forced by one or more external variables. The stability of such a system is characterized by its resilience, i.e. its capacity to absorb disturbance and re-organize while undergoing change, so as to retain essentially similar function, structure, identity and feedbacks. It is in the capacity of a system to cope with pressures and adversities such as exploitation, warming, governance restrictions, competition, etc. that resilience embraces human and natural systems as complex entities continually adapting through cycles of change. In this paper we explore processes at four linked spatial domains in the Arctic Ocean and link it to ecosystem resilience and re-organization characteristics. From this we derive a series of hypotheses concerning the biological responses to future physical changes and suggest ways how Panarchy theory can be applied to observational strategies to help detect early signs of environmental shifts affecting marine system services and functions. We close by discussing possible implications of the Panarchy framework for policy and governance.

The nature of spatial transitions in the Arctic.

Treesearch

H. E. Epstein; J. Beringer; W. A. Gould; A. H. Lloyd; C. D. Thompson; F. S. Chapin III; G. J. Michaelson; C. L. Ping; T. S. Rupp; D. A. Walker

2004-01-01

Aim Describe the spatial and temporal properties of transitions in the Arctic and develop a conceptual understanding of the nature of these spatial transitions in the face of directional environmental change. Location Arctic tundra ecosystems of the North Slope of Alaska and the tundraforest region of the Seward Peninsula, Alaska. Methods We synthesize information from...

Squeezing the arctic carbon balloon

Treesearch

Evan S. Kane

2012-01-01

The advancement of trees into Arctic tundra can increase total aboveground carbon storage. A study now shows, however, that greater plant growth also enhances belowground decomposition, resulting in a net loss of carbon from the ecosystem.

Collaborative Research: Improving Decadal Prediction of Arctic Climate Variability and Change Using a Regional Arctic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gutowski, William J.

This project developed and applied a regional Arctic System model for enhanced decadal predictions. It built on successful research by four of the current PIs with support from the DOE Climate Change Prediction Program, which has resulted in the development of a fully coupled Regional Arctic Climate Model (RACM) consisting of atmosphere, land-hydrology, ocean and sea ice components. An expanded RACM, a Regional Arctic System Model (RASM), has been set up to include ice sheets, ice caps, mountain glaciers, and dynamic vegetation to allow investigation of coupled physical processes responsible for decadal-scale climate change and variability in the Arctic. RASMmore » can have high spatial resolution (~4-20 times higher than currently practical in global models) to advance modeling of critical processes and determine the need for their explicit representation in Global Earth System Models (GESMs). The pan-Arctic region is a key indicator of the state of global climate through polar amplification. However, a system-level understanding of critical arctic processes and feedbacks needs further development. Rapid climate change has occurred in a number of Arctic System components during the past few decades, including retreat of the perennial sea ice cover, increased surface melting of the Greenland ice sheet, acceleration and thinning of outlet glaciers, reduced snow cover, thawing permafrost, and shifts in vegetation. Such changes could have significant ramifications for global sea level, the ocean thermohaline circulation and heat budget, ecosystems, native communities, natural resource exploration, and commercial transportation. The overarching goal of the RASM project has been to advance understanding of past and present states of arctic climate and to improve seasonal to decadal predictions. To do this the project has focused on variability and long-term change of energy and freshwater flows through the arctic climate system. The three foci of this research are

Modeling Arctic sea-ice algae: Physical drivers of spatial distribution and algae phenology

NASA Astrophysics Data System (ADS)

Castellani, Giulia; Losch, Martin; Lange, Benjamin A.; Flores, Hauke

2017-09-01

Algae growing in sea ice represent a source of carbon for sympagic and pelagic ecosystems and contribute to the biological carbon pump. The biophysical habitat of sea ice on large scales and the physical drivers of algae phenology are key to understanding Arctic ecosystem dynamics and for predicting its response to ongoing Arctic climate change. In addition, quantifying potential feedback mechanisms between algae and physical processes is particularly important during a time of great change. These mechanisms include a shading effect due to the presence of algae and increased basal ice melt. The present study shows pan-Arctic results obtained from a new Sea Ice Model for Bottom Algae (SIMBA) coupled with a 3-D sea-ice-ocean model. The model is evaluated with data collected during a ship-based campaign to the Eastern Central Arctic in summer 2012. The algal bloom is triggered by light and shows a latitudinal dependency. Snow and ice also play a key role in ice algal growth. Simulations show that after the spring bloom, algae are nutrient limited before the end of summer and finally they leave the ice habitat during ice melt. The spatial distribution of ice algae at the end of summer agrees with available observations, and it emphasizes the importance of thicker sea-ice regions for hosting biomass. Particular attention is given to the distinction between level ice and ridged ice. Ridge-associated algae are strongly light limited, but they can thrive toward the end of summer, and represent an additional carbon source during the transition into polar night.

Toward Sub-seasonal to Seasonal Arctic Sea Ice Forecasting Using the Regional Arctic System Model (RASM)

NASA Astrophysics Data System (ADS)

Kamal, S.; Maslowski, W.; Roberts, A.; Osinski, R.; Cassano, J. J.; Seefeldt, M. W.

2017-12-01

The Regional Arctic system model has been developed and used to advance the current state of Arctic modeling and increase the skill of sea ice forecast. RASM is a fully coupled, limited-area model that includes the atmosphere, ocean, sea ice, land hydrology and runoff routing components and the flux coupler to exchange information among them. Boundary conditions are derived from NCEP Climate Forecasting System Reanalyses (CFSR) or Era Iterim (ERA-I) for hindcast simulations or from NCEP Coupled Forecast System Model version 2 (CFSv2) for seasonal forecasts. We have used RASM to produce sea ice forecasts for September 2016 and 2017, in contribution to the Sea Ice Outlook (SIO) of the Sea Ice Prediction Network (SIPN). Each year, we produced three SIOs for the September minimum, initialized on June 1, July 1 and August 1. In 2016, predictions used a simple linear regression model to correct for systematic biases and included the mean September sea ice extent, the daily minimum and the week of the minimum. In 2017, we produced a 12-member ensemble on June 1 and July 1, and 28-member ensemble August 1. The predictions of September 2017 included the pan-Arctic and regional Alaskan sea ice extent, daily and monthly mean pan-Arctic maps of sea ice probability, concentration and thickness. No bias correction was applied to the 2017 forecasts. Finally, we will also discuss future plans for RASM forecasts, which include increased resolution for model components, ecosystem predictions with marine biogeochemistry extensions (mBGC) to the ocean and sea ice components, and feasibility of optional boundary conditions using the Navy Global Environmental Model (NAVGEM).

Interactions among shrub cover and the soil microclimate may determine future Arctic carbon budgets.

PubMed

Cahoon, Sean M P; Sullivan, Patrick F; Shaver, Gaius R; Welker, Jeffrey M; Post, Eric; Holyoak, Marcel

2012-12-01

Arctic and Boreal terrestrial ecosystems are important components of the climate system because they contain vast amounts of soil carbon (C). Evidence suggests that deciduous shrubs are increasing in abundance, but the implications for ecosystem C budgets remain uncertain. Using midsummer CO(2) flux data from 21 sites spanning 16° of latitude in the Arctic and Boreal biomes, we show that air temperature explains c. one-half of the variation in ecosystem respiration (ER) and that ER drives the pattern in net ecosystem CO(2) exchange across ecosystems. Woody sites were slightly stronger C sinks compared with herbaceous communities. However, woody sites with warm soils (> 10 °C) were net sources of CO(2) , whereas woody sites with cold soils (< 10 °C) were strong sinks. Our results indicate that transition to a shrub-dominated Arctic will increase the rate of C cycling, and may lead to net C loss if soil temperatures rise. © 2012 Blackwell Publishing Ltd/CNRS.

The Arctic Report Card: Communicating the State of the Rapidly Changing Arctic to a Diverse Audience via the Worldwide Web

NASA Astrophysics Data System (ADS)

Jeffries, M. O.; Richter-Menge, J.; Overland, J. E.; Soreide, N. N.

2013-12-01

Rapid change is occurring throughout the Arctic environmental system. The goal of the Arctic Report Card is to communicate the nature of the many changes to a diverse audience via the Worldwide Web. First published in 2006, the Arctic Report Card is a peer-reviewed publication containing clear, reliable and concise scientific information on the current state of the Arctic environment relative to observational records. Available only online, it is intended to be an authoritative source for scientists, teachers, students, decision-makers, policy-makers and the general public interested in the Arctic environment and science. The Arctic Report Card is organized into five sections: Atmosphere; Sea Ice & Ocean; Marine Ecosystem; Terrestrial Ecosystem; Terrestrial Cryosphere. Arctic Report Card 2012, the sixth annual update, comprised 20 essays on physical and biological topics prepared by an international team of 141 scientists from 15 different countries. For those who want a quick summary, the Arctic Report Card home page provides highlights of key events and findings, and a short video that is also available on YouTube. The release of the Report Card each autumn is preceded by a NOAA press release followed by a press conference, when the Web site is made public. The release of Arctic Report Card 2012 at an AGU Fall Meeting press conference on 5 December 2012 was subsequently reported by leading media organizations. The NOAA Arctic Web site, of which the Report Card is a part, is consistently at the top of Google search results for the keyword 'arctic', and the Arctic Report Card Web site tops search results for keyword "arctic report" - pragmatic indications of a Web site's importance and popularity. As another indication of the Web site's impact, in December 2012, the month when the 2012 update was released, the Arctic Report Card Web site was accessed by 19,851 unique sites in 105 countries, and 4765 Web site URLs referred to the Arctic Report Card. The 2012 Arctic

Practical Strategies for Integrating Final Ecosystem Goods and Services into Community Decision-Making.

EPA Science Inventory

The concept of Final Ecosystem Goods and Services (FEGS) explicitly connects ecosystem services to the people that benefit from them. This report presents a number of practical strategies for incorporating FEGS, and more broadly ecosystem services, into the decision-making proces...

Marine Mammals and Climate Change in the Pacific Arctic: Impacts & Resilience

NASA Astrophysics Data System (ADS)

Moore, S. E.

2014-12-01

Extreme reductions in Arctic sea ice extent and thickness have become a hallmark of climate change, but impacts to the marine ecosystem are poorly understood. As top predators, marine mammals must adapt to biological responses to physical forcing and thereby become sentinels to ecosystem variability and reorganization. Recent sea ice retreats have influenced the ecology of marine mammals in the Pacific Arctic sector. Walruses now often haul out by the thousands along the NW Alaska coast in late summer, and reports of harbor porpoise, humpback, fin and minke whales in the Chukchi Sea demonstrate that these temperate species routinely occur there. In 2010, satellite tagged bowhead whales from Atlantic and Pacific populations met in the Northwest Passage, an overlap thought precluded by sea ice since the Holocene. To forage effectively, baleen whales must target dense patches of zooplankton and small fishes. In the Pacific Arctic, bowhead and gray whales appear to be responding to enhanced prey availability delivered both by new production and advection pathways. Two programs, the Distributed Biological Observatory (DBO) and the Synthesis of Arctic Research (SOAR), include tracking of marine mammal and prey species' responses to ecosystem shifts associated with sea ice loss. Both programs provide an integrated-ecosystem baseline in support of the development of a web-based Marine Mammal Health Map, envisioned as a component of the U.S. Integrated Ocean Observing System (IOOS). An overarching goal is to identify ecological patterns for marine mammals in the 'new' Arctic, as a foundation for integrative research, local response and adaptive management.

Tracking Biological and Ecosystem Responses to Changing Environmental Conditions in the Pacific Arctic

NASA Astrophysics Data System (ADS)

Grebmeier, J. M.; Cooper, L. W.; Frey, K. E.; Moore, S. E.

2014-12-01

Changing seasonal sea ice conditions and seawater temperatures strongly influence biological processes and marine ecosystems at high latitudes. In the Pacific Arctic, persistent regions termed "hotspots", are localized areas with high benthic macroinfaunal biomass that have been documented over four decades (see Figure). These regions are now being more formally tracked to relate physical forcing and ecosystem response as an Arctic Distributed Biological Observatory (DBO) supported by the US National Ocean Policy Implementation Plan and international partners. These hotspots are important foraging areas for upper trophic level benthic feeders, such as marine mammals and seabirds. South of St. Lawrence Island (SLI) in the northern Bering Sea, benthic feeding spectacled eiders, bearded seals and walruses are important winter consumers of infauna, such as bivalves and polychaetes. Gray whales have historically been a major summer consumer of benthic amphipods in the Chirikov Basin to the north of SLI, although summertime sightings of gray whales declined in the Chirikov from the 1980s up until at least 2002. The SE Chukchi Sea hotspot, as are the other hotspots, is maintained by export of high chlorophyll a that is produced locally as well as advected by water masses transiting northward through the system. Both walrus and gray whales are known to forage in this hotspot seasonally on high biomass levels of benthic prey. Notably the center of the highest benthic biomass regions has shifted northward in three of the DBO hotspots in recent years. This has coincided with changing sediment grain size, an indicator of current speed, and is also likely a response to changes in primary production in the region. Studies of these broad biological responses to changing physical drivers have been facilitated through development of the DBO cooperative effort by both US and international scientists. The DBO includes a series of coordinated, multi-trophic level observations that

Agenda and Meeting Summary from Final Workshop on Arctic Black Carbon: Reduction of Black Carbon from Diesel Sources

EPA Pesticide Factsheets

The U.S. Environmental Protection Agency, Battelle Memorial Institute and WWF-Russia organized the final workshop on Arctic Black Carbon: Reduction of Black Carbon from Diesel Sources on November 5, 2014 in Murmansk, Russia.

The NGEE Arctic Data Archive -- Portal for Archiving and Distributing Data and Documentation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boden, Thomas A; Palanisamy, Giri; Devarakonda, Ranjeet

2014-01-01

The Next-Generation Ecosystem Experiments (NGEE Arctic) project is committed to implementing a rigorous and high-quality data management program. The goal is to implement innovative and cost-effective guidelines and tools for collecting, archiving, and sharing data within the project, the larger scientific community, and the public. The NGEE Arctic web site is the framework for implementing these data management and data sharing tools. The open sharing of NGEE Arctic data among project researchers, the broader scientific community, and the public is critical to meeting the scientific goals and objectives of the NGEE Arctic project and critical to advancing the mission ofmore » the Department of Energy (DOE), Office of Science, Biological and Environmental (BER) Terrestrial Ecosystem Science (TES) program.« less

The changing seasonal climate in the Arctic.

PubMed

Bintanja, R; van der Linden, E C

2013-01-01

Ongoing and projected greenhouse warming clearly manifests itself in the Arctic regions, which warm faster than any other part of the world. One of the key features of amplified Arctic warming concerns Arctic winter warming (AWW), which exceeds summer warming by at least a factor of 4. Here we use observation-driven reanalyses and state-of-the-art climate models in a variety of standardised climate change simulations to show that AWW is strongly linked to winter sea ice retreat through the associated release of surplus ocean heat gained in summer through the ice-albedo feedback (~25%), and to infrared radiation feedbacks (~75%). Arctic summer warming is surprisingly modest, even after summer sea ice has completely disappeared. Quantifying the seasonally varying changes in Arctic temperature and sea ice and the associated feedbacks helps to more accurately quantify the likelihood of Arctic's climate changes, and to assess their impact on local ecosystems and socio-economic activities.

The changing seasonal climate in the Arctic

PubMed Central

Bintanja, R.; van der Linden, E. C.

2013-01-01

Ongoing and projected greenhouse warming clearly manifests itself in the Arctic regions, which warm faster than any other part of the world. One of the key features of amplified Arctic warming concerns Arctic winter warming (AWW), which exceeds summer warming by at least a factor of 4. Here we use observation-driven reanalyses and state-of-the-art climate models in a variety of standardised climate change simulations to show that AWW is strongly linked to winter sea ice retreat through the associated release of surplus ocean heat gained in summer through the ice-albedo feedback (~25%), and to infrared radiation feedbacks (~75%). Arctic summer warming is surprisingly modest, even after summer sea ice has completely disappeared. Quantifying the seasonally varying changes in Arctic temperature and sea ice and the associated feedbacks helps to more accurately quantify the likelihood of Arctic's climate changes, and to assess their impact on local ecosystems and socio-economic activities. PMID:23532038

Fire and ecosystem change in the Arctic across the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Denis, E. H.; Pedentchouk, N.; Schouten, S.; Pagani, M.; Freeman, K. H.

2016-12-01

Fire, an important component of ecosystems at a range of spatial and temporal scales, affects vegetation distribution, the carbon cycle, and climate. In turn, climate influences fuel composition (e.g., amount and type of vegetation), fuel availability (e.g., vegetation that can burn based on precipitation and temperature), and ignition sources (e.g., lightning). Climate studies predict increased wildfire activity in future decades, but mechanisms that control the relationship between climate and fire are complex. Reconstructing environmental conditions during past warming events (e.g., the Paleocene-Eocene Thermal Maximum (PETM)) will help elucidate climate-vegetation-fire relationships that are expressed over long durations (1,000 - 10,000 yrs). The abrupt global warming during the PETM dramatically altered vegetation and hydrologic patterns, and, possibly, fire occurrence. To investigate coincident changes in climate, vegetation, and fire occurrence, we studied biomarkers, including polycyclic aromatic hydrocarbons (PAHs), terpenoids, and alkanes from the PETM interval at IODP site 302 (the Lomonosov Ridge) in the Arctic Ocean. Both pollen and biomarker records indicate angiosperms abundance increased during the PETM relative to gymnosperms, reflecting a significant ecological shift to angiosperm-dominated vegetation. PAH abundances increased relative to plant biomarkers throughout the PETM, which suggests PAH production increased relative to plant productivity. Increased PAH production associated with the angiosperm vegetation shift indicates a greater prevalence of more fire-prone species. A time lag between increased moisture transport (based on published δD of n-alkanes data) to the Arctic and increased angiosperms and PAH production suggests wetter conditions, followed by increased air temperatures, favored angiosperms and combined to enhance fire occurrence.

Trophic pathways supporting Arctic grayling in a small stream on the Arctic Coastal Plain, Alaska

USGS Publications Warehouse

McFarland, Jason J.; Wipfli, Mark S.; Whitman, Matthew S.

2018-01-01

Beaded streams are prominent across the Arctic Coastal Plain (ACP) of Alaska, yet prey flow and food web dynamics supporting fish inhabiting these streams are poorly understood. Arctic grayling (Thymallus arcticus) are a widely distributed upper-level consumer on the ACP and migrate into beaded streams to forage during the short 3-month open-water season. We investigated energy pathways and key prey resources that support grayling in a representative beaded stream, Crea Creek. We measured terrestrial invertebrates entering the stream from predominant riparian vegetation types, prey types supporting a range of fish size classes, and how riparian plants and fish size influenced foraging habits. We found that riparian plants influenced the quantity of terrestrial invertebrates entering Crea Creek; however, these differences were not reflected in fish diets. Prey type and size ingested varied with grayling size and season. Small grayling (<15 cm fork length (FL)) consumed mostly aquatic invertebrates early in the summer, and terrestrial invertebrates later in summer, while larger fish (>15 cm FL) foraged most heavily on ninespine stickleback (Pungitius pungitius) throughout the summer, indicating that grayling can be insectivorous and piscivorous, depending on size. These findings underscore the potential importance of small streams in Arctic ecosystems as key summer foraging habitats for fish. Understanding trophic pathways supporting stream fishes in these systems will help interpret whether and how petroleum development and climate change may affect energy flow and stream productivity, terrestrial–aquatic linkages and fishes in Arctic ecosystems.

Arctic climate tipping points.

PubMed

Lenton, Timothy M

2012-02-01

There is widespread concern that anthropogenic global warming will trigger Arctic climate tipping points. The Arctic has a long history of natural, abrupt climate changes, which together with current observations and model projections, can help us to identify which parts of the Arctic climate system might pass future tipping points. Here the climate tipping points are defined, noting that not all of them involve bifurcations leading to irreversible change. Past abrupt climate changes in the Arctic are briefly reviewed. Then, the current behaviour of a range of Arctic systems is summarised. Looking ahead, a range of potential tipping phenomena are described. This leads to a revised and expanded list of potential Arctic climate tipping elements, whose likelihood is assessed, in terms of how much warming will be required to tip them. Finally, the available responses are considered, especially the prospects for avoiding Arctic climate tipping points.

Rare earth elements in freshwater, marine, and terrestrial ecosystems in the eastern Canadian Arctic.

PubMed

MacMillan, Gwyneth Anne; Chételat, John; Heath, Joel P; Mickpegak, Raymond; Amyot, Marc

2017-10-18

Few ecotoxicological studies exist for rare earth elements (REEs), particularly field-based studies on their bioaccumulation and food web dynamics. REE mining has led to significant environmental impacts in several countries (China, Brazil, U.S.), yet little is known about the fate and transport of these contaminants of emerging concern. Northern ecosystems are potentially vulnerable to REE enrichment from prospective mining projects at high latitudes. To understand how REEs behave in remote northern food webs, we measured REE concentrations and carbon and nitrogen stable isotope ratios (∂ 15 N, ∂ 13 C) in biota from marine, freshwater, and terrestrial ecosystems of the eastern Canadian Arctic (N = 339). Wildlife harvesting and tissue sampling was partly conducted by local hunters through a community-based monitoring project. Results show that REEs generally follow a coherent bioaccumulation pattern for sample tissues, with some anomalies for redox-sensitive elements (Ce, Eu). Highest REE concentrations were found at low trophic levels, especially in vegetation and aquatic invertebrates. Terrestrial herbivores, ringed seal, and fish had low total REE levels in muscle tissue (∑REE for 15 elements <0.1 nmol g -1 ), yet accumulation was an order of magnitude higher in liver tissues. Age- and length-dependent REE accumulation also suggest that REE uptake is faster than elimination for some species. Overall, REE bioaccumulation patterns appear to be species- and tissue-specific, with limited potential for biomagnification. This study provides novel data on the behaviour of REEs in ecosystems and will be useful for environmental impact assessment of REE enrichment in northern regions.

Climate change impacts on wildlife in a High Arctic archipelago - Svalbard, Norway.

PubMed

Descamps, Sébastien; Aars, Jon; Fuglei, Eva; Kovacs, Kit M; Lydersen, Christian; Pavlova, Olga; Pedersen, Åshild Ø; Ravolainen, Virve; Strøm, Hallvard

2017-02-01

The Arctic is warming more rapidly than other region on the planet, and the northern Barents Sea, including the Svalbard Archipelago, is experiencing the fastest temperature increases within the circumpolar Arctic, along with the highest rate of sea ice loss. These physical changes are affecting a broad array of resident Arctic organisms as well as some migrants that occupy the region seasonally. Herein, evidence of climate change impacts on terrestrial and marine wildlife in Svalbard is reviewed, with a focus on bird and mammal species. In the terrestrial ecosystem, increased winter air temperatures and concomitant increases in the frequency of 'rain-on-snow' events are one of the most important facets of climate change with respect to impacts on flora and fauna. Winter rain creates ice that blocks access to food for herbivores and synchronizes the population dynamics of the herbivore-predator guild. In the marine ecosystem, increases in sea temperature and reductions in sea ice are influencing the entire food web. These changes are affecting the foraging and breeding ecology of most marine birds and mammals and are associated with an increase in abundance of several temperate fish, seabird and marine mammal species. Our review indicates that even though a few species are benefiting from a warming climate, most Arctic endemic species in Svalbard are experiencing negative consequences induced by the warming environment. Our review emphasizes the tight relationships between the marine and terrestrial ecosystems in this High Arctic archipelago. Detecting changes in trophic relationships within and between these ecosystems requires long-term (multidecadal) demographic, population- and ecosystem-based monitoring, the results of which are necessary to set appropriate conservation priorities in relation to climate warming. © 2016 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.

FINAL ECOSYSTEM GOODS AND SERVICES CLASSIFICATION SYSTEM (FEGS-CS)

EPA Science Inventory

This document defines and classifies 338 Final Ecosystem Goods and Services (FEGS), each defined and uniquely numbered by a combination of environmental class or sub-class and a beneficiary category or sub-category. The introductory section provides the rationale and conceptual ...

Geospatial Analysis of Climate-Related Changes in North American Arctic Ecosystems and Implications for Terrestrial Flora and Fauna

NASA Astrophysics Data System (ADS)

Amirazodi, S.; Griffin, R.

2016-12-01

Climate change induces range shifts among many terrestrial species in Arctic regions. At best, warming often forces poleward migration if a stable environment is to be maintained. At worst, marginal ecosystems may disappear entirely without a contiguous shift allowing migratory escape to similar environs. These changing migration patterns and poleward range expansion push species into higher latitudes where ecosystems are less stable and more sensitive to change. This project focuses on ecosystem geography and interspecies relationships and interactions by analyzing seasonality and changes over time in variables including the following: temperature, precipitation, vegetation, physical boundaries, population demographics, permafrost, sea ice, and food and water availability. Publicly available data from remote sensing platforms are used throughout, and processed with both commercially available and open sourced GIS tools. This analysis describes observed range changes for selected North American species, and attempts to provide insight into the causes and effects of these phenomena. As the responses to climate change are complex and varied, the goal is to produce the aforementioned results in an easily understood set of geospatial representations to better support decision making regarding conservation prioritization and enable adaptive responses and mitigation strategies.

Progress report for project modeling Arctic barrier island-lagoon system response to projected Arctic warming

USGS Publications Warehouse

Erikson, Li H.; Gibbs, Ann E.; Richmond, Bruce M.; Storlazzi, Curt; B.M. Jones,

2012-01-01

Changes in Arctic coastal ecosystems in response to global warming may be some of the most severe on the planet. A better understanding and analysis of the rates at which these changes are expected to occur over the coming decades is crucial in order to delineate high-priority areas that are likely to be affected by climate changes. In this study we investigate the likelihood of changes to habitat-supporting barrier island – lagoon systems in response to projected changes in atmospheric and oceanographic forcing associated with Arctic warming. To better understand the relative importance of processes responsible for the current and future coastal landscape, key parameters related to increasing arctic temperatures are investigated and used to establish boundary conditions for models that simulate barrier island migration and inundation of deltaic deposits and low-lying tundra. The modeling effort investigates the dominance and relative importance of physical processes shaping the modern Arctic coastline as well as decadal responses due to projected conditions out to the year 2100.

Soil Biota and Litter Decay in High Arctic Ecosystems

NASA Astrophysics Data System (ADS)

González, G.; Rivera, F.; Makarova, O.; Gould, W. A.

2006-12-01

Frost heave action contributes to the formation of non-sorted circles in the High Arctic. Non-sorted circles tend to heave more than the surrounding tundra due to deeper thaw and the formation of ice lenses. Thus, the geomorphology, soils and vegetation on the centers of the patterned-ground feature (non-sorted circles) as compared to the surrounding soils (inter-circles) can be different. We established a decomposition experiment to look at in situ decay rates of the most dominant graminoid species on non-sorted circles and adjacent inter-circle soils along a climatic gradient in the Canadian High Arctic as a component of a larger study looking at the biocomplexity of small-featured patterned ground ecosystems. Additionally, we investigated variation in soil chemical properties and biota, including soil microarthropods and microbial composition and biomass, as they relate to climate, topographic position, and litter decay rates. Our three sites locations, from coldest to warmest, are Isachsen, Ellef Ringnes Island (ER), NU (bioclimatic subzone A); Mould Bay (MB), Prince Patrick Island, NT (bioclimatic subzone B), and Green Cabin (GC), Aulavik National Park, Thomsen River, Banks Island, NT (bioclimatic subzone C). Our sample design included the selection of 15 non-sorted circles and adjacent inter-circle areas within the zonal vegetation at each site (a total of 90 sites), and a second set of 3 non-sorted circles and adjacent inter-circle areas in dry, mesic and wet tundra at each of the sites. Soil invertebrates were sampled at each site using both pitfall traps, soil microbial biomass was determined using substrate induced respiration and bacterial populations were determined using the most probable number method. Decomposition rates were measured using litterbags and as the percent of mass remaining of Carex misandra, Luzula nivalis and Alopecuris alpinus in GC, MB and ER, respectively. Our findings indicate these graminoid species decayed significantly over

Increases in Growing Season Length and Changes in Precipitation at Six Different Arctic and Subarctic Ecosystems from 1906-Present

NASA Astrophysics Data System (ADS)

Culler, L. E.; Finger, R.; Plane, E.; Ayres, M.; Virginia, R. A.

2015-12-01

Ecological dynamics across the Arctic are responding to rapid changes in climate. As a whole, the Arctic has warmed at approximately twice the rate of the rest of the world, but changes in temperature and precipitation experienced at regional and local scales are most important for coupled human-natural systems. In addition, biologically-relevant climate indices are necessary for quantifying ecological responses of terrestrial and aquatic systems to varying climate. We compared climatic changes at six different Arctic and sub-Arctic locations, including two in Greenland (Kangerlussuaq, Sisimiut), one in Sweden (Abisko), and three in Alaska (Barrow, Nome, Fairbanks). We amassed weather data (daily temperature and precipitation), dating as far back as 1906, from public-access databases and used these data to calculate indices such as length of growing season, growing season degree days (GDD), and growing season precipitation. Annual GDD increased at all locations (average of 13% increase in GDD since 1980), but especially in western Greenland (16 and 37% in Kangerlussuaq and Sisimiut, respectively). Changes in growing season precipitation were more variable, with only Barrow, AK and Abisko, Sweden experiencing increased precipitation. All other sites experienced stable or slightly declining precipitation. Increasing temperatures and relatively stable precipitation translates to increased evapotranspiration potential, which influences soil moisture, lake depth, vegetation, carbon emissions, and fire susceptibility. Understanding local and regional trends in temperature and precipitation can help explain observed phenological changes and other processes at population, community, and ecosystem levels. In addition, identification of locations most susceptible to future change will allow scientists to closely monitor their ecological dynamics, anticipate changes in coupled human-natural systems, and consider adaptation plans for the most rapidly changing systems.

Predicting Changes in Arctic Tundra Vegetation: Towards an Understanding of Plant Trait Uncertainty

NASA Astrophysics Data System (ADS)

Euskirchen, E. S.; Serbin, S.; Carman, T.; Iversen, C. M.; Salmon, V.; Helene, G.; McGuire, A. D.

2017-12-01

Arctic tundra plant communities are currently undergoing unprecedented changes in both composition and distribution under a warming climate. Predicting how these dynamics may play out in the future is important since these vegetation shifts impact both biogeochemical and biogeophysical processes. More precise estimates of these future vegetation shifts is a key challenge due to both a scarcity of data with which to parameterize vegetation models, particularly in the Arctic, as well as a limited understanding of the importance of each of the model parameters and how they may vary over space and time. Here, we incorporate newly available field data from arctic Alaska into a dynamic vegetation model specifically developed to take into account a particularly wide array of plant species as well as the permafrost soils of the arctic tundra (the Terrestrial Ecosystem Model with Dynamic Vegetation and Dynamic Organic Soil, Terrestrial Ecosystem Model; DVM-DOS-TEM). We integrate the model within the Predicative Ecosystem Analyzer (PEcAn), an open-source integrated ecological bioinformatics toolbox that facilitates the flows of information into and out of process models and model-data integration. We use PEcAn to evaluate the plant functional traits that contribute most to model variability based on a sensitivity analysis. We perform this analysis for the dominant types of tundra in arctic Alaska, including heath, shrub, tussock and wet sedge tundra. The results from this analysis will help inform future data collection in arctic tundra and reduce model uncertainty, thereby improving our ability to simulate Arctic vegetation structure and function in response to global change.

Modeling seasonality of ice and ocean carbon production in the Arctic

NASA Astrophysics Data System (ADS)

Jin, M.; Deal, C. M.; Ji, R.

2011-12-01

In the Arctic Ocean, both phytoplankton and sea ice algae are important contributors to the primary production and the arctic food web. Copepod in the arctic regions have developed their feeding habit depending on the timing between the ice algal bloom and the subsequent phytoplankton bloom. A mismatch of the timing due to climate changes could have dramatic consequences on the food web as shown by some regional observations. In this study, a global coupled ice-ocean-ecosystem model was used to assess the seasonality of the ice algal and phytoplankton blooms in the arctic. The ice-ocean ecosystem modules are fully coupled in the physical model POP-CICE (Parallel Ocean Program- Los Alamos Sea Ice Model). The model results are compared with various observations. The modeled ice and ocean carbon production were analyzed by regions and their linkage to the physical environment changes (such as changes of ice concentration and water temperature, and light intensity etc.) between low- and high-ice years.

Will Arctic ground squirrels impede or accelerate climate-induced vegetation changes to the Arctic tundra?

NASA Astrophysics Data System (ADS)

Dalton, J.; Flower, C. E.; Brown, J.; Gonzalez-Meler, M. A.; Whelan, C.

2014-12-01

Considerable attention has been given to the climate feedbacks associated with predicted vegetation shifts in the Arctic tundra in response to global environmental change. However, little is known regarding the extent to which consumers can facilitate or respond to shrub expansion. Arctic ground squirrels, the largest and most northern ground squirrel, are abundant and widespread throughout the North American tundra. Their broad diet of seeds, flowers, herbage, bird's eggs and meat speaks to the need to breed, feed, and fatten in a span of some 12-16 weeks that separate their 8-9 month bouts of hibernation with the potential consequence to impact ecosystem dynamics. Therefore Arctic ground squirrels are a good candidate to evaluate whether consumers are mere responders (bottom-up effects) or drivers (top-down) of the observed and predicted vegetation changes. As a start towards this question, we measured the foraging intensity (giving-up densities) of Arctic ground squirrels in experimental food patches within which the squirrels experience diminishing returns as they seek the raisins and peanuts that we provided at the Toolik Lake field station in northern Alaska. If the squirrels show their highest feeding intensity in the shrubs, they may impede vegetation shifts by slowing the establishment and expansion of shrubs in the tundra. Conversely, if they show their lowest feeding intensity within shrub dominated areas, they may accelerate vegetation shifts. We found neither. Feeding intensity varied most among transects and times of day, and least along a tundra-to-shrub vegetation gradient. This suggests that the impacts of squirrels will be heterogeneous - in places responders and in others drivers. We should not be surprised then to see patches of accelerated and impeded vegetation changes in the tundra ecosystem. Some of these patterns may be predictable from the foraging behavior of Arctic ground squirrels.

Climate-driven changes in functional biogeography of Arctic marine fish communities

PubMed Central

Primicerio, Raul; Kortsch, Susanne; Aune, Magnus; Dolgov, Andrey V.; Fossheim, Maria; Aschan, Michaela M.

2017-01-01

Climate change triggers poleward shifts in species distribution leading to changes in biogeography. In the marine environment, fish respond quickly to warming, causing community-wide reorganizations, which result in profound changes in ecosystem functioning. Functional biogeography provides a framework to address how ecosystem functioning may be affected by climate change over large spatial scales. However, there are few studies on functional biogeography in the marine environment, and none in the Arctic, where climate-driven changes are most rapid and extensive. We investigated the impact of climate warming on the functional biogeography of the Barents Sea, which is characterized by a sharp zoogeographic divide separating boreal from Arctic species. Our unique dataset covered 52 fish species, 15 functional traits, and 3,660 stations sampled during the recent warming period. We found that the functional traits characterizing Arctic fish communities, mainly composed of small-sized bottom-dwelling benthivores, are being rapidly replaced by traits of incoming boreal species, particularly the larger, longer lived, and more piscivorous species. The changes in functional traits detected in the Arctic can be predicted based on the characteristics of species expected to undergo quick poleward shifts in response to warming. These are the large, generalist, motile species, such as cod and haddock. We show how functional biogeography can provide important insights into the relationship between species composition, diversity, ecosystem functioning, and environmental drivers. This represents invaluable knowledge in a period when communities and ecosystems experience rapid climate-driven changes across biogeographical regions. PMID:29087943

Introduction to special section on Annual Cycles on the Arctic Ocean Shelf

NASA Astrophysics Data System (ADS)

Fortier, Louis; Cochran, J. Kirk

2008-03-01

The perennial sea-ice cover of the Arctic Ocean is shrinking rapidly in response to the anthropogenic warming of Earth's lower atmosphere. From September 2002 to September 2004 the Canadian Arctic Shelf Exchange Study (CASES) logged over 14,500 scientist-days at sea to document the potential impacts of a shift in sea-ice regime on the ecosystem of the Mackenzie Shelf in the southeastern Beaufort Sea. In particular, teams from Canada, Denmark, Japan, Norway, Spain, the United Kingdom, and the United States totaling over 200 scientists took rotations on the CCS Amundsen to study all aspects of the ecosystem during a 385-day over-wintering expedition in the region from September 2003 to September 2004. The resulting wealth of information has revealed an unexpectedly active food web under the winter sea ice of the coastal Beaufort Sea. From the thermodynamics of snow to the reconstruction of local paleo-climate, this special section focuses on how sea-ice cover dynamics dictate biological processes and biogeochemical fluxes on and at the margin of the shallow Arctic continental shelf. The highly successful CASES program has initiated ongoing time series of key measurements of the response of the marine ecosystem to change that have been expanded to other Arctic regions through the ArcticNet project and the International Polar Year.

Importance of particle-associated bacterial heterotrophy in a coastal Arctic ecosystem

NASA Astrophysics Data System (ADS)

Garneau, Marie-Ève; Vincent, Warwick F.; Terrado, Ramon; Lovejoy, Connie

2009-01-01

estuarine stations with highest POM content. Particle-associated bacteria are an important functional component of this Arctic ecosystem. Under a warmer climate, they are likely to play an increasing role in coastal biogeochemistry and carbon fluxes as a result of permafrost melting and increased particle transport from the tundra to coastal waters.

Spatial distribution of aquatic marine fungi across the western Arctic and sub-arctic.

PubMed

Hassett, Brandon T; Ducluzeau, Anne-Lise L; Collins, Roy E; Gradinger, Rolf

2017-02-01

Fungi are important parasites of primary producers and nutrient cyclers in aquatic ecosystems. In the Pacific-Arctic domain, fungal parasitism is linked to light intensities and algal stress that can elevate disease incidence on algae and reduce diatom concentrations. Fungi are vastly understudied in the marine realm and knowledge of their function is constrained by the current understanding of fungal distribution and drivers on global scales. To investigate the spatial distribution of fungi in the western Arctic and sub-Arctic, we used high throughput methods to sequence 18S rRNA, cloned and sequenced 28S rRNA and microscopically counted chytrid-infected diatoms. We identified a broad distribution of fungal taxa predominated by Chytridiomycota and Dikarya. Phylogenetic analysis of our Chytridiomycota clones placed Arctic marine fungi sister to the order Lobulomycetales. This clade of fungi predominated in fungal communities under ice with low snowpack. Microscopic examination of fixed seawater and sea ice samples revealed chytrids parasitizing diatoms collected across the Arctic that notably infected 25% of a single diatom species in the Bering Sea. The Pezizomycotina comprised > 95% of eukaryotic sequence reads in Greenland, providing preliminary evidence for osmotrophs being a substitute for algae as the base of food webs. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

Using paleolimnology to track the impacts of early Arctic peoples on freshwater ecosystems from southern Baffin Island, Nunavut

NASA Astrophysics Data System (ADS)

Michelutti, Neal; McCleary, Kathryn M.; Antoniades, Dermot; Sutherland, Patricia; Blais, Jules M.; Douglas, Marianne S. V.; Smol, John P.

2013-09-01

Paleolimnological approaches can be used to determine the ways in which past Arctic peoples have affected the ecosystems in which they live, and simultaneously to reconstruct the climate and other aspects of the environment that may have influenced local populations. Here we analyze sediment cores from seven ponds on the south-western coast of Baffin Island, Nunavut, in order to assess the impacts of early Arctic peoples on freshwater ecosystems. Prior to the historic Inuit occupation, the study area was extensively inhabited by Thule culture Inuit (ca 1200-1600 AD) and by an earlier Arctic group, the Dorset culture Palaeo-Eskimos (ca 500 BC-1500 AD) and their predecessors from as early as 2500 BC. The study ponds were selected to cover a gradient of the intensity of human activity in their catchments. The ecological impacts of early hunting societies can be detected using paleolimnology because the butchering of marine mammals released nutrients that eutrophied nearby ponds and left distinct geochemical signals in the sediments. The degree of eutrophication in the small freshwater ponds depended on the length of the occupation, as well as the amount and type of marine mammals taken as primary prey items (eg, whales, walrus, or seals). All sediment cores were AMS 14C dated to establish their chronologies, and analyzed for diatoms and stable isotopes of nitrogen (δ15N). Both diatoms and sedimentary δ15N have been previously demonstrated to respond sensitively to nutrient enrichment from Inuit whalers. Our δ15N and diatom data record nutrient enrichment in lakes surrounded by either long-term Thule or Dorset settlements. The Dorset sites that were the locations of periodic seasonal gatherings did not register any evidence of eutrophication in the nearby ponds, reflecting the shorter, less intensive nature of these occupations. Similarly, nearby control ponds with no evidence of significant human activity in their catchments showed little-to-no changes in δ15N

Plant traits and trait-based vegetation modeling in the Arctic

NASA Astrophysics Data System (ADS)

Xu, C.; Sevanto, S.; Iversen, C. M.; Salmon, V. G.; Rogers, A.; Wullschleger, S.; Wilson, C. J.

2017-12-01

Arctic tundra environments are characterized by extremely cold temperatures, strong winds, short growing season and thin, nutrient-poor soil layer impacted by permafrost. To survive in this environment vascular plants have developed traits that simultaneously promote high productivity under favorable environments, and survival in harsh conditions. To improve representation of Arctic tundra vegetation in Earth System Models we surveyed plant trait data bases for key trait parameters that influence modeled ecosystem carbon balance, and compared the traits within plant families occurring in the boreal, temperate and arctic zones. The parameters include photosynthetic carbon uptake efficiency (Vcmax and Jmax), root:shoot ratio, and root and leaf nitrogen content, and we focused on woody shrubs. Our results suggest that root nitrogen content in non-nitrogen fixing tundra shrubs is lower than in representatives of the same families in the boreal or temperate zone. High tissue nitrogen concentrations have been related to high vulnerability to drought. The low root nitrogen concentrations in tundra shrubs may thus be an indication of acclimation to shallow soils, and frequent freezing that has a similar impact on the plant conductive tissue as drought. With current nitrogen availability, nitrogen limitation reduces the benefits of increased temperatures and longer growing seasons to the tundra ecosystem carbon balance. Thawing of permafrost will increase nitrogen availability, and promote plant growth and carbon uptake, but it could also make the shrubs more vulnerable to freeze-thaw cycles, with the overall result of reduced shrub coverage. The final outcome of warming temperatures and thawing of permafrost on tundra shrubs will thus depend on the relative speed of warming and plant acclimation.

Monitoring Ecosystem Dynamics Ecosystem Using Hyperspectral Reflectance and a Robotic Tram System in Barrow Alaska

NASA Astrophysics Data System (ADS)

Goswami, S.; Gamon, J. A.; Tweedie, C. E.

2012-12-01

Understanding the future state of the earth system requires improved knowledge of ecosystem dynamics and long term observations of how ecosystem structures and functions are being impacted by global change. Improving remote sensing methods is essential for such advancement because satellite remote sensing is the only means by which landscape to continental-scale change can be observed. The Arctic appears to be impacted by climate change more than any other region on Earth. Arctic terrestrial ecosystems comprise only 6% of the land surface area on Earth yet contain an estimated 25% of global soil organic carbon, most of which is stored in permafrost. If projected increases in plant productivity do not offset forecast losses of soil carbon to the atmosphere as greenhouse gases, regional to global greenhouse warming could be enhanced. Soil moisture is an important control of land-atmosphere carbon exchange in arctic terrestrial ecosystems. However, few studies to date have examined using remote sensing, or developed remote sensing methods for observing the complex interplay between soil moisture and plant phenology and productivity in arctic landscapes. This study was motivated by this knowledge gap and addressed the following questions as a contribution to a large scale, multi investigator flooding and draining experiment funded by the National Science Foundation near Barrow, Alaska from 2005 - 2009. 1. How can optical remote sensing be used to monitor the surface hydrology of arctic landscapes? 2. What are the spatio-temporal dynamics of land-surface phenology (NDVI) in the study area and do hydrological treatment has any effect on inter-annual patterns? A new spectral index, the normalized difference surface water index (NDSWI) was developed and tested at multiple spatial and temporal scales. NDSWI uses the 460nm (blue) and 1000nm (IR) bands and was developed to capture surface hydrological dynamics in the study area using the robotic tram system. When applied to

The changing Arctic carbon cycle: using the past to understand terrestrial-aquatic linkages

NASA Astrophysics Data System (ADS)

Anderson, N. J.; van Hardenbroek, M.; Jones, V.; McGowan, S.; Langdon, P. G.; Whiteford, E.; Turner, S.; Edwards, M. E.

2016-12-01

Predicted shifts in terrestrial vegetation cover associated with Arctic warming are altering the delivery and processing of carbon to aquatic ecosystems. This process could determine whether lakes are net carbon sources or sinks and, because lake density is high in many Arctic areas, may alter regional carbon budgets. Lake sediment records integrate information from within the lake and its catchment and can be used quantify past vegetation shifts associated with known climatic episodes of warmer (Holocene Thermal Maximum) and cooler (Neoglacial) conditions. We analysed sediment cores located in different Arctic vegetation biomes (tundra, shrub, forested) in Greenland, Norway and Alaska and used biochemical (algal pigments, stable isotopes) remains to evaluate whether past vegetation shifts were associated with changes in ecosystem carbon processing and biodiversity. When lake catchments were sparsely vegetated and soil vegetation was limited ultra-violet radiation (UVR) screening pigments indicate clear lake waters, scarce dissolved organic carbon/ matter (DOC/M). Moderate vegetation development (birch scrub in Norway; herb tundra in Greenland) appears to enhance delivery of DOM to lakes, and to stimulate algal production which is apparently linked to heterotrophic carbon processing pathways (e.g. algal mixotrophy, nutrient release via the microbial loop). Mature forest cover (in Alaska and Norway) supressed lake autotrophic production, most likely because coloured DOM delivered from catchment vegetation limited light availability. During wetter periods when mires developed lake carbon processing also changed, indicating that hydrological delivery of terrestrial DOM is also important. Therefore, future changes in Arctic vegetation and precipitation patterns are highly likely to alter the way that arctic ecosystems process carbon. Our approach provides an understanding of how ecosystem diversity and carbon processing respond to past climate change and the difficulty

Changes in arctic and boreal ecosystem productivity in response to changes in growing season length

NASA Astrophysics Data System (ADS)

Hmimina, G.; Yu, R.; Billesbach, D. P.; Huemmrich, K. F.; Gamon, J. A.

2017-12-01

Large-scale greening and browning trends have been reported in northern terrestrial ecosystems over the last two decades. The greening is interpreted as an increased productivity in response to increases in temperature. Boreal and arctic ecosystem productivity is expected to increase as the length of growing seasons increases, resulting in a bigger northern carbon sink pool. While evidences of such greening based on the use of remotely-sensed vegetation indices are compelling, analysis over the sparse network of flux tower sites available in northern latitudes paint a more complex story, and raise some issues as to whether vegetation indices based on NIR reflectance at large spatial scales are suited to the analysis of very fragmented landscapes that exhibit strong patterns in snow and standing water cover. In a broader sense, whether "greenness" is a sufficiently good proxy of ecosystem productivity in northern latitudes is unclear. The current work focused on deriving continuous estimates of ecosystem potential productivity and photosynthesis limitation over a network of flux towers, and on analyzing the relationships between potential yearly productivity and the length of the growing season over time and space. A novel partitioning method was used to derive ecophysiological parameters from sparse carbon fluxes measurements, and those parameters were then used to delimit the growing season and to estimate potential yearly productivity over a wide range of ecosystems. The relationships obtained between those two metrics were then computed for each of the 23 studied sites, exhibiting a wide range of different responses to changes in growing season length. While an overall significant increasing productivity trend was found (R²=0.12) suggesting increased productivity, the more northern sites exhibited a consistent decreasing trend (0.11 The attribution of these trends to either changes in potential productivity or productivity limitation by abiotic factors will be

Artificial warming of arctic meadow under pollution stress: Experimental design

USDA-ARS?s Scientific Manuscript database

Boreal and arctic terrestrial ecosystems are central to the climate change debate, notably because future warming is expected to be disproportionate as compared to world averages. Likewise, greenhouse gas (GHG) release from terrestrial ecosystems exposed to climate warming is expected to be the larg...

The Evolving Arctic: Current State of U.S. Arctic Policy

DTIC Science & Technology

2013-09-01

global warming on the fragile Arctic ecosystem, Canada has taken a proactive approach to protect the environment and its inhabitants. For example in...Whether you are an expert in global warming or not, the fact is there is more water there every day than there has been in the past; that breeds...Environmental Damage, and Interruption of Native Subsistence Whaling /Fishing Due to a Lack of Oil Spill- Response Equipment

Arctic marine fishes and their fisheries in light of global change

PubMed Central

Christiansen, Jørgen S; Mecklenburg, Catherine W; Karamushko, Oleg V

2014-01-01

In light of ocean warming and loss of Arctic sea ice, harvested marine fishes of boreal origin (and their fisheries) move poleward into yet unexploited parts of the Arctic seas. Industrial fisheries, already in place on many Arctic shelves, will radically affect the local fish species as they turn up as unprecedented bycatch. Arctic marine fishes are indispensable to ecosystem structuring and functioning, but they are still beyond credible assessment due to lack of basic biological data. The time for conservation actions is now, and precautionary management practices by the Arctic coastal states are needed to mitigate the impact of industrial fisheries in Arctic waters. We outline four possible conservation actions: scientific credibility, ‘green technology’, legitimate management and overarching coordination. PMID:24105993

Arctic Change Detection: Multiple Observations and Recent Explanations

NASA Astrophysics Data System (ADS)

Soreide, N. N.; Overland, J. E.; Calder, J.

2004-12-01

The recently released Arctic Climate Impact Assessment (ACIA) Report documents Arctic-wide changes and impacts; it provides a long-term perspective for peoples, governments and scientists in coping with these changes. Further, investigation of the last three decades of multivariate biophysical data sets(climate, land and marine ecosystems, cryosphere) and century-long weather records, show two main types of Arctic variability. These are: 1) long-term trends as represented by loss of sea-ice and tundra area and their biological response, and 2) decadal variability in atmospheric forcing and its direct impacts. Three main conclusions are possible: * Temperature anomalies in the last 15 years are unique in the Arctic instrumental record (1880-2003). Historically, there were regional/decadal warm events during winter and spring in the 1930s to 1950s, but meteorological analysis shows that these surface air temperature anomalies are the result of intrinsic variability in regional flow patterns, as contrasted with the Arctic-wide Arctic Oscillation (AO) influence of the 1990s. * These changes are primarily driven by changes in atmospheric circulation, and thus are subject to north/south gradients in hemispheric radiative forcing from volcanic aerosols, insolation cycles and CO2 increase. These north/south differences drive temperature advection in the trough-ridge structure of the AO. This conclusion is based primarily on model results and impacts from volcanos. * Change is likely to be irreversible over at least the next decade. In the previous five years, many ecosystems, such as the Bering Sea and east Greenland, are showing more year-to-year persistence, despite considerable variability in the AO and other climate indices. We hypothesize that the changes occurring in the Arctic are beginning to be significant enough to make the Arctic less sensitive to cold swings in atmospheric variability, although direct mechanisms are unclear. A next step in the post-ACIA period

A veterinary perspective on One Health in the Arctic.

PubMed

Sonne, Christian; Letcher, Robert James; Jenssen, Bjørn Munro; Desforges, Jean-Pierre; Eulaers, Igor; Andersen-Ranberg, Emilie; Gustavson, Kim; Styrishave, Bjarne; Dietz, Rune

2017-12-16

Exposure to long-range transported industrial chemicals, climate change and diseases is posing a risk to the overall health and populations of Arctic wildlife. Since local communities are relying on the same marine food web as marine mammals in the Arctic, it requires a One Health approach to understand the holistic ecosystem health including that of humans. Here we collect and identify gaps in the current knowledge of health in the Arctic and present the veterinary perspective of One Health and ecosystem dynamics. The review shows that exposure to persistent organic pollutants (POPs) is having multiple organ-system effects across taxa, including impacts on neuroendocrine disruption, immune suppression and decreased bone density among others. Furthermore, the warming Arctic climate is suspected to influence abiotic and biotic long-range transport and exposure pathways of contaminants to the Arctic resulting in increases in POP exposure of both wildlife and human populations. Exposure to vector-borne diseases and zoonoses may increase as well through range expansion and introduction of invasive species. It will be important in the future to investigate the effects of these multiple stressors on wildlife and local people to better predict the individual-level health risks. It is within this framework that One Health approaches offer promising opportunities to survey and pinpoint environmental changes that have effects on wildlife and human health.

Partitioning net ecosystem exchange of CO2 into gross primary production and ecosystem respiration in northern high-latitude ecosystems

NASA Astrophysics Data System (ADS)

Lund, M.; Zona, D.; Jackowicz-Korczynski, M.; Xu, X.

2017-12-01

The eddy covariance methodology is the primary tool for studying landscape-scale land-atmosphere exchange of greenhouse gases. Since the choice of instrumental setup and processing algorithms may influence the results, efforts within the international flux community have been made towards methodological harmonization and standardization. Performing eddy covariance measurements in high-latitude, Arctic tundra sites involves several challenges, related not only to remoteness and harsh climate conditions but also to the choice of processing algorithms. Partitioning of net ecosystem exchange (NEE) of CO2 into gross primary production (GPP) and ecosystem respiration (Reco) in the FLUXNET2015 dataset is made using either Nighttime or Daytime methods. These variables, GPP and Reco, are essential for calibration and validation of Earth system models. North of the Arctic Circle, sun remains visible at local midnight for a period of time, the number of days per year with midnight sun being dependent on latitude. The absence of nighttime conditions during Arctic summers renders the Nighttime method uncertain, however, no extensive assessment on the implications for flux partitioning has yet been made. In this study, we will assess the performance and validity of both partitioning methods along a latitudinal transect of northern sites included in the FLUXNET2015 dataset. We will evaluate the partitioned flux components against model simulations using the Community Land Model (CLM). Our results will be valuable for users interested in simulating Arctic and global carbon cycling.

Citizen scientists reveal: Marine litter pollutes Arctic beaches and affects wild life.

PubMed

Bergmann, Melanie; Lutz, Birgit; Tekman, Mine B; Gutow, Lars

2017-12-15

Recent data indicate accumulation areas of marine litter in Arctic waters and significant increases over time. Beaches on remote Arctic islands may be sinks for marine litter and reflect pollution levels of the surrounding waters particularly well. We provide the first quantitative data from surveys carried out by citizen scientists on six beaches of Svalbard. Litter quantities recorded by cruise tourists varied from 9-524gm -2 and were similar to those from densely populated areas. Plastics accounted for >80% of the overall litter, most of which originated from fisheries. Photographs provided by citizens show deleterious effects of beach litter on Arctic wildlife, which is already under strong pressure from global climate change. Our study highlights the potential of citizen scientists to provide scientifically valuable data on the pollution of sensitive remote ecosystems. The results stress once more that current legislative frameworks are insufficient to tackle the pollution of Arctic ecosystems. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

State of the Arctic Coast 2010: Scientific Review and Outlook

NASA Astrophysics Data System (ADS)

Rachold, V.; Forbes, D. L.; Kremer, H.; Lantuit, H.

2010-12-01

The coast is a key interface in the Arctic environment. It is a locus of human activity, a rich band of biodiversity, critical habitat, and high productivity, and among the most dynamic components of the circumpolar landscape. The Arctic coastal interface is a sensitive and important zone of interaction between land and sea, a region that provides essential ecosystem services and supports indigenous human lifestyles; a zone of expanding infrastructure investment and growing security concerns; and an area in which climate warming is expected to trigger landscape instability, rapid responses to change, and increased hazard exposure. Starting with a collaborative workshop in October 2007, the International Arctic Science Committee (IASC), the Land-Ocean Interactions in the Coastal Zone (LOICZ) Project and the International Permafrost Association (IPA) decided to jointly initiate an assessment of the state of the Arctic coast. The goal of this report is to draw on initial findings regarding climate change and human dimensions for the Arctic as a whole provided by the Arctic Climate Impact Assessment (ACIA) and Arctic Human Development Report (AHDR) to develop a comprehensive picture of status and current and anticipated change in the most sensitive Arctic coastal areas. Underlying is the concept of a social ecological system perspective that explores the implications of change for the interaction of humans with nature. The report is aimed to be a first step towards a continuously updated coastal assessment and to identify key issues seeking future scientific concern in an international Earth system research agenda. The report titled “State of the Arctic Coast 2010: Scientific Review and Outlook” is the outcome of this collaborative effort. It is organized in three parts: the first provides an assessment of the state of Arctic coastal systems under three broad disciplinary themes - physical systems, ecological systems, and human concerns in the coastal zone; the

Climate-driven changes in functional biogeography of Arctic marine fish communities.

PubMed

Frainer, André; Primicerio, Raul; Kortsch, Susanne; Aune, Magnus; Dolgov, Andrey V; Fossheim, Maria; Aschan, Michaela M

2017-11-14

Climate change triggers poleward shifts in species distribution leading to changes in biogeography. In the marine environment, fish respond quickly to warming, causing community-wide reorganizations, which result in profound changes in ecosystem functioning. Functional biogeography provides a framework to address how ecosystem functioning may be affected by climate change over large spatial scales. However, there are few studies on functional biogeography in the marine environment, and none in the Arctic, where climate-driven changes are most rapid and extensive. We investigated the impact of climate warming on the functional biogeography of the Barents Sea, which is characterized by a sharp zoogeographic divide separating boreal from Arctic species. Our unique dataset covered 52 fish species, 15 functional traits, and 3,660 stations sampled during the recent warming period. We found that the functional traits characterizing Arctic fish communities, mainly composed of small-sized bottom-dwelling benthivores, are being rapidly replaced by traits of incoming boreal species, particularly the larger, longer lived, and more piscivorous species. The changes in functional traits detected in the Arctic can be predicted based on the characteristics of species expected to undergo quick poleward shifts in response to warming. These are the large, generalist, motile species, such as cod and haddock. We show how functional biogeography can provide important insights into the relationship between species composition, diversity, ecosystem functioning, and environmental drivers. This represents invaluable knowledge in a period when communities and ecosystems experience rapid climate-driven changes across biogeographical regions. Copyright © 2017 the Author(s). Published by PNAS.

Final Technical Report for Project "Improving the Simulation of Arctic Clouds in CCSM3"

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stephen J. Vavrus

2008-11-15

amount in the CCSM3 climate model. J. Climate, 21, 5673-5687.). The article also provides a novel synthesis of surface- and satellite-based Arctic cloud observations that show how much the new freezedry parameterization improves the simulated cloud amount in high latitudes (Fig. 3). Freezedry has been incorporated into the CCSM3.5 version, in which it successfully limits the excessive polar clouds, and may be used in CCSM4. Material from this work is also appearing in a synthesis article on future Arctic cloud changes (Vavrus, D. Waliser, J. Francis, and A. Schweiger, 'Simulations of 20th and 21st century Arctic cloud amount in the global climate models assessed in the IPCC AR4', accepted in Climate Dynamics) and was used in a collaborative paper on Arctic cloud-sea ice coupling (Schweiger, A., R. Lindsay, S. Vavrus, and J. Francis, 2008: Relationships between Arctic sea ice and clouds during autumn. J. Climate, 21, 4799-4810.). This research was presented at the 2007 CCSM Annual Workshop, as well as the CCSM's 2007 Atmospheric Model Working Group and Polar Working Group Meetings. The findings were also shown at the 2007 Climate Change Prediction Program's Science Team Meeting. In addition, I served as an instructor at the International Arctic Research Center's (IARC) Summer School on Arctic Climate Modeling in Fairbanks this summer, where I presented on the challenges and techniques used in simulating polar clouds. I also contributed to the development of a new Arctic System Model by attending a workshop in Colorado this summer on this fledgling project. Finally, an outreach activity for the general public has been the development of an interactive web site () that displays Arctic cloud amount in the CMIP3 climate model archive under present and future scenarios. This site allows users to make polar and global maps of a variety of climate variables to investigate the individual and ensemble-mean GCM response to

Timing, Magnitude and Sources of Ecosystem Respiration in High Arctic Tundra of NW Greenland

NASA Astrophysics Data System (ADS)

Lupascu, M.; Xu, X.; Lett, C.; Maseyk, K. S.; Lindsey, D. S.; Thomas, J. S.; Welker, J. M.; Czimczik, C. I.

2011-12-01

High arctic ecosystems with low vegetation density contain significant stocks of organic carbon (C) in the form of soil organic matter that range in age from modern to ancient. How rapidly these C pools can be mineralized and lost to the atmosphere as CO2 (ecosystem respiration, ER) as a consequence of warming and, or changes in precipitation is a major uncertainty in our understanding of current and future arctic biogeochemistry and for predicting future levels of atmospheric CO2. In a 2-year study (2010-2011), we monitored seasonal changes in the magnitude, timing and sources of ER and soil pore space CO2 in the High Arctic of NW Greenland under current and simulated, future climate conditions. Measurements were taken from May to August at a multi-factorial, long-term climate change experiment in prostrate dwarf-shrub tundra on patterned ground with 5 treatments: (T1) +2oC warming, (T2) +4oC warming, (W) +50% summer precipitation, (T2W) +4oC + 50% summer precipitation, and (C) control. ER (using opaque chambers) and soil CO2 concentrations (wells) were monitored daily via infrared spectroscopy (LI-COR 800 & 840). The source of CO2 was inferred from its radiocarbon (14C) content analyzed at the AMS facility in UCI. CO2 was sampled monthly using molecular sieve traps (chambers) or evacuated canisters (wells). Highest rates of ER are observed on vegetated ground with a maximum in mid summer - reflecting a peak in plant productivity and soil temperature. Respiration rates from bare ground remain similar throughout the summer. Additional soil moisture, administered or due to precipitation events, strongly enhances ER from both vegetated and bare ground. Daily ER budget for the sampling period was of 53.1 mmol C m-2 day-1 for the (C) vegetated areas compared to the 60.0 for the (T2), 68.1 for the (T2W) or the 79.9 for the (W) treatment. ER was highly correlated to temperature (eg. C = 0.8; T2W = 0.8) until middle of July, when heavy precipitation started to occur. In

Carbon loss from an unprecedented Arctic tundra wildfire.

PubMed

Mack, Michelle C; Bret-Harte, M Syndonia; Hollingsworth, Teresa N; Jandt, Randi R; Schuur, Edward A G; Shaver, Gaius R; Verbyla, David L

2011-07-27

Arctic tundra soils store large amounts of carbon (C) in organic soil layers hundreds to thousands of years old that insulate, and in some cases maintain, permafrost soils. Fire has been largely absent from most of this biome since the early Holocene epoch, but its frequency and extent are increasing, probably in response to climate warming. The effect of fires on the C balance of tundra landscapes, however, remains largely unknown. The Anaktuvuk River fire in 2007 burned 1,039 square kilometres of Alaska's Arctic slope, making it the largest fire on record for the tundra biome and doubling the cumulative area burned since 1950 (ref. 5). Here we report that tundra ecosystems lost 2,016 ± 435 g C m(-2) in the fire, an amount two orders of magnitude larger than annual net C exchange in undisturbed tundra. Sixty per cent of this C loss was from soil organic matter, and radiocarbon dating of residual soil layers revealed that the maximum age of soil C lost was 50 years. Scaled to the entire burned area, the fire released approximately 2.1 teragrams of C to the atmosphere, an amount similar in magnitude to the annual net C sink for the entire Arctic tundra biome averaged over the last quarter of the twentieth century. The magnitude of ecosystem C lost by fire, relative to both ecosystem and biome-scale fluxes, demonstrates that a climate-driven increase in tundra fire disturbance may represent a positive feedback, potentially offsetting Arctic greening and influencing the net C balance of the tundra biome.

Seasonal cues of Arctic grayling movement in a small Arctic stream: the importance of surface water connectivity

USGS Publications Warehouse

Heim, Kurt C.; Wipfli, Mark S.; Whitman, Matthew S.; Arp, Christopher D.; Adams, Jeff; Falke, Jeffrey A.

2015-01-01

In Arctic ecosystems, freshwater fish migrate seasonally between productive shallow water habitats that freeze in winter and deep overwinter refuge in rivers and lakes. How these movements relate to seasonal hydrology is not well understood. We used passive integrated transponder tags and stream wide antennae to track 1035 Arctic grayling in Crea Creek, a seasonally flowing beaded stream on the Arctic Coastal Plain, Alaska. Migration of juvenile and adult fish into Crea Creek peaked in June immediately after ice break-up in the stream. Fish that entered the stream during periods of high flow and cold stream temperature traveled farther upstream than those entering during periods of lower flow and warmer temperature. We used generalized linear models to relate migration of adult and juvenile fish out of Crea Creek to hydrology. Most adults migrated in late June – early July, and there was best support (Akaike weight = 0.46; w i ) for a model indicating that the rate of migration increased with decreasing discharge. Juvenile migration occurred in two peaks; the early peak consisted of larger juveniles and coincided with adult migration, while the later peak occurred shortly before freeze-up in September and included smaller juveniles. A model that included discharge, minimum stream temperature, year, season, and mean size of potential migrants was most strongly supported (w i  = 0.86). Juvenile migration rate increased sharply as daily minimum stream temperature decreased, suggesting fish respond to impending freeze-up. We found fish movements to be intimately tied to the strong seasonality of discharge and temperature, and demonstrate the importance of small stream connectivity for migratory Arctic grayling during the entire open-water period. The ongoing and anticipated effects of climate change and petroleum development on Arctic hydrology (e.g. reduced stream connectivity, earlier peak flows, increased evapotranspiration) have important implications

Arctic marine fishes and their fisheries in light of global change.

PubMed

Christiansen, Jørgen S; Mecklenburg, Catherine W; Karamushko, Oleg V

2014-02-01

In light of ocean warming and loss of Arctic sea ice, harvested marine fishes of boreal origin (and their fisheries) move poleward into yet unexploited parts of the Arctic seas. Industrial fisheries, already in place on many Arctic shelves, will radically affect the local fish species as they turn up as unprecedented bycatch. Arctic marine fishes are indispensable to ecosystem structuring and functioning, but they are still beyond credible assessment due to lack of basic biological data. The time for conservation actions is now, and precautionary management practices by the Arctic coastal states are needed to mitigate the impact of industrial fisheries in Arctic waters. We outline four possible conservation actions: scientific credibility, 'green technology', legitimate management and overarching coordination. © 2013 The Authors Global Change Biology Published by John Wiley & Sons Ltd.

A (Mis)Match of User Needs, Science Priorities, and Funder Support: A Case Study of Arctic Sea Ice Knowledge

NASA Astrophysics Data System (ADS)

Sheffield Guy, L.; Wiggins, H. V.; Turner-Bogren, E. J.; Myers, B.

2016-12-01

Declining Arctic sea ice, and its impacts on the Arctic and globe, is a topic of increasing attention by scientists, diverse stakeholder groups, and the media. Research on Arctic sea ice is broad and inter-disciplinary, ranging from new technologies to monitor sea ice, to process studies, to examining the impacts of declining sea ice on ecosystems and people. There remain barriers, however, in transferring scientific knowledge of sea ice to serve decision-maker needs. This poster will examine possible causes of these barriers—including issues of communications across disciplines and perspectives, professional culture, funding agency restrictions, and the state of the science—through the lens of Arctic sea ice efforts that have occurred over the past several years. The poster will draw on experiences from the Sea Ice for Walrus Outlook (https://www.arcus.org/search-program/siwo), the Sea Ice Outlook (https://www.arcus.org/sipn/sea-ice-outlook), and various science planning exercises. Finally, the poster will synthesize relevant efforts in this arena and highlight opportunities for improvement.

Artificial Warming of Arctic Meadow under Pollution Stress: Experimental design

NASA Astrophysics Data System (ADS)

Moni, Christophe; Silvennoinen, Hanna; Fjelldal, Erling; Brenden, Marius; Kimball, Bruce; Rasse, Daniel

2014-05-01

Boreal and arctic terrestrial ecosystems are central to the climate change debate, notably because future warming is expected to be disproportionate as compared to world averages. Likewise, greenhouse gas (GHG) release from terrestrial ecosystems exposed to climate warming is expected to be the largest in the arctic. Artic agriculture, in the form of cultivated grasslands, is a unique and economically relevant feature of Northern Norway (e.g. Finnmark Province). In Eastern Finnmark, these agro-ecosystems are under the additional stressor of heavy metal and sulfur pollution generated by metal smelters of NW Russia. Warming and its interaction with heavy metal dynamics will influence meadow productivity, species composition and GHG emissions, as mediated by responses of soil microbial communities. Adaptation and mitigation measurements will be needed. Biochar application, which immobilizes heavy metal, is a promising adaptation method to promote positive growth response in arctic meadows exposed to a warming climate. In the MeadoWarm project we conduct an ecosystem warming experiment combined to biochar adaptation treatments in the heavy-metal polluted meadows of Eastern Finnmark. In summary, the general objective of this study is twofold: 1) to determine the response of arctic agricultural ecosystems under environmental stress to increased temperatures, both in terms of plant growth, soil organisms and GHG emissions, and 2) to determine if biochar application can serve as a positive adaptation (plant growth) and mitigation (GHG emission) strategy for these ecosystems under warming conditions. Here, we present the experimental site and the designed open-field warming facility. The selected site is an arctic meadow located at the Svanhovd Research station less than 10km west from the Russian mining city of Nikel. A splitplot design with 5 replicates for each treatment is used to test the effect of biochar amendment and a 3oC warming on the Arctic meadow. Ten circular

Large increases in Arctic biogenic volatile emissions are a direct effect of warming

NASA Astrophysics Data System (ADS)

Kramshøj, Magnus; Vedel-Petersen, Ida; Schollert, Michelle; Rinnan, Åsmund; Nymand, Josephine; Ro-Poulsen, Helge; Rinnan, Riikka

2016-05-01

Biogenic volatile organic compounds are reactive gases that can contribute to atmospheric aerosol formation. Their emission from vegetation is dependent on temperature and light availability. Increasing temperature, changing cloud cover and shifting composition of vegetation communities can be expected to affect emissions in the Arctic, where the ongoing climate changes are particularly severe. Here we present biogenic volatile organic compound emission data from Arctic tundra exposed to six years of experimental warming or reduced sunlight treatment in a randomized block design. By separately assessing the emission response of the whole ecosystem, plant shoots and soil in four measurements covering the growing season, we have identified that warming increased the emissions directly rather than via a change in the plant biomass and species composition. Warming caused a 260% increase in total emission rate for the ecosystem and a 90% increase in emission rates for plants, while having no effect on soil emissions. Compared to the control, reduced sunlight decreased emissions by 69% for the ecosystem, 61-65% for plants and 78% for soil. The detected strong emission response is considerably higher than observed at more southern latitudes, emphasizing the high temperature sensitivity of ecosystem processes in the changing Arctic.

Plankton ecosystem functioning and nitrogen fluxes in the most oligotrophic waters of the Beaufort Sea, Arctic Ocean: a modeling study

NASA Astrophysics Data System (ADS)

Le Fouest, V.; Zakardjian, B.; Xie, H.; Raimbault, P.; Joux, F.; Babin, M.

2012-10-01

The Arctic Ocean (AO) undergoes profound changes of its physical and biotic environments due to climate change. The greater light exposure and stratification alter its plankton ecosystem structure, functioning and productivity promoting oligotrophy in some areas as the Beaufort Sea. A one-dimension (1-D) physical-biological coupled model based on the large multiparametric database of the Malina project in the Beaufort Sea was used (i) to infer the functioning and nitrogen fluxes within the summer plankton ecosystem and (ii) to assess the model sensitivity to key light-associated processes involved in nutrient recycling and phytoplankton growth. The coupled model suggested that ammonium photochemically produced from photosensitive dissolved organic nitrogen (i.e. photoammonification process) was a necessary nitrogen source to achieve the observed levels of microbial biomass and production. It contributed to ca. two-thirds and one-third of the simulated surface (0-10 m) and depth-integrated primary and bacterial production, respectively. The model also suggested that carbon to chlorophyll ratios for small (< 5 μm) phytoplankton (ca. 15-45 g g-1) lower than those commonly used in biogeochemical models applied to the AO were required to simulate the observed herbivorous versus microbial food web competition and realistic nitrogen fluxes in the Beaufort Sea oligotrophic waters. In face of accelerating Arctic warming, more attention should be paid in the future to the mechanistic processes involved in food webs and functional groups competition, nutrient recycling and primary production in poorly productive waters of the AO as they are expected to expand rapidly.

Net ecosystem exchange of CO2 with rapidly changing high Arctic landscapes.

PubMed

Emmerton, Craig A; St Louis, Vincent L; Humphreys, Elyn R; Gamon, John A; Barker, Joel D; Pastorello, Gilberto Z

2016-03-01

High Arctic landscapes are expansive and changing rapidly. However, our understanding of their functional responses and potential to mitigate or enhance anthropogenic climate change is limited by few measurements. We collected eddy covariance measurements to quantify the net ecosystem exchange (NEE) of CO2 with polar semidesert and meadow wetland landscapes at the highest latitude location measured to date (82°N). We coupled these rare data with ground and satellite vegetation production measurements (Normalized Difference Vegetation Index; NDVI) to evaluate the effectiveness of upscaling local to regional NEE. During the growing season, the dry polar semidesert landscape was a near-zero sink of atmospheric CO2 (NEE: -0.3 ± 13.5 g C m(-2) ). A nearby meadow wetland accumulated over 300 times more carbon (NEE: -79.3 ± 20.0 g C m(-2) ) than the polar semidesert landscape, and was similar to meadow wetland NEE at much more southerly latitudes. Polar semidesert NEE was most influenced by moisture, with wetter surface soils resulting in greater soil respiration and CO2 emissions. At the meadow wetland, soil heating enhanced plant growth, which in turn increased CO2 uptake. Our upscaling assessment found that polar semidesert NDVI measured on-site was low (mean: 0.120-0.157) and similar to satellite measurements (mean: 0.155-0.163). However, weak plant growth resulted in poor satellite NDVI-NEE relationships and created challenges for remotely detecting changes in the cycling of carbon on the polar semidesert landscape. The meadow wetland appeared more suitable to assess plant production and NEE via remote sensing; however, high Arctic wetland extent is constrained by topography to small areas that may be difficult to resolve with large satellite pixels. We predict that until summer precipitation and humidity increases enough to offset poor soil moisture retention, climate-related changes to productivity on polar semideserts may be restricted. © 2015 John

Patterns and processes influencing helminth parasites of Arctic coastal communities during climate change.

PubMed

Galaktionov, K V

2017-07-01

This review analyses the scarce available data on biodiversity and transmission of helminths in Arctic coastal ecosystems and the potential impact of climate changes on them. The focus is on the helminths of seabirds, dominant parasites in coastal ecosystems. Their fauna in the Arctic is depauperate because of the lack of suitable intermediate hosts and unfavourable conditions for species with free-living larvae. An increasing proportion of crustaceans in the diet of Arctic seabirds would result in a higher infection intensity of cestodes and acanthocephalans, and may also promote the infection of seabirds with non-specific helminths. In this way, the latter may find favourable conditions for colonization of new hosts. Climate changes may alter the composition of the helminth fauna, their infection levels in hosts and ways of transmission in coastal communities. Immigration of boreal invertebrates and fish into Arctic seas may allow the circulation of helminths using them as intermediate hosts. Changing migratory routes of animals would alter the distribution of their parasites, facilitating, in particular, their trans-Arctic transfer. Prolongation of the seasonal 'transmission window' may increase the parasitic load on host populations. Changes in Arctic marine food webs would have an overriding influence on the helminths' circulation. This process may be influenced by the predicted decreased of salinity in Arctic seas, increased storm activity, coastal erosion, ocean acidification, decline of Arctic ice, etc. Greater parasitological research efforts are needed to assess the influence of factors related to Arctic climate change on the transmission of helminths.

Understanding Litter Input Controls on Soil Organic Matter Turnover and Formation are Essential for Improving Carbon-Climate Feedback Predictions for Arctic, Tundra Ecosystems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wallenstein, Matthew

The Arctic region stored vast amounts of carbon (C) in soils over thousands of years because decomposition has been limited by cold, wet conditions. Arctic soils now contain roughly as much C that is contained in all other soils across the globe combined. However, climate warming could unlock this oil C as decomposition accelerates and permafrost thaws. In addition to temperature-driven acceleration of decomposition, several additional processes could either counteract or augment warming-induced SOM losses. For example, increased plant growth under a warmer climate will increase organic matter inputs to soils, which could fuel further soil decomposition by microbes, butmore » will also increase the production of new SOM. Whether Arctic ecosystems store or release carbon in the future depends in part on the balance between these two counteracting processes. By differentiating SOM decomposition and formation and understanding the drivers of these processes, we will better understand how these systems function. We did not find evidence of priming under current conditions, defined as an increase in the decomposition of native SOM stocks. This suggests that decomposition is unlikely to be further accelerated through this mechanism. We did find that decomposition of native SOM did occur when nitrogen was added to these soils, suggesting that nitrogen limits decomposition in these systems. Our results highlight the resilience and extraordinary C storage capacity of these soils, and suggest shrub expansion may partially mitigate C losses from decomposition of old SOM as Arctic soils warm.« less

Replacement cost valuation of Northern Pintail (Anas acuta) subsistence harvest in Arctic and sub-Arctic North America

USGS Publications Warehouse

Goldstein, Joshua H.; Thogmartin, Wayne E.; Bagstad, Kenneth J.; Dubovsky, James A.; Mattsson, Brady J.; Semmens, Darius J.; López-Hoffman, Laura; Diffendorfer, James E.

2014-01-01

Migratory species provide economically beneficial ecosystem services to people throughout their range, yet often, information is lacking about the magnitude and spatial distribution of these benefits at regional scales. We conducted a case study for Northern Pintails (hereafter pintail) in which we quantified regional and sub-regional economic values of subsistence harvest to indigenous communities in Arctic and sub-Arctic North America. As a first step, we used the replacement cost method to quantify the cost of replacing pintail subsistence harvest with the most similar commercially available protein (chicken). For an estimated annual subsistence harvest of ˜15,000 pintail, our mean estimate of the total replacement cost was ˜$63,000 yr−1 ($2010 USD), with sub-regional values ranging from \\$263 yr−1 to \\$21,930 yr−1. Our results provide an order-of-magnitude, conservative estimate of one component of the regional ecosystem-service values of pintails, providing perspective on how spatially explicit values can inform migratory species conservation.

Live from the Arctic

NASA Astrophysics Data System (ADS)

Warnick, W. K.; Haines-Stiles, G.; Warburton, J.; Sunwood, K.

2003-12-01

For reasons of geography and geophysics, the poles of our planet, the Arctic and Antarctica, are places where climate change appears first: they are global canaries in the mine shaft. But while Antarctica (its penguins and ozone hole, for example) has been relatively well-documented in recent books, TV programs and journalism, the far North has received somewhat less attention. This project builds on and advances what has been done to date to share the people, places, and stories of the North with all Americans through multiple media, over several years. In a collaborative project between the Arctic Research Consortium of the United States (ARCUS) and PASSPORT TO KNOWLEDGE, Live from the Arctic will bring the Arctic environment to the public through a series of primetime broadcasts, live and taped programming, interactive virtual field trips, and webcasts. The five-year project will culminate during the 2007-2008 International Polar Year (IPY). Live from the Arctic will: A. Promote global understanding about the value and world -wide significance of the Arctic, B. Bring cutting-edge research to both non-formal and formal education communities, C. Provide opportunities for collaboration between arctic scientists, arctic communities, and the general public. Content will focus on the following four themes. 1. Pan-Arctic Changes and Impacts on Land (i.e. snow cover; permafrost; glaciers; hydrology; species composition, distribution, and abundance; subsistence harvesting) 2. Pan-Arctic Changes and Impacts in the Sea (i.e. salinity, temperature, currents, nutrients, sea ice, marine ecosystems (including people, marine mammals and fisheries) 3. Pan-Arctic Changes and Impacts in the Atmosphere (i.e. precipitation and evaporation; effects on humans and their communities) 4. Global Perspectives (i.e. effects on humans and communities, impacts to rest of the world) In The Earth is Faster Now, a recent collection of comments by members of indigenous arctic peoples, arctic

The Arctic Research Consortium of the United States

NASA Astrophysics Data System (ADS)

Warnick, W. K.; Wiggins, H. V.

2007-12-01

The Arctic Research Consortium of the United States (ARCUS) is a nonprofit membership organization composed of universities and institutions that have a substantial commitment to research in the Arctic. ARCUS was formed in 1988 to serve as a forum for planning, facilitating, coordinating, and implementing interdisciplinary studies of the Arctic; to act as a synthesizer and disseminator of scientific information on arctic research; and to educate scientists and the general public about the needs and opportunities for research in the Arctic. ARCUS, in collaboration with the broad science community, relevant agencies and organizations, and other stakeholders, coordinates science planning and educational activities across disciplinary and organizational boundaries. Examples of current ARCUS science planning activities include: serving as the project office for the multi-agency Study of Environmental Arctic Change (SEARCH) program and providing support to the related Bering Ecosystem Study (BEST), and serving as the Science Management Office for the National Science Foundation (NSF) Arctic System Science (ARCSS) Program. ARCUS' central educational activity is PolarTREC (Teachers and Researchers Exploring and Collaborating), an International Polar Year (IPY) program whereby K-12 educators and researchers work together in hands-on field experiences in the Arctic and Antarctic to advance polar science education. Additional science planning, educational, information, and outreach activities include the Witness the Arctic newsletter, the Arctic Visiting Speakers' Series, the ArcticInfo listserve, the Internet Media Archive (IMA), the annual Arctic Forum conference, and many others. More information about these and other ARCUS activities can be found at the ARCUS website at www.arcus.org.

Changing Arctic ecosystems - measuring and forecasting the response of Alaska's terrestrial ecosystem to a warming climate

USGS Publications Warehouse

Pearce, John M.; DeGange, Anthony R.; Flint, Paul L.; Fondell, Tom F.; Gustine, David D.; Holland-Bartels, Leslie E.; Hope, Andrew G.; Hupp, Jerry W.; Koch, Joshua C.; Schmutz, Joel A.; Talbot, Sandra L.; Ward, David; Whalen, Mary E.

2012-01-01

The Arctic Coastal Plain of northern Alaska is a complex landscape of lakes, streams, and wetlands scattered across low relief tundra that is underlain by permafrost. This region of the Arctic has experienced a warming trend over the past three decades, leading to thawing of on-shore permafrost and the disappearance of sea ice at an unprecedented rate. The loss of sea ice has increased ocean wave action, leading to higher rates of erosion and salt water inundation of coastal habitats. Warming temperatures also have advanced the overall phenology of the region, including earlier snowmelt, lake ice thaw, and plant growth. As a result, many migratory species now arrive in the Arctic several days earlier in spring than in the 1970s. Predicted warming trends for the future will continue to alter plant growth, ice thaw, and other basic landscape processes. These changes will undoubtedly result in different responses by wildlife (fish, birds, and mammals) and the food they rely upon (plants, invertebrates, and fish). However, the type of response by different wildlife populations and their habitats-either positively or negatively-remains largely unknown.

Physiological and ecological effects of increasing temperature on fish production in lakes of Arctic Alaska

USGS Publications Warehouse

Carey, Michael P.; Zimmerman, Christian E.

2014-01-01

Lake ecosystems in the Arctic are changing rapidly due to climate warming. Lakes are sensitive integrators of climate-induced changes and prominent features across the Arctic landscape, especially in lowland permafrost regions such as the Arctic Coastal Plain of Alaska. Despite many studies on the implications of climate warming, how fish populations will respond to lake changes is uncertain for Arctic ecosystems. Least Cisco (Coregonus sardinella) is a bellwether for Arctic lakes as an important consumer and prey resource. To explore the consequences of climate warming, we used a bioenergetics model to simulate changes in Least Cisco production under future climate scenarios for lakes on the Arctic Coastal Plain. First, we used current temperatures to fit Least Cisco consumption to observed annual growth. We then estimated growth, holding food availability, and then feeding rate constant, for future projections of temperature. Projected warmer water temperatures resulted in reduced Least Cisco production, especially for larger size classes, when food availability was held constant. While holding feeding rate constant, production of Least Cisco increased under all future scenarios with progressively more growth in warmer temperatures. Higher variability occurred with longer projections of time mirroring the expanding uncertainty in climate predictions further into the future. In addition to direct temperature effects on Least Cisco growth, we also considered changes in lake ice phenology and prey resources for Least Cisco. A shorter period of ice cover resulted in increased production, similar to warming temperatures. Altering prey quality had a larger effect on fish production in summer than winter and increased relative growth of younger rather than older age classes of Least Cisco. Overall, we predicted increased production of Least Cisco due to climate warming in lakes of Arctic Alaska. Understanding the implications of increased production of Least Cisco to

Physiological and ecological effects of increasing temperature on fish production in lakes of Arctic Alaska.

PubMed

Carey, Michael P; Zimmerman, Christian E

2014-05-01

Lake ecosystems in the Arctic are changing rapidly due to climate warming. Lakes are sensitive integrators of climate-induced changes and prominent features across the Arctic landscape, especially in lowland permafrost regions such as the Arctic Coastal Plain of Alaska. Despite many studies on the implications of climate warming, how fish populations will respond to lake changes is uncertain for Arctic ecosystems. Least Cisco (Coregonus sardinella) is a bellwether for Arctic lakes as an important consumer and prey resource. To explore the consequences of climate warming, we used a bioenergetics model to simulate changes in Least Cisco production under future climate scenarios for lakes on the Arctic Coastal Plain. First, we used current temperatures to fit Least Cisco consumption to observed annual growth. We then estimated growth, holding food availability, and then feeding rate constant, for future projections of temperature. Projected warmer water temperatures resulted in reduced Least Cisco production, especially for larger size classes, when food availability was held constant. While holding feeding rate constant, production of Least Cisco increased under all future scenarios with progressively more growth in warmer temperatures. Higher variability occurred with longer projections of time mirroring the expanding uncertainty in climate predictions further into the future. In addition to direct temperature effects on Least Cisco growth, we also considered changes in lake ice phenology and prey resources for Least Cisco. A shorter period of ice cover resulted in increased production, similar to warming temperatures. Altering prey quality had a larger effect on fish production in summer than winter and increased relative growth of younger rather than older age classes of Least Cisco. Overall, we predicted increased production of Least Cisco due to climate warming in lakes of Arctic Alaska. Understanding the implications of increased production of Least Cisco to

Arctic ecosystem reaction on permafrost melting as a result of 40 years anthropogenic impact

NASA Astrophysics Data System (ADS)

Petrzhik, Nataliya; Matyshak, George; Myshonkov, Alexander; Petrov, Dmitry

2017-04-01

Arctic ecosystems are sensitive indicators of environmental change. The increasing of anthropogenic impact perturb the natural ecosystems balance, first of all significant changes happen in soil and vegetation. It is necessary to study the permafrost ecosystem response, as the permafrost covers the quarter of the world and more than a half of Russia. Since 1960 the oil and gas industry grows in Russia. The hydrocarbons can be transferred by pipelines only in the heated state. The main effect of construction and operation of pipeline is the heating of soil and permafrost degradation. The goal of this study was to estimate the response of landscapes and permafrost ecosystem of north of West Siberia to the cumulative action of pipelines. The main objective was to investigate the warming impact on the properties and function of the soil along the pipelines in permafrost zone. The studied object was vegetation and soil cover of the north of Western Siberia ecosystems after the action of pipelines. The areas with maximum effect of heat lines were selected by remote sensing. Ten transects of 50 meters in length with sampling points every 5 meters from pipeline to undisturbed background area were selected in three different natural zones. The soil and vegetation cover was described, sampled, active layer of soil and the power of organic horizon were measured, the hydrothermal regime of soils in a layer of 0-10 cm was measured, the emission of greenhouse gas was studied. In the laboratory, the content of labile carbon, microbial biomass carbon, basal and substrate-induced respiration were measured. The main effect of the pipelines impact is the active degradation of permafrost and changes in hydrothermal settings. From background to broken areas the following settings changing: the depth of thawing increase in 10 times; the soil temperature changes from 4 to 10,5 ° C in taiga, from 4.5 to 13,5 ° C in tundra, from 5.5 to 12 ° C in forest-tundra; the soil moisture reduces

Environmental behaviour of short-chain chlorinated paraffins in aquatic and terrestrial ecosystems of Ny-Ålesund and London Island, Svalbard, in the Arctic.

PubMed

Li, Huijuan; Fu, Jianjie; Pan, Wenxiao; Wang, Pu; Li, Yingming; Zhang, Qinghua; Wang, Yawei; Zhang, Aiqian; Liang, Yong; Jiang, Guibin

2017-07-15

The environmental behaviour of short-chain chlorinated paraffins (SCCPs) was investigated in both aquatic and terrestrial ecosystems in the Arctic. The mean concentrations of SCCPs in the aquatic and terrestrial samples were 178.9ng/g dry weight (dw) and 157.2ng/g dw, respectively. Short carbon chain (C 10 ) and less-chlorinated (Cl 6 ) congener groups were predominant in the Arctic samples, accounting for 48.6% and 34.8% of the total SCCPs, respectively. The enrichment of lighter SCCP congener groups (i.e., fewer chlorine atoms with shorter carbon chain lengths) indicated that the fractionation process occurred during long-range transport. The biomagnification factor (BMF) was 0.46 from gammarid to cod, which indicated that the SCCPs did not biomagnify between these two species. The soil-vegetation bioaccumulation factor (BAF) of SCCPs was 29.9, and C 13 and Cl 7, 8 congener groups tended to accumulate in the terrestrial vegetation. Regression analysis (BAFs=10.9×#C+5.6×#Cl-125.2, R=0.53, P<0.01) showed that the number of carbon and chlorine atoms influenced the bioaccumulative behaviour of SCCPs and suggested that the number of carbon atoms had a greater influence on the BAFs of SCCPs in the terrestrial ecosystem than did the number of chlorine atoms. Copyright © 2017 Elsevier B.V. All rights reserved.

Modelling carbon responses of tundra ecosystems to historical and projected climate: Sensitivity of pan-Arctic carbon storage to temporal and spatial variation in climate

USGS Publications Warehouse

McGuire, A.D.; Clein, Joy S.; Melillo, J.M.; Kicklighter, D.W.; Meier, R.A.; Vorosmarty, C.J.; Serreze, Mark C.

2000-01-01

Historical and projected climate trends for high latitudes show substantial temporal and spatial variability. To identify uncertainties in simulating carbon (C) dynamics for pan-Arctic tundra, we compare the historical and projected responses of tundra C storage from 1921 to 2100 between simulations by the Terrestrial Ecosystem Model (TEM) for the pan-Arctic and the Kuparuk River Basin, which was the focus of an integrated study of C dynamics from 1994 to 1996. In the historical period from 1921 to 1994, the responses of net primary production (NPP) and heterotrophic respiration (RH) simulated for the Kuparuk River Basin and the pan-Arctic are correlated with the same factors; NPP is positively correlated with net nitrogen mineralization (NMIN) and RH is negatively correlated with mean annual soil moisture. In comparison to the historical period, the spatially aggregated responses of NPP and RH for the Kuparuk River Basin and the pan-Arctic in our simulations for the projected period have different sensitivities to temperature, soil moisture and NMIN. In addition to being sensitive to soil moisture during the projected period, RH is also sensitive to temperature and there is a significant correlation between RH and NMIN. We interpret the increases in NPP during the projected period as being driven primarily by increases in NMIN, and that the correlation between NPP and temperature in the projected period is a result primarily of the causal linkage between temperature, RH, and NMIN. Although similar factors appear to be controlling simulated regional-and biome-scale C dynamics, simulated C dynamics at the two scales differ in magnitude with higher increases in C storage simulated for the Kuparuk River Basin than for the pan-Arctic at the end of the historical period and throughout the projected period. Also, the results of the simulations indicate that responses of C storage show different climate sensitivities at regional and pan-Arctic spatial scales and that

The Circumpolar Arctic vegetation map

USGS Publications Warehouse

Walker, Donald A.; Raynolds, Martha K.; Daniels, F.J.A.; Einarsson, E.; Elvebakk, A.; Gould, W.A.; Katenin, A.E.; Kholod, S.S.; Markon, C.J.; Melnikov, E.S.; Moskalenko, N.G.; Talbot, S. S.; Yurtsev, B.A.; Bliss, L.C.; Edlund, S.A.; Zoltai, S.C.; Wilhelm, M.; Bay, C.; Gudjonsson, G.; Ananjeva, G.V.; Drozdov, D.S.; Konchenko, L.A.; Korostelev, Y.V.; Ponomareva, O.E.; Matveyeva, N.V.; Safranova, I.N.; Shelkunova, R.; Polezhaev, A.N.; Johansen, B.E.; Maier, H.A.; Murray, D.F.; Fleming, Michael D.; Trahan, N.G.; Charron, T.M.; Lauritzen, S.M.; Vairin, B.A.

2005-01-01

Question: What are the major vegetation units in the Arctic, what is their composition, and how are they distributed among major bioclimate subzones and countries? Location: The Arctic tundra region, north of the tree line. Methods: A photo-interpretive approach was used to delineate the vegetation onto an Advanced Very High Resolution Radiometer (AVHRR) base image. Mapping experts within nine Arctic regions prepared draft maps using geographic information technology (ArcInfo) of their portion of the Arctic, and these were later synthesized to make the final map. Area analysis of the map was done according to bioclimate subzones, and country. The integrated mapping procedures resulted in other maps of vegetation, topography, soils, landscapes, lake cover, substrate pH, and above-ground biomass. Results: The final map was published at 1:7 500 000 scale map. Within the Arctic (total area = 7.11 x 106 km 2), about 5.05 ?? 106 km2 is vegetated. The remainder is ice covered. The map legend generally portrays the zonal vegetation within each map polygon. About 26% of the vegetated area is erect shrublands, 18% peaty graminoid tundras, 13% mountain complexes, 12% barrens, 11% mineral graminoid tundras, 11% prostrate-shrub tundras, and 7% wetlands. Canada has by far the most terrain in the High Arctic mostly associated with abundant barren types and prostrate dwarf-shrub tundra, whereas Russia has the largest area in the Low Arctic, predominantly low-shrub tundra. Conclusions: The CAVM is the first vegetation map of an entire global biome at a comparable resolution. The consistent treatment of the vegetation across the circumpolar Arctic, abundant ancillary material, and digital database should promote the application to numerous land-use, and climate-change applications and will make updating the map relatively easy. ?? IAVS; Opulus Press.

Global Mercury Pathways in the Arctic Ecosystem

NASA Astrophysics Data System (ADS)

Lahoutifard, N.; Lean, D.

2003-12-01

The sudden depletions of atmospheric mercury which occur during the Arctic spring are believed to involve oxidation of gaseous elemental mercury, Hg(0), rendering it less volatile and more soluble. The Hg(II) oxidation product(s) are more susceptible to deposition, consistent with the observation of dramatic increases in snow mercury levels during depletion events. Temporal correlations with ozone depletion events and the proliferation of BrO radicals support the hypothesis that oxidation of Hg(0) occurs in the gas phase and results in its conversion to RGM (Reactive Gaseous Mercury). The mechanisms of Hg(0) oxidation and particularly Hg(II) reduction are as yet unproven. In order to evaluate the feasibility of proposed chemical processes involving mercury in the Arctic atmosphere and its pathway after deposition on the snow from the air, we investigated mercury speciation in air and snow pack at Resolute, Nunavut, Canada (latitude 75° N) prior to and during snow melt during spring 2003. Quantitative, real-time information on emission, air transport and deposition were combined with experimental studies of the distribution and concentrations of different mercury species, methyl mercury, anions, total organic carbon and total inorganic carbon in snow samples. The effect of solar radiation and photoreductants on mercury in snow samples was also investigated. In this work, we quantify mercury removed from the air, and deposited on the snow and the transformation to inorganic and methyl mercury.

Modeling leaf phenology variation by groupings of species within and across ecosystems in northern Alaska

NASA Astrophysics Data System (ADS)

Euskirchen, E. S.; Carman, T. B.; McGuire, A. D.

2012-12-01

The phenology of arctic ecosystems is driven primarily by abiotic forces, with temperature acting as the main determinant of growing season onset and leaf budburst and in the spring. However, while the plant species in arctic ecosystems require differing amounts of accumulated heat for leaf-out, dynamic vegetation models simulated over a regional to global scale typically assume some average leaf-out for all of the species within an ecosystem. Here, we make use of air temperature records and observational data of spring leaf phenology collected across dominant groupings of species (dwarf birch shrubs, willow shrubs, other deciduous shrubs, grasses, sedges, and forbs) in arctic and ecotonal boreal ecosystems in Alaska. We then parameterize a dynamic vegetation model based on these data for four types of tundra ecosystems (heath tundra, shrub tundra, wet sedge tundra, and tussock tundra), as well as ecotonal boreal white spruce forest. This implementation improves the timing of the onset of carbon uptake in the spring, permitting a more accurate assessment of the contribution of each grouping of species to ecosystem performance. Furthermore, this implementation provides a more nuanced perspective on light competition among species and across ecosystems. For example, in the shrub tundra, the sedges and grasses leaf-out before the shade-inducing willow and dwarf birch, thereby providing the sedges and grasses time to accumulate biomass before shading effects arise. Also in the shrub tundra, the forbs leaf-out last, and are therefore, more prone to shading impacts by the taller willow and dwarf birch shrubs. However, in the wet sedge and heath tundra ecosystems, the forbs leaf-out before the shrubs, and are therefore less prone to shading impacts early in the growing season. These findings indicate the importance of leaf phenology data collection by species and across the various ecosystem types within the highly heterogeneous Arctic landscape. These findings also

SEARCH: Study of Environmental Arctic Change—A System-scale, Cross-disciplinary Arctic Research Program

NASA Astrophysics Data System (ADS)

Wiggins, H. V.; Eicken, H.; Fox, S. E.; Search Science Steering Committee

2010-12-01

The Study of Environmental Arctic Change (SEARCH) is a multi-agency effort to understand system-scale arctic change. Interrelated environmental changes in the Arctic are affecting ecosystems and living resources and are impacting local and global communities. The SEARCH program is guided by the Science Steering Committee (SSC), the Interagency Program Management Committee (IPMC), and focused panels. Over 150 projects and activities contribute to SEARCH implementation. The Observing Change component is underway through the National Science Foundation’s (NSF) Arctic Observing Network (AON), NOAA-sponsored atmospheric and sea ice observations, and other relevant national and international efforts. The Understanding Change component of SEARCH consists of modeling and analysis efforts, with strong linkages to relevant programs such as NSF’s Arctic System Science (ARCSS) Program. The SEARCH Sea Ice Outlook (http://www.arcus.org/search/seaiceoutlook/index.php) is an "Understanding Change" synthesis effort that aims to advance our understanding of the arctic sea ice system. The Responding to Change element currently includes initial planning efforts by the International Study of Arctic Change (ISAC) program as well as a newly-launched "Sea Ice for Walrus Outlook," which is a weekly report of sea ice conditions geared to Alaska Native walrus subsistence hunters, coastal communities, and others interested in sea ice and walrus (http://www.arcus.org/search/siwo). SEARCH is sponsored by eight U.S. agencies, including: the National Science Foundation (NSF), the National Oceanic and Atmospheric Administration (NOAA), the National Aeronautics and Space Administration (NASA), the Department of Defense (DOD), the Department of Energy (DOE), the Department of the Interior (DOI), the Smithsonian Institution, and the U.S. Department of Agriculture (USDA). The U.S. Arctic Research Commission participates as an IPMC observer. For further information, please visit the website: http

The response of aboveground plant productivity to earlier snowmelt and summer warming in an Arctic ecosystem

NASA Astrophysics Data System (ADS)

Livensperger, C.; Steltzer, H.; Darrouzet-Nardi, A.; Sullivan, P.; Wallenstein, M. D.; Weintraub, M. N.

2012-12-01

Plant communities in the Arctic are undergoing changes in structure and function due to shifts in seasonality from changing winters and summer warming. These changes will impact biogeochemical cycling, surface energy balance, and functioning of vertebrate and invertebrate communities. To examine seasonal controls on aboveground net primary production (ANPP) in a moist acidic tundra ecosystem in northern Alaska, we shifted the growing season by accelerating snowmelt (using radiation absorbing shadecloth) and warming air and soil temperature (using 1 m2 open-top chambers), individually and in combination. After three years, we measured ANPP by harvesting up to 16 individual ramets, tillers and rhizomes for each of 7 plant species, including two deciduous shrubs, two graminoids, two evergreen shrubs and one forb during peak season. Our results show that ANPP per stem summed across the 7 species increased when snow melt occurred earlier. However, standing biomass, excluding current year growth, was also greater. The ratio of ANPP/standing biomass decreased in all treatments compared to the control. ANPP per unit standing biomass summed for the four shrub species decreases due to summer warming alone or in combination with early snowmelt; however early snowmelt alone did not lead to lower ANPP for the shrubs. ANPP per tiller or rhizome summed for the three herbaceous species increased in response to summer warming. Understanding the differential response of plants to changing seasonality will inform predictions of future Arctic plant community structure and function.

A Recommended Set of Key Arctic Indicators

NASA Astrophysics Data System (ADS)

Stanitski, D.; Druckenmiller, M.; Fetterer, F. M.; Gerst, M.; Intrieri, J. M.; Kenney, M. A.; Meier, W.; Overland, J. E.; Stroeve, J.; Trainor, S.

2017-12-01

The Arctic is an interconnected and environmentally sensitive system of ice, ocean, land, atmosphere, ecosystems, and people. From local to pan-Arctic scales, the area has already undergone major changes in physical and societal systems and will continue at a pace that is greater than twice the global average. Key Arctic indicators can quantify these changes. Indicators serve as the bridge between complex information and policy makers, stakeholders, and the general public, revealing trends and information people need to make important socioeconomic decisions. This presentation evaluates and compiles more than 70 physical, biological, societal and economic indicators into an approachable summary that defines the changing Arctic. We divided indicators into "existing," "in development," "possible," and "aspirational". In preparing a paper on Arctic Indicators for a special issue of the journal Climatic Change, our group established a set of selection criteria to identify indicators to specifically guide decision-makers in their responses to climate change. A goal of the analysis is to select a manageable composite list of recommended indicators based on sustained, reliable data sources with known user communities. The selected list is also based on the development of a conceptual model that identifies components and processes critical to our understanding of the Arctic region. This list of key indicators is designed to inform the plans and priorities of multiple groups such as the U.S. Global Change Research Program (USGCRP), Interagency Arctic Research Policy Committee (IARPC), and the Arctic Council.

Climate change and the ecology and evolution of Arctic vertebrates.

PubMed

Gilg, Olivier; Kovacs, Kit M; Aars, Jon; Fort, Jérôme; Gauthier, Gilles; Grémillet, David; Ims, Rolf A; Meltofte, Hans; Moreau, Jérôme; Post, Eric; Schmidt, Niels Martin; Yannic, Glenn; Bollache, Loïc

2012-02-01

Climate change is taking place more rapidly and severely in the Arctic than anywhere on the globe, exposing Arctic vertebrates to a host of impacts. Changes in the cryosphere dominate the physical changes that already affect these animals, but increasing air temperatures, changes in precipitation, and ocean acidification will also affect Arctic ecosystems in the future. Adaptation via natural selection is problematic in such a rapidly changing environment. Adjustment via phenotypic plasticity is therefore likely to dominate Arctic vertebrate responses in the short term, and many such adjustments have already been documented. Changes in phenology and range will occur for most species but will only partly mitigate climate change impacts, which are particularly difficult to forecast due to the many interactions within and between trophic levels. Even though Arctic species richness is increasing via immigration from the South, many Arctic vertebrates are expected to become increasingly threatened during this century. © 2012 New York Academy of Sciences.

Future Arctic Research: Integrative Approaches to Scientific and Methodological Challenges

NASA Astrophysics Data System (ADS)

Schmale, Julia; Lisowska, Maja; Smieszek, Malgorzata

2013-08-01

Climate change has significant consequences for both the natural environment and the socioeconomics in the Arctic. The complex interplay between the changing atmosphere, cryosphere, and ocean is responsible for a multitude of feedbacks and cascading effects leading to changes in the marine and terrestrial ecosystems, the sea ice cycle, and atmospheric circulation patterns. The warming Arctic has also become a region of economic interest as shipping, natural resource exploitation, and tourism are becoming achievable and lucrative with declining sea ice. Such climatic and anthropogenic developments are leading to profound changes in the Arctic, its people, and their cultural heritage.

Monitoring boreal ecosystem phenology with integrated active/passive microwave remote sensing

NASA Technical Reports Server (NTRS)

McDonald, K. C.; Njoku, E.; Kimball, J.; Running, S.; Thompson, C.; Lee, J. K.

2002-01-01

The important role of the high latitudes in the functioning of global processes is becoming well established. The size and remoteness of arctic and boreal ecosystems, however, pose a challenge to quantification of both terrestrial ecosystem processes and their feedbacks to regional and global climate conditions. Boreal and arctic regions form a complex land cover mosaic where vegetation structure, condition and distribution are strongly regulated by environmental factors such as moisture availability, permafrost, growing season length, disturbance and soil nutrients.

Unexpected Levels of Biological Activity during the Polar Night Offer New Perspectives on a Warming Arctic.

PubMed

Berge, Jørgen; Daase, Malin; Renaud, Paul E; Ambrose, William G; Darnis, Gerald; Last, Kim S; Leu, Eva; Cohen, Jonathan H; Johnsen, Geir; Moline, Mark A; Cottier, Finlo; Varpe, Øystein; Shunatova, Natalia; Bałazy, Piotr; Morata, Nathalie; Massabuau, Jean-Charles; Falk-Petersen, Stig; Kosobokova, Ksenia; Hoppe, Clara J M; Węsławski, Jan Marcin; Kukliński, Piotr; Legeżyńska, Joanna; Nikishina, Daria; Cusa, Marine; Kędra, Monika; Włodarska-Kowalczuk, Maria; Vogedes, Daniel; Camus, Lionel; Tran, Damien; Michaud, Emma; Gabrielsen, Tove M; Granovitch, Andrei; Gonchar, Anya; Krapp, Rupert; Callesen, Trine A

2015-10-05

The current understanding of Arctic ecosystems is deeply rooted in the classical view of a bottom-up controlled system with strong physical forcing and seasonality in primary-production regimes. Consequently, the Arctic polar night is commonly disregarded as a time of year when biological activities are reduced to a minimum due to a reduced food supply. Here, based upon a multidisciplinary ecosystem-scale study from the polar night at 79°N, we present an entirely different view. Instead of an ecosystem that has entered a resting state, we document a system with high activity levels and biological interactions across most trophic levels. In some habitats, biological diversity and presence of juvenile stages were elevated in winter months compared to the more productive and sunlit periods. Ultimately, our results suggest a different perspective regarding ecosystem function that will be of importance for future environmental management and decision making, especially at a time when Arctic regions are experiencing accelerated environmental change [1]. Copyright © 2015 Elsevier Ltd. All rights reserved.

Extreme anthropogenic loads and the northern ecosystem condition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kryuckkov, V.V.

1993-11-01

In the extreme North, the polar region of siberian Russia, the largest mining and processing enterprises for metallic and nonmetallic ores, coal, oil, and gas are situated. The extremely vulnerable boreal and polar ecosystems of the north are responding adversely to the impact of these activities, and are in danger of collapse because of them. The mechanisms of such impacts, their formation, continuous extension, and merger have been studied. The deforested and destroyed areas of former forest-tundra and taiga ecosystems resemble the Arctic zones of a much harsher environment more than the typical Arctic zones where they occur. 5 refs.,more » 3 figs., 2 tabs.« less

Is the Climate of Bering Sea Warming and Affecting the Ecosystem?

NASA Astrophysics Data System (ADS)

Overland, James E.; Stabeno, Phyllis J.

2004-08-01

Observations from the Bering Sea are good indicators of decadal shifts in climate, as the Bering is a transition region between the cold, dry Arctic air mass to the north, and the moist, relatively warm maritime air mass to the south. The Bering Sea is also a transition region between Arctic and sub-Arctic ecosystems; this boundary can be loosely identified with the extent of winter sea-ice cover. Like a similar transition zone in the eastern North Atlantic, the Bering Sea is experiencing a northward biogeographical shift in response to changing temperature and atmospheric forcing. If this shift continues over the next decade, it will have major impacts on commercial and subsistence harvests as Arctic species are displaced by sub-Arctic species. The stakes are enormous, as this rich and diverse ecosystem currently provides 47% of the U.S. fishery production by weight, and is home to 80% of the U.S. sea bird population, 95% of northern fur seals, and major populations of Steller sea lions, walrus, and whales.

Ecosystem model of the entire Beaufort Sea marine ecosystem: a tool for assessing food-web structure and ecosystem changes from 1970 to 2014

NASA Astrophysics Data System (ADS)

Suprenand, P. M.; Hoover, C.

2016-02-01

The Beaufort Sea coastal-marine ecosystem is approximately a 476,000 km2 area in the Arctic Ocean, which extends from -112.5 to -158° longitude to 67.5 to 75° latitude. Within this Arctic Ocean area the United States (Alaskan) indigenous communities of Barrow, Kaktovik, and Nuiqsut, and the Canadian (Northwest Territories) indigenous communities of Aklavik, Inuvik, Tuktoyaktuk, Paulatuk, Ulukhaktok, and Sachs Harbour, subsist by harvesting marine mammals, fish, and invertebrates from the Beaufort Sea to provide the majority of their community foods annually. The ecosystem in which the indigenous communities harvest is considered a polar habitat that includes many specialized species, such as polar bears that rely on sea-ice for foraging activities and denning, or ice algae that are attached to the cryosphere. However, the polar habitat has been experiencing a diminishing sea-ice extent, age, and seasonal duration, with concomitant increases in sea surface temperatures (SSTs), since the 1970s. Changes in sea-ice and SST have consequences to the Beaufort Sea coastal-marine ecosystem, which includes animal habitat losses, alterations to trophodynamics, and impacts to subsistence community harvesting. The present study was aimed at capturing trophodynamic changes in the Beaufort Sea coastal-marine ecosystem from 1970 to 2014 using a fitted spatial-temporal model (Ecopath with Ecosim and Ecospace) that utilizes forcing and mediation functions to describe animal/trophodynamic relationships with sea-ice and sea surface temperature, as well as individual community harvesting efforts. Model outputs reveals similar trends in animals population changes (e.g., increasing bowhead whale stock), changes in apex predator diets (e.g., polar bears eating less ringed seal), and changes in animal distributions (e.g., polar bears remaining closer to land over time). The Beaufort Sea model is a dynamic tool for Arctic Ocean natural resource management in the years to come.

The Arctic Research Consortium of the United States (ARCUS)

NASA Astrophysics Data System (ADS)

Wiggins, H. V.; Warnick, W. K.

2008-12-01

The Arctic Research Consortium of the United States (ARCUS) is a nonprofit membership organization composed of universities and institutions that have a substantial commitment to research in the Arctic. ARCUS was formed in 1988 to serve as a forum for planning, facilitating, coordinating, and implementing interdisciplinary studies of the Arctic; to act as a synthesizer and disseminator of scientific information on arctic research; and to educate scientists and the general public about the needs and opportunities for research in the Arctic. ARCUS, in collaboration with the broader science community, relevant agencies and organizations, and other stakeholders, coordinates science planning and educational activities across disciplinary and organizational boundaries. Examples of current ARCUS science planning activities include: serving as the project office for the multi- agency Study of Environmental Arctic Change (SEARCH) program, providing support to the related Bering Ecosystem Study (BEST), and serving as the Science Management Office for the National Science Foundation (NSF) Arctic System Science (ARCSS) Program. ARCUS" central educational activity is PolarTREC (Teachers and Researchers Exploring and Collaborating), an International Polar Year (IPY) program whereby K-12 educators and researchers work together in hands-on field experiences in the Arctic and Antarctic to advance polar science education. Additional science planning, educational, information, and outreach activities include, among many others, the Witness the Arctic newsletter, the Arctic Visiting Speakers" Series, the ArcticInfo listserve, the Internet Media Archive (IMA), and the annual Arctic Forum conference. More information about these and other ARCUS activities can be found at the ARCUS website at: http://www.arcus.org.

The Arctic Research Consortium of the United States (ARCUS)

NASA Astrophysics Data System (ADS)

Creek, K. R.; Fox, S. E.; Wiggins, H. V.

2010-12-01

The Arctic Research Consortium of the United States (ARCUS) is a nonprofit membership organization composed of universities and institutions that have a substantial commitment to research in the Arctic. ARCUS was formed in 1988 to serve as a forum for planning, facilitating, coordinating, and implementing interdisciplinary studies of the Arctic; to act as a synthesizer and disseminator of scientific information on arctic research; and to educate scientists and the general public about the needs and opportunities for research in the Arctic. ARCUS, in collaboration with the broader science community, relevant agencies and organizations, and other stakeholders, coordinates science planning and educational activities across disciplinary and organizational boundaries. Examples of current ARCUS science planning activities include: serving as the project office for the multi-agency Study of Environmental Arctic Change (SEARCH) program, providing support to the related Bering Ecosystem Study (BEST), and serving as the Science Management Office for the National Science Foundation (NSF) Arctic System Science (ARCSS) Program. ARCUS’ central educational activity is PolarTREC (Teachers and Researchers Exploring and Collaborating), an International Polar Year (IPY) program whereby K-12 educators and researchers work together in hands-on field experiences in the Arctic and Antarctic to advance polar science education. Additional science planning, educational, information, and outreach activities include, among many others, the Witness the Arctic newsletter, the Arctic Visiting Speakers’ Series, the ArcticInfo listserve, the Internet Media Archive (IMA), and the annual Arctic Forum conference. More information about these and other ARCUS activities can be found at the ARCUS website at: http://www.arcus.org.

ArcticDEM; A Publically Available, High Resolution Elevation Model of the Arctic

NASA Astrophysics Data System (ADS)

Morin, Paul; Porter, Claire; Cloutier, Michael; Howat, Ian; Noh, Myoung-Jong; Willis, Michael; Bates, Brian; Willamson, Cathleen; Peterman, Kennith

2016-04-01

A Digital Elevation Model (DEM) of the Arctic is needed for a large number of reasons, including: measuring and understanding rapid, ongoing changes to the Arctic landscape resulting from climate change and human use and mitigation and adaptation planning for Arctic communities. The topography of the Arctic is more poorly mapped than most other regions of Earth due to logistical costs and the limits of satellite missions with low-latitude inclinations. A convergence of civilian, high-quality sub-meter stereo imagery; petascale computing and open source photogrammetry software has made it possible to produce a complete, very high resolution (2 to 8-meter posting), elevation model of the Arctic. A partnership between the US National Geospatial-intelligence Agency and a team led by the US National Science Foundation funded Polar Geospatial Center is using stereo imagery from DigitalGlobe's Worldview-1, 2 and 3 satellites and the Ohio State University's Surface Extraction with TIN-based Search-space Minimization (SETSM) software running on the University of Illinois's Blue Water supercomputer to address this challenge. The final product will be a seemless, 2-m posting digital surface model mosaic of the entire Arctic above 60 North including all of Alaska, Greenland and Kamchatka. We will also make available the more than 300,000 individual time-stamped DSM strip pairs that were used to assemble the mosaic. The Arctic DEM will have a vertical precision of better than 0.5m and can be used to examine changes in land surfaces such as those caused by permafrost degradation or the evolution of arctic rivers and floodplains. The data set can also be used to highlight changing geomorphology due to Earth surface mass transport processes occurring in active volcanic and glacial environments. When complete the ArcticDEM will catapult the Arctic from the worst to among the best mapped regions on Earth.

Morphology-dependent water budgets and nutrient fluxes in arctic thaw ponds

USGS Publications Warehouse

Koch, Joshua C.; Gurney, Kirsty; Wipfli, Mark S.

2014-01-01

Thaw ponds on the Arctic Coastal Plain of Alaska are productive ecosystems, providing habitat and food resources for many fish and bird species. Permafrost in this region creates unique pond morphologies: deep troughs, shallow low-centred polygons (LCPs) and larger coalescent ponds. By monitoring seasonal trends in pond volume and chemistry, we evaluated whether pond morphology and size affect water temperature and desiccation, and nitrogen (N) and phosphorus (P) fluxes. Evaporation was the largest early-summer water flux in all pond types. LCPs dried quickly and displayed high early-summer nutrient concentrations and losses. Troughs consistently received solute-rich subsurface inflows, which accounted for 12 to 42 per cent of their volume and may explain higher P in the troughs. N to P ratios increased and ammonium concentrations decreased with pond volume, suggesting that P and inorganic N availability may limit ecosystem productivity in older, larger ponds. Arctic summer temperatures will likely increase in the future, which may accelerate mid-summer desiccation. Given their morphology, troughs may remain wet, become warmer and derive greater nutrient loads from their thawing banks. Overall, seasonal- to decadal-scale warming may increase ecosystem productivity in troughs relative to other Arctic Coastal Plain ponds. 

Is it 'boom times' for baleen whales in the Pacific Arctic region?

PubMed

Moore, Sue E

2016-09-01

The marine ecosystem in the Pacific Arctic region has experienced dramatic transformation, most obvious by the loss of sea ice volume (75%), late-summer areal extent (50%) and change in phenology (four to six weeks longer open-water period). This alteration has resulted in an opening of habitat for subarctic species of baleen whales, many of which are recovering in number from severe depletions from commercial whaling in the nineteenth and twentieth centuries. Specifically, humpback, fin and minke whales (Megaptera novaeangliae, Balaenoptera physalus and Balaenoptera acutorostrata) are now regularly reported during summer and autumn in the southern Chukchi Sea. These predators of zooplankton and forage fishes join the seasonally resident grey whale (Eschrichtius robustus) and the arctic-endemic bowhead whale (Balaena mysticetus) in the expanding open-ocean habitat of the Pacific Arctic. Questions arising include: (i) what changes in whale-prey production and delivery mechanisms have accompanied the loss of sea ice, and (ii) how are these five baleen whale species partitioning the expanding ice-free habitat? While there has been no programme of research specifically focused on these questions, an examination of seasonal occurrence, foraging plasticity and (for bowhead whales) body condition suggests that the current state of Pacific Arctic marine ecosystem may be 'boom times' for baleen whales. These favourable conditions may be moderated, however, by future shifts in ecosystem structure and/or negative impacts to cetaceans related to increased commercial activities in the region. © 2016 The Author(s).

Small species indicate big changes? Arctic report card

USDA-ARS?s Scientific Manuscript database

As Arctic climate warms, how will terrestrial ecosystems and the communities that they support respond in the coming decades? Small mammals including shrews and their associated parasites can serve as key indicators and proxies of accelerating perturbation, contributing to general models for anticip...

The impact of lower sea-ice extent on Arctic greenhouse-gas exchange

USGS Publications Warehouse

Parmentier, Frans-Jan W.; Christensen, Torben R.; Sørensen, Lise Lotte; Rysgaard, Søren; McGuire, A. David; Miller, Paul A.; Walker, Donald A.

2013-01-01

In September 2012, Arctic sea-ice extent plummeted to a new record low: two times lower than the 1979–2000 average. Often, record lows in sea-ice cover are hailed as an example of climate change impacts in the Arctic. Less apparent, however, are the implications of reduced sea-ice cover in the Arctic Ocean for marine–atmosphere CO2 exchange. Sea-ice decline has been connected to increasing air temperatures at high latitudes. Temperature is a key controlling factor in the terrestrial exchange of CO2 and methane, and therefore the greenhouse-gas balance of the Arctic. Despite the large potential for feedbacks, many studies do not connect the diminishing sea-ice extent with changes in the interaction of the marine and terrestrial Arctic with the atmosphere. In this Review, we assess how current understanding of the Arctic Ocean and high-latitude ecosystems can be used to predict the impact of a lower sea-ice cover on Arctic greenhouse-gas exchange.

Isotopic and Geochemical Fingerprinting of a Polygonal Arctic Ecosystem

NASA Astrophysics Data System (ADS)

Throckmorton, H.; Heikoop, J. M.; Newman, B. D.; Wilson, C. J.; Wullschleger, S. D.

2015-12-01

Arctic tundra contain large C stocks and may be an important source of CO2 and CH4 over the next century due to a rapidly changing climate, degrading permafrost, and redistribution of water across high latitude landscapes. This presentation synthesizes geochemical and isotopic data and examines vertical and lateral factors and processes critical to predicting the C, N, and water balance of tundra ecosystems. Stable water isotope analyses (delta 2H and delta 18O) indicate that summer rain is the dominant source for active layer groundwater, with melting seasonal ice contributing to deeper pore waters in late summer. Microtopography and water table effects on geochemistry were apparent from a comprehensive spatial examination of active layer biogeochemistry, showing a number of significant differences in the concentrations of cations and anions for high- vs. low-centered polygons, microtopographic features (polygonal centers vs. troughs), and with depth. Results have implications for future nutrient availability with projected permafrost degradation and landscape evolution, suggesting greater availability of limiting nutrients (sulfate, phosphate, and nitrate) where polygons undergo a shift from low- to high-centered. Nitrate isotopes (delta 15N and delta 18O) indicated a predominantly microbial source for nitrate in high centered polygons active layers. However, atmospheric nitrate was preserved in permafrost, and may serve as a potential indicator of permafrost degradation. Additionally, results suggest that older, deeper C sources may be promoting a shift in methanogenic pathway, from predominantly acetoclastic to hydrogenotrophic. This mechanistic shift is attributed to the source and quality of available organic substrate. Overall, results showed substantial lateral and vertical variability in biogeochemical, biogeophysical, and hydrological processes across microtopographic- to landscape scales that needs to be accounted for in fine and intermediate scale

Science Partnerships for a Sustainable Arctic: the Marine Mammal Nexus (Invited)

NASA Astrophysics Data System (ADS)

Moore, S. E.

2010-12-01

Marine mammals are both icons of Arctic marine ecosystems and fundamental to Native subsistence nutrition and culture. Eight species are endemic to the Pacific Arctic, including the polar bear, walrus, ice seals (4 species), beluga and bowhead whales. Studies of walrus and bowheads have been conducted over the past 30 years, to estimate population size and elucidate patterns of movement and abundance. With regard to the three pillars of the SEARCH program, these long-term OBSERVATIONS provide a foundation for research seeking to UNDERSTAND and RESPOND to the effects of rapid climate change on the marine ecosystem. Specifically, research on the coastal ecosystem near Barrow, Alaska focuses on late-summer feeding habitat for bowheads in an area where whales are hunted in autumn. This work is a partnership among agency, academic and local scientists and the residents of Barrow, all of whom seek to better UNDERSTAND how recent dramatic changes in sea ice, winds and offshore industrial activities influence whale movements and behavior. In regard to RESPONDING to climate change, the nascent Sea Ice for Walrus Outlook (SIWO) is a science partnership that projects sea ice and wind conditions for five villages in the Bering Strait region. The objective of the SIWO is to provide information on physical conditions in the marine environment at spatial and temporal scales relevant to walrus hunters. Marine mammals are a strong and dynamic nexus for partnerships among scientists, Arctic residents, resource managers and the general public - as such, they are essential elements to any science plan for a sustainable Arctic.

Large herbivore grazing affects the vegetation structure and greenhouse gas balance in a high arctic mire

NASA Astrophysics Data System (ADS)

Falk, Julie Maria; Schmidt, Niels Martin; Christensen, Torben R.; Ström, Lena

2015-04-01

Herbivory is an important part of most ecosystems and affects the ecosystems’ carbon balance both directly and indirectly. Little is known about herbivory and its impact on the carbon balance in high arctic mire ecosystems. We hypothesized that trampling and grazing by large herbivores influences the vegetation density and composition and thereby also the carbon balance. In 2010, we established fenced exclosures in high arctic Greenland to prevent muskoxen (Ovibos moschatus) from grazing. During the growing seasons of 2011 to 2013 we measured CO2 and CH4 fluxes in these ungrazed blocks and compared them to blocks subjected to natural grazing. Additionally, we measured depth of the water table and active layer, soil temperature, and in 2011 and 2013 an inventory of the vegetation density and composition were made. In 2013 a significant decrease in total number of vascular plant (33-44%) and Eriophorum scheuchzeri (51-53%) tillers were found in ungrazed plots, the moss-layer and amount of litter had also increased substantially in these plots. This resulted in a significant decrease in net ecosystem uptake of CO2 (47%) and likewise a decrease in CH4 emission (44%) in ungrazed plots in 2013. While the future of the muskoxen in a changing arctic is unknown, this experiment points to a potentially large effect of large herbivores on the carbon balance in natural Arctic ecosystems. It thus sheds light on the importance of grazing mammals, and hence adds to our understanding of natural ecosystem greenhouse gas balance in the past and in the future.

Modeling plankton ecosystem functioning and nitrogen fluxes in the oligotrophic waters of the Beaufort Sea, Arctic Ocean: a focus on light-driven processes

NASA Astrophysics Data System (ADS)

Le Fouest, V.; Zakardjian, B.; Xie, H.; Raimbault, P.; Joux, F.; Babin, M.

2013-07-01

The Arctic Ocean (AO) undergoes profound changes of its physical and biotic environments due to climate change. In some areas of the Beaufort Sea, the stronger haline stratification observed in summer alters the plankton ecosystem structure, functioning and productivity, promoting oligotrophy. A one-dimension (1-D) physical-biological coupled model based on the large multiparametric database of the Malina project in the Beaufort Sea was used (i) to infer the plankton ecosystem functioning and related nitrogen fluxes and (ii) to assess the model sensitivity to key light-driven processes involved in nutrient recycling and phytoplankton growth. The coupled model suggested that ammonium photochemically produced from photosensitive dissolved organic nitrogen (i.e., photoammonification process) was a necessary nitrogen source to achieve the observed levels of microbial biomass and production. Photoammonification directly and indirectly (by stimulating the microbial food web activity) contributed to 70% and 18.5% of the 0-10 m and whole water column, respectively, simulated primary production (respectively 66% and 16% for the bacterial production). The model also suggested that variable carbon to chlorophyll ratios were required to simulate the observed herbivorous versus microbial food web competition and realistic nitrogen fluxes in the Beaufort Sea oligotrophic waters. In face of accelerating Arctic warming, more attention should be paid in the future to the mechanistic processes involved in food webs and functional group competition, nutrient recycling and primary production in poorly productive waters of the AO, as they are expected to expand rapidly.

Short-cut transport path for Asian dust directly to the Arctic: a case study

NASA Astrophysics Data System (ADS)

Huang, Zhongwei; Huang, Jianping; Hayasaka, Tadahiro; Wang, Shanshan; Zhou, Tian; Jin, Hongchun

2015-11-01

Asian dust can be transported long distances from the Taklimakan or Gobi desert to North America across the Pacific Ocean, and it has been found to have a significant impact on ecosystems, climate, and human health. Although it is well known that Asian dust is transported all over the globe, there are limited observations reporting Asian dust transported to the Arctic. We report a case study of a large-scale heavy dust storm over East Asia on 19 March 2010, as shown by ground-based and space-borne multi-sensor observations, as well as NCEP/NCAR reanalysis data and HYSPLIT trajectories. Our analysis suggests that Asian dust aerosols were transported from northwest China to the Arctic within 5 days, crossing eastern China, Japan and Siberia before reaching the Arctic. The results indicate that Asian dust can be transported for long distances along a previously unreported transport path. Evidence from other dust events over the past decade (2001-2010) also supports our results, indicating that dust from 25.2% of Asian dust events has potentially been transported directly to the Arctic. The transport of Asian dust to the Arctic is due to cyclones and the enhanced East Asia Trough (EAT), which are very common synoptic systems over East Asia. This suggests that many other large dust events would have generated long-range transport of dust to the Arctic along this path in the past. Thus, Asian dust potentially affects the Arctic climate and ecosystem, making climate change in the Arctic much more complex to be fully understood.

Influence of sea ice on Arctic coasts

NASA Astrophysics Data System (ADS)

Barnhart, K. R.; Kay, J. E.; Overeem, I.; Anderson, R. S.

2017-12-01

Coasts form the dynamic interface between the terrestrial and oceanic systems. In the Arctic, and in much of the world, the coast is a focal point for population, infrastructure, biodiversity, and ecosystem services. A key difference between Arctic and temperate coasts is the presence of sea ice. Changes in sea ice cover can influence the coast because (1) the length of the sea ice-free season controls the time over which nearshore water can interact with the land, and (2) the location of the sea ice edge controls the fetch over which storm winds can interact with open ocean water, which in turn governs nearshore water level and wave field. We first focus on the interaction of sea ice and ice-rich coasts. We combine satellite records of sea ice with a model for wind-driven storm surge and waves to estimate how changes in the sea ice-free season have impacted the nearshore hydrodynamic environment along Alaska's Beaufort Sea Coast for the period 1979-2012. This region has experienced some of the greatest changes in both sea ice cover and coastal erosion rates in the Arctic: the median length of the open-water season has expanded by 90 percent, while coastal erosion rates have more than doubled from 8.7 to 19 m yr-1. At Drew Point, NW winds increase shoreline water levels that control the incision of a submarine notch, the rate-limiting step of coastal retreat. The maximum water-level setup at Drew Point has increased consistently with increasing fetch. We extend our analysis to the entire Arctic using both satellite-based observations and global coupled climate model output from the Community Earth System Model Large Ensemble (CESM-LE) project. This 30-member ensemble employs a 1-degree version of the CESM-CAM5 historical forcing for the period 1920-2005, and RCP 8.5 forcing from 2005-2100. A control model run with constant pre-industrial (1850) forcing characterizes internal variability in a constant climate. Finally, we compare observations and model results to

Physiological and ecological effects of increasing temperature on fish production in lakes of Arctic Alaska

PubMed Central

Carey, Michael P; Zimmerman, Christian E

2014-01-01

Lake ecosystems in the Arctic are changing rapidly due to climate warming. Lakes are sensitive integrators of climate-induced changes and prominent features across the Arctic landscape, especially in lowland permafrost regions such as the Arctic Coastal Plain of Alaska. Despite many studies on the implications of climate warming, how fish populations will respond to lake changes is uncertain for Arctic ecosystems. Least Cisco (Coregonus sardinella) is a bellwether for Arctic lakes as an important consumer and prey resource. To explore the consequences of climate warming, we used a bioenergetics model to simulate changes in Least Cisco production under future climate scenarios for lakes on the Arctic Coastal Plain. First, we used current temperatures to fit Least Cisco consumption to observed annual growth. We then estimated growth, holding food availability, and then feeding rate constant, for future projections of temperature. Projected warmer water temperatures resulted in reduced Least Cisco production, especially for larger size classes, when food availability was held constant. While holding feeding rate constant, production of Least Cisco increased under all future scenarios with progressively more growth in warmer temperatures. Higher variability occurred with longer projections of time mirroring the expanding uncertainty in climate predictions further into the future. In addition to direct temperature effects on Least Cisco growth, we also considered changes in lake ice phenology and prey resources for Least Cisco. A shorter period of ice cover resulted in increased production, similar to warming temperatures. Altering prey quality had a larger effect on fish production in summer than winter and increased relative growth of younger rather than older age classes of Least Cisco. Overall, we predicted increased production of Least Cisco due to climate warming in lakes of Arctic Alaska. Understanding the implications of increased production of Least Cisco to

The Arctic Circle

NASA Astrophysics Data System (ADS)

McDonald, Siobhan

2016-04-01

My name is Siobhan McDonald. I am a visual artist living and working in Dublin. My studio is based in The School of Science at University College Dublin where I was Artist in Residence 2013-2015. A fascination with time and the changeable nature of landmass has led to ongoing conversations with scientists and research institutions across the interweaving disciplines of botany, biology and geology. I am developing a body of work following a recent research trip to the North Pole where I studied the disappearing landscape of the Arctic. Prompted by my experience of the Arctic shelf receding, this new work addresses issues of the instability of the earth's materiality. The work is grounded in an investigation of material processes, exploring the dynamic forces that transform matter and energy. This project combines art and science in a fascinating exploration of one of the Earth's last relatively untouched wilderness areas - the High Arctic to bring audiences on journeys to both real and artistically re-imagined Arctic spaces. CRYSTALLINE'S pivotal process is collaboration: with The European Space Agency; curator Helen Carey; palaeontologist Prof. Jenny McElwain, UCD; and with composer Irene Buckley. CRYSTALLINE explores our desire to make corporeal contact with geological phenomena in Polar Regions. From January 2016, in my collaboration with Jenny McElwain, I will focus on the study of plants and atmospheres from the Arctic regions as far back as 400 million years ago, to explore the essential 'nature' that, invisible to the eye, acts as imaginary portholes into other times. This work will be informed by my arctic tracings of sounds and images recorded in the glaciers of this disappearing frozen landscape. In doing so, the urgencies around the tipping of natural balances in this fragile region will be revealed. The final work will emerge from my forthcoming residency at the ESA in spring 2016. Here I will conduct a series of workshops in ESA Madrid to work with

Approaches to determining Final Ecosystem Goods and Services: Benefits and Beneficiaries

EPA Science Inventory

By nature, the concept of ‘Final’ Ecosystem Goods and Services (FEGS) poses the question; to what or to whom are these goods and services final? We identify two main approaches theoreticians and practitioners are using to define and perceive FEGS (note: we recognize t...

Enhanced role of eddies in the Arctic marine biological pump

PubMed Central

Watanabe, Eiji; Onodera, Jonaotaro; Harada, Naomi; Honda, Makio C.; Kimoto, Katsunori; Kikuchi, Takashi; Nishino, Shigeto; Matsuno, Kohei; Yamaguchi, Atsushi; Ishida, Akio; Kishi, Michio J.

2014-01-01

The future conditions of Arctic sea ice and marine ecosystems are of interest not only to climate scientists, but also to economic and governmental bodies. However, the lack of widespread, year-long biogeochemical observations remains an obstacle to understanding the complicated variability of the Arctic marine biological pump. Here we show an early winter maximum of sinking biogenic flux in the western Arctic Ocean and illustrate the importance of shelf-break eddies to biological pumping from wide shelves to adjacent deep basins using a combination of year-long mooring observations and three-dimensional numerical modelling. The sinking flux trapped in the present study included considerable fresh organic material with soft tissues and was an order of magnitude larger than previous estimates. We predict that further reductions in sea ice will promote the entry of Pacific-origin biological species into the Arctic basin and accelerate biogeochemical cycles connecting the Arctic and subarctic oceans. PMID:24862402

Life around the North Water ecosystem: Natural and social drivers of change over a millennium.

PubMed

Hastrup, Kirsten; Andersen, Astrid Oberborbeck; Grønnow, Bjarne; Heide-Jørgensen, Mads Peter

2018-04-01

The formation of the North Water in Smith Sound about 4500 years ago, as evidenced by the establishment of bird colonies and human presence, also initiated a long-term anthropogenic agent as part of this High Arctic ecosystem. Different epochs have influenced the human occupation in the area: immigration pulses from Canada and Alaska, trade with meteorite iron throughout the Arctic, introduction of new technologies by whalers and explorers, exploitation of resources by foreigners, political sequestration, export of fox and seal skins and later narwhal products, and recently fishing. Physical drivers in terms of weather and climate affecting the northern hemisphere also impact accessibility and productivity of the ecosystem, with cascading effects on social drivers, again acting back on the natural ecologies. Despite its apparent isolation, the ecosystem had and still has wide ranging spatial ramifications that extend beyond the High Arctic, and include human activity. The challenge is to determine what is internal and what is external to an ecosystem.

Climate change alters the structure of arctic marine food webs due to poleward shifts of boreal generalists.

PubMed

Kortsch, Susanne; Primicerio, Raul; Fossheim, Maria; Dolgov, Andrey V; Aschan, Michaela

2015-09-07

Climate-driven poleward shifts, leading to changes in species composition and relative abundances, have been recently documented in the Arctic. Among the fastest moving species are boreal generalist fish which are expected to affect arctic marine food web structure and ecosystem functioning substantially. Here, we address structural changes at the food web level induced by poleward shifts via topological network analysis of highly resolved boreal and arctic food webs of the Barents Sea. We detected considerable differences in structural properties and link configuration between the boreal and the arctic food webs, the latter being more modular and less connected. We found that a main characteristic of the boreal fish moving poleward into the arctic region of the Barents Sea is high generalism, a property that increases connectance and reduces modularity in the arctic marine food web. Our results reveal that habitats form natural boundaries for food web modules, and that generalists play an important functional role in coupling pelagic and benthic modules. We posit that these habitat couplers have the potential to promote the transfer of energy and matter between habitats, but also the spread of pertubations, thereby changing arctic marine food web structure considerably with implications for ecosystem dynamics and functioning. © 2015 The Authors.

Climate change alters the structure of arctic marine food webs due to poleward shifts of boreal generalists

PubMed Central

Kortsch, Susanne; Primicerio, Raul; Fossheim, Maria; Dolgov, Andrey V.; Aschan, Michaela

2015-01-01

Climate-driven poleward shifts, leading to changes in species composition and relative abundances, have been recently documented in the Arctic. Among the fastest moving species are boreal generalist fish which are expected to affect arctic marine food web structure and ecosystem functioning substantially. Here, we address structural changes at the food web level induced by poleward shifts via topological network analysis of highly resolved boreal and arctic food webs of the Barents Sea. We detected considerable differences in structural properties and link configuration between the boreal and the arctic food webs, the latter being more modular and less connected. We found that a main characteristic of the boreal fish moving poleward into the arctic region of the Barents Sea is high generalism, a property that increases connectance and reduces modularity in the arctic marine food web. Our results reveal that habitats form natural boundaries for food web modules, and that generalists play an important functional role in coupling pelagic and benthic modules. We posit that these habitat couplers have the potential to promote the transfer of energy and matter between habitats, but also the spread of pertubations, thereby changing arctic marine food web structure considerably with implications for ecosystem dynamics and functioning. PMID:26336179

Role of Siderophores in Dissimilatory Iron Reduction in Arctic Soils : Effect of Direct Amendment of Siderophores to Arctic Soil

NASA Astrophysics Data System (ADS)

Srinivas, A. J.; Dinsdale, E. A.; Lipson, D.

2014-12-01

Dissimilatory iron reduction (DIR), where ferric iron (Fe3+) is reduced to ferrous iron (Fe2+) anaerobically, is an important respiratory pathway used by soil bacteria. DIR contributes to carbon dioxide (CO2) efflux from the wet sedge tundra biome in the Arctic Coastal Plain (ACP) in Alaska, and could competitively inhibit the production of methane, a stronger greenhouse gas than CO2, from arctic soils. The occurrence of DIR as a dominant anaerobic process depends on the availability of substantial levels of Fe3+ in soils. Siderophores are metabolites made by microbes to dissolve Fe3+ from soil minerals in iron deficient systems, making Fe3+ soluble for micronutrient uptake. However, as the ACP is not iron deficient, siderophores in arctic soils may play a vital role in anaerobic respiration by dissolving Fe3+ for DIR. We studied the effects of direct siderophore addition to arctic soils through a field study conducted in Barrow, Alaska, and a laboratory incubation study conducted at San Diego State University. In the field experiment, 50μM deferroxamine mesylate (a siderophore), 50μM trisodium nitrilotriacetate (an organic chelator) or an equal volume of water was added to isolated experimental plots, replicated in clusters across the landscape. Fe2+ concentrations were measured in soil pore water samples collected periodically to measure DIR over time in each. In the laboratory experiment, frozen soil samples obtained from drained thaw lake basins in the ACP, were cut into cores and treated with the above-mentioned compounds to the same final concentrations. Along with measuring Fe2+ concentrations, CO2 output was also measured to monitor DIR over time in each core. Experimental addition of siderophores to soils in both the field and laboratory resulted in increased concentrations of soluble Fe3+ and a sustained increase in Fe2+concentrations over time, along with increased respiration rates in siderophore-amended cores. These results show increased DIR in

Unraveling the intricate dynamics of planktonic Arctic marine food webs. A sensitivity analysis of a well-documented food web model

NASA Astrophysics Data System (ADS)

Saint-Béat, Blanche; Maps, Frédéric; Babin, Marcel

2018-01-01

The extreme and variable environment shapes the functioning of Arctic ecosystems and the life cycles of its species. This delicate balance is now threatened by the unprecedented pace and magnitude of global climate change and anthropogenic pressure. Understanding the long-term consequences of these changes remains an elusive, yet pressing, goal. Our work was specifically aimed at identifying which biological processes impact Arctic planktonic ecosystem functioning, and how. Ecological Network Analysis (ENA) indices reveal emergent ecosystem properties that are not accessible through simple in situ observation. These indices are based on the architecture of carbon flows within food webs. But, despite the recent increase in in situ measurements from Arctic seas, many flow values remain unknown. Linear inverse modeling (LIM) allows missing flow values to be estimated from existing flow observations and, subsequent reconstruction of ecosystem food webs. Through a sensitivity analysis on a LIM model of the Amundsen Gulf in the Canadian Arctic, we were able to determine which processes affected the emergent properties of the planktonic ecosystem. The analysis highlighted the importance of an accurate knowledge of the various processes controlling bacterial production (e.g. bacterial growth efficiency and viral lysis). More importantly, a change in the fate of the microzooplankton within the food web can be monitored through the trophic level of mesozooplankton. It can be used as a "canary in the coal mine" signal, a forewarner of larger ecosystem change.

Evidence and implications of recent climate change in northern Alaska and other arctic regions.

Treesearch

Larry D. Hinzman; Neil D. Bettez; W. Robert Bolton; F. Stuart Chapin; Mark B. Dyurgerov; Chris L. Fastie; Brad Griffith; Robert D. Hollister; Allen Hope; Henry P. Huntington; Anne M. Jensen; Gensuou J. Jia; Torre Jorgenson; Douglas L. Kane; David R. Klein; Gary Kofinas; Amanda H. Lynch; Andrea H. Lloyd; A. David McGuire; Frederick E. Nelson; Walter C. Oechel; Thomas E. Osterkamp; Charles H. Racine; Vladimir E. Romanovsky; Robert S. Stone; Douglas A. Stow; Matthew Sturm; Craig E. Tweedie; George L. Vourlitis; Marilyn D. Walker; Donald A. Walker; Patrick J. Webber; Jeffrey M. Welker; Kevin S. Winker; Kenji Yoshikawa

2005-01-01

The Arctic climate is changing. Permafrost is warming, hydrological processes are changing and biological and social systems are also evolving in response to these changing conditions. Knowing how the structure and function of arctic terrestrial ecosystems are responding to recent and persistent climate change is paramount to understanding the future state of the Earth...

Changing arctic ecosystems—What is causing the rapid increase of snow geese in northern Alaska?

USGS Publications Warehouse

Hupp, Jerry W.; Ward, David H.; Whalen, Mary E.; Pearce, John M.

2015-09-10

Through the Changing Arctic Ecosystems (CAE) initiative, the U.S. Geological Survey (USGS) informs key resource management decisions for Arctic Alaska by providing scientific information on current and future ecosystem response to a warming climate. The Arctic Coastal Plain (ACP) of northern Alaska is a key study area within the USGS CAE initiative. This region has experienced a warming trend over the past decades, leading to decreased sea ice, permafrost thaw, and an advancement of spring phenology. The number of birds on the ACP also is changing, marked by increased populations of the four species of geese that nest in the region. The Snow Goose (Chen caerulescens) is the most rapidly increasing of these species. USGS CAE research is quantifying these changes and their implications for management agencies.

Is it ‘boom times’ for baleen whales in the Pacific Arctic region?

PubMed Central

2016-01-01

The marine ecosystem in the Pacific Arctic region has experienced dramatic transformation, most obvious by the loss of sea ice volume (75%), late-summer areal extent (50%) and change in phenology (four to six weeks longer open-water period). This alteration has resulted in an opening of habitat for subarctic species of baleen whales, many of which are recovering in number from severe depletions from commercial whaling in the nineteenth and twentieth centuries. Specifically, humpback, fin and minke whales (Megaptera novaeangliae, Balaenoptera physalus and Balaenoptera acutorostrata) are now regularly reported during summer and autumn in the southern Chukchi Sea. These predators of zooplankton and forage fishes join the seasonally resident grey whale (Eschrichtius robustus) and the arctic-endemic bowhead whale (Balaena mysticetus) in the expanding open-ocean habitat of the Pacific Arctic. Questions arising include: (i) what changes in whale-prey production and delivery mechanisms have accompanied the loss of sea ice, and (ii) how are these five baleen whale species partitioning the expanding ice-free habitat? While there has been no programme of research specifically focused on these questions, an examination of seasonal occurrence, foraging plasticity and (for bowhead whales) body condition suggests that the current state of Pacific Arctic marine ecosystem may be ‘boom times’ for baleen whales. These favourable conditions may be moderated, however, by future shifts in ecosystem structure and/or negative impacts to cetaceans related to increased commercial activities in the region. PMID:27601724

Ecosystem extent and fragmentation

USGS Publications Warehouse

Sayre, Roger; Hansen, Matt

2017-01-01

One of the candidate essential biodiversity variable (EBV) groups described in the seminal paper by Pereira et al. (2014) concerns Ecosystem Structure. This EBV group is distinguished from another EBV group which encompasses aspects of Ecosystem Function. While the Ecosystem Function EBV treats ecosystem processes like nutrient cycling, primary production, trophic interactions, etc., the Ecosystem Structure EBV relates to the set of biophysical properties of ecosystems that create biophysical environmental context, confer biophysical structure, and occur geographically. The Ecosystem Extent and Fragmentation EBV is one of the EBVs in the Ecosystem Structure EBV group.Ecosystems are understood to exist at multiple scales, from very large areas (macro-ecosystems) like the Arctic tundra, for example, to something as small as a tree in an Amazonian rain forest. As such, ecosystems occupy space and therefore can be mapped across any geography of interest, whether that area of interest be a site, a nation, a region, a continent, or the planet. One of the most obvious and seemingly straightforward EBVs is Ecosystem Extent and Fragmentation. Ecosystem extent refers to the location and geographic distribution of ecosystems across landscapes or in the oceans, while ecosystem fragmentation refers to the spatial pattern and connectivity of ecosystem occurrences on the landscape.

Fourth international circumpolar arctic vegetation mapping workshop

USGS Publications Warehouse

Raynolds, Martha K.; Markon, C.J.

2002-01-01

During the week of April 10, 2001, the Fourth International Circumpolar Arctic Vegetation Mapping Workshop was held in Moscow, Russia. The purpose of this meeting was to bring together the vegetation scientists working on the Circumpolar Arctic Vegetation Map (CAVM) to (1) review the progress of current mapping activities, (2) discuss and agree upon a standard set of arctic tundra subzones, (3) plan for the production and dissemination of a draft map, and (4) begin work on a legend for the final map.

Nitrate is an important nitrogen source for Arctic tundra plants.

PubMed

Liu, Xue-Yan; Koba, Keisuke; Koyama, Lina A; Hobbie, Sarah E; Weiss, Marissa S; Inagaki, Yoshiyuki; Shaver, Gaius R; Giblin, Anne E; Hobara, Satoru; Nadelhoffer, Knute J; Sommerkorn, Martin; Rastetter, Edward B; Kling, George W; Laundre, James A; Yano, Yuriko; Makabe, Akiko; Yano, Midori; Liu, Cong-Qiang

2018-03-27

Plant nitrogen (N) use is a key component of the N cycle in terrestrial ecosystems. The supply of N to plants affects community species composition and ecosystem processes such as photosynthesis and carbon (C) accumulation. However, the availabilities and relative importance of different N forms to plants are not well understood. While nitrate (NO 3 - ) is a major N form used by plants worldwide, it is discounted as a N source for Arctic tundra plants because of extremely low NO 3 - concentrations in Arctic tundra soils, undetectable soil nitrification, and plant-tissue NO 3 - that is typically below detection limits. Here we reexamine NO 3 - use by tundra plants using a sensitive denitrifier method to analyze plant-tissue NO 3 - Soil-derived NO 3 - was detected in tundra plant tissues, and tundra plants took up soil NO 3 - at comparable rates to plants from relatively NO 3 - -rich ecosystems in other biomes. Nitrate assimilation determined by 15 N enrichments of leaf NO 3 - relative to soil NO 3 - accounted for 4 to 52% (as estimated by a Bayesian isotope-mixing model) of species-specific total leaf N of Alaskan tundra plants. Our finding that in situ soil NO 3 - availability for tundra plants is high has important implications for Arctic ecosystems, not only in determining species compositions, but also in determining the loss of N from soils via leaching and denitrification. Plant N uptake and soil N losses can strongly influence C uptake and accumulation in tundra soils. Accordingly, this evidence of NO 3 - availability in tundra soils is crucial for predicting C storage in tundra. Copyright © 2018 the Author(s). Published by PNAS.

Ground-based Remote Sensing for Quantifying Subsurface and Surface Co-variability to Scale Arctic Ecosystem Functioning

NASA Astrophysics Data System (ADS)

Oktem, R.; Wainwright, H. M.; Curtis, J. B.; Dafflon, B.; Peterson, J.; Ulrich, C.; Hubbard, S. S.; Torn, M. S.

2016-12-01

Predicting carbon cycling in Arctic requires quantifying tightly coupled surface and subsurface processes including permafrost, hydrology, vegetation and soil biogeochemistry. The challenge has been a lack of means to remotely sense key ecosystem properties in high resolution and over large areas. A particular challenge has been characterizing soil properties that are known to be highly heterogeneous. In this study, we exploit tightly-coupled above/belowground ecosystem functioning (e.g., the correlations among soil moisture, vegetation and carbon fluxes) to estimate subsurface and other key properties over large areas. To test this concept, we have installed a ground-based remote sensing platform - a track-mounted tram system - along a 70 m transect in the ice-wedge polygonal tundra near Barrow, Alaska. The tram carries a suite of near-surface remote sensing sensors, including sonic depth, thermal IR, NDVI and multispectral sensors. Joint analysis with multiple ground-based measurements (soil temperature, active layer soil moisture, and carbon fluxes) was performed to quantify correlations and the dynamics of above/belowground processes at unprecedented resolution, both temporally and spatially. We analyzed the datasets with particular focus on correlating key subsurface and ecosystem properties with surface properties that can be measured by satellite/airborne remote sensing over a large area. Our results provided several new insights about system behavior and also opens the door for new characterization approaches. We documented that: (1) soil temperature (at >5 cm depth; critical for permafrost thaw) was decoupled from soil surface temperature and was influenced strongly by soil moisture, (2) NDVI and greenness index were highly correlated with both soil moisture and gross primary productivity (based on chamber flux data), and (3) surface deformation (which can be measured by InSAR) was a good proxy for thaw depth dynamics at non-inundated locations.

CARVE Measurements of Atmospheric Methane Concentrations and Emissions in Arctic and Boreal Alaska

NASA Astrophysics Data System (ADS)

Miller, C. E.; Miller, J. B.; Chang, R. Y.; Sweeney, C.; Karion, A.; Wofsy, S. C.; Henderson, J.; Eluszkiewicz, J.; Mountain, M.; Oechel, W. C.

2013-12-01

The Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) is a NASA Earth Ventures (EV-1) investigation designed to quantify correlations between atmospheric and surface state variables for the Alaskan terrestrial ecosystems through intensive seasonal aircraft campaigns, ground-based observations, and analysis sustained over a 5-year mission. CARVE bridges critical gaps in our knowledge and understanding of Arctic ecosystems, linkages between the Arctic hydrologic and terrestrial carbon cycles, and the feedbacks from fires and thawing permafrost. We present CARVE airborne measurements of spatial and temporal patterns in atmospheric CH4 concentrations and estimated surface-atmosphere emissions for Arctic and Boreal Alaska. Continuous in situ CH4, CO2 and CO data are supplemented by periodic whole air flask samples from which 13CH4 and non-methane hydrocarbons are used to assess the relative contributions of wetlands, fossil fuel combustion, and oil and gas production to the observed CH4 signals. The CARVE project has also initiated monthly 14CH4 sampling at Barrow, AK (BRW) and the CARVE Tower in Fox, AK (CRV) to evaluate seasonal changes in the fraction of old carbon being mobilized via methanogenesis.

National Oceanic and Atmospheric Administration(NOAA) Arctic Climate Change Studies: A Contribution to IPY

NASA Astrophysics Data System (ADS)

Calder, J.; Overland, J.; Uttal, T.; Richter-Menge, J.; Rigor, I.; Crane, K.

2004-12-01

NOAA has initiated four activities that respond to the Arctic Climate Impact Assessment(ACIA) recommendations and represent contributions toward the IPY: 1) Arctic cloud, radiation and aerosol observatories, 2) documentation and attribution of changes in sea-ice thickness through direct measurement and modeling, 3) deriving added value from existing multivariate and historical data, and 4) following physical and biological changes in the northern Bering and Chukchi Seas. Northeast Canada, the central Arctic coast of Russia and the continuing site at Barrow have been chosen as desirable radiation/cloud locations as they exhibit different responses to Arctic Oscillation variability. NOAA is closely collaborating with Canadian groups to establish an observatory at Eureka. NOAA has begun deployment of a network of ice-tethered ice mass balance buoys complemented by several ice profiling sonars. In combination with other sea ice investigators, the Arctic buoy program, and satellites, changes can be monitored more effectively in sea ice throughout the Arctic. Retrospective data analyses includes analysis of Arctic clouds and radiation from surface and satellite measurements, correction of systematic errors in TOVS radiance data sets for the Arctic which began in 1979, addressing the feasibility of an Arctic System Reanalysis, and an Arctic Change Detection project that incorporates historical and recent physical and biological observations and news items at a website, www.arctic.noaa.gov. NOAA has begun a long-term effort to detect change in ecosystem indicators in the northern Bering and Chukchi Seas that could provide a model for other northern marine ecosystems. The first efforts were undertaken in summer 2004 during a joint Russian-US cruise that mapped the regions physical, chemical and biological parameters to set the stage for future operations over the longer term. A line of biophysical moorings provide detection of the expected warming of this area. A

The role of DOM in nitrogen processing in streams across arctic regions affected by fire

NASA Astrophysics Data System (ADS)

Rodriguez-Cardona, B.; Schade, J. D.; Holmes, R. M.; Natali, S.; Mann, P. J.; Wymore, A.; Coble, A. A.; Prokishkin, A. S.; Zito, P.; Podgorski, D. C.; Spencer, R. G.; McDowell, W. H.

2017-12-01

In stream ecosystems, inputs of dissolved organic carbon (DOC) have a strong influence on nitrogen (N) processing. Previous studies have demonstrated that increases in DOC concentrations can promote greater N removal in many stream ecosystems. Most of what we know about C and N coupling comes from studies of temperate streams; less is known about this relationship in the Arctic. Streams in Arctic ecosystems are facing rapid changes in climate and disturbance regimes, in particular increasing fire frequencies that are likely to alter biogeochemical cycles. Although fires can lead to increases in NO3 concentrations in streams, the effects of fire on DOC (concentration and composition) have been difficult to generalize. We studied the relationships between DOC and N in two locations; the Central Siberian Plateau, Russia and the Yukon-Kuskokwim (YK) River Delta, Alaska. Streams in both regions show increases in NO3 concentrations after fire, while DOC concentrations decrease in Siberia but increase in streams within the YK-Delta. These patterns in DOC and NO3 create a gradient in DOC and nutrient concentrations, allowing us to study this coupling in a wider Pan-Arctic scope. In order to assess the role of DOC in Arctic N processing, we conducted NO3 and NH4 additions to stream microcosms at the Alaskan site as well as whole-stream additions in Siberia. We hypothesized that nutrient uptake would be high in older burn sites of Siberia and recently burned sites in the YK-Delta, due to greater DOC concentrations and availability. Our results suggest that nitrogen dynamics in the Alaskan sites is strongly responsive to C availability, but is less so in Siberian sites. The potential impacts of permafrost thawing and fires on DOM and nutrient dynamics thus appear to not be consistent across the Arctic suggesting that different regions of the Arctic have unique biogeochemical controls.

Tundra biome research in Alaska: the structure and function of cold-dominated ecosystems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, J.; West, G.C.

1970-11-01

The objective of the Tundra Biome Program is to acquire a basic understanding of tundra, both alpine and arctic, and taiga. Collectively these are referred to as the cold-dominated ecosystems. The program's broad objectives are threefold: To develop a predictive understanding of how the wet arctic tundra ecosystem operates, particularly as exemplified in the Barrow, Alaska, area; to obtain the necessary data base from the variety of cold-dominated ecosystem types represented in the United States, so that their behavior can be modeled and simulated, and the results compared with similar studies underway in other circumpolar countries; to bring basic environmentalmore » knowledge to bear on problems of degradation, maintenance, and restoration of the temperature-sensitive and cold-dominated tundra/taiga ecosystems. (GRA)« less

Mapping the future expansion of Arctic open water

NASA Astrophysics Data System (ADS)

Barnhart, Katherine R.; Miller, Christopher R.; Overeem, Irina; Kay, Jennifer E.

2016-03-01

Sea ice impacts most of the Arctic environment, from ocean circulation and marine ecosystems to animal migration and marine transportation. Sea ice has thinned and decreased in age over the observational record. Ice extent has decreased. Reduced ice cover has warmed the surface ocean, accelerated coastal erosion and impacted biological productivity. Declines in Arctic sea-ice extent cannot be explained by internal climate variability alone and can be attributed to anthropogenic effects. However, extent is a poor measure of ice decline at specific locations as it integrates over the entire Arctic basin and thus contains no spatial information. The open water season, in contrast, is a metric that represents the duration of open water over a year at an individual location. Here we present maps of the open water season over the period 1920-2100 using daily output from a 30-member initial-condition ensemble of business-as-usual climate simulations that characterize the expansion of Arctic open water, determine when the open water season will move away from pre-industrial conditions (`shift’ time) and identify when human forcing will take the Arctic sea-ice system outside its normal bounds (`emergence’ time). The majority of the Arctic nearshore regions began shifting in 1990 and will begin leaving the range of internal variability in 2040. Models suggest that ice will cover coastal regions for only half of the year by 2070.

Climate-driven regime shifts in Arctic marine benthos

PubMed Central

Kortsch, Susanne; Primicerio, Raul; Beuchel, Frank; Renaud, Paul E.; Rodrigues, João; Lønne, Ole Jørgen; Gulliksen, Bjørn

2012-01-01

Climate warming can trigger abrupt ecosystem changes in the Arctic. Despite the considerable interest in characterizing and understanding the ecological impact of rapid climate warming in the Arctic, few long time series exist that allow addressing these research goals. During a 30-y period (1980–2010) of gradually increasing seawater temperature and decreasing sea ice cover in Svalbard, we document rapid and extensive structural changes in the rocky-bottom communities of two Arctic fjords. The most striking component of the benthic reorganization was an abrupt fivefold increase in macroalgal cover in 1995 in Kongsfjord and an eightfold increase in 2000 in Smeerenburgfjord. Simultaneous changes in the abundance of benthic invertebrates suggest that the macroalgae played a key structuring role in these communities. The abrupt, substantial, and persistent nature of the changes observed is indicative of a climate-driven ecological regime shift. The ecological processes thought to drive the observed regime shifts are likely to promote the borealization of these Arctic marine communities in the coming years. PMID:22891319

Arctic sea-ice syntheses: Charting across scope, scale, and knowledge systems

NASA Astrophysics Data System (ADS)

Druckenmiller, M. L.; Perovich, D. K.; Francis, J. A.

2017-12-01

Arctic sea ice supports and intersects a multitude of societal benefit areas, including regulating regional and global climates, structuring marine food webs, providing for traditional food provisioning by indigenous peoples, and constraining marine shipping and access. At the same time, sea ice is one of the most rapidly changing elements of the Arctic environment and serves as a source of key physical indicators for monitoring Arctic change. Before the present scientific interest in Arctic sea ice for climate research, it has long been, and remains, a focus of applied research for industry and national security. For generations, the icy coastal seas of the North have also provided a basis for the sharing of local and indigenous knowledge between Arctic residents and researchers, including anthropologists, biologists, and geoscientists. This presentation will summarize an ongoing review of existing synthesis studies of Arctic sea ice. We will chart efforts to achieve system-level understanding across geography, temporal scales, and the ecosystem services that Arctic sea ice supports. In doing so, we aim to illuminate the role of interdisciplinary science, together with local and indigenous experts, in advancing knowledge of the roles of sea ice in the Arctic system and beyond, reveal the historical and scientific evolution of sea-ice research, and assess current gaps in system-scale understanding.

The Arctic National Wildlife Refuge: An Interdisciplinary Unit.

ERIC Educational Resources Information Center

Thieman, Gayle; Geil, Mike

This paper presents a set of interdisciplinary lessons for teaching about the Arctic National Wildlife Refuge (Alaska). Lessons include a petroleum product treasure hunt, an examination of life without petroleum, the development of a wildlife poster, an exploration of the tundra ecosystem and the plants and animals that live there, identification…

Life on the edge: insect ecology in arctic environments.

PubMed

Strathdee, A T; Bale, J S

1998-01-01

The restricted Arctic insect fauna is usually explained by a lack of recolonization since the last glacial period, inadequate supply of suitable resources, or insufficient adaptation to such a harsh environment. These hypotheses and others that attempt to explain the latitudinal gradient of species distributions and abundance are reviewed. Arctic habitats available to insects are strongly heterogeneous, requiring a similarly diverse array of adaptive responses, characteristic of those species that have colonized and survived in such a stressful climate. Important adaptations in morphology (size, wings), behavior (activity patterns, thermoregulation), life cycles, and ecophysiology (cold hardiness, anaerobiosis, desiccation resistance) are discussed. The current focus of global climate change research on polar regions is identified, particularly the opportunity to study fundamental ecological processes and spatial dynamics in the relatively simple Arctic ecosystems.

Trajectory of the arctic as an integrated system

USGS Publications Warehouse

Hinzman, Larry; Deal, Clara; McGuire, Anthony David; Mernild, Sebastian H.; Polyakov, Igor V.; Walsh, John E.

2013-01-01

Although much remains to be learned about the Arctic and its component processes, many of the most urgent scientific, engineering, and social questions can only be approached through a broader system perspective. Here, we address interactions between components of the Arctic System and assess feedbacks and the extent to which feedbacks (1) are now underway in the Arctic; and (2) will shape the future trajectory of the Arctic system. We examine interdependent connections among atmospheric processes, oceanic processes, sea-ice dynamics, marine and terrestrial ecosystems, land surface stocks of carbon and water, glaciers and ice caps, and the Greenland ice sheet. Our emphasis on the interactions between components, both historical and anticipated, is targeted on the feedbacks, pathways, and processes that link these different components of the Arctic system. We present evidence that the physical components of the Arctic climate system are currently in extreme states, and that there is no indication that the system will deviate from this anomalous trajectory in the foreseeable future. The feedback for which the evidence of ongoing changes is most compelling is the surface albedo-temperature feedback, which is amplifying temperature changes over land (primarily in spring) and ocean (primarily in autumn-winter). Other feedbacks likely to emerge are those in which key processes include surface fluxes of trace gases, changes in the distribution of vegetation, changes in surface soil moisture, changes in atmospheric water vapor arising from higher temperatures and greater areas of open ocean, impacts of Arctic freshwater fluxes on the meridional overturning circulation of the ocean, and changes in Arctic clouds resulting from changes in water vapor content.

Trajectory of the Arctic as an integrated system.

PubMed

Hinzman, Larry D; Deal, Clara J; McGuire, A David; Mernild, Sebastian H; Polyakov, Igor V; Walsh, John E

2013-12-01

Although much remains to be learned about the Arctic and its component processes, many of the most urgent scientific, engineering, and social questions can only be approached through a broader system perspective. Here, we address interactions between components of the Arctic system and assess feedbacks and the extent to which feedbacks (1) are now underway in the Arctic and (2) will shape the future trajectory of the Arctic system. We examine interdependent connections among atmospheric processes, oceanic processes, sea-ice dynamics, marine and terrestrial ecosystems, land surface stocks of carbon and water, glaciers and ice caps, and the Greenland ice sheet. Our emphasis on the interactions between components, both historical and anticipated, is targeted on the feedbacks, pathways, and processes that link these different components of the Arctic system. We present evidence that the physical components of the Arctic climate system are currently in extreme states, and that there is no indication that the system will deviate from this anomalous trajectory in the foreseeable future. The feedback for which the evidence of ongoing changes is most compelling is the surface albedo-temperature feedback, which is amplifying temperature changes over land (primarily in spring) and ocean (primarily in autumn-winter). Other feedbacks likely to emerge are those in which key processes include surface fluxes of trace gases, changes in the distribution of vegetation, changes in surface soil moisture, changes in atmospheric water vapor arising from higher temperatures and greater areas of open ocean, impacts of Arctic freshwater fluxes on the meridional overturning circulation of the ocean, and changes in Arctic clouds resulting from changes in water vapor content.

Nitrate is an important nitrogen source for Arctic tundra plants

PubMed Central

Liu, Xue-Yan; Koyama, Lina A.; Weiss, Marissa S.; Inagaki, Yoshiyuki; Shaver, Gaius R.; Giblin, Anne E.; Hobara, Satoru; Nadelhoffer, Knute J.; Sommerkorn, Martin; Rastetter, Edward B.; Kling, George W.; Laundre, James A.; Yano, Yuriko; Makabe, Akiko; Yano, Midori; Liu, Cong-Qiang

2018-01-01

Plant nitrogen (N) use is a key component of the N cycle in terrestrial ecosystems. The supply of N to plants affects community species composition and ecosystem processes such as photosynthesis and carbon (C) accumulation. However, the availabilities and relative importance of different N forms to plants are not well understood. While nitrate (NO3−) is a major N form used by plants worldwide, it is discounted as a N source for Arctic tundra plants because of extremely low NO3− concentrations in Arctic tundra soils, undetectable soil nitrification, and plant-tissue NO3− that is typically below detection limits. Here we reexamine NO3− use by tundra plants using a sensitive denitrifier method to analyze plant-tissue NO3−. Soil-derived NO3− was detected in tundra plant tissues, and tundra plants took up soil NO3− at comparable rates to plants from relatively NO3−-rich ecosystems in other biomes. Nitrate assimilation determined by 15N enrichments of leaf NO3− relative to soil NO3− accounted for 4 to 52% (as estimated by a Bayesian isotope-mixing model) of species-specific total leaf N of Alaskan tundra plants. Our finding that in situ soil NO3− availability for tundra plants is high has important implications for Arctic ecosystems, not only in determining species compositions, but also in determining the loss of N from soils via leaching and denitrification. Plant N uptake and soil N losses can strongly influence C uptake and accumulation in tundra soils. Accordingly, this evidence of NO3− availability in tundra soils is crucial for predicting C storage in tundra. PMID:29540568

Seasonal thickness changes of Arctic sea ice north of Svalbard and implications for satellite remote sensing, ecosystem, and environmental management

NASA Astrophysics Data System (ADS)

Gerland, S.; Rösel, A.; King, J.; Spreen, G.; Divine, D.; Eltoft, T.; Gallet, J. C.; Hudson, S. R.; Itkin, P.; Krumpen, T.; Liston, G. E.; Merkouriadi, I.; Negrel, J.; Nicolaus, M.; Polashenski, C.; Assmy, P.; Barber, D. G.; Duarte, P.; Doulgeris, A. P.; Haas, C.; Hughes, N.; Johansson, M.; Meier, W.; Perovich, D. K.; Provost, C.; Richter-Menge, J.; Skourup, H.; Wagner, P.; Wilkinson, J.; Granskog, M. A.; Steen, H.

2016-12-01

Sea-ice thickness is a crucial parameter to consider when assessing the status of Arctic sea ice, whether for environmental management, monitoring projects, or regional or pan-arctic assessments. Modern satellite remote sensing techniques allow us to monitor ice extent and to estimate sea-ice thickness changes; but accurate quantifications of sea-ice thickness distribution rely on in situ and airborne surveys. From January to June 2015, an international expedition (N-ICE2015) took place in the Arctic Ocean north of Svalbard, with the Norwegian research vessel RV Lance frozen into drifting sea ice. In total, four drifts, with four different floes were made during that time. Sea-ice and snow thickness measurements were conducted on all main ice types present in the region, first year ice, multiyear ice, and young ice. Measurement methods included ground and helicopter based electromagnetic surveys, drillings, hot-wire installations, snow-sonde transects, snow stakes, and ice mass balance and snow buoys. Ice thickness distributions revealed modal thicknesses in spring between 1.6 and 1.7 m, which is lower than reported for the region from comparable studies in 2009 (2.4 m) and 2011 (1.8 m). Knowledge about the ice thickness distribution in a region is crucial to the understanding of climate processes, and also relevant to other disciplines. Sea-ice thickness data collected during N-ICE2015 can also give us insights into how ice and snow thicknesses affect ecosystem processes. In this presentation, we will explore the influence of snow cover and ocean properties on ice thickness, and the role of sea-ice thickness in air-ice-ocean interactions. We will also demonstrate how information about ice thickness aids classification of different sea ice types from SAR satellite remote sensing, which has real-world applications for shipping and ice forecasting, and how sea ice thickness data contributes to climate assessments.

Volatile organic compound emissions from arctic vegetation highly responsive to experimental warming

NASA Astrophysics Data System (ADS)

Rinnan, Riikka; Kramshøj, Magnus; Lindwall, Frida; Schollert, Michelle; Svendsen, Sarah H.; Valolahti, Hanna

2017-04-01

Arctic areas are experiencing amplified climate warming that proceeds twice as fast as the global temperature increase. The increasing temperature is already causing evident alterations, e.g. changes in the vegetation cover as well as thawing of permafrost. Climate warming and the concomitant biotic and abiotic changes are likely to have strong direct and indirect effects on emission of volatile organic compounds (VOCs) from arctic vegetation. We used long-term field manipulation experiments in the Subarctic, Low Arctic and High Arctic to assess effects of climate change on VOC emissions from vegetation communities. In these experiments, we applied passive warming with open-top chambers alone and in combination with other experimental treatments in well-replicated experimental designs. Volatile emissions were sampled in situ by drawing air from plant enclosures and custom-built chambers into adsorbent cartridges, which were analyzed by thermal desorption and gas chromatography-mass spectrometry in laboratory. Emission increases by a factor of 2-5 were observed under experimental warming by only a few degrees, and the strong response seems universal for dry, mesic and wet ecosystems. In some cases, these vegetation community level responses were partly due to warming-induced increases in the VOC-emitting plant biomass, changes in species composition and the following increase in the amount of leaf litter (Valolahti et al. 2015). In other cases, the responses appeared before any vegetation changes took place (Lindwall et al. 2016) or even despite a decrease in plant biomass (Kramshøj et al. 2016). VOC emissions from arctic ecosystems seem more responsive to experimental warming than other ecosystem processes. We can thus expect large increases in future VOC emissions from this area due to the direct effects of temperature increase, and due to increasing plant biomass and a longer growing season. References Kramshøj M., Vedel-Petersen I., Schollert M., Rinnan �

Environmental and vegetation controls on the spatial variability of CH4 emission from wet-sedge and tussock tundra ecosystems in the Arctic.

PubMed

McEwing, Katherine Rose; Fisher, James Paul; Zona, Donatella

Despite multiple studies investigating the environmental controls on CH 4 fluxes from arctic tundra ecosystems, the high spatial variability of CH 4 emissions is not fully understood. This makes the upscaling of CH 4 fluxes from plot to regional scale, particularly challenging. The goal of this study is to refine our knowledge of the spatial variability and controls on CH 4 emission from tundra ecosystems. CH 4 fluxes were measured in four sites across a variety of wet-sedge and tussock tundra ecosystems in Alaska using chambers and a Los Gatos CO 2 and CH 4 gas analyser. All sites were found to be sources of CH 4 , with northern sites (in Barrow) showing similar CH 4 emission rates to the southernmost site (ca. 300 km south, Ivotuk). Gross primary productivity (GPP), water level and soil temperature were the most important environmental controls on CH 4 emission. Greater vascular plant cover was linked with higher CH 4 emission, but this increased emission with increased vascular plant cover was much higher (86 %) in the drier sites, than the wettest sites (30 %), suggesting that transport and/or substrate availability were crucial limiting factors for CH 4 emission in these tundra ecosystems. Overall, this study provides an increased understanding of the fine scale spatial controls on CH 4 flux, in particular the key role that plant cover and GPP play in enhancing CH 4 emissions from tundra soils.

Future Arctic climate changes: Adaptation and mitigation time scales

NASA Astrophysics Data System (ADS)

Overland, James E.; Wang, Muyin; Walsh, John E.; Stroeve, Julienne C.

2014-02-01

The climate in the Arctic is changing faster than in midlatitudes. This is shown by increased temperatures, loss of summer sea ice, earlier snow melt, impacts on ecosystems, and increased economic access. Arctic sea ice volume has decreased by 75% since the 1980s. Long-lasting global anthropogenic forcing from carbon dioxide has increased over the previous decades and is anticipated to increase over the next decades. Temperature increases in response to greenhouse gases are amplified in the Arctic through feedback processes associated with shifts in albedo, ocean and land heat storage, and near-surface longwave radiation fluxes. Thus, for the next few decades out to 2040, continuing environmental changes in the Arctic are very likely, and the appropriate response is to plan for adaptation to these changes. For example, it is very likely that the Arctic Ocean will become seasonally nearly sea ice free before 2050 and possibly within a decade or two, which in turn will further increase Arctic temperatures, economic access, and ecological shifts. Mitigation becomes an important option to reduce potential Arctic impacts in the second half of the 21st century. Using the most recent set of climate model projections (CMIP5), multimodel mean temperature projections show an Arctic-wide end of century increase of +13°C in late fall and +5°C in late spring for a business-as-usual emission scenario (RCP8.5) in contrast to +7°C in late fall and +3°C in late spring if civilization follows a mitigation scenario (RCP4.5). Such temperature increases demonstrate the heightened sensitivity of the Arctic to greenhouse gas forcing.

Genomics in a changing arctic: critical questions await the molecular ecologist.

PubMed

Wullschleger, Stan D; Breen, Amy L; Iversen, Colleen M; Olson, Matthew S; Näsholm, Torgny; Ganeteg, Ulrika; Wallenstein, Matthew D; Weston, David J

2015-05-01

Molecular ecology is poised to tackle a host of interesting questions in the coming years. The Arctic provides a unique and rapidly changing environment with a suite of emerging research needs that can be addressed through genetics and genomics. Here we highlight recent research on boreal and tundra ecosystems and put forth a series of questions related to plant and microbial responses to climate change that can benefit from technologies and analytical approaches contained within the molecular ecologist's toolbox. These questions include understanding (i) the mechanisms of plant acquisition and uptake of N in cold soils, (ii) how these processes are mediated by root traits, (iii) the role played by the plant microbiome in cycling C and nutrients within high-latitude ecosystems and (iv) plant adaptation to extreme Arctic climates. We highlight how contributions can be made in these areas through studies that target model and nonmodel organisms and emphasize that the sequencing of the Populus and Salix genomes provides a valuable resource for scientific discoveries related to the plant microbiome and plant adaptation in the Arctic. Moreover, there exists an exciting role to play in model development, including incorporating genetic and evolutionary knowledge into ecosystem and Earth System Models. In this regard, the molecular ecologist provides a valuable perspective on plant genetics as a driver for community biodiversity, and how ecological and evolutionary forces govern community dynamics in a rapidly changing climate. © 2015 John Wiley & Sons Ltd.

Living in an oasis: Rapid transformations, resilience, and resistance in the North Water Area societies and ecosystems.

PubMed

Jeppesen, Erik; Appelt, Martin; Hastrup, Kirsten; Grønnow, Bjarne; Mosbech, Anders; Smol, John P; Davidson, Thomas A

2018-04-01

Based on lake sediment data, archaeological findings, and historical records, we describe rapid transformations, resilience and resistance in societies and ecosystems, and their interactions in the past in the North Water area related to changes in climate and historical events. Examples are the formation of the polynya itself and the early arrival of people, ca. 4500 years ago, and later major human immigrations (different societies, cultural encounters, or abandonment) from other regions in the Arctic. While the early immigrations had relatively modest and localised effect on the ecosystem, the later-incoming culture in the early thirteenth century was marked by extensive migrations into and out of the area and abrupt shifts in hunting technologies. This has had long-lasting consequences for the local lake ecosystems. Large natural transformations in the ecosystems have also occurred over relatively short time periods related to changes in the polynya. Finally, we discuss the future perspectives for the North Water area given the many threats, but also opportunities.

Observed and Potential Responses of Upland Tundra Ecosystems to a Changing Climate: Results from the Arctic Long-Term Ecological Research Project, North Slope, Alaska, USA

NASA Astrophysics Data System (ADS)

Bowden, W. B.

2014-12-01

permafrost in the arctic region approaches the 0ºC tipping point, the combination of presses and pulses may radically and rapidly alter upland tundra terrestrial and aquatic ecosystems. These changes will almost certainly occur more rapidly than would be the case if the region were influenced by the press of warming temperature alone.

Global warming triggers the loss of a key Arctic refugium

PubMed Central

Rühland, K. M.; Paterson, A. M.; Keller, W.; Michelutti, N.; Smol, J. P.

2013-01-01

We document the rapid transformation of one of the Earth's last remaining Arctic refugia, a change that is being driven by global warming. In stark contrast to the amplified warming observed throughout much of the Arctic, the Hudson Bay Lowlands (HBL) of subarctic Canada has maintained cool temperatures, largely due to the counteracting effects of persistent sea ice. However, since the mid-1990s, climate of the HBL has passed a tipping point, the pace and magnitude of which is exceptional even by Arctic standards, exceeding the range of regional long-term variability. Using high-resolution, palaeolimnological records of algal remains in dated lake sediment cores, we report that, within this short period of intense warming, striking biological changes have occurred in the region's freshwater ecosystems. The delayed and intense warming in this remote region provides a natural observatory for testing ecosystem resilience under a rapidly changing climate, in the absence of direct anthropogenic influences. The environmental repercussions of this climate change are of global significance, influencing the huge store of carbon in the region's extensive peatlands, the world's southern-most polar bear population that depends upon Hudson Bay sea ice and permafrost for survival, and native communities who rely on this landscape for sustenance. PMID:24107529

Global warming triggers the loss of a key Arctic refugium.

PubMed

Rühland, K M; Paterson, A M; Keller, W; Michelutti, N; Smol, J P

2013-12-07

We document the rapid transformation of one of the Earth's last remaining Arctic refugia, a change that is being driven by global warming. In stark contrast to the amplified warming observed throughout much of the Arctic, the Hudson Bay Lowlands (HBL) of subarctic Canada has maintained cool temperatures, largely due to the counteracting effects of persistent sea ice. However, since the mid-1990s, climate of the HBL has passed a tipping point, the pace and magnitude of which is exceptional even by Arctic standards, exceeding the range of regional long-term variability. Using high-resolution, palaeolimnological records of algal remains in dated lake sediment cores, we report that, within this short period of intense warming, striking biological changes have occurred in the region's freshwater ecosystems. The delayed and intense warming in this remote region provides a natural observatory for testing ecosystem resilience under a rapidly changing climate, in the absence of direct anthropogenic influences. The environmental repercussions of this climate change are of global significance, influencing the huge store of carbon in the region's extensive peatlands, the world's southern-most polar bear population that depends upon Hudson Bay sea ice and permafrost for survival, and native communities who rely on this landscape for sustenance.

Mechanistic Representation of Soil C Dynamics: for Arctic Ecosystem

NASA Astrophysics Data System (ADS)

Dwivedi, D.; Riley, W. J.; Bisht, G.

2013-12-01

Arctic and sub-Arctic soils store vast amounts of carbon, approximately 1700 billion metric tones of frozen organic carbon. This carbon is susceptible to release to the atmosphere due to environmental changes (e.g., rapidly evolving landscape, warming); however, the mechanisms responsible for this susceptibility of soil organic matter (SOM) are not well understood, and uncertainties exist in terms of their representation in Earth System models. The representation of SOM dynamics in Earth System Models is critical for future climate prediction. To investigate the impacts of various physical (e.g., multi-phase transport, sorption, desorption, temperature), chemical (e.g., pH), and biological (e.g., microbial activity, enzyme dynamics) factors on SOM stability, we have developed CENTURY-like (describing labile and recalcitrant pools) and complex (describing multiple archetypal polymers and monomers C substrate groups) reaction networks. These reaction networks are integrated in a three-dimensional, multi-phase reactive transport solver (PFLOTRAN) and include representations of bacterial and fungal activity as well as population dynamics, gaseous and aqueous advection, and adsorption and desorption. We test and compare these reaction networks in PFLOTRAN to accurately predict depth-resolved soil organic matter (SOM) in the subsurface. We present results showing impacts of abiotic controls (e.g., surface interactions and temperature) on the long-term stabilization of SOM under permafrost conditions.

Extensive under-ice turbulence microstructure measurements in the central Arctic Ocean in 2015

NASA Astrophysics Data System (ADS)

Rabe, Benjamin; Janout, Markus; Graupner, Rainer; Hoelemann, Jens; Hampe, Hendrik; Hoppmann, Mario; Horn, Myriel; Juhls, Bennet; Korhonen, Meri; Nikolopoulos, Anna; Pisarev, Sergey; Randelhoff, Achim; Savy, John-Philippe; Villacieros, Nicolas

2016-04-01

The Arctic Ocean is a strongly stratified low-energy environment, where tides are weak and the upper ocean is protected by an ice cover during much of the year. Interior mixing processes are dominated by double diffusion. The upper Arctic Ocean features a cold surface mixed layer, which, separated by a sharp halocline, protects the sea ice from the warmer underlying Atlantic- and Pacific-derived water masses. These water masses carry nutrients that are important for the Arctic ecosystem. Hence vertical fluxes of heat, salt, and nutrients are crucial components in understanding the Arctic ecosystem. Yet, direct flux measurements are difficult to obtain and hence sparse. In 2015, two multidisciplinary R/V Polarstern expeditions to the Arctic Ocean resulted in a series of under-ice turbulence microstructure measurements. These cover different locations across the Eurasian and Makarov Basins, during the melt season in spring and early summer as well as during freeze-up in late summer. Sampling was carried out from ice floes with repeated profiles resulting in 4-24 hour-long time series. 2015 featured anomalously warm atmospheric conditions during summer followed by unusually low temperatures in September. Our measurements show elevated dissipation rates at the base of the mixed layer throughout all stations, with significantly higher levels above the Eurasian continental slope when compared with the Arctic Basin. Additional peaks were found between the mixed layer and the halocline, in particular at stations where Pacific Summer water was present. This contribution provides first flux estimates and presents first conclusions regarding the impact of atmospheric and sea ice conditions on vertical mixing in 2015.

Arctic shorebirds in North America: A decade of monitoring

USGS Publications Warehouse

Bart, Jonathan R.; Johnston, Victoria H.

2012-01-01

Each year shorebirds from North and South America migrate thousands of miles to spend the summer in the Arctic. There they feed in shoreline marshes and estuaries along some of the most productive and pristine coasts anywhere. With so much available food they are able to reproduce almost explosively; and as winter approaches, they retreat south along with their offspring, to return to the Arctic the following spring. This remarkable pattern of movement and activity has been the object of intensive study by an international team of ornithologists who have spent a decade counting, surveying, and observing these shorebirds. In this important synthetic work, they address multiple questions about these migratory bird populations. How many birds occupy Arctic ecosystems each summer? How long do visiting shorebirds linger before heading south? How fecund are these birds? Where exactly do they migrate and where exactly do they return? Are their populations growing or shrinking? The results of this study are crucial for better understanding how environmental policies will influence Arctic habitats as well as the far-ranging winter habitats used by migratory shorebirds.

Modern pollen data from the Canadian Arctic, 1972-1973

NASA Astrophysics Data System (ADS)

Nichols, Harvey; Stolze, Susann

2017-05-01

This data descriptor reports results of a 1972-73 baseline study of modern pollen deposition in the Canadian Arctic to originally aid interpretation of Holocene pollen diagrams from that region, especially focussed on the arctic tree-line. The data set is geographically unique due to its extent, and allows the assessment of the effects of modern climate change on northern ecosystems, including fluctuations of the a arctic tree-line. Repeated sampling was conducted along an interior transect at 29 sites from the Boreal Forest to the High Arctic, with five additional coastal sites covering a total distance of 3,200 km. Static pollen samplers captured both local pollen and long-distance pollen wind-blown from the Boreal Forest. Moss and lichen polsters provided multi-year pollen fallout to assess the effectiveness of the static pollen samplers. The local vegetation was recorded at each site. This descriptor provides information on data archived at the World Data Center PANGAEA, which includes spreadsheets detailing site and sample information as well as raw and processed pollen data obtained on over 500 samples.

Modern pollen data from the Canadian Arctic, 1972-1973.

PubMed

Nichols, Harvey; Stolze, Susann

2017-05-16

This data descriptor reports results of a 1972-73 baseline study of modern pollen deposition in the Canadian Arctic to originally aid interpretation of Holocene pollen diagrams from that region, especially focussed on the arctic tree-line. The data set is geographically unique due to its extent, and allows the assessment of the effects of modern climate change on northern ecosystems, including fluctuations of the a arctic tree-line. Repeated sampling was conducted along an interior transect at 29 sites from the Boreal Forest to the High Arctic, with five additional coastal sites covering a total distance of 3,200 km. Static pollen samplers captured both local pollen and long-distance pollen wind-blown from the Boreal Forest. Moss and lichen polsters provided multi-year pollen fallout to assess the effectiveness of the static pollen samplers. The local vegetation was recorded at each site. This descriptor provides information on data archived at the World Data Center PANGAEA, which includes spreadsheets detailing site and sample information as well as raw and processed pollen data obtained on over 500 samples.

Biological response to climate change in the Arctic Ocean: The view from the past

USGS Publications Warehouse

Cronin, Thomas M.; Cronin, Matthew A.

2017-01-01

The Arctic Ocean is undergoing rapid climatic changes including higher ocean temperatures, reduced sea ice, glacier and Greenland Ice Sheet melting, greater marine productivity, and altered carbon cycling. Until recently, the relationship between climate and Arctic biological systems was poorly known, but this has changed substantially as advances in paleoclimatology, micropaleontology, vertebrate paleontology, and molecular genetics show that Arctic ecosystem history reflects global and regional climatic changes over all timescales and climate states (103–107 years). Arctic climatic extremes include 25°C hyperthermal periods during the Paleocene-Eocene (56–46 million years ago, Ma), Quaternary glacial periods when thick ice shelves and sea ice cover rendered the Arctic Ocean nearly uninhabitable, seasonally sea-ice-free interglacials and abrupt climate reversals. Climate-driven biological impacts included large changes in species diversity, primary productivity, species’ geographic range shifts into and out of the Arctic, community restructuring, and possible hybridization, but evidence is not sufficient to determine whether or when major episodes of extinction occurred.

Increased sensitivity and variability of phytotoxicity responses in Arctic soils to a reference toxicant, boric acid.

PubMed

Anaka, Alison; Wickstrom, Mark; Siciliano, Steven Douglas

2008-03-01

Industrial and human activities in the Arctic regions may pose a risk to terrestrial Arctic ecosystem functions. One of the most common terrestrial toxicological end points, primary productivity, typically is assessed using a plant phytotoxicity test. Because of cryoturbation, a soil mixing process common in polar regions, we hypothesized that phytotoxicity test results in Arctic soils would be highly variable compared to other terrestrial ecosystems. The variability associated with phytotoxicity tests was evaluated using Environment Canada's standardized plant toxicity test in three cryoturbated soils from Canada's Arctic exposed to a reference toxicant, boric acid. Northern wheatgrass (Elymus lanceolatus) not only was more sensitive to toxicants in Arctic soils, its response to toxicants was more variable compared to that in temperate soils. The phytotoxicity of boric acid in cryosols was much greater than commonly reported in other soils, with a boric acid concentration of less than 150 microg/g soil needed to inhibit root and shoot growth by 20%. Large variability also was found in the phytotoxicity test results, with coefficients of variation for 10 samples ranging from 160 to 79%. The increased toxicity of boric acid in cryosols and variability in test response was not explained by soil properties. Based on our admittedly limited data set of three different Arctic soils, we recommend that more than 30 samples be taken from each control and potentially impacted area to accurately assess contaminant effects at sites in northern Canada. Such intensive sampling will insure that false-negative results for toxicant impacts in Arctic soils are minimized.

A Cloud-enabled Service-oriented Spatial Web Portal for Facilitating Arctic Data Discovery, Integration, and Utilization

NASA Astrophysics Data System (ADS)

dias, S. B.; Yang, C.; Li, Z.; XIA, J.; Liu, K.; Gui, Z.; Li, W.

2013-12-01

Global climate change has become one of the biggest concerns for human kind in the 21st century due to its broad impacts on society and ecosystems across the world. Arctic has been observed as one of the most vulnerable regions to the climate change. In order to understand the impacts of climate change on the natural environment, ecosystems, biodiversity and others in the Arctic region, and thus to better support the planning and decision making process, cross-disciplinary researches are required to monitor and analyze changes of Arctic regions such as water, sea level, biodiversity and so on. Conducting such research demands the efficient utilization of various geospatially referenced data, web services and information related to Arctic region. In this paper, we propose a cloud-enabled and service-oriented Spatial Web Portal (SWP) to support the discovery, integration and utilization of Arctic related geospatial resources, serving as a building block of polar CI. This SWP leverages the following techniques: 1) a hybrid searching mechanism combining centralized local search, distributed catalogue search and specialized Internet search for effectively discovering Arctic data and web services from multiple sources; 2) a service-oriented quality-enabled framework for seamless integration and utilization of various geospatial resources; and 3) a cloud-enabled parallel spatial index building approach to facilitate near-real time resource indexing and searching. A proof-of-concept prototype is developed to demonstrate the feasibility of the proposed SWP, using an example of analyzing the Arctic snow cover change over the past 50 years.

The virtues of localism and arctic wilderness politics

Treesearch

James N. Gladden

2007-01-01

An analysis of co-managing structures and land use issues in three case studies of arctic wilderness politics shows that more formal and informal power sharing by government officials with local people results in less conflict. Greater input and control by nearby communities may also help to protect wilderness ecosystems and traditional values of northern cultures....

Climate of the Arctic marine environment.

PubMed

Walsh, John E

2008-03-01

The climate of the Arctic marine environment is characterized by strong seasonality in the incoming solar radiation and by tremendous spatial variations arising from a variety of surface types, including open ocean, sea ice, large islands, and proximity to major landmasses. Interannual and decadal-scale variations are prominent features of Arctic climate, complicating the distinction between natural and anthropogenically driven variations. Nevertheless, climate models consistently indicate that the Arctic is the most climatically sensitive region of the Northern Hemisphere, especially near the sea ice margins. The Arctic marine environment has shown changes over the past several decades, and these changes are part of a broader global warming that exceeds the range of natural variability over the past 1000 years. Record minima of sea ice coverage during the past few summers and increased melt from Greenland have important implications for the hydrographic regime of the Arctic marine environment. The recent changes in the atmosphere (temperature, precipitation, pressure), sea ice, and ocean appear to be a coordinated response to systematic variations of the large-scale atmospheric circulation, superimposed on a general warming that is likely associated with increasing greenhouse gases. The changes have been sufficiently large in some sectors (e.g., the Bering/Chukchi Seas) that consequences for marine ecosystems appear to be underway. Global climate models indicate an additional warming of several degrees Celsius in much of the Arctic marine environment by 2050. However, the warming is seasonal (largest in autumn and winter), spatially variable, and closely associated with further retreat of sea ice. Additional changes predicted for 2050 are a general decrease of sea level pressure (largest in the Bering sector) and an increase of precipitation. While predictions of changes in storminess cannot be made with confidence, the predicted reduction of sea ice cover will

Microbial cell retention in a melting High Arctic snowpack, Svalbard

NASA Astrophysics Data System (ADS)

Zarsky, Jakub; Björkman, Mats; Kühnel, Rafael; Hell, Katherina; Hodson, Andy; Sattler, Birgit; Psenner, Roland

2014-05-01

to the final 38 cm. The major ion composition (IC), pH, conductivity and cell abundances were measured. Results and conlusions The removal of microbial cells from a high arctic snowpack resembles an elution sequence similar to that of hydrophobic compounds a process that helps glaciers retain a microbial biomass upon their surface, even after the demise of the snow cover. The snowpack and the glacier surface therefore act as an accumulator of cells during the melt season. This suggests that wet snowpacks, even on the surface of high arctic glaciers, are likely to be dynamic ecosystems in their own right. In our study, a clear ion elution sequence was observed that resembled earlier reports and caused high concentrations of ions in snowpack runoff at the start of the snow melt, which rapidly decreased as snow melt proceeded. Chloride, sulfate, nitrate, sodium and potassium experienced a 50 % elution before 20 - 25 % of the snowpack water content was lost. By contrast, cell removal only reached the 50 % level after ~70 % snowpack depletion. In contrast to our expectations, the calculated cell budget between the initial and final snowpack (including the cell loss by elution), revealed a significant increase of the total cell numbers, i.e. more than twice the original number. Assuming aeolian deposition processes to be low, this suggests cell proliferation as a contribution to the observed "retention effect". Precipitation was the major cell contributor to the snowpack upon Midtre Lovénbreen. An overall low cell concentration was therefore found within the snowpack stratigraphy, where snow layers frequently showed cell abundances similar to those of cloud water. This was in contrast to the nearby and more wind exposed sites examined in the Kongsfjorden area in 2007. However, layers of higher dust deposition were concomitant with one order of magnitude higher cell abundances, indicating that wind dispersal from locally exposed rocks supplements the atmospheric cell input.

Long term records of lake clarity as an indicator for final ecosystem goods and services of lakes

EPA Science Inventory

We reviewed available long-term records of lake clarity (via secchi disc readings) as an indicator of final ecosystem goods and services of lakes. Lake water quality assessments are often based on biophysical indicators not explicitly or quantifiably linked to the ecosystem servi...

Recovery of three arctic stream reaches from experimental nutrient enrichment

USGS Publications Warehouse

Benstead, J.P.; Green, A.C.; Deegan, Linda A.; Peterson, B.J.; Slavik, K.; Bowden, W.B.; Hershey, A.E.

2007-01-01

1. Nutrient enrichment and resulting eutrophication is a widespread anthropogenic influence on freshwater ecosystems, but recovery from nutrient enrichment is poorly understood, especially in stream environments. We examined multi-year patterns in community recovery from experimental low-concentration nutrient enrichment (N + P or P only) in three reaches of two Arctic tundra streams (Kuparuk River and Oksrukuyik Creek) on the North Slope of Alaska (U.S.A.). 2. Rates of recovery varied among community components and depended on duration of enrichment (2-13 consecutive growing seasons). Biomass of epilithic algae returned to reference levels rapidly (within 2 years), regardless of nutrients added or enrichment duration. Aquatic bryophyte cover, which increased greatly in the Kuparuk River only after long-term enrichment (8 years), took 8 years of recovery to approach reference levels, after storms had scoured most remnant moss in the recovering reach. 3. Multi-year persistence of bryophytes in the Kuparuk River appeared to prevent recovery of insect populations that had either been positively (e.g. the mayfly Ephemerella, most chironomid midge taxa) or negatively (e.g. the tube-building chironomid Orthocladius rivulorum) affected by this shift in dominant primary producer. These lags in recovery (of >3 years) were probably driven by the persistent effect of bryophytes on physical benthic habitat. 4. Summer growth rates of Arctic grayling (both adults and young-of-year) in Oksrukuyik Creek (fertilised for 6 years with no bryophyte colonisation), which were consistently increased by nutrient addition, returned to reference rates within 1-2 years. 5. Rates of recovery of these virtually pristine Arctic stream ecosystems from low-level nutrient enrichment appeared to be controlled largely by duration of enrichment, mediated through physical habitat shifts caused by eventual bryophyte colonisation, and subsequent physical disturbance that removed bryophytes. Nutrient

Year-round Regional CO2 Fluxes from Boreal and Tundra Ecosystems in Alaska

NASA Astrophysics Data System (ADS)

Commane, R.; Lindaas, J.; Benmergui, J. S.; Luus, K. A.; Chang, R. Y. W.; Daube, B. C.; Euskirchen, E. S.; Henderson, J.; Karion, A.; Miller, J. B.; Miller, S. M.; Parazoo, N.; Randerson, J. T.; Sweeney, C.; Tans, P. P.; Thoning, K. W.; Veraverbeke, S.; Miller, C. E.; Wofsy, S. C.

2016-12-01

High-latitude ecosystems could release large amounts of carbon dioxide (CO2) to the atmosphere in a warmer climate. We derive temporally and spatially resolved year-round CO2 fluxes in Alaska from a synthesis of airborne and tower CO2 observations in 2012-2014. We find that tundra ecosystems were net sources of atmospheric CO2. We discuss these flux estimates in the context of long-term CO2 measurements at Barrow, AK, to asses the long term trend in carbon fluxes in the Arctic. Many Earth System Models incorrectly simulate net carbon uptake in Alaska presently. Our results imply that annual net emission of CO2 to the atmosphere may have increased markedly in this region of the Arctic in response to warming climate, supporting the view that climate-carbon feedback is strongly positive in the high Arctic.

Arctic Climate and Atmospheric Planetary Waves

NASA Technical Reports Server (NTRS)

Cavalieri, D. J.; Haekkinen, S.

2000-01-01

Analysis of a fifty-year record (1946-1995) of monthly-averaged sea level pressure data provides a link between the phases of planetary-scale sea level pressure waves and Arctic Ocean and ice variability. Results of this analysis show: (1) a breakdown of the dominant wave I pattern in the late 1960's, (2) shifts in the mean phase of waves 1 and 2 since this breakdown, (3) an eastward shift in the phases of both waves 1 and 2 during the years of simulated cyclonic Arctic Ocean circulation relative to their phases during the years of anticyclonic circulation, (4) a strong decadal variability of wave phase associated with simulated Arctic Ocean circulation changes. Finally, the Arctic atmospheric circulation patterns that emerge when waves 1 and 2 are in their extreme eastern and western positions suggest an alternative approach to determine significant forcing patterns of sea ice and high-latitude variability.

The effects of land cover and land use change on the contemporary carbon balance of the arctic and boreal terrestrial ecosystems of northern Eurasia

USGS Publications Warehouse

Hayes, Daniel J.; McGuire, A. David; Kicklighter, David W.; Burnside , Todd J.; Melillo, Jerry M.

2010-01-01

Recent changes in climate, disturbance regimes and land use and management systems in Northern Eurasia have the potential to disrupt the terrestrial sink of atmospheric CO2 in a way that accelerates global climate change. To determine the recent trends in the carbon balance of the arctic and boreal ecosystems of this region, we performed a retrospective analysis of terrestrial carbon dynamics across northern Eurasia over a recent 10-year period using a terrestrial biogeochemical process model. The results of the simulations suggest a shift in direction of the net flux from the terrestrial sink of earlier decades to a net source on the order of 45 Tg C year−1between 1997 and 2006. The simulation framework and subsequent analyses presented in this study attribute this shift to a large loss of carbon from boreal forest ecosystems, which experienced a trend of decreasing precipitation and a large area burned during this time period.

Temporal Variation of NDVI and the Drivers of Climate Variables in the Arctic Tundra Transition Zone

NASA Astrophysics Data System (ADS)

Lee, J.; Ryu, Y.; Lee, Y. K.

2016-12-01

The Arctic is a sensitive region to temperature, which is drastically increasing with climate change. Vegetation in transition zones of the sub-arctic tundra biome are most sensitive to the warming climate, as temperature in the Arctic ecosystem is one of important limiting factors of vegetation growth and decomposition. Previous research in the transition zone show that there is a difference of sensible heat flux (21 Wm-2), Leaf Area Index increase from 0.58 - 2.76 and canopy height from 0.1 - 6.1m across dwarf and tall shrubs to forest, however, we lack understanding of NDVI trend of this zone. To better understand the vegetation in transition zones of the arctic ecosystem, we analyze the long-term trend of NDVI (AVHRR 3g GIMMs data), temperature and precipitation (Climate Research Unit data) trend from 1982 - 2010 in Council, Alaska that is a region where arctic tundra is transitioning to boreal forest. We also analyze how the climatic factors, temperature or precipitation, affect NDVI. Annual precipitation had the highest interannual variability compared to temperature and NDVI. There was an overall decreasing trend of annual maximum NDVI (y = -0.0019x+4.7). During 1982 to 2003, NDVI and temperature had a similar pattern, but when temperature suddenly jumped to 13.2°C in 2004, NDVI and precipitation declined. This study highlights that temperature increase does not always lead to greening, but after a certain threshold they may cause damage to sub-arctic tundra vegetation.

Trends in NDVI and tundra community composition in the Arctic of NE Alaska between 1984 and 2009

Treesearch

Robert R. Pattison; Janet C. Jorgenson; Martha K. Raynolds; Jeffery M. Welker

2015-01-01

As Arctic ecosystems experience increases in surface air temperatures, plot-level analyses of tundra vegetation composition suggest that there are important changes occurring in tundra communities that are typified by increases in shrubs and declines in non-vascular species. At the same time analyses of NDVI indicate that the Arctic tundra is greening. Few studies have...

Losing ground: past history and future fate of Arctic small mammals in a changing climate.

PubMed

Prost, Stefan; Guralnick, Robert P; Waltari, Eric; Fedorov, Vadim B; Kuzmina, Elena; Smirnov, Nickolay; van Kolfschoten, Thijs; Hofreiter, Michael; Vrieling, Klaas

2013-06-01

According to the IPCC, the global average temperature is likely to increase by 1.4-5.8 °C over the period from 1990 to 2100. In Polar regions, the magnitude of such climatic changes is even larger than in temperate and tropical biomes. This amplified response is particularly worrisome given that the so-far moderate warming is already impacting Arctic ecosystems. Predicting species responses to rapid warming in the near future can be informed by investigating past responses, as, like the rest of the planet, the Arctic experienced recurrent cycles of temperature increase and decrease (glacial-interglacial changes) in the past. In this study, we compare the response of two important prey species of the Arctic ecosystem, the collared lemming and the narrow-skulled vole, to Late Quaternary climate change. Using ancient DNA and Ecological Niche Modeling (ENM), we show that the two species, which occupy similar, but not identical ecological niches, show markedly different responses to climatic and environmental changes within broadly similar habitats. We empirically demonstrate, utilizing coalescent model-testing approaches, that collared lemming populations decreased substantially after the Last Glacial Maximum; a result consistent with distributional loss over the same period based on ENM results. Given this strong association, we projected the current niche onto future climate conditions based on IPCC 4.0 scenarios, and forecast accelerating loss of habitat along southern range boundaries with likely associated demographic consequences. Narrow-skulled vole distribution and demography, by contrast, was only moderately impacted by past climatic changes, but predicted future changes may begin to affect their current western range boundaries. Our work, founded on multiple lines of evidence suggests a future of rapidly geographically shifting Arctic small mammal prey communities, some of whom are on the edge of existence, and whose fate may have ramifications for the

Arctic climate response to geoengineering with stratospheric sulfate aerosols

NASA Astrophysics Data System (ADS)

McCusker, K. E.; Battisti, D. S.; Bitz, C. M.

2010-12-01

Recent warming and record summer sea-ice area minimums have spurred expressions of concern for arctic ecosystems, permafrost, and polar bear populations, among other things. Geoengineering by stratospheric sulfate aerosol injections to deliberately cancel the anthropogenic temperature rise has been put forth as a possible solution to restoring Arctic (and global) climate to modern conditions. However, climate is particularly sensitive in the northern high latitudes, responding easily to radiative forcing changes. To that end, we explore the extent to which tropical injections of stratospheric sulfate aerosol can accomplish regional cancellation in the Arctic. We use the Community Climate System Model version 3 global climate model to execute simulations with combinations of doubled CO2 and imposed stratospheric sulfate burdens to investigate the effects on high latitude climate. We further explore the sensitivity of the polar climate to ocean dynamics by running a suite of simulations with and without ocean dynamics, transiently and to equilibrium respectively. We find that, although annual, global mean temperature cancellation is accomplished, there is over-cooling on land in Arctic summer, but residual warming in Arctic winter, which is largely due to atmospheric circulation changes. Furthermore, the spatial extent of these features and their concurrent impacts on sea-ice properties are modified by the inclusion of ocean dynamical feedbacks.

Better retention through game-play - EcoChains: Arctic Crisis card game

NASA Astrophysics Data System (ADS)

Pfirman, S. L.; Lee, J.; O'Garra, T.; Bachrach, E.

2015-12-01

Increasingly games are being used in formal and informal education with the goal of improving student/participant understanding of content knowledge through enhanced engagement. While most games are fun by design, few controlled studies have been conducted to assess games' potential for learning gains in comparison with traditional educational approaches. Without evidence for learning, it can be difficult to justify incorporating STEM games in curricula and other programming. In this study we assess the impact of a game called EcoChains (http://thepolarhub.org/project/ecochains-arctic-crisis) on learning, using a controlled experiment. The EcoChains: Arctic Crisis card game gives players the opportunity to learn about the components of an Arctic marine food web, the reliance of some species on sea ice, and the potential impacts of future changes on the ecosystem. EcoChains was developed under the Polar Learning and Responding: PoLAR Climate Change Education Partnership (thepolarhub.org). EcoChains aligns with Next Generation Science Standards LS2 Ecosystems: Interactions, Energy, and Dynamics and ESS3 Earth and Human Activity. Participants in this experiment (n=41) were randomly assigned to either play EcoChains or to read a magazine-style article with similar content (the control). Questionnaires, mapping exercises and a 4-week follow-up survey were used to identify changes in participant knowledge of climate change and the Arctic region, attitudes and beliefs about climate change and its impacts, information-seeking behaviors, systems thinking, impressions of and engagement with the intervention experience. Analysis indicates that the game was as effective as, and in some respects more effective than, the article at teaching participants about climate change and the Arctic region and ecosystems. The follow up survey found that game players recalled new information better than those who read the article. Participants were also more engaged in the game than the

Recent warming leads to a rapid borealization of fish communities in the Arctic

NASA Astrophysics Data System (ADS)

Fossheim, Maria; Primicerio, Raul; Johannesen, Edda; Ingvaldsen, Randi B.; Aschan, Michaela M.; Dolgov, Andrey V.

2015-07-01

Arctic marine ecosystems are warming twice as fast as the global average. As a consequence of warming, many incoming species experience increasing abundances and expanding distribution ranges in the Arctic. The Arctic is expected to have the largest species turnover with regard to invading and locally extinct species, with a modelled invasion intensity of five times the global average. Studies in this region might therefore give valuable insights into community-wide shifts of species driven by climate warming. We found that the recent warming in the Barents Sea has led to a change in spatial distribution of fish communities, with boreal communities expanding northwards at a pace reflecting the local climate velocities. Increased abundance and distribution areas of large, migratory fish predators explain the observed community-wide distributional shifts. These shifts change the ecological interactions experienced by Arctic fish species. The Arctic shelf fish community retracted northwards to deeper areas bordering the deep polar basin. Depth might limit further retraction of some of the fish species in the Arctic shelf community. We conclude that climate warming is inducing structural change over large spatial scales at high latitudes, leading to a borealization of fish communities in the Arctic.

Regional and inter-annual variability in Atlantic zooplankton en route to the Arctic Ocean: potential effects of multi-path Atlantic water advection through Fram Strait and the Barents Sea

NASA Astrophysics Data System (ADS)

Kwasniewski, Slawomir; Gluchowska, Marta; Trudnowska, Emilia; Ormanczyk, Mateusz; Walczowski, Waldemar; Beszczynska-Moeller, Agnieszka

2016-04-01

The Arctic is among the regions where the climate change effects on ecosystem will be the most rapid and consequential, with Arctic amplification recognized as an integral part of the process. Great part of the changes are forced by advection of warm waters from the North Atlantic and the expected modifications of Arctic marine ecosystem will be induced not only by changing environmental conditions but also as a result of introducing Atlantic biota. Thus, the knowledge of physical and biological heterogeneity of Atlantic inflow is requisite for understanding the effects of climate change on biological diversity and ecosystem functioning in the Arctic. The complex and variable two-branched structure of the Atlantic Water flow via Fram Strait and the Barents Sea most likely has a strong influence on the ocean biology in these regions, especially in the pelagic realm. Zooplankton are key components of marine ecosystems which form essential links between primary producers and grazer/predator consumers, thus they are important for functioning of the biological carbon pump. Changes in zooplankton distribution and abundance may have cascading effects on ecosystem functioning, with regulatory effects on climate. Based on data collected in summers of 2012-2014, within the scope of the Polish-Norwegian PAVE research project, we investigate zooplankton distribution, abundance and selected structural characteristics of communities, in relation to water mass properties in the Atlantic Water complex flow to the Arctic Ocean. The main questions addressed here are: what are the differences in zooplankton patterns between the Fram Strait and Barents Sea branches, and how does the inter-annual variability of Atlantic Water advection relate to changes in zooplankton? The results of the investigation are precondition for foreseeing changes in the pelagic realm in the Arctic Ocean and are necessary for constructing and tuning plankton components of ecosystem models.

Convective forcing of mercury and ozone in the Arctic boundary layer induced by leads in sea ice.

PubMed

Moore, Christopher W; Obrist, Daniel; Steffen, Alexandra; Staebler, Ralf M; Douglas, Thomas A; Richter, Andreas; Nghiem, Son V

2014-02-06

The ongoing regime shift of Arctic sea ice from perennial to seasonal ice is associated with more dynamic patterns of opening and closing sea-ice leads (large transient channels of open water in the ice), which may affect atmospheric and biogeochemical cycles in the Arctic. Mercury and ozone are rapidly removed from the atmospheric boundary layer during depletion events in the Arctic, caused by destruction of ozone along with oxidation of gaseous elemental mercury (Hg(0)) to oxidized mercury (Hg(II)) in the atmosphere and its subsequent deposition to snow and ice. Ozone depletion events can change the oxidative capacity of the air by affecting atmospheric hydroxyl radical chemistry, whereas atmospheric mercury depletion events can increase the deposition of mercury to the Arctic, some of which can enter ecosystems during snowmelt. Here we present near-surface measurements of atmospheric mercury and ozone from two Arctic field campaigns near Barrow, Alaska. We find that coastal depletion events are directly linked to sea-ice dynamics. A consolidated ice cover facilitates the depletion of Hg(0) and ozone, but these immediately recover to near-background concentrations in the upwind presence of open sea-ice leads. We attribute the rapid recoveries of Hg(0) and ozone to lead-initiated shallow convection in the stable Arctic boundary layer, which mixes Hg(0) and ozone from undepleted air masses aloft. This convective forcing provides additional Hg(0) to the surface layer at a time of active depletion chemistry, where it is subject to renewed oxidation. Future work will need to establish the degree to which large-scale changes in sea-ice dynamics across the Arctic alter ozone chemistry and mercury deposition in fragile Arctic ecosystems.

Enhanced Arctic Amplification Began at the Mid-Brunhes Event ~400,000 years ago.

PubMed

Cronin, T M; Dwyer, G S; Caverly, E K; Farmer, J; DeNinno, L H; Rodriguez-Lazaro, J; Gemery, L

2017-11-03

Arctic Ocean temperatures influence ecosystems, sea ice, species diversity, biogeochemical cycling, seafloor methane stability, deep-sea circulation, and CO 2 cycling. Today's Arctic Ocean and surrounding regions are undergoing climatic changes often attributed to "Arctic amplification" - that is, amplified warming in Arctic regions due to sea-ice loss and other processes, relative to global mean temperature. However, the long-term evolution of Arctic amplification is poorly constrained due to lack of continuous sediment proxy records of Arctic Ocean temperature, sea ice cover and circulation. Here we present reconstructions of Arctic Ocean intermediate depth water (AIW) temperatures and sea-ice cover spanning the last ~ 1.5 million years (Ma) of orbitally-paced glacial/interglacial cycles (GIC). Using Mg/Ca paleothermometry of the ostracode Krithe and sea-ice planktic and benthic indicator species, we suggest that the Mid-Brunhes Event (MBE), a major climate transition ~ 400-350 ka, involved fundamental changes in AIW temperature and sea-ice variability. Enhanced Arctic amplification at the MBE suggests a major climate threshold was reached at ~ 400 ka involving Atlantic Meridional Overturning Circulation (AMOC), inflowing warm Atlantic Layer water, ice sheet, sea-ice and ice-shelf feedbacks, and sensitivity to higher post-MBE interglacial CO 2 concentrations.

Enhanced Arctic amplification began at the Mid-Brunhes Event 430,000 years ago

USGS Publications Warehouse

Cronin, Thomas M.; Dwyer, Gary S.; Caverly, Emma; Farmer, Jesse; DeNinno, Lauren H.; Rodriguez-Lazaro, Julio; Gemery, Laura

2017-01-01

Arctic Ocean temperatures influence ecosystems, sea ice, species diversity, biogeochemical cycling, seafloor methane stability, deep-sea circulation, and CO2 cycling. Today's Arctic Ocean and surrounding regions are undergoing climatic changes often attributed to "Arctic amplification" - that is, amplified warming in Arctic regions due to sea-ice loss and other processes, relative to global mean temperature. However, the long-term evolution of Arctic amplification is poorly constrained due to lack of continuous sediment proxy records of Arctic Ocean temperature, sea ice cover and circulation. Here we present reconstructions of Arctic Ocean intermediate depth water (AIW) temperatures and sea-ice cover spanning the last ~ 1.5 million years (Ma) of orbitally-paced glacial/interglacial cycles (GIC). Using Mg/Ca paleothermometry of the ostracode Krithe and sea-ice planktic and benthic indicator species, we suggest that the Mid-Brunhes Event (MBE), a major climate transition ~ 400-350 ka, involved fundamental changes in AIW temperature and sea-ice variability. Enhanced Arctic amplification at the MBE suggests a major climate threshold was reached at ~ 400 ka involving Atlantic Meridional Overturning Circulation (AMOC), inflowing warm Atlantic Layer water, ice sheet, sea-ice and ice-shelf feedbacks, and sensitivity to higher post-MBE interglacial CO2 concentrations.

Human-polar bear interactions in a changing Arctic: Existing and emerging concerns

USGS Publications Warehouse

Atwood, Todd C.; Simac, Kristin; Breck, Stewart; York, Geoff; Wilder, James

2017-01-01

The behavior and sociality of polar bears (Ursus maritimus) have been shaped by evolved preferences for sea ice habitat and preying on marine mammals. However, human behavior is causing changes to the Arctic marine ecosystem through the influence of greenhouse gas emissions that drive long-term change in ecosystem processes and via the presence of in situ stressors associated with increasing human activities. These changes are making it more difficult for polar bears to reliably use their traditional habitats and maintain fitness. Here, we provide an overview of how human activities in the Arctic are likely to change a polar bear’s behavior and to influence their resilience to environmental change. Developing a more thorough understanding of polar bear behavior and their capacity for flexibility in response to anthropogenic disturbances and subsequent mitigations may lead to successful near-term management interventions.

Genomics in a changing arctic: critical questions await the molecular ecologist

DOE PAGES

Wullschleger, Stan D.; Breen, Amy L.; Iversen, Colleen M.; ...

2015-04-20

Molecular ecology is poised to tackle a host of interesting questions in the coming years. Of particular importance to the molecular ecologist are new technologies and analytical approaches that provide opportunities to address questions previously unapproachable.The Arctic provides a unique and rapidly changing environment with a suite of emerging research needs that can be addressed through genetics and genomics. Here we highlight recent research on boreal and tundra ecosystems and put forth a series of questions related to plant and microbial responses to climate change that can benefit from technologies and analytical approaches contained within the molecular ecologist's toolbox. Thesemore » questions include understanding (i) the mechanisms of plant acquisition and uptake of N in cold soils, (ii) how these processes are mediated by root traits, (iii) the role played by the plant microbiome in cycling C and nutrients within high-latitude ecosystems and (iv) plant adaptation to extreme Arctic climates. We highlight how contributions can be made in these areas through studies that target model and nonmodel organisms and emphasize that the sequencing of the Populus and Salix genomes provides a valuable resource for scientific discoveries related to the plant microbiome and plant adaptation in the Arctic. Moreover, there exists an exciting role to play in model development, including incorporating genetic and evolutionary knowledge into ecosystem and Earth System Models. In this regard, the molecular ecologist provides a valuable perspective on plant genetics as a driver for community biodiversity, and how ecological and evolutionary forces govern community dynamics in a rapidly changing climate.« less

Freshwater discharges drive high levels of methylmercury in Arctic marine biota.

PubMed

Schartup, Amina T; Balcom, Prentiss H; Soerensen, Anne L; Gosnell, Kathleen J; Calder, Ryan S D; Mason, Robert P; Sunderland, Elsie M

2015-09-22

Elevated levels of neurotoxic methylmercury in Arctic food-webs pose health risks for indigenous populations that consume large quantities of marine mammals and fish. Estuaries provide critical hunting and fishing territory for these populations, and, until recently, benthic sediment was thought to be the main methylmercury source for coastal fish. New hydroelectric developments are being proposed in many northern ecosystems, and the ecological impacts of this industry relative to accelerating climate changes are poorly characterized. Here we evaluate the competing impacts of climate-driven changes in northern ecosystems and reservoir flooding on methylmercury production and bioaccumulation through a case study of a stratified sub-Arctic estuarine fjord in Labrador, Canada. Methylmercury bioaccumulation in zooplankton is higher than in midlatitude ecosystems. Direct measurements and modeling show that currently the largest methylmercury source is production in oxic surface seawater. Water-column methylation is highest in stratified surface waters near the river mouth because of the stimulating effects of terrestrial organic matter on methylating microbes. We attribute enhanced biomagnification in plankton to a thin layer of marine snow widely observed in stratified systems that concentrates microbial methylation and multiple trophic levels of zooplankton in a vertically restricted zone. Large freshwater inputs and the extensive Arctic Ocean continental shelf mean these processes are likely widespread and will be enhanced by future increases in water-column stratification, exacerbating high biological methylmercury concentrations. Soil flooding experiments indicate that near-term changes expected from reservoir creation will increase methylmercury inputs to the estuary by 25-200%, overwhelming climate-driven changes over the next decade.

Genomics in a changing arctic: critical questions await the molecular ecologist

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wullschleger, Stan D.; Breen, Amy L.; Iversen, Colleen M.

Molecular ecology is poised to tackle a host of interesting questions in the coming years. Of particular importance to the molecular ecologist are new technologies and analytical approaches that provide opportunities to address questions previously unapproachable.The Arctic provides a unique and rapidly changing environment with a suite of emerging research needs that can be addressed through genetics and genomics. Here we highlight recent research on boreal and tundra ecosystems and put forth a series of questions related to plant and microbial responses to climate change that can benefit from technologies and analytical approaches contained within the molecular ecologist's toolbox. Thesemore » questions include understanding (i) the mechanisms of plant acquisition and uptake of N in cold soils, (ii) how these processes are mediated by root traits, (iii) the role played by the plant microbiome in cycling C and nutrients within high-latitude ecosystems and (iv) plant adaptation to extreme Arctic climates. We highlight how contributions can be made in these areas through studies that target model and nonmodel organisms and emphasize that the sequencing of the Populus and Salix genomes provides a valuable resource for scientific discoveries related to the plant microbiome and plant adaptation in the Arctic. Moreover, there exists an exciting role to play in model development, including incorporating genetic and evolutionary knowledge into ecosystem and Earth System Models. In this regard, the molecular ecologist provides a valuable perspective on plant genetics as a driver for community biodiversity, and how ecological and evolutionary forces govern community dynamics in a rapidly changing climate.« less

Variability in Canopy Transpiration with Atmospheric Drivers and Permafrost Thaw Depth in an Arctic Siberian Larch Forest

NASA Astrophysics Data System (ADS)

Loranty, M. M.; Berner, L. T.; Alexander, H. D.; Davydov, S. P.

2014-12-01

Arctic ecosystems are experiencing rapid change associated with amplified rates of climate warming. A general increase in vegetation productivity has been among the expected responses for terrestrial ecosystems in the Arctic. However, recent evidence from satellite derived productivity metrics has revealed a high degree of spatial heterogeneity in the magnitude, and even the direction, of productivity trends in recent decades. Declines in productivity may seem counterintuitive in what are traditionally thought to be temperature limited ecosystems. However a warmer and drier atmosphere in conjunction with changing permafrost conditions may impose hydrologic stresses on vegetation as well. Many Siberian ecosystems receive annual precipitation inputs characteristics of arid and semiarid regions. Boreal forests persist because permafrost acts as an aquatard trapping water near the surface and because historically cool growing season temperatures have kept atmospheric evaporative demand relatively low. As climate change simultaneously warms the atmosphere and deepens the active layer it is likely that vegetation will experience a higher degree of hydrologic limitation, perhaps necessitating the reallocation of resources. Here we use sap flux observations of canopy transpiration to understand the influence of atmospheric and permafrost conditions on the function of an arctic boreal forest in northeastern Siberia. We find that individual trees exhibit stronger responses to atmospheric vapor pressure deficit (D) as the growing season progresses. Further, the magnitude of this response appears to be positively correlated with changes in the depth of permafrost thaw. These results imply that arctic boreal forests will need to adapt to increasing hydrologic stress in order to benefit from what are typically thought of as increasingly favorable growing conditions with continued climate change.

Lepidoptera Larvae as an Indicator of Multi-trophic Level Responses to Changing Seasonality in an Arctic Tundra Ecosystem

NASA Astrophysics Data System (ADS)

Daly, K. M.; Steltzer, H.; Boelman, N.; Weintraub, M. N.; Darrouzet-Nardi, A.; Wallenstein, M. D.; Sullivan, P.; Gough, L.; Rich, M.; Hendrix, C.; Kielland, K.; Philip, K.; Doak, P.; Ferris, C.; Sikes, D.

2011-12-01

Earlier snowmelt and warming temperatures in the Arctic will impact multiple trophic levels through the timing and availability of food resources. Lepidoptera are a vital link within the ecosystem; their roles include pollinator, parasitized host for other pollinating insects, and essential food source for migrating birds and their fledglings. Multiple environmental cues including temperature initiate plant growth, and in turn, trigger the emergence of Lepidoptera and the migrations of birds. If snowmelt is accelerated and temperature is increased, it is expected that the Lepidoptera larvae will respond to early plant growth by increasing their abundance within areas that have accelerated snowmelt and warmer conditions. In May of 2011 in a moist acidic tussock tundra system, we accelerated snowmelt by 15 days through the use of radiation-absorbing fabric and warmed air and soil temperatures using open-top chambers, individually and in combination. Every 1-2 days from May 27th to July 8th, 2 minute searches were performed for Lepidoptera larvae in all treatments; when an animal was found, their micro-habitat, surface temperature, behavior, food source, and time of day were noted. The length, body and head width were measured, and the animals were examined for braconid wasp and tachinid fly parasites. Lepidoptera larvae collected in pitfall traps from May 26th to July 7th were also examined and measured. Total density of parasitized larvae accounted for 54% of observed specimens and 50% of pitfall specimens, indicating that Lepidoptera larvae serve an integral role as a host for other pollinators. Total larvae density was highest within the accelerated snowmelt plots compared to the control plots; 66% of observed live specimens and 63% of pitfall specimens were found within the accelerated snowmelt plots. Ninety percent of the total observed animals were found within the open-top warming chambers. Peak density of animals occurred at Solar Noon between 14:00 -15

Gender specific reproductive strategies of an arctic key species (Boreogadus saida) and implications of climate change.

PubMed

Nahrgang, Jasmine; Varpe, Oystein; Korshunova, Ekaterina; Murzina, Svetlana; Hallanger, Ingeborg G; Vieweg, Ireen; Berge, Jørgen

2014-01-01

The Arctic climate is changing at an unprecedented rate. What consequences this may have on the Arctic marine ecosystem depends to a large degree on how its species will respond both directly to elevated temperatures and more indirectly through ecological interactions. But despite an alarming recent warming of the Arctic with accompanying sea ice loss, reports evaluating ecological impacts of climate change in the Arctic remain sparse. Here, based upon a large-scale field study, we present basic new knowledge regarding the life history traits for one of the most important species in the entire Arctic, the polar cod (Boreogadus saida). Furthermore, by comparing regions of contrasting climatic influence (domains), we present evidence as to how its growth and reproductive success is impaired in the warmer of the two domains. As the future Arctic is predicted to resemble today's Atlantic domains, we forecast changes in growth and life history characteristics of polar cod that will lead to alteration of its role as an Arctic keystone species. This will in turn affect community dynamics and energy transfer in the entire Arctic food chain.

Climate, icing, and wild arctic reindeer: past relationships and future prospects.

PubMed

Hansen, Brage Bremset; Aanes, Ronny; Herfindal, Ivar; Kohler, Jack; Saether, Bernt-Erik

2011-10-01

Across the Arctic, heavy rain-on-snow (ROS) is an "extreme" climatic event that is expected to become increasingly frequent with global warming. This has potentially large ecosystem implications through changes in snowpack properties and ground-icing, which can block the access to herbivores' winter food and thereby suppress their population growth rates. However, the supporting empirical evidence for this is still limited. We monitored late winter snowpack properties to examine the causes and consequences of ground-icing in a Svalbard reindeer (Rangifer tarandus platyrhynchus) metapopulation. In this high-arctic area, heavy ROS occurred annually, and ground-ice covered from 25% to 96% of low-altitude habitat in the sampling period (2000-2010). The extent of ground-icing increased with the annual number of days with heavy ROS (> or = 10 mm) and had a strong negative effect on reindeer population growth rates. Our results have important implications as a downscaled climate projection (2021-2050) suggests a substantial future increase in ROS and icing. The present study is the first to demonstrate empirically that warmer and wetter winter climate influences large herbivore population dynamics by generating ice-locked pastures. This may serve as an early warning of the importance of changes in winter climate and extreme weather events in arctic ecosystems.

75 FR 30383 - NOAA's Arctic Vision and Strategy; Comment Period Extension

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-01

... evidence of widespread and dramatic ongoing change. As a result, critical environmental, economic, and... public comment period by fifteen days. The Arctic has profound significance for climate and functioning of ecosystems around the globe. The region is particularly vulnerable and prone to rapid change...

Intermittent Flooding of Arctic Lagoon Wet Sedge Areas: an investigation of past and future conditions at Arey Lagoon, Eastern Arctic Alaska

NASA Astrophysics Data System (ADS)

Gibbs, A.; Erikson, L. H.; Richmond, B. M.

2017-12-01

Arctic lagoons and mainland coasts support highly productive ecosystems, where soft substrate and coastal wet sedge fringing the shores act as feeding grounds and nurseries for a variety of marine fish and waterfowl. Much tundra vegetation is intolerant to saltwater flooding, but some vegetation cherished by geese for example, is maintained by flooding one to two times per month. The balance of northern ecosystems such as these may be in jeopardy as the Arctic climate is rapidly changing. In this study, sea level rise and 21st century storms are simulated with a numerical model to evaluate changes in ocean-driven flooding of low-lying tundra and coastal wet sedge that fringe the shores of Arey Lagoon, located in eastern Arctic Alaska. Numerically modeled extreme surge levels are projected to increase from a historical range of 0.5 m - 1.3 m (1976-2010) to 1.0 m - 2.0 m by end-of-century (2011-2100). The maximum storm surge of the projected time-period translates to > 6 km2 of flooded tundra, much of which consists of salt-intolerant vegetation. Monthly flood extents that might be expected to maintain halophytic vegetation were calculated by extracting the maximum monthly water levels of months that had more than 21 days ( 70%) of ice-free conditions. Median monthly water levels are shown to range from 0.46 m in 1981-1990 to 0.91 m by the final decades of the 21st century. The temporal trend is strongly linear (r2 = 0.82). An overlay of these water elevations onto a 10 m resolution elevation model shows that monthly flood extents will increase by 26% by the end of the century compared to the present decade (2011 to 2020) (from 2.86 km2 to 3.60 km2). The rate at which the flood extents are projected to increase will dictate if inland succession of salt-tolerant vegetation will survive. By combining the frequency and magnitude of extreme storm surge events with the progression of modeled monthly inland flood extents, it might be possible to identify areas along this

Modern pollen data from the Canadian Arctic, 1972–1973

PubMed Central

Nichols, Harvey; Stolze, Susann

2017-01-01

This data descriptor reports results of a 1972–73 baseline study of modern pollen deposition in the Canadian Arctic to originally aid interpretation of Holocene pollen diagrams from that region, especially focussed on the arctic tree-line. The data set is geographically unique due to its extent, and allows the assessment of the effects of modern climate change on northern ecosystems, including fluctuations of the a arctic tree-line. Repeated sampling was conducted along an interior transect at 29 sites from the Boreal Forest to the High Arctic, with five additional coastal sites covering a total distance of 3,200 km. Static pollen samplers captured both local pollen and long-distance pollen wind-blown from the Boreal Forest. Moss and lichen polsters provided multi-year pollen fallout to assess the effectiveness of the static pollen samplers. The local vegetation was recorded at each site. This descriptor provides information on data archived at the World Data Center PANGAEA, which includes spreadsheets detailing site and sample information as well as raw and processed pollen data obtained on over 500 samples. PMID:28509898

Warming Effects on Enzyme Activities are Predominant in Sub-surface Soils of an Arctic Tundra Ecosystem over 6-Year Field Manipulation

NASA Astrophysics Data System (ADS)

Kang, H.; Seo, J.; Kim, M.; Jung, J. Y.; Lee, Y. K.

2017-12-01

Arctic tundra ecosystems are of great importance because they store a large amount of carbon as un-decomposed organic matter. Global climate change is expected to affect enzyme activities and heterotrophic respiration in Arctic soils, which may accelerate greenhouse gas (GHG) emission through positive biological feedbacks. Unlike laboratory-based incubation experiments, field measurements often show different warming effects on decomposition of organic carbon and releases of GHGs. In the present study, we conducted a field-based warming experiment in Cambridge Bay, Canada (69°07'48″N, 105°03'36″W) by employing passive chambers during growing seasons over 6 years. A suite of enzyme activities (ß-glucosidase, cellobiohydrolase, N-acetylglucosaminidase, leucine aminopeptidase and phenol oxidase), microbial community structure (NGS), microbial abundances (gene copy numbers of bacteria and fungi), and soil chemical properties have been monitored in two depths (0-5 cm and 5-10 cm) of tundra soils, which were exposed to four different treatments (`control', `warming-only', `water-addition only', and both `warming and water-addition'). Phenol oxidase activity increased substantially, and bacterial community structure and abundance changed in the early stage (after 1 year's warming manipulation), but these changes disappeared afterwards. Most hydrolases were enhanced in surface soils by `water-addition only' over the period. However, the long-term effects of warming appeared in sub-surface soils where both `warming only' and `warming and water addition' increased hydrolase activities. Overall results of this study indicate that the warming effects on enzyme activities in surface soils are only short-term (phenol oxidase) or masked by water-limitation (hydrolases). However, hydrolases activities in sub-surface soils are more strongly enhanced than surface soils by warming, probably due to the lack of water limitation. Meanwhile, negative correlations between hydrolase

Nutrient Limitation of Microbial Mediated Decomposition and Arctic Soil Chronology

NASA Astrophysics Data System (ADS)

Melle, C. J.; Darrouzet-Nardi, A.; Wallenstein, M. D.

2012-12-01

Soils of northern permafrost regions currently contain twice as much carbon as the entire Earth's atmosphere. Traditionally, environmental constraints have limited microbial activity resulting in restricted decomposition of soil organic matter in these systems and accumulation of massive amounts of soil organic carbon (SOC), however climate change is reducing the constraints of decomposition in arctic permafrost regions. Carbon cycling in nutrient poor, arctic ecosystems is tightly coupled to other biogeochemical cycles. Several studies have suggested strong nitrogen limitations of primary productivity and potentially warm-season microbial activity in these nutrient deficient soils. Nitrogen is required for microbial extracellular enzyme production which drives the decomposition of soil organic matter (SOM). Nitrogen limited arctic soils may also experience limitation via labile carbon availability despite the SOM rich environment due to low extracellular enzyme production. Few studies have directly addressed nutrient induced microbial limitation in SOC rich arctic tundra soils, and even less is known about the potential for nutrient co-limitation. Additionally, through the process of becoming deglaciated, sites within close proximity to one another may have experienced drastic differences in their effective soil ages due to the varied length of their active histories. Many soil properties and nutrient deficiencies are directly related to soil age, however this chronology has not previously been a focus of research on nutrient limitation of arctic soil microbial activity. Understanding of nutrient limitations, as well as potential co-limitation, on arctic soil microbial activity has important implications for carbon cycling and the ultimate fate of the current arctic SOC reservoir. Analyses of nutrient limitation on soils of a single site are not adequate for fully understanding the controls on soil microbial activity across a vast land mass with large variation in

A distributed atmosphere-sea ice-ocean observatory in the central Arctic Ocean: concept and first results

NASA Astrophysics Data System (ADS)

Hoppmann, Mario; Nicolaus, Marcel; Rabe, Benjamin; Wenzhöfer, Frank; Katlein, Christian; Scholz, Daniel; Valcic, Lovro

2017-04-01

To understand the current evolution of the Arctic Ocean towards a less extensive, thinner and younger sea ice cover is one of the biggest challenges in climate research. Especially the lack of simultaneous in-situ observations of sea ice, ocean and atmospheric properties leads to significant knowledge gaps in their complex interactions, and how the associated processes impact the polar marine ecosystem. Here we present a concept for the implementation of a long-term strategy to monitor the most essential climate- and ecosystem parameters in the central Arctic Ocean, year round and synchronously. The basis of this strategy is the development and enhancement of a number of innovative autonomous observational platforms, such as rugged weather stations, ice mass balance buoys, ice-tethered bio-optical buoys and upper ocean profilers. The deployment of those complementing platforms in a distributed network enables the simultaneous collection of physical and biogeochemical in-situ data on basin scales and year round, including the largely undersampled winter periods. A key advantage over other observatory systems is that the data is sent via satellite in near-real time, contributing to numerical weather predictions through the Global Telecommunication System (GTS) and to the International Arctic Buoy Programme (IABP). The first instruments were installed on ice floes in the Eurasian Basin in spring 2015 and 2016, yielding exceptional records of essential climate- and ecosystem-relevant parameters in one of the most inaccessible regions of this planet. Over the next 4 years, and including the observational periods of the Year of Polar Prediction (YOPP, 2017-2019) and the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC, 2020), the distributed observatory will be maintained by deployment of additional instruments in the central Arctic each year, benefitting from international logistical efforts.

Prolonging the arctic pulse: long-term exploitation of cached eggs by arctic foxes when lemmings are scarce.

PubMed

Samelius, Gustaf; Alisauskas, Ray T; Hobson, Keith A; Larivière, Serge

2007-09-01

1. Many ecosystems are characterized by pulses of dramatically higher than normal levels of foods (pulsed resources) to which animals often respond by caching foods for future use. However, the extent to which animals use cached foods and how this varies in relation to fluctuations in other foods is poorly understood in most animals. 2. Arctic foxes Alopex lagopus (L.) cache thousands of eggs annually at large goose colonies where eggs are often superabundant during the nesting period by geese. We estimated the contribution of cached eggs to arctic fox diets in spring and autumn, when geese were not present in the study area, by comparing stable isotope ratios (delta(13)C and delta(15)N) of fox tissues with those of their foods using a multisource mixing model in Program IsoSource. 3. The contribution of cached eggs to arctic fox diets was inversely related to collared lemming Dicrostonyx groenlandicus (Traill) abundance; the contribution of cached eggs to overall fox diets increased from < 28% in years when collared lemmings were abundant to 30-74% in years when collared lemmings were scarce. 4. Further, arctic foxes used cached eggs well into the following spring (almost 1 year after eggs were acquired) - a pattern that differs from that of carnivores generally storing foods for only a few days before consumption. 5. This study showed that long-term use of eggs that were cached when geese were superabundant at the colony in summer varied with fluctuations in collared lemming abundance (a key component in arctic fox diets throughout most of their range) and suggests that cached eggs functioned as a buffer when collared lemmings were scarce.

Shifts in the distribution of molting Spectacled Eiders (Somateria fischeri) indicate ecosystem change in the Arctic

USGS Publications Warehouse

Sexson, Matthew; Petersen, Margaret; Breed, Greg A.; Powell, Abby N.

2016-01-01

Shifts in the distribution of benthivorous predators provide an indication of underlying environmental changes in benthic-mediated ecosystems. Spectacled Eiders (Somateria fischeri) are benthivorous sea ducks that spend the nonbreeding portion of their annual cycle in the Bering, Chukchi, Beaufort, and East Siberian seas. Sea ducks generally molt in biologically productive areas with abundant prey. If the distribution of eiders at molting areas matches prey abundance, spatial shifts may indicate changes in environmental conditions in the Arctic. We used a randomization procedure to test for shifts in the distribution of satellite telemetry locations received from Spectacled Eiders in the 1990s and 2008–2011 within 4 late-summer, ice-free molting areas: Indigirka–Kolyma, northern Russia; Ledyard Bay, eastern Chukchi Sea; Norton Sound, northeastern Bering Sea; and Mechigmenskiy Gulf, northwestern Bering Sea. We also tested for interannual and interdecadal changes in dive depth required to reach prey, which might affect the energetic costs of foraging during the molting period. Transmitter-marked birds used each molting area in each year, although the distribution of Spectacled Eiders shifted within each area. Interdecadal shifts in Ledyard Bay and Norton Sound decreased dive depth in recent years, although minor differences in depth were biologically negligible in relation to the energetic expense of feather growth. Shifts in Mechigmenskiy Gulf and Indigirka–Kolyma did not occur consistently within or among decades, which suggests greater interannual variability among environmental factors that influence distribution in these areas. Shifts in each molting area suggest dynamic ecosystem processes, with implications for Spectacled Eiders if changes result in novel competition or predation, or in shifting prey regimes.

Changes in the structure and function of northern Alaskan ecosystems when considering variable leaf-out times across groupings of species in a dynamic vegetation model

USGS Publications Warehouse

Euskirchen, E.S.; Carman, T.B.; McGuire, Anthony David

2013-01-01

The phenology of arctic ecosystems is driven primarily by abiotic forces, with temperature acting as the main determinant of growing season onset and leaf budburst in the spring. However, while the plant species in arctic ecosystems require differing amounts of accumulated heat for leaf-out, dynamic vegetation models simulated over regional to global scales typically assume some average leaf-out for all of the species within an ecosystem. Here, we make use of air temperature records and observations of spring leaf phenology collected across dominant groupings of species (dwarf birch shrubs, willow shrubs, other deciduous shrubs, grasses, sedges, and forbs) in arctic and boreal ecosystems in Alaska. We then parameterize a dynamic vegetation model based on these data for four types of tundra ecosystems (heath tundra, shrub tundra, wet sedge tundra, and tussock tundra), as well as ecotonal boreal white spruce forest, and perform model simulations for the years 1970 -2100. Over the course of the model simulations, we found changes in ecosystem composition under this new phenology algorithm compared to simulations with the previous phenology algorithm. These changes were the result of the differential timing of leaf-out, as well as the ability for the groupings of species to compete for nitrogen and light availability. Regionally, there were differences in the trends of the carbon pools and fluxes between the new phenology algorithm and the previous phenology algorithm, although these differences depended on the future climate scenario. These findings indicate the importance of leaf phenology data collection by species and across the various ecosystem types within the highly heterogeneous Arctic landscape, and that dynamic vegetation models should consider variation in leaf-out by groupings of species within these ecosystems to make more accurate projections of future plant distributions and carbon cycling in Arctic regions.

Changes in the structure and function of northern Alaskan ecosystems when considering variable leaf-out times across groupings of species in a dynamic vegetation model.

PubMed

Euskirchen, Eugénie S; Carman, Tobey B; McGuire, A David

2014-03-01

The phenology of arctic ecosystems is driven primarily by abiotic forces, with temperature acting as the main determinant of growing season onset and leaf budburst in the spring. However, while the plant species in arctic ecosystems require differing amounts of accumulated heat for leaf-out, dynamic vegetation models simulated over regional to global scales typically assume some average leaf-out for all of the species within an ecosystem. Here, we make use of air temperature records and observations of spring leaf phenology collected across dominant groupings of species (dwarf birch shrubs, willow shrubs, other deciduous shrubs, grasses, sedges, and forbs) in arctic and boreal ecosystems in Alaska. We then parameterize a dynamic vegetation model based on these data for four types of tundra ecosystems (heath tundra, shrub tundra, wet sedge tundra, and tussock tundra), as well as ecotonal boreal white spruce forest, and perform model simulations for the years 1970-2100. Over the course of the model simulations, we found changes in ecosystem composition under this new phenology algorithm compared with simulations with the previous phenology algorithm. These changes were the result of the differential timing of leaf-out, as well as the ability for the groupings of species to compete for nitrogen and light availability. Regionally, there were differences in the trends of the carbon pools and fluxes between the new phenology algorithm and the previous phenology algorithm, although these differences depended on the future climate scenario. These findings indicate the importance of leaf phenology data collection by species and across the various ecosystem types within the highly heterogeneous Arctic landscape, and that dynamic vegetation models should consider variation in leaf-out by groupings of species within these ecosystems to make more accurate projections of future plant distributions and carbon cycling in Arctic regions. © 2013 John Wiley & Sons Ltd.

Survival of ship biofouling assemblages during and after voyages to the Canadian Arctic.

PubMed

Chan, Farrah T; MacIsaac, Hugh J; Bailey, Sarah A

2016-01-01

Human-mediated vectors often inadvertently translocate species assemblages to new environments. Examining the dynamics of entrained species assemblages during transport can provide insights into the introduction risk associated with these vectors. Ship biofouling is a major transport vector of nonindigenous species in coastal ecosystems globally, yet its magnitude in the Arctic is poorly understood. To determine whether biofouling organisms on ships can survive passages in Arctic waters, we examined how biofouling assemblage structure changed before, during, and after eight round-trip military voyages from temperate to Arctic ports in Canada. Species richness first decreased (~70% loss) and then recovered (~27% loss compared to the original assemblages), as ships travelled to and from the Arctic, respectively, whereas total abundance typically declined over time (~55% total loss). Biofouling community structure differed significantly before and during Arctic transits as well as between those sampled during and after voyages. Assemblage structure varied across different parts of the hull; however, temporal changes were independent of hull location, suggesting that niche areas did not provide protection for biofouling organisms against adverse conditions in the Arctic. Biofouling algae appear to be more tolerant of transport conditions during Arctic voyages than are mobile, sessile, and sedentary invertebrates. Our results suggest that biofouling assemblages on ships generally have poor survivorship during Arctic voyages. Nonetheless, some potential for transporting nonindigenous species to the Arctic via ship biofouling remains, as at least six taxa new to the Canadian Arctic, including a nonindigenous cirripede, appeared to have survived transits from temperate to Arctic ports.

Arctic and Arctic-like rabies viruses: distribution, phylogeny and evolutionary history

PubMed Central

KUZMIN, I. V.; HUGHES, G. J.; BOTVINKIN, A. D.; GRIBENCHA, S. G.; RUPPRECHT, C. E.

2008-01-01

SUMMARY Forty-one newly sequenced isolates of Arctic and Arctic-like rabies viruses, were genetically compared to each other and to those available from GenBank. Four phylogenetic lineages of Arctic viruses were identified. Arctic-1 viruses circulate in Ontario, Arctic-2 viruses circulate in Siberia and Alaska, Arctic-3 viruses circulate circumpolarly, and a newly described lineage Arctic-4 circulates locally in Alaska. The oldest available isolates from Siberia (between 1950 and 1960) belong to the Arctic-2 and Arctic-3 lineages and share 98·6–99·2% N gene identity with contemporary viruses. Two lineages of Arctic-like viruses were identified in southern Asia and the Middle East (Arctic-like-1) and eastern Asia (Arctic-like-2). A time-scaled tree demonstrates that the time of the most recent common ancestor (TMRCA) of Arctic and Arctic-like viruses is dated between 1255 and 1786. Evolution of the Arctic viruses has occurred through a northerly spread. The Arctic-like-2 lineage diverged first, whereas Arctic viruses share a TMRCA with Arctic-like-1 viruses. PMID:17599781

Arctic and Arctic-like rabies viruses: distribution, phylogeny and evolutionary history.

PubMed

Kuzmin, I V; Hughes, G J; Botvinkin, A D; Gribencha, S G; Rupprecht, C E

2008-04-01

Forty-one newly sequenced isolates of Arctic and Arctic-like rabies viruses, were genetically compared to each other and to those available from GenBank. Four phylogenetic lineages of Arctic viruses were identified. Arctic-1 viruses circulate in Ontario, Arctic-2 viruses circulate in Siberia and Alaska, Arctic-3 viruses circulate circumpolarly, and a newly described lineage Arctic-4 circulates locally in Alaska. The oldest available isolates from Siberia (between 1950 and 1960) belong to the Arctic-2 and Arctic-3 lineages and share 98.6-99.2% N gene identity with contemporary viruses. Two lineages of Arctic-like viruses were identified in southern Asia and the Middle East (Arctic-like-1) and eastern Asia (Arctic-like-2). A time-scaled tree demonstrates that the time of the most recent common ancestor (TMRCA) of Arctic and Arctic-like viruses is dated between 1255 and 1786. Evolution of the Arctic viruses has occurred through a northerly spread. The Arctic-like-2 lineage diverged first, whereas Arctic viruses share a TMRCA with Arctic-like-1 viruses.

Advancing High Spatial and Spectral Resolution Remote Sensing for Observing Plant Community Response to Environmental Variability and Change in the Alaskan Arctic

NASA Astrophysics Data System (ADS)

Vargas Zesati, Sergio A.

The Arctic is being impacted by climate change more than any other region on Earth. Impacts to terrestrial ecosystems have the potential to manifest through feedbacks with other components of the Earth System. Of particular concern is the potential for the massive store of soil organic carbon to be released from arctic permafrost to the atmosphere where it could exacerbate greenhouse warming and impact global climate and biogeochemical cycles. Even though substantial gains to our understanding of the changing Arctic have been made, especially over the past decade, linking research results from plot to regional scales remains a challenge due to the lack of adequate low/mid-altitude sampling platforms, logistic constraints, and the lack of cross-scale validation of research methodologies. The prime motivation of this study is to advance observational capacities suitable for documenting multi-scale environmental change in arctic terrestrial landscapes through the development and testing of novel ground-based and low altitude remote sensing methods. Specifically this study addressed the following questions: • How well can low-cost kite aerial photography and advanced computer vision techniques model the microtopographic heterogeneity of changing tundra surfaces? • How does imagery from kite aerial photography and fixed time-lapse digital cameras (pheno-cams) compare in their capacity to monitor plot-level phenological dynamics of arctic vegetation communities? • Can the use of multi-scale digital imaging systems be scaled to improve measurements of ecosystem properties and processes at the landscape level? • How do results from ground-based and low altitude digital remote sensing of the spatiotemporal variability in ecosystem processes compare with those from satellite remote sensing platforms? Key findings from this study suggest that cost-effective alternative digital imaging and remote sensing methods are suitable for monitoring and quantifying plot to

Biological Chlorine Cycling in Arctic Peat Soils

NASA Astrophysics Data System (ADS)

Zlamal, J. E.; Raab, T. K.; Lipson, D.

2014-12-01

. Incubations were conducted in the laboratory providing arctic soils with Clorg, and measurements taken to assess rates of organohalide respiration show an increase in chloride production due to microbial activity. Investigating these soils with diverse techniques affirms the importance of Cl-cycling in a pristine arctic tundra ecosystem.

Life history traits in a cyclic ecosystem: a field experiment on the arctic fox.

PubMed

Meijer, Tomas; Elmhagen, Bodil; Eide, Nina E; Angerbjörn, Anders

2013-10-01

The reproduction of many species depends strongly on variation in food availability. The main prey of the arctic fox in Fennoscandia are cyclic small rodents, and its number of litters and litter size vary depending on the phase of the rodent cycle. In this experiment, we studied if the arctic fox adjusts its reproduction as a direct response to food abundance, in accordance with the food limitation hypothesis, or if there are additional phase-dependent trade-offs that influence its reproduction. We analysed the weaning success, i.e. proportion of arctic fox pairs established during mating that wean a litter in summer, of 422 pairs of which 361 were supplementary winter fed, as well as the weaned litter size of 203 litters of which 115 were supplementary winter fed. Females without supplementary winter food over-produced cubs in relation to food abundance in the small rodent increase phase, i.e. the litter size was equal to that in the peak phase when food was more abundant. The litter size for unfed females was 6.38 in the increase phase, 7.11 in the peak phase and 3.84 in the decrease phase. The litter size for supplementary winter-fed litters was 7.95 in the increase phase, 10.61 in the peak phase and 7.86 in the decrease phase. Thus, feeding had a positive effect on litter size, but it did not diminish the strong impact of the small rodent phase, supporting phase-dependent trade-offs in addition to food determining arctic fox reproduction.

The Long and Winding Road of Arctic Change Research

NASA Astrophysics Data System (ADS)

Mark, S.

2016-12-01

In the quest to better understand the local, regional and global drivers and impacts of Arctic change, we must not forget that the questions being asked today build on more than a century of research. There were giants before us. Perhaps the first observational evidence that the Arctic was responding to increasing carbon dioxide levels came from a 1986 study by Lachenbruch and Marshall of permafrost temperatures from boreholes in northernmost Alaska. In 1991, Detlef Quadfasel provided the first data on what appeared to be shifts in the ocean circulation, and hints then emerged that the sea ice cover at summer's end was receding. It was then noted that air temperatures over some parts of the Arctic were rising and others were cooling, attended by shifts in weather patterns. While some of this resembled what climate models were projecting, much of it looked like natural climate variability, driven variously by processes internal to the Arctic or linked to lower latitudes via the behavior of the NAO and the Arctic Oscillation. But the changes kept coming. Through a largely self-organizing process, led in considerable part by a small number of leading voices and with the strong support of funding agencies, scientists from diverse disciplines around the world began to find the answers. By the first decade of the 21st century, it was understood that large natural variability in Arctic climate, linked to both within-Arctic and lower-latitude drivers, was superimposed upon warming due to rising greenhouse gas levels, and that what was happening in the Arctic was already influencing lower latitudes. Many issues remain to be resolved. What are the relative roles of different drivers of Arctic amplification? Does Arctic amplification influence weather patterns beyond the Arctic? Will thawing terrestrial or subsea permafrost lead to substantial carbon emissions to the atmosphere, exacerbating global warming? How will sea ice loss affect Arctic ecosystems? How much will the

Measurements and modeling of CO 2 concentration and isotopes to improve process-level understanding of Arctic and boreal carbon cycling. Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keeling, Ralph F.

The major goal of this project was to improve understanding of processes that control the exchanges of CO 2 between the atmosphere and the land biosphere on decadal and longer time scales. The approach involves measuring the changes in atmospheric CO 2 concentration and the isotopes of CO 2 ( 13C/ 12C and 18O/ 16O) at background stations and uses these and other datasets to challenge and improve numerical models of the earth system. The project particularly emphasized the use of these data to improve understanding of changes occurring in boreal and arctic ecosystems over the past 50 years andmore » to seek from these data improved understanding of large-scale processes impacting carbon cycling, such as the responses to warming, CO 2 fertilization, and disturbance. The project also led to advances in the understanding of changes in water-use efficiency of land ecosystems globally based on trends in 13C/ 12C. The core element of this project was providing partial support for continuing measurements of CO 2 concentrations and isotopes from the Scripps CO 2 program, initiated by C. D. Keeling in the 1960s. The measurements included analysis of flasks collected at an array of ten stations distributed from the Arctic to the Antarctic. The project also supported modeling studies and interpretive work to help understand the origins of the large ~50% increase in the amplitude of the atmospheric CO 2 cycle detected at high northern latitudes between 1960 and present and to understand the long-term trend in carbon 13C/ 12C of CO 2. The seasonal cycle work was advanced through collaborations with colleagues at MPI Jena and Imperial College« less

Mapping wildfire burn severity in the Arctic Tundra from downsampled MODIS data

USGS Publications Warehouse

Kolden, Crystal A.; Rogan, John

2013-01-01

Wildfires are historically infrequent in the arctic tundra, but are projected to increase with climate warming. Fire effects on tundra ecosystems are poorly understood and difficult to quantify in a remote region where a short growing season severely limits ground data collection. Remote sensing has been widely utilized to characterize wildfire regimes, but primarily from the Landsat sensor, which has limited data acquisition in the Arctic. Here, coarse-resolution remotely sensed data are assessed as a means to quantify wildfire burn severity of the 2007 Anaktuvuk River Fire in Alaska, the largest tundra wildfire ever recorded on Alaska's North Slope. Data from Landsat Thematic Mapper (TM) and downsampled Moderate-resolution Imaging Spectroradiometer (MODIS) were processed to spectral indices and correlated to observed metrics of surface, subsurface, and comprehensive burn severity. Spectral indices were strongly correlated to surface severity (maximum R2 = 0.88) and slightly less strongly correlated to substrate severity. Downsampled MODIS data showed a decrease in severity one year post-fire, corroborating rapid vegetation regeneration observed on the burned site. These results indicate that widely-used spectral indices and downsampled coarse-resolution data provide a reasonable supplement to often-limited ground data collection for analysis and long-term monitoring of wildfire effects in arctic ecosystems.

Climate events synchronize the dynamics of a resident vertebrate community in the high Arctic.

PubMed

Hansen, Brage B; Grøtan, Vidar; Aanes, Ronny; Sæther, Bernt-Erik; Stien, Audun; Fuglei, Eva; Ims, Rolf A; Yoccoz, Nigel G; Pedersen, Ashild Ø

2013-01-18

Recently accumulated evidence has documented a climate impact on the demography and dynamics of single species, yet the impact at the community level is poorly understood. Here, we show that in Svalbard in the high Arctic, extreme weather events synchronize population fluctuations across an entire community of resident vertebrate herbivores and cause lagged correlations with the secondary consumer, the arctic fox. This synchronization is mainly driven by heavy rain on snow that encapsulates the vegetation in ice and blocks winter forage availability for herbivores. Thus, indirect and bottom-up climate forcing drives the population dynamics across all overwintering vertebrates. Icing is predicted to become more frequent in the circumpolar Arctic and may therefore strongly affect terrestrial ecosystem characteristics.

Gender Specific Reproductive Strategies of an Arctic Key Species (Boreogadus saida) and Implications of Climate Change

PubMed Central

Nahrgang, Jasmine; Varpe, Øystein; Korshunova, Ekaterina; Murzina, Svetlana; Hallanger, Ingeborg G.; Vieweg, Ireen; Berge, Jørgen

2014-01-01

The Arctic climate is changing at an unprecedented rate. What consequences this may have on the Arctic marine ecosystem depends to a large degree on how its species will respond both directly to elevated temperatures and more indirectly through ecological interactions. But despite an alarming recent warming of the Arctic with accompanying sea ice loss, reports evaluating ecological impacts of climate change in the Arctic remain sparse. Here, based upon a large-scale field study, we present basic new knowledge regarding the life history traits for one of the most important species in the entire Arctic, the polar cod (Boreogadus saida). Furthermore, by comparing regions of contrasting climatic influence (domains), we present evidence as to how its growth and reproductive success is impaired in the warmer of the two domains. As the future Arctic is predicted to resemble today's Atlantic domains, we forecast changes in growth and life history characteristics of polar cod that will lead to alteration of its role as an Arctic keystone species. This will in turn affect community dynamics and energy transfer in the entire Arctic food chain. PMID:24871481

What is going on up there? - The Chukchi Sea Ecosystem Mooring

NASA Astrophysics Data System (ADS)

Janzen, C.; McCammon, M.; Danielson, S. L.; Winsor, P.; Hopcroft, R. R.; Lalande, C.; Stafford, K.; Hauri, C.; McDonnell, A. M. P.

2016-02-01

As Arctic regions are projected to strongly reflect the impacts of a changing climate, an effort is underway to make sustained, year-round measurements of concurrent physical and biogeochemical parameters in the Arctic. Deploying highly instrumented year-round moorings in the water is no simple feat, given harsh Arctic conditions that include the presence of sea ice and deep ice keels during much of the year. Enter the late-breaking ecosystem mooring located in the northeast Chukchi Sea. This mooring complements established biophysical moorings elsewhere in the northern Bering and Chukchi seas, including those maintained by NOAA-PMEL (M8), UW-APL (Bering Strait) and JAMSTEC moorings. (southern Chukchi and Barrow Canyon). The mooring described here is located on the southern flank of Hanna Shoal and provides a multi-disciplinary approach to year-round observations within a biological hotspot. The Chukchi Ecosystem Mooring is equipped with a sensor suite aimed to monitor and document the state of ocean acidification, nutrient and carbon cycles, particles, waves, currents and physical properties, and even passive and active acoustic monitoring for zooplankton, fish, and marine mammals. Having the simultaneous interdisciplinary measurements provides data valuable to an ecosystem-based approach to research and resource management. The fully outfitted observatory is providing an unprecedented view into the mechanistic workings of the Chukchi Shelf Ecosystem. The first mooring was deployed in September 2014 and recovered in August 2015. The August 2015 deployment consisted of three moorings, each with incremental sensor packages to complete the ecosystem sensor suite. The mooring construction and instrumentation are described in detail, including introduction to the advances in sensor technologies that enable such deployments. Year one data recovery summaries and plots are provided to demonstrate the capabilities.

FRAM (FRontiers in Arctic marine Monitoring: The FRAM Ocean Observing System) planned efforts for integrated water column biogeochemistry

NASA Astrophysics Data System (ADS)

Nielsdóttir, Maria; Salter, Ian; Kanzow, Torsten; Boetius, Antje

2015-04-01

The Arctic is a region undergoing rapid environmental change and will be subject to multiple stressors in the coming decades. Reductions in sea ice concentration; warming, increased terrigenous inputs and Atlantification are all expected to exert a significant impact on the structure and function of Arctic ecosystems. The Fram Strait is a particularly important region because it acts as a gateway in the exchange of Atlantic and Arctic water masses. The logistical constraints in conducting year round biogeochemical measurements in such areas impose a significant limitation to our understanding of these complicated ecosystems. To address these important challenges the German ministry of research has funded a multi-million Euro infrastructure project (FRAM). Over the next five years FRAM will develop a remote access and autonomous sampling infrastructure to improve the temporal and spatial resolution of biogeochemical measurements in the Fram Strait and central Arctic. Here we present a summary of sampling strategies, technological innovations and biogeochemical parameters that will be addressed over the duration of the project. Specific emphasis will be placed on platforms for monitoring nutrient dynamics, carbonate chemistry, organic carbon flux and the development of a sustained microbial observatory.

Modelling carbon responses of tundra ecosystems to historical and projected climate: A comparison of a plot- and a global-scale ecosystem model to identify process-based uncertainties

USGS Publications Warehouse

Clein, Joy S.; Kwiatkowski, B.L.; McGuire, A.D.; Hobbie, J.E.; Rastetter, E.B.; Melillo, J.M.; Kicklighter, D.W.

2000-01-01

We are developing a process-based modelling approach to investigate how carbon (C) storage of tundra across the entire Arctic will respond to projected climate change. To implement the approach, the processes that are least understood, and thus have the most uncertainty, need to be identified and studied. In this paper, we identified a key uncertainty by comparing the responses of C storage in tussock tundra at one site between the simulations of two models - one a global-scale ecosystem model (Terrestrial Ecosystem Model, TEM) and one a plot-scale ecosystem model (General Ecosystem Model, GEM). The simulations spanned the historical period (1921-94) and the projected period (1995-2100). In the historical period, the model simulations of net primary production (NPP) differed in their sensitivity to variability in climate. However, the long-term changes in C storage were similar in both simulations, because the dynamics of heterotrophic respiration (RH) were similar in both models. In contrast, the responses of C storage in the two model simulations diverged during the projected period. In the GEM simulation for this period, increases in RH tracked increases in NPP, whereas in the TEM simulation increases in RH lagged increases in NPP. We were able to make the long-term C dynamics of the two simulations agree by parameterizing TEM to the fast soil C pools of GEM. We concluded that the differences between the long-term C dynamics of the two simulations lay in modelling the role of the recalcitrant soil C. These differences, which reflect an incomplete understanding of soil processes, lead to quite different projections of the response of pan-Arctic C storage to global change. For example, the reference parameterization of TEM resulted in an estimate of cumulative C storage of 2032 g C m-2 for moist tundra north of 50??N, which was substantially higher than the 463 g C m-2 estimated for a parameterization of fast soil C dynamics. This uncertainty in the depiction of

Comparing growth rates of Arctic Cod Boreogadus saida across the Chukchi and Beaufort Seas

NASA Astrophysics Data System (ADS)

Frothingham, A. M.; Norcross, B.

2016-02-01

Dramatic changes to the Arctic have highlighted the need for a greater understanding of the present ecosystem. Arctic Cod, Boreogadus saida, commonly dominate fish assemblages in the Arctic region and inhabit two geographically unique seas in the U.S. Due to the importance of Arctic Cod in the Arctic food web, establishing current benchmark information such as growth rates, will provide a better understanding as to how the species will adapt to the effects of climate change. To investigate differences in Arctic Cod life history across nearly 1500 km of vital habitat, growth rates were examined using a von Bertalanffy growth equation. Arctic Cod were collected from 2009 to 2014 from the Chukchi and Beaufort seas. Arctic Cod collected from the Chukchi Sea had an overall smaller maximum achievable length (210 mm) compared to the Beaufort Sea (253 mm) despite a larger sample size in the Chukchi Sea (n=1569) than the Beaufort Sea (n=1140). Growth rates indicated faster growth in the Chukchi Sea (K =0.33) than in the Beaufort Sea (K= 0.29). Arctic Cod collected from the Chukchi Sea had similar achievable maximum lengths throughout, but those collected from the southern Chukchi Sea grew at faster rates (K=0.45).Arctic Cod in the eastern Beaufort Sea region had a higher overall maximum achievable length (243 mm) than in the western Beaufort Sea region (186 mm). Knowledge about contemporary growth rates of Arctic Cod in the Chukchi and Beaufort Seas can be used in future comparisons to evaluate potential effects of increasing climate change and anthropogenic influences.

A potential loss of carbon associated with greater plant growth in the European Arctic

NASA Astrophysics Data System (ADS)

Hartley, Iain P.; Garnett, Mark H.; Sommerkorn, Martin; Hopkins, David W.; Fletcher, Benjamin J.; Sloan, Victoria L.; Phoenix, Gareth K.; Wookey, Philip A.

2012-12-01

Rapid warming is expected to increase plant growth in the Arctic, and result in trees gradually colonizing tundra. Models predict that enhanced carbon (C) storage in plant biomass may help offset atmospheric CO2 increases and reduce rates of climate change. However, in some Arctic ecosystems, high plant productivity is associated with rapid cycling and low storage of soil C (refs , , ); thus, as plant growth increases, soil C may be lost through enhanced decomposition. Here we show that, in northern Sweden, total ecosystem C storage is greater in tundra heath (owing to greater soil C stocks) than in more productive mountain-birch forest. Furthermore, we demonstrate that in the forest, high plant activity during the middle of the growing season stimulates the decomposition of older soil organic matter. Such a response, referred to as positive priming, helps explain the low soil C storage in the forest when compared with the tundra. We suggest that, as more productive forest communities colonize tundra, the decomposition of the large C stocks in tundra soils could be stimulated. Thus, counter-intuitively, increased plant growth in the European Arctic could result in C being released to the atmosphere, accelerating climate change.

High Diversity of Planctomycetes in Soils of Two Lichen-Dominated Sub-Arctic Ecosystems of Northwestern Siberia

PubMed Central

Ivanova, Anastasia A.; Kulichevskaya, Irina S.; Merkel, Alexander Y.; Toshchakov, Stepan V.; Dedysh, Svetlana N.

2016-01-01

A wide variety of terrestrial ecosystems in tundra have a ground vegetation cover composed of reindeer lichens (genera Cladonia and Cetraria). The microbial communities of two lichen-dominated ecosystems typical of the sub-arctic zone of northwestern Siberia, that is a forested tundra soil and a shallow acidic peatland, were examined in our study. As revealed by molecular analyses, soil and peat layers just beneath the lichen cover were abundantly colonized by bacteria from the phylum Planctomycetes. Highest abundance of planctomycetes detected by fluorescence in situ hybridization was in the range 2.2–2.7 × 107 cells per gram of wet weight. 16S rRNA gene fragments from the Planctomycetes comprised 8–13% of total 16S rRNA gene reads retrieved using Illumina pair-end sequencing from the soil and peat samples. Lichen-associated assemblages of planctomycetes displayed unexpectedly high diversity, with a total of 89,662 reads representing 1723 operational taxonomic units determined at 97% sequence identity. The soil of forested tundra was dominated by uncultivated members of the family Planctomycetaceae (53–71% of total Planctomycetes-like reads), while sequences affiliated with the Phycisphaera-related group WD2101 (recently assigned to the order Tepidisphaerales) were most abundant in peat (28–51% of total reads). Representatives of the Isosphaera–Singulisphaera group (14–28% of total reads) and the lineages defined by the genera Gemmata (1–4%) and Planctopirus–Rubinisphaera (1–3%) were present in both habitats. Two strains of Singulisphaera-like bacteria were isolated from studied soil and peat samples. These planctomycetes displayed good tolerance of low temperatures (4–15°C) and were capable of growth on a number of polysaccharides, including lichenan, a characteristic component of lichen-derived phytomass. PMID:28066382

Isolating the anthropogenic component of Arctic warming

DOE PAGES

Chylek, Petr; Hengartner, Nicholas; Lesins, Glen; ...

2014-05-28

Structural equation modeling is used in statistical applications as both confirmatory and exploratory modeling to test models and to suggest the most plausible explanation for a relationship between the independent and the dependent variables. Although structural analysis cannot prove causation, it can suggest the most plausible set of factors that influence the observed variable. Here, we apply structural model analysis to the annual mean Arctic surface air temperature from 1900 to 2012 to find the most effective set of predictors and to isolate the anthropogenic component of the recent Arctic warming by subtracting the effects of natural forcing and variabilitymore » from the observed temperature. We also find that anthropogenic greenhouse gases and aerosols radiative forcing and the Atlantic Multidecadal Oscillation internal mode dominate Arctic temperature variability. Finally, our structural model analysis of observational data suggests that about half of the recent Arctic warming of 0.64 K/decade may have anthropogenic causes.« less

Arctic Ocean Pathways in the 21st century

NASA Astrophysics Data System (ADS)

Aksenov, Yevgeny; van Gennip, Simon J.; Kelly, Stephen J.; Popova, Ekaterina E.; Yool, Andrew

2017-04-01

In the last three decades, changes in the Arctic environment have been occurring at an increasing rate. The opening up of large areas of previously sea ice-covered ocean affects the marine environment with potential impacts on Arctic ecosystems, including through changes in Arctic access, industries and societies. Changes to sea ice and surface winds result in large-scale shifts in ocean circulation and oceanic pathways. This study presents a high-resolution analysis of the projected ocean circulation and pathways of the Arctic water masses across the 21st century. The analysis is based on an eddy-permitting high-resolution global simulation of the ocean general circulation model NEMO (Nucleus for European Modelling of the Ocean) at the 1/4-degree horizontal resolution. The atmospheric forcing is from HadGEM2-ES model output from IPCC Assessment Report 5 (AR5) simulations performed for Coupled Model Intercomparison Project 5 (CMIP5), and follow the Representative Concentration Pathway 8.5 (RCP8.5) scenario. During the 21st century the AO experiences a significant warming, with sea surface temperature increased by in excess of 4 deg. C. Annual mean Arctic sea ice thickness drops to less than 0.5m, and the Arctic Ocean is ice-free in summer from the mid-century. We use an off-line tracer technique to investigate Arctic pathways of the Atlantic and Pacific waters (AW and PW respectively) under this future climate. The AW tracers have been released in the eastern Fram Strait and in the western Barents Sea, whereas the PW tracer has been seeded in the Bering Strait. In the second half of the century the upper 1000 m ocean circulation shows a reduction in the eastward AW flow along the continental slopes towards the Makarov and Canada basins and a deviation of the PW flow away from the Beaufort Sea towards the Siberian coast. Strengthening of Arctic boundary current and intensification of the cyclonic gyre in the Nansen basin of the Arctic Ocean is accompanied by

Microtopographic and depth controls on active layer chemistry in Arctic polygonal ground

DOE PAGES

Newman, Brent D.; Throckmorton, Heather M.; Graham, David E.; ...

2015-03-24

Polygonal ground is a signature characteristic of Arctic lowlands, and carbon release from permafrost thaw can alter feedbacks to Arctic ecosystems and climate. This study describes the first comprehensive spatial examination of active layer biogeochemistry that extends across high- and low-centered, ice wedge polygons, their features, and with depth. Water chemistry measurements of 54 analytes were made on surface and active layer pore waters collected near Barrow, Alaska, USA. Significant differences were observed between high- and low-centered polygons suggesting that polygon types may be useful for landscape-scale geochemical classification. However, differences were found for polygon features (centers and troughs) formore » analytes that were not significant for polygon type, suggesting that finer-scale features affect biogeochemistry differently from polygon types. Depth variations were also significant, demonstrating important multidimensional aspects of polygonal ground biogeochemistry. These results have major implications for understanding how polygonal ground ecosystems function, and how they may respond to future change.« less

Leaf and fine root carbon stocks and turnover are coupled across Arctic ecosystems.

PubMed

Sloan, Victoria L; Fletcher, Benjamin J; Press, Malcolm C; Williams, Mathew; Phoenix, Gareth K

2013-12-01

Estimates of vegetation carbon pools and their turnover rates are central to understanding and modelling ecosystem responses to climate change and their feedbacks to climate. In the Arctic, a region containing globally important stores of soil carbon, and where the most rapid climate change is expected over the coming century, plant communities have on average sixfold more biomass below ground than above ground, but knowledge of the root carbon pool sizes and turnover rates is limited. Here, we show that across eight plant communities, there is a significant positive relationship between leaf and fine root turnover rates (r(2) = 0.68, P < 0.05), and that the turnover rates of both leaf (r(2) = 0.63, P < 0.05) and fine root (r(2) = 0.55, P < 0.05) pools are strongly correlated with leaf area index (LAI, leaf area per unit ground area). This coupling of root and leaf dynamics supports the theory of a whole-plant economics spectrum. We also show that the size of the fine root carbon pool initially increases linearly with increasing LAI, and then levels off at LAI = 1 m(2) m(-2), suggesting a functional balance between investment in leaves and fine roots at the whole community scale. These ecological relationships not only demonstrate close links between above and below-ground plant carbon dynamics but also allow plant carbon pool sizes and their turnover rates to be predicted from the single readily quantifiable (and remotely sensed) parameter of LAI, including the possibility of estimating root data from satellites. © 2013 John Wiley & Sons Ltd.

Arctic Ice Management: an integrated approach to climate engineering

NASA Astrophysics Data System (ADS)

Desch, S. J.; Hartnett, H. E.; Groppi, C. E.; Romaniello, S. J.

2017-12-01

The warming climate is having the most rapid and pronounced effects in the high Arctic. The loss of Arctic sea ice is not only changing the physical oceanography of the Arctic Ocean and its coastlines; it is also promoting new conversations about the dangers and benefits for trade, transportation, and industry in the Arctic. The rate of decrease of summer sea ice in the Arctic is currently -300 km3 yr-1, a rate that will lead to complete loss of end-summer sea ice as soon as 2030. Preventing the strong positive feedbacks and increased warming due to sea ice albedo loss must be an important component of climate mitigation strategies. Here, we explore a direct engineering approach we call Arctic Ice Management (AIM) to reduce the loss of Arctic sea ice. We predict that pumping seawater onto the ice surface during the Arctic winter using wind-powered pumps can thicken sea ice by up to 1 m per year, reversing the current loss rates and prolonging the time until the Arctic Ocean is ice-free. Thickening sea ice would not change CO2 levels, which are the underlying cause of ice loss, but it would prevent some of the strongest feedbacks and would buy time to develop the tools and governance systems necessary to achieve carbon-neutrality. We advocate exploration of AIM as a mitigation strategy employed in parallel with CO2 reduction efforts. The opportunity and risk profiles of AIM differ from other geoengineering proposals. While similar in principle to solar radiation management, AIM may present fewer large-scale environmental risks. AIM is separate from greenhouse gas emission reduction or sequestration, but might help prevent accelerated release of methane from thawing permafrost. Further, AIM might be usefully employed at regional and local scales to preserve Arctic ecosystems and possibly reduce the effects of ice-loss induced coastal erosion. Through presentation of the AIM concept, we hope to spark new conversations between scientists, stakeholders, and decision

The unseen iceberg: Plant roots in arctic tundra

USGS Publications Warehouse

Iverson, Colleen M.; Sloan, Victoria L.; Sullivan, Patrick F.; Euskirchen, E.S.; McGuire, A. David; Norby, Richard J.; Walker, Anthony P.; Warren, Jeffrey M.; Wullschleger, Stan D.

2015-01-01

Plant roots play a critical role in ecosystem function in arctic tundra, but root dynamics in these ecosystems are poorly understood. To address this knowledge gap, we synthesized available literature on tundra roots, including their distribution, dynamics and contribution to ecosystem carbon and nutrient fluxes, and highlighted key aspects of their representation in terrestrial biosphere models. Across all tundra ecosystems, belowground plant biomass exceeded aboveground biomass, with the exception of polar desert tundra. Roots were shallowly distributed in the thin layer of soil that thaws annually, and were often found in surface organic soil horizons. Root traits – including distribution, chemistry, anatomy and resource partitioning – play an important role in controlling plant species competition, and therefore ecosystem carbon and nutrient fluxes, under changing climatic conditions, but have only been quantified for a small fraction of tundra plants. Further, the annual production and mortality of fine roots are key components of ecosystem processes in tundra, but extant data are sparse. Tundra root traits and dynamics should be the focus of future research efforts. Better representation of the dynamics and characteristics of tundra roots will improve the utility of models for the evaluation of the responses of tundra ecosystems to changing environmental conditions.

The unseen iceberg: plant roots in arctic tundra.

PubMed

Iversen, Colleen M; Sloan, Victoria L; Sullivan, Patrick F; Euskirchen, Eugenie S; McGuire, A David; Norby, Richard J; Walker, Anthony P; Warren, Jeffrey M; Wullschleger, Stan D

2015-01-01

Plant roots play a critical role in ecosystem function in arctic tundra, but root dynamics in these ecosystems are poorly understood. To address this knowledge gap, we synthesized available literature on tundra roots, including their distribution, dynamics and contribution to ecosystem carbon and nutrient fluxes, and highlighted key aspects of their representation in terrestrial biosphere models. Across all tundra ecosystems, belowground plant biomass exceeded aboveground biomass, with the exception of polar desert tundra. Roots were shallowly distributed in the thin layer of soil that thaws annually, and were often found in surface organic soil horizons. Root traits - including distribution, chemistry, anatomy and resource partitioning - play an important role in controlling plant species competition, and therefore ecosystem carbon and nutrient fluxes, under changing climatic conditions, but have only been quantified for a small fraction of tundra plants. Further, the annual production and mortality of fine roots are key components of ecosystem processes in tundra, but extant data are sparse. Tundra root traits and dynamics should be the focus of future research efforts. Better representation of the dynamics and characteristics of tundra roots will improve the utility of models for the evaluation of the responses of tundra ecosystems to changing environmental conditions. No claim to original US Government works New Phytologist © 2014 New Phytologist Trust.

Photosynthesis, Earth System Models and the Arctic

NASA Astrophysics Data System (ADS)

Rogers, A.; Sloan, V. L.; Xu, C.; Wullschleger, S. D.

2013-12-01

The primary goal of Earth System Models (ESMs) is to improve understanding and projection of future global change. In order to do this they must accurately represent the huge carbon fluxes associated with the terrestrial carbon cycle. Photosynthetic CO2 uptake is the largest of these fluxes, and is well described by the Farquhar, von Caemmerer and Berry (FvCB) model of photosynthesis. Most ESMs use a derivation of the FvCB model to calculate gross primary productivity (GPP). One of the key parameters required by the FvCB model is an estimate of the maximum rate of carboxylation by the enzyme Rubisco (Vc,max). In ESMs the parameter Vc,max is usually fixed for a given plant functional type (PFT). Although Arctic GPP a small flux relative to global GPP, uncertainty is large. Only four ESMs currently have an explicit Arctic PFT and the data used to derive Vc,max for the Arctic PFT in these models relies on small data sets and unjustified assumptions. As part of a multidisciplinary project to improve the representation of the Arctic in ESMs (Next Generation Ecosystem Experiments - Arctic) we examined the derivation of Vc,max in current Arctic PFTs and estimated Vc,max for 12 species representing both dominant vegetation and key PFTs growing on the Barrow Environmental Observatory, Barrow, AK. The values of Vc,max currently used to represent Arctic PFTs in ESMs are 70% lower than the values we measured in these species. Separate measurements of CO2 assimilation (A) made at ambient conditions were compared with A modeled using the Vc,max values we measured in Barrow and those used by the ESMs. The A modeled with the Vc,max values used by the ESMs was 80% lower than the observed A. When our measured Vc,max values were used, modeled A was within 5% of observed A. Examination of the derivation of Vc,max in ESMs identified that the cause of the relatively low Vc,max value was the result of underestimating both the leaf N content and the investment of that N in Rubisco. Here

Using Domestic and Free-Ranging Arctic Canid Models for Environmental Molecular Toxicology Research.

PubMed

Harley, John R; Bammler, Theo K; Farin, Federico M; Beyer, Richard P; Kavanagh, Terrance J; Dunlap, Kriya L; Knott, Katrina K; Ylitalo, Gina M; O'Hara, Todd M

2016-02-16

The use of sentinel species for population and ecosystem health assessments has been advocated as part of a One Health perspective. The Arctic is experiencing rapid change, including climate and environmental shifts, as well as increased resource development, which will alter exposure of biota to environmental agents of disease. Arctic canid species have wide geographic ranges and feeding ecologies and are often exposed to high concentrations of both terrestrial and marine-based contaminants. The domestic dog (Canis lupus familiaris) has been used in biomedical research for a number of years and has been advocated as a sentinel for human health due to its proximity to humans and, in some instances, similar diet. Exploiting the potential of molecular tools for describing the toxicogenomics of Arctic canids is critical for their development as biomedical models as well as environmental sentinels. Here, we present three approaches analyzing toxicogenomics of Arctic contaminants in both domestic and free-ranging canids (Arctic fox, Vulpes lagopus). We describe a number of confounding variables that must be addressed when conducting toxicogenomics studies in canid and other mammalian models. The ability for canids to act as models for Arctic molecular toxicology research is unique and significant for advancing our understanding and expanding the tool box for assessing the changing landscape of environmental agents of disease in the Arctic.

Landsat time series analysis documents beaver migration into permafrost landscapes of arctic Alaska

NASA Astrophysics Data System (ADS)

Jones, B. M.; Tape, K. D.; Nitze, I.; Arp, C. D.; Grosse, G.; Zimmerman, C. E.

2017-12-01

Landscape-scale impacts of climate change in the Arctic include increases in growing season length, shrubby vegetation, winter river discharge, snowfall, summer and winter water temperatures, and decreases in river and lake ice thickness. Combined, these changes may have created conditions that are suitable for beaver colonization of low Arctic tundra regions. We developed a semi-automated workflow that analyzes Landsat imagery time series to determine the extent to which beavers may have colonized permafrost landscapes in arctic Alaska since 1999. We tested this approach on the Lower Noatak, Wulik, and Kivalina river watersheds in northwest Alaska and identified 83 locations representing potential beaver activity. Seventy locations indicated wetting trends and 13 indicated drying trends. Verification of each site using high-resolution satellite imagery showed that 80 % of the wetting locations represented beaver activity (damming and pond formation), 11 % were unrelated to beavers, and 9 % could not readily be distinguished as being beaver related or not. For the drying locations, 31 % represented beaver activity (pond drying due to dam abandonment), 62 % were unrelated to beavers, and 7 % were undetermined. Comparison of the beaver activity database with historic aerial photography from ca. 1950 and ca. 1980 indicates that beavers have recently colonized or recolonized riparian corridors in northwest Alaska. Remote sensing time series observations associated with the migration of beavers in permafrost landscapes in arctic Alaska include thermokarst lake expansion and drainage, thaw slump initiation, ice wedge degradation, thermokarst shore fen development, and possibly development of lake and river taliks. Additionally, beaver colonization in the Arctic may alter channel courses, thermal regimes, hyporheic flow, riparian vegetation, and winter ice regimes that could impact ecosystem structure and function in this region. In particular, the combination of beaver

Role of small-sized copepods in the lipid-driven Arctic marine food web

NASA Astrophysics Data System (ADS)

Daase, M.; Boissonnot, L.; Graeve, M.; Søreide, J.; Niehoff, B.

2016-02-01

Despite of the low individual biomass of small-sized copepods such as the calanoid Pseudocalanus minutus and the cyclopoid Oithona similis, they are extremely numerous which make them an important trophic component in Arctic marine ecosystems. Due to the strong seasonality in light and thus primary production and food availability, the accumulation of lipid reserves is a key feature in Arctic marine ecosystems. However, very few studies exist on the lipid biochemistry of small copepods such as P. minutus and O. similis. In order to investigate the importance of these species in terms of transfer of lipids from primary production to higher trophic levels, feeding experiments were conducted, based on animals from Billefjorden, a high-Arctic fjord in Svalbard, Norway. A mixture of 13C labeled flagellates and diatoms was fed to the animals and the transfer and assimilation of lipid carbon, fatty acids and fatty alcohols was analyzed with gas chromatography-IRMS technique (CSIA). The results revealed that both species were incorporating dietary lipids in high quantities. The highest accumulation occurred in P. minutus in which 54.4% of the lipids were exchanged after 21 days, whereas 9.4% were assimilated in O. similis. Hence, at least this amount of carbon was used for metabolism and replaced by feeding. The lipid composition of the copepods did not reflect exactly the algal lipids, and differed between P. minutus and O. similis. Our results suggested intrinsic preferences in the accumulation of particular fatty acids, probably related to species-specific body requirements. This emphasizes the importance of also food quality in Arctic marine systems. Due to the relatively high lipid turnover rates in particularly in P. minutus, also small copepods are important drivers of the lipid-driven Arctic marine food web.

Recent change of artic tundra ecosystems from a net carbon dioxide sink to a source

Treesearch

Walter C. Oechel; Steven J. Hastings; George Vourlitis; Mitchell Jenkins; George Riechers; Nancy Grulke

1993-01-01

Arctic tundra has been a net sink for carbon dioxide during historic and recent geological times1-4, and large amounts of carbon are stored in the soils of northern ecosystems. Many regions of the Arctic are warmer now than they have been in the past5-10, and this warming may cause the soil to change from a carbon dioxide...

Soil Carbon Distribution along a Hill Slope in the Siberian Arctic

NASA Astrophysics Data System (ADS)

Ludwig, S.; Bunn, A. G.; Schade, J. D.

2011-12-01

Arctic ecosystems are warming at an accelerated rate relative to lower latitudes, and this warming has significant global significance. In particular, the thawing of permafrost soils has the potential to strongly influence global carbon cycling and the functioning of terrestrial and aquatic ecosystems. Our overarching scientific goal is to study the impact of thawing permafrost on the transport and processing of carbon and other nutrients as they move with water from terrestrial ecosystems to the Arctic Ocean. Transport of materials from soil to headwater aquatic ecosystems is the first step in this movement. Processes occurring along hill slopes strongly influence the form and concentration of material available for transport. These processes include downhill accumulation of materials due to groundwater movement, or alternatively, local effects of changes in soil and vegetation characteristics. In this project, we studied a hill slope adjacent to a small first order stream in the Kolyma River in Eastern Siberia. We sampled soil at several points along three transects from the top of the hill to the riparian zone by coring and homogenizing the entire active layer at each point. We measured soil organic matter content, soil moisture, water extractable dissolved organic carbon (DOC), total dissolved nitrogen (TDN), NH4, NO3, soluble reactive phosphorus (SRP), and CDOM absorbance. We also measured soil respiration using a laboratory-based biological oxygen demand protocol conducted on soil-water slurries. Active layer depth decreased down the hillslope, while soil moisture, organic matter, and DOC all increased down the hillslope. CDOM absorbance increased downhill, which indicates a decrease in molecular weight of organic compounds at the bottom of the hill. This suggests either an input of newer carbon or processing of high molecular weight DOM down the slope. Soil respiration also increased downhill and was likely driven in part by increased OM in the shallower

Soil Surface Organic Layers in Alaska's Arctic Foothills: Development, Distribution and Microclimatic Feedbacks

NASA Astrophysics Data System (ADS)

Baughman, C. A.; Mann, D. H.; Verbyla, D.; Valentine, D.; Kunz, M. L.; Heiser, P. A.

2013-12-01

Accumulated organic matter at the ground surface plays an important role in arctic ecosystems. These soil surface organic layers (SSOLs) influence temperature, moisture, and chemistry in the underlying mineral soil and, on a global basis, comprise enormous stores of labile carbon. Understanding the dynamics of SSOLs is prerequisite to modeling the responses of arctic ecosystem processes to climate changes. Here, we ask three questions regarding SSOLs in the Arctic Foothills in northern Alaska: 1) What environmental factors control their spatial distribution? 2) How long do they take to form? 3) What is the relationship between SSOL thickness and mineral soil temperature through the growing season? The best topographically-controlled predictors of SSOL thickness and spatial distribution are duration of sunlight during the growing-season, upslope drainage area, slope gradient, and elevation. SSOLs begin to form within several decades following disturbance but require 500-700 years to reach equilibrium states. Once formed, mature SSOLs lower peak growing-season temperature and mean annual temperature in the underlying mineral horizon by 8° and 3° C respectively, which reduces available growing degree days within the upper mineral soil by nearly 80%. How ongoing climate change in northern Alaska will affect the region's SSOLs is an open and potentially crucial question.

Oceanographic Aspects of Recent Changes in the Arctic

NASA Astrophysics Data System (ADS)

Morison, J. H.

2002-12-01

In the Arctic recent decadal-scale changes have marked the atmosphere, ocean, and land. Connections between the oceanographic changes and large-scale atmospheric circulation changes are emerging. Surface atmospheric pressure has shown a declining trend over the Arctic. In the 1990s, the Arctic Ocean circulation took on a more cyclonic character, and the front separating Atlantic-derived waters of the Eurasian Basin and the Pacific-derived waters of the Canadian Basin shifted counterclockwise. The temperature of Atlantic water in the Arctic Ocean reached record levels. The cold halocline, which isolates the surface from the warm Atlantic water, grew thinner disappearing entirely from the Amundsen Basin at one point [Steele and Boyd, 1998]. Arctic sea ice extent has decreased 3% per decade since the 1970s [Parkinson et al., 1999]. Sea ice thickness over much of the Arctic decreased 43% between 1958-1976 and 1993-1997 [Rothrock et al., 1999]. Arctic ecosystems have responded to these changes. Sea ice studies in the late 1990s indicate that the sea ice algal species composition changed from decades before, with the species recently being characterized by more brackish and freshwater forms. Barents Sea fisheries have shifted north following reductions in ice extent. Pacific salmon species have been found entering rivers in the Arctic. There is evidence that this complex of pan-Arctic changes is connected with the rising trend in the Arctic Oscillation (AO) or Northern Hemisphere atmospheric polar vortex in the 1990s. Theoretical evidence that a positive trend in the AO index might be indicative of greenhouse warming raises the possibility that the recent complex of changes is an Arctic characteristic of global climate change. Also, the changes in ice cover manifest a connection between the complex of change and global climate through ice-albedo feedback, by which reductions in ice cover reduce the amount of sunlight reflected from the earth's surface. Another important

Otolith Length-Fish Length Relationships of Eleven US Arctic Fish Species and Their Application to Ice Seal Diet Studies

NASA Astrophysics Data System (ADS)

Walker, K. L.; Norcross, B.

2016-02-01

The Arctic ecosystem has moved into the spotlight of scientific research in recent years due to increased climate change and oil and gas exploration. Arctic fishes and Arctic marine mammals represent key parts of this ecosystem, with fish being a common part of ice seal diets in the Arctic. Determining sizes of fish consumed by ice seals is difficult because otoliths are often the only part left of the fish after digestion. Otolith length is known to be positively related to fish length. By developing species-specific otolith-body morphometric relationships for Arctic marine fishes, fish length can be determined for fish prey found in seal stomachs. Fish were collected during ice free months in the Beaufort and Chukchi seas 2009 - 2014, and the most prevalent species captured were chosen for analysis. Otoliths from eleven fish species from seven families were measured. All species had strong linear relationships between otolith length and fish total length. Nine species had coefficient of determination values over 0.75, indicating that most of the variability in the otolith to fish length relationship was explained by the linear regression. These relationships will be applied to otoliths found in stomachs of three species of ice seals (spotted Phoca largha, ringed Pusa hispida, and bearded Erignathus barbatus) and used to estimate fish total length at time of consumption. Fish lengths can in turn be used to calculate fish weight, enabling further investigation into ice seal energetic demands. This application will aid in understanding how ice seals interact with fish communities in the US Arctic and directly contribute to diet comparisons among and within ice seal species. A better understanding of predator-prey interactions in the US Arctic will aid in predicting how ice seal and fish species will adapt to a changing Arctic.

ESRP approach to using final ecosystem services

EPA Science Inventory

The U.S. Environmental Protection Agency has developed the ecosystem Services Research Program (ESRP) as one of its major research efforts. The goal of this program is to create “A comprehensive theory and practice for quantifying ecosystem services so that their value and their...

Arctic water tracks retain phosphorus and transport ammonium

NASA Astrophysics Data System (ADS)

Harms, T.; Cook, C. L.; Wlostowski, A. N.; Godsey, S.; Gooseff, M. N.

2017-12-01

Hydrologic flowpaths propagate biogeochemical signals among adjacent ecosystems, but reactions may attenuate signals by retaining, removing, or transforming dissolved and suspended materials. The theory of nutrient spiraling describes these simultaneous reaction and transport processes, but its application has been limited to stream channels. We applied nutrient spiraling theory to water tracks, zero-order channels draining Arctic hillslopes that contain perennially saturated soils and flow at the surface either perennially or in response to precipitation. In the Arctic, experimental warming results in increased availability of nitrogen, the limiting nutrient for hillslope vegetation at the study site, which may be delivered to aquatic ecosystems by water tracks. Increased intensity of rain events, deeper snowpack, earlier snowmelt, and increasing thaw depth resulting from climate change might support increased transport of nutrients, but the reactive capacity of hillslope flowpaths, including sorption and uptake by plants and microbes, could counter transport to regulate solute flux. Characteristics of flowpaths might influence the opportunity for reaction, where slower flowpaths increase the contact time between solutes and soils or roots. We measured nitrogen and phosphorus uptake and transient storage of water tracks through the growing season and found that water tracks retain inorganic phosphorus, but transport ammonium. Nutrient uptake was unrelated to transient storage, suggesting high capacity for nutrient retention by shallow organic soils and vegetation. These observations indicate that increased availability of ammonium, the biogeochemical signal of warming tundra, is propagated by hillslope flowpaths, whereas water tracks attenuate delivery of phosphorus to aquatic ecosystems, where its availability typically limits production.

Tundra shrubification and tree-line advance amplify arctic climate warming: results from an individual-based dynamic vegetation model

NASA Astrophysics Data System (ADS)

Zhang, Wenxin; Miller, Paul A.; Smith, Benjamin; Wania, Rita; Koenigk, Torben; Döscher, Ralf

2013-09-01

One major challenge to the improvement of regional climate scenarios for the northern high latitudes is to understand land surface feedbacks associated with vegetation shifts and ecosystem biogeochemical cycling. We employed a customized, Arctic version of the individual-based dynamic vegetation model LPJ-GUESS to simulate the dynamics of upland and wetland ecosystems under a regional climate model-downscaled future climate projection for the Arctic and Subarctic. The simulated vegetation distribution (1961-1990) agreed well with a composite map of actual arctic vegetation. In the future (2051-2080), a poleward advance of the forest-tundra boundary, an expansion of tall shrub tundra, and a dominance shift from deciduous to evergreen boreal conifer forest over northern Eurasia were simulated. Ecosystems continued to sink carbon for the next few decades, although the size of these sinks diminished by the late 21st century. Hot spots of increased CH4 emission were identified in the peatlands near Hudson Bay and western Siberia. In terms of their net impact on regional climate forcing, positive feedbacks associated with the negative effects of tree-line, shrub cover and forest phenology changes on snow-season albedo, as well as the larger sources of CH4, may potentially dominate over negative feedbacks due to increased carbon sequestration and increased latent heat flux.

Aragonite undersaturation in the Arctic Ocean: effects of ocean acidification and sea ice melt.

PubMed

Yamamoto-Kawai, Michiyo; McLaughlin, Fiona A; Carmack, Eddy C; Nishino, Shigeto; Shimada, Koji

2009-11-20

The increase in anthropogenic carbon dioxide emissions and attendant increase in ocean acidification and sea ice melt act together to decrease the saturation state of calcium carbonate in the Canada Basin of the Arctic Ocean. In 2008, surface waters were undersaturated with respect to aragonite, a relatively soluble form of calcium carbonate found in plankton and invertebrates. Undersaturation was found to be a direct consequence of the recent extensive melting of sea ice in the Canada Basin. In addition, the retreat of the ice edge well past the shelf-break has produced conditions favorable to enhanced upwelling of subsurface, aragonite-undersaturated water onto the Arctic continental shelf. Undersaturation will affect both planktonic and benthic calcifying biota and therefore the composition of the Arctic ecosystem.

Islands of the Arctic

NASA Astrophysics Data System (ADS)

Dowdeswell, Julian; Hambrey, Michael

2002-11-01

The Arctic islands are characterized by beautiful mountains and glaciers, in which the wildlife lives in delicate balance with its environment. It is a fragile region with a long history of exploration and exploitation that is now experiencing rapid environmental change. All of these themes are explored in Islands of the Arctic, a richly illustrated volume with superb photographs from the Canadian Arctic archipelago, Greenland, Svalbard and the Russian Arctic. It begins with the various processes shaping the landscape: glaciers, rivers and coastal processes, the role of ice in the oceans and the weather and climate. Julian Dowdeswell and Michael Hambrey describe the flora and fauna in addition to the human influences on the environment, from the sustainable approach of the Inuit, to the devastating damage inflicted by hunters and issues arising from the presence of military security installations. Finally, they consider the future prospects of the Arctic islands Julian Dowdeswell is Director of the Scott Polar Research Institute and Professor of Physical Geography at 0he University of Cambridge. He received the Polar Medal from Queen Elizabeth for his contributions to the study of glacier geophysics and the Gill Memorial Award from the Royal Geographical Society. He is chair of the Publications Committee of the International Glaciological Society and head of the Glaciers and Ice Sheets Division of the International Commission for Snow and Ice. Michael Hambrey is Director of the Centre for Glaciology at the University of Wales, Aberystwyth. A past recipient of the Polar Medal, he was also given the Earth Science Editors' Outstanding Publication Award for Glaciers (Cambridge University Press). Hambrey is also the author of Glacial Environments (British Columbia, 1994).

Serosurvey for Toxoplasma gondii in arctic foxes and possible sources of infection in the high Arctic of Svalbard.

PubMed

Prestrud, Kristin Wear; Asbakk, Kjetil; Fuglei, Eva; Mørk, Torill; Stien, Audun; Ropstad, Erik; Tryland, Morten; Gabrielsen, Geir Wing; Lydersen, Christian; Kovacs, Kit M; Loonen, Maarten J J E; Sagerup, Kjetil; Oksanen, Antti

2007-11-30

Samples (blood or tissue fluid) from 594 arctic foxes (Alopex lagopus), 390 Svalbard reindeer (Rangifer tarandus platyrhynchus), 361 sibling voles (Microtus rossiaemeridionalis), 17 walruses (Odobenus rosmarus), 149 barnacle geese (Branta leucopsis), 58 kittiwakes (Rissa tridactyla), and 27 glaucous gulls (Larus hyperboreus) from Svalbard and nearby waters were assayed for antibodies against Toxoplasma gondii using a direct agglutination test. The proportion of seropositive animals was 43% in arctic foxes, 7% in barnacle geese, and 6% (1 of 17) in walruses. There were no seropositive Svalbard reindeer, sibling voles, glaucous gulls, or kittiwakes. The prevalence in the arctic fox was relatively high compared to previous reports from canid populations. There are no wild felids in Svalbard and domestic cats are prohibited, and the absence of antibodies against T. gondii among the herbivorous Svalbard reindeer and voles indicates that transmission of the parasite by oocysts is not likely to be an important mechanism in the Svalbard ecosystem. Our results suggest that migratory birds, such as the barnacle goose, may be the most important vectors bringing the parasite to Svalbard. In addition to transmission through infected prey and carrion, the age-seroprevalence profile in the fox population suggests that their infection levels are enhanced by vertical transmission.

Extreme nitrogen deposition can change methane oxidation rate in moist acidic tundra soil in Arctic regions

NASA Astrophysics Data System (ADS)

Lee, J.; Kim, J.; Kang, H.

2017-12-01

Recently, extreme nitrogen(N) deposition events are observed in Arctic regions where over 90% of the annual N deposition occurred in just a few days. Since Arctic ecosystems are typically N-limited, input of extremely high amount of N could substantially affect ecosystem processes. CH4 is a potent greenhouse gas that has 25 times greater global warming potential than CO2 over a 100-year time frame. Ammonium is known as an inhibitor of methane oxidation and nitrate also shows inhibitory effect on it in temperate ecosystems. However, effects of N addition on Arctic ecosystems are still elusive. We conducted a lab-scale incubation experiment with moist acidic tundra (MAT) soil from Council, Alaska to investigate the effect of extreme N deposition events on methane oxidation. Zero point five % methane was added to the head space to determine the potential methane oxidation rate of MAT soil. Three treatments (NH4NO3-AN, (NH4)2SO4-AS, KNO3-PN) were used to compare effects of ammonium, nitrate and salts. All treatments were added in 3 levels: 10μg N gd.w-1(10), 50μg N gd.w-1(50) and 100μg N gd.w-1(100). AN10 and AN50 increased methane oxidation rate 1.7, 6% respectively. However, AN100 shows -8.5% of inhibitory effect. In AS added samples, all 3 concentrations (AN10, AN50, AN100) stimulated methane oxidation rate with 4.7, 8.9, 4%, respectively. On the contrary, PN50 (-9%) and PN100 (-59.5%) exhibited a significant inhibitory effect. We also analyzed the microbial gene abundance and community structures of methane oxidizing bacteria using a DNA-based fingerprinting method (T-RFLP) Our study results suggest that NH4+ can stimulate methane oxidation in Arctic MAT soil, while NO3- can inhibit methane oxidation significantly.

ArcticDEM Validation and Accuracy Assessment

NASA Astrophysics Data System (ADS)

Candela, S. G.; Howat, I.; Noh, M. J.; Porter, C. C.; Morin, P. J.

2017-12-01

ArcticDEM comprises a growing inventory Digital Elevation Models (DEMs) covering all land above 60°N. As of August, 2017, ArcticDEM had openly released 2-m resolution, individual DEM covering over 51 million km2, which includes areas of repeat coverage for change detection, as well as over 15 million km2 of 5-m resolution seamless mosaics. By the end of the project, over 80 million km2 of 2-m DEMs will be produced, averaging four repeats of the 20 million km2 Arctic landmass. ArcticDEM is produced from sub-meter resolution, stereoscopic imagery using open source software (SETSM) on the NCSA Blue Waters supercomputer. These DEMs have known biases of several meters due to errors in the sensor models generated from satellite positioning. These systematic errors are removed through three-dimensional registration to high-precision Lidar or other control datasets. ArcticDEM is registered to seasonally-subsetted ICESat elevations due its global coverage and high report accuracy ( 10 cm). The vertical accuracy of ArcticDEM is then obtained from the statistics of the fit to the ICESat point cloud, which averages -0.01 m ± 0.07 m. ICESat, however, has a relatively coarse measurement footprint ( 70 m) which may impact the precision of the registration. Further, the ICESat data predates the ArcticDEM imagery by a decade, so that temporal changes in the surface may also impact the registration. Finally, biases may exist between different the different sensors in the ArcticDEM constellation. Here we assess the accuracy of ArcticDEM and the ICESat registration through comparison to multiple high-resolution airborne lidar datasets that were acquired within one year of the imagery used in ArcticDEM. We find the ICESat dataset is performing as anticipated, introducing no systematic bias during the coregistration process, and reducing vertical errors to within the uncertainty of the airborne Lidars. Preliminary sensor comparisons show no significant difference post coregistration

Transitions in High-Arctic Vegetation Growth Patterns and Ecosystem Productivity from 2000-2013 Tracked with Cameras

NASA Astrophysics Data System (ADS)

Westergaard-Nielsen, A.; Hansen, B. U.; Klosterman, S.; Pedersen, S. H.; Schmidt, N. M.; Abermann, J.; Lund, M.

2015-12-01

The changes in vegetation seasonality in high northern latitudes resulting from changes atmospheric temperatures and precipitation are still not well understood. Continued monitoring and research is therefore needed. In this study we use 13 years of time lapse camera data and climate data from high-Arctic Northeast Greenland to assess the seasonal response of a dwarf shrub heath, grassland, and fens to snow cover, soil moisture, and atmospheric and soil temperatures. Based on the camera data, we computed a greenness index which was subsequently used to analyze transition dates in vegetation seasonality. We show that snow cover and subsequent water from the melting snow pack is highly important for the seasonality. We found a significant advancement in start of growing season of 12 days but not a significant increase in growing season length. Both the timing and greenness index value of peak of growing season was significantly correlated to the available water in the pre-melt snow pack, mostly pronounced in vegetation with limited soil water. The end of growing season was likewise significantly correlated to the water equivalents in the pre-melt snowpack. Moreover, the vegetation greenness was highly correlated to GPP, and shifts in seasonality as tracked by the greenness index are thus expected to have direct influence on ecosystem productivity.

Tundra landform and vegetation productivity trend maps for the Arctic Coastal Plain of northern Alaska

NASA Astrophysics Data System (ADS)

Lara, Mark J.; Nitze, Ingmar; Grosse, Guido; McGuire, A. David

2018-04-01

Arctic tundra landscapes are composed of a complex mosaic of patterned ground features, varying in soil moisture, vegetation composition, and surface hydrology over small spatial scales (10-100 m). The importance of microtopography and associated geomorphic landforms in influencing ecosystem structure and function is well founded, however, spatial data products describing local to regional scale distribution of patterned ground or polygonal tundra geomorphology are largely unavailable. Thus, our understanding of local impacts on regional scale processes (e.g., carbon dynamics) may be limited. We produced two key spatiotemporal datasets spanning the Arctic Coastal Plain of northern Alaska (~60,000 km2) to evaluate climate-geomorphological controls on arctic tundra productivity change, using (1) a novel 30 m classification of polygonal tundra geomorphology and (2) decadal-trends in surface greenness using the Landsat archive (1999-2014). These datasets can be easily integrated and adapted in an array of local to regional applications such as (1) upscaling plot-level measurements (e.g., carbon/energy fluxes), (2) mapping of soils, vegetation, or permafrost, and/or (3) initializing ecosystem biogeochemistry, hydrology, and/or habitat modeling.

Tundra landform and vegetation productivity trend maps for the Arctic Coastal Plain of northern Alaska

PubMed Central

Lara, Mark J.; Nitze, Ingmar; Grosse, Guido; McGuire, A. David

2018-01-01

Arctic tundra landscapes are composed of a complex mosaic of patterned ground features, varying in soil moisture, vegetation composition, and surface hydrology over small spatial scales (10–100 m). The importance of microtopography and associated geomorphic landforms in influencing ecosystem structure and function is well founded, however, spatial data products describing local to regional scale distribution of patterned ground or polygonal tundra geomorphology are largely unavailable. Thus, our understanding of local impacts on regional scale processes (e.g., carbon dynamics) may be limited. We produced two key spatiotemporal datasets spanning the Arctic Coastal Plain of northern Alaska (~60,000 km2) to evaluate climate-geomorphological controls on arctic tundra productivity change, using (1) a novel 30 m classification of polygonal tundra geomorphology and (2) decadal-trends in surface greenness using the Landsat archive (1999–2014). These datasets can be easily integrated and adapted in an array of local to regional applications such as (1) upscaling plot-level measurements (e.g., carbon/energy fluxes), (2) mapping of soils, vegetation, or permafrost, and/or (3) initializing ecosystem biogeochemistry, hydrology, and/or habitat modeling. PMID:29633984

Tundra landform and vegetation productivity trend maps for the Arctic Coastal Plain of northern Alaska.

PubMed

Lara, Mark J; Nitze, Ingmar; Grosse, Guido; McGuire, A David

2018-04-10

Arctic tundra landscapes are composed of a complex mosaic of patterned ground features, varying in soil moisture, vegetation composition, and surface hydrology over small spatial scales (10-100 m). The importance of microtopography and associated geomorphic landforms in influencing ecosystem structure and function is well founded, however, spatial data products describing local to regional scale distribution of patterned ground or polygonal tundra geomorphology are largely unavailable. Thus, our understanding of local impacts on regional scale processes (e.g., carbon dynamics) may be limited. We produced two key spatiotemporal datasets spanning the Arctic Coastal Plain of northern Alaska (~60,000 km 2 ) to evaluate climate-geomorphological controls on arctic tundra productivity change, using (1) a novel 30 m classification of polygonal tundra geomorphology and (2) decadal-trends in surface greenness using the Landsat archive (1999-2014). These datasets can be easily integrated and adapted in an array of local to regional applications such as (1) upscaling plot-level measurements (e.g., carbon/energy fluxes), (2) mapping of soils, vegetation, or permafrost, and/or (3) initializing ecosystem biogeochemistry, hydrology, and/or habitat modeling.

Tundra landform and vegetation productivity trend maps for the Arctic Coastal Plain of northern Alaska

USGS Publications Warehouse

Lara, Mark J.; Nitze, Ingmar; Grosse, Guido; McGuire, A. David

2018-01-01

Arctic tundra landscapes are composed of a complex mosaic of patterned ground features, varying in soil moisture, vegetation composition, and surface hydrology over small spatial scales (10–100 m). The importance of microtopography and associated geomorphic landforms in influencing ecosystem structure and function is well founded, however, spatial data products describing local to regional scale distribution of patterned ground or polygonal tundra geomorphology are largely unavailable. Thus, our understanding of local impacts on regional scale processes (e.g., carbon dynamics) may be limited. We produced two key spatiotemporal datasets spanning the Arctic Coastal Plain of northern Alaska (~60,000 km2) to evaluate climate-geomorphological controls on arctic tundra productivity change, using (1) a novel 30 m classification of polygonal tundra geomorphology and (2) decadal-trends in surface greenness using the Landsat archive (1999–2014). These datasets can be easily integrated and adapted in an array of local to regional applications such as (1) upscaling plot-level measurements (e.g., carbon/energy fluxes), (2) mapping of soils, vegetation, or permafrost, and/or (3) initializing ecosystem biogeochemistry, hydrology, and/or habitat modeling.

Filamentous phages prevalent in Pseudoalteromonas spp. confer properties advantageous to host survival in Arctic sea ice

PubMed Central

Yu, Zi-Chao; Chen, Xiu-Lan; Shen, Qing-Tao; Zhao, Dian-Li; Tang, Bai-Lu; Su, Hai-Nan; Wu, Zhao-Yu; Qin, Qi-Long; Xie, Bin-Bin; Zhang, Xi-Ying; Yu, Yong; Zhou, Bai-Cheng; Chen, Bo; Zhang, Yu-Zhong

2015-01-01

Sea ice is one of the most frigid environments for marine microbes. In contrast to other ocean ecosystems, microbes in permanent sea ice are space confined and subject to many extreme conditions, which change on a seasonal basis. How these microbial communities are regulated to survive the extreme sea ice environment is largely unknown. Here, we show that filamentous phages regulate the host bacterial community to improve survival of the host in permanent Arctic sea ice. We isolated a filamentous phage, f327, from an Arctic sea ice Pseudoalteromonas strain, and we demonstrated that this type of phage is widely distributed in Arctic sea ice. Growth experiments and transcriptome analysis indicated that this phage decreases the host growth rate, cell density and tolerance to NaCl and H2O2, but enhances its motility and chemotaxis. Our results suggest that the presence of the filamentous phage may be beneficial for survival of the host community in sea ice in winter, which is characterized by polar night, nutrient deficiency and high salinity, and that the filamentous phage may help avoid over blooming of the host in sea ice in summer, which is characterized by polar day, rich nutrient availability, intense radiation and high concentration of H2O2. Thus, while they cannot kill the host cells by lysing them, filamentous phages confer properties advantageous to host survival in the Arctic sea ice environment. Our study provides a foremost insight into the ecological role of filamentous phages in the Arctic sea ice ecosystem. PMID:25303713

Vegetation, plant biomass, and net primary productivity patterns in the Canadian Arctic

NASA Astrophysics Data System (ADS)

Gould, W. A.; Raynolds, M.; Walker, D. A.

2003-01-01

We have developed maps of dominant vegetation types, plant functional types, percent vegetation cover, aboveground plant biomass, and above and belowground annual net primary productivity for Canada north of the northern limit of trees. The area mapped covers 2.5 million km2 including glaciers. Ice-free land covers 2.3 million km2 and represents 42% of all ice-free land in the Circumpolar Arctic. The maps combine information on climate, soils, geology, hydrology, remotely sensed vegetation classifications, previous vegetation studies, and regional expertise to define polygons drawn using photo-interpretation of a 1:4,000,000 scale advanced very high resolution radiometer (AVHRR) color infrared image basemap. Polygons are linked to vegetation description, associated properties, and descriptive literature through a series of lookup tables in a graphic information systems (GIS) database developed as a component of the Circumpolar Arctic Vegetation Map (CAVM) project. Polygons are classified into 20 landcover types including 17 vegetation types. Half of the region is sparsely vegetated (<50% vegetation cover), primarily in the High Arctic (bioclimatic subzones A-C). Whereas most (86%) of the estimated aboveground plant biomass (1.5 × 1015 g) and 87% of the estimated above and belowground annual net primary productivity (2.28 × 1014 g yr-1) are concentrated in the Low Arctic (subzones D and E). The maps present more explicit spatial patterns of vegetation and ecosystem attributes than have been previously available, the GIS database is useful in summarizing ecosystem properties and can be easily updated and integrated into circumpolar mapping efforts, and the derived estimates fall within the range of current published estimates.

DNA barcoding of Arctic Ocean holozooplankton for species identification and recognition

NASA Astrophysics Data System (ADS)

Bucklin, Ann; Hopcroft, Russell R.; Kosobokova, Ksenia N.; Nigro, Lisa M.; Ortman, Brian D.; Jennings, Robert M.; Sweetman, Christopher J.

2010-01-01

Zooplankton species diversity and distribution are important measures of environmental change in the Arctic Ocean, and may serve as 'rapid-responders' of climate-induced changes in this fragile ecosystem. The scarcity of taxonomists hampers detailed and up-to-date monitoring of these patterns for the rarer and more problematic species. DNA barcodes (short DNA sequences for species recognition and discovery) provide an alternative approach to accurate identification of known species, and can speed routine analysis of zooplankton samples. During 2004-2008, zooplankton samples were collected during cruises to the central Arctic Ocean and Chukchi Sea. A ˜700 base-pair region of the mitochondrial cytochrome oxidase I (mtCOI) gene was amplified and sequenced for 82 identified specimens of 41 species, including cnidarians (six hydrozoans, one scyphozoan), arthropod crustaceans (five amphipods, 24 copepods, one decapod, and one euphausiid); two chaetognaths; and one nemertean. Phylogenetic analysis used the Neighbor-Joining algorithm with Kimura-2-Parameter (K-2-P) distances, with 1000-fold bootstrapping. K-2-P genetic distances between individuals of the same species ranged from 0.0 to 0.2; genetic distances between species ranged widely from 0.1 to 0.7. The mtCOI gene tree showed monophyly (at 100% bootstrap value) for each of the 26 species for which more than one individual was analyzed. Of seven genera for which more than one species was analyzed, four were shown to be monophyletic; three genera were not resolved. At higher taxonomic levels, only the crustacean order Copepoda was resolved, with bootstrap value of 83%. The mtCOI barcodes accurately discriminated and identified known species of 10 taxonomic groups of Arctic Ocean holozooplankton. A comprehensive DNA barcode database for the estimated 300 described species of Arctic holozooplankton will allow rapid assessment of species diversity and distribution in this climate-vulnerable ocean ecosystem.

Pan-Arctic Distribution of Bioavailable Dissolved Organic Matter and Linkages With Productivity in Ocean Margins

NASA Astrophysics Data System (ADS)

Shen, Yuan; Benner, Ronald; Kaiser, Karl; Fichot, Cédric G.; Whitledge, Terry E.

2018-02-01

Rapid environmental changes in the Arctic Ocean affect plankton productivity and the bioavailability of dissolved organic matter (DOM) that supports microbial food webs. We report concentrations of dissolved organic carbon (DOC) and yields of amino acids (indicators of labile DOM) in surface waters across major Arctic margins. Concentrations of DOC and bioavailability of DOM showed large pan-Arctic variability that corresponded to varying hydrological conditions and ecosystem productivity, respectively. Widespread hot spots of labile DOM were observed over productive inflow shelves (Chukchi and Barents Seas), in contrast to oligotrophic interior margins (Kara, Laptev, East Siberian, and Beaufort Seas). Amino acid yields in outflow gateways (Canadian Archipelago and Baffin Bay) indicated the prevalence of semilabile DOM in sea ice covered regions and sporadic production of labile DOM in ice-free waters. Comparing these observations with surface circulation patterns indicated varying shelf subsidies of bioavailable DOM to Arctic deep basins.

Genomics of Arctic cod

USGS Publications Warehouse

Wilson, Robert E.; Sage, George K.; Sonsthagen, Sarah A.; Gravley, Megan C.; Menning, Damian; Talbot, Sandra L.

2017-01-01

The Arctic cod (Boreogadus saida) is an abundant marine fish that plays a vital role in the marine food web. To better understand the population genetic structure and the role of natural selection acting on the maternally-inherited mitochondrial genome (mitogenome), a molecule often associated with adaptations to temperature, we analyzed genetic data collected from 11 biparentally-inherited nuclear microsatellite DNA loci and nucleotide sequence data from from the mitochondrial DNA (mtDNA) cytochrome b (cytb) gene and, for a subset of individuals, the entire mitogenome. In addition, due to potential of species misidentification with morphologically similar Polar cod (Arctogadus glacialis), we used ddRAD-Seq data to determine the level of divergence between species and identify species-specific markers. Based on the findings presented here, Arctic cod across the Pacific Arctic (Bering, Chukchi, and Beaufort Seas) comprise a single panmictic population with high genetic diversity compared to other gadids. High genetic diversity was indicated across all 13 protein-coding genes in the mitogenome. In addition, we found moderate levels of genetic diversity in the nuclear microsatellite loci, with highest diversity found in the Chukchi Sea. Our analyses of markers from both marker classes (nuclear microsatellite fragment data and mtDNA cytb sequence data) failed to uncover a signal of microgeographic genetic structure within Arctic cod across the three regions, within the Alaskan Beaufort Sea, or between near-shore or offshore habitats. Further, data from a subset of mitogenomes revealed no genetic differentiation between Bering, Chukchi, and Beaufort seas populations for Arctic cod, Saffron cod (Eleginus gracilis), or Walleye pollock (Gadus chalcogrammus). However, we uncovered significant differences in the distribution of microsatellite alleles between the southern Chukchi and central and eastern Beaufort Sea samples of Arctic cod. Finally, using ddRAD-Seq data, we

An arctic community of symbiotic fungi assembled by long-distance dispersers: phylogenetic diversity of ectomycorrhizal basidiomycetes in Svalbard based on soil and sporocarp DNA

Treesearch

J. Geml; I. Timling; C.H. Robinson; N. Lennon; H.C. Nusbaum; C. Brochmann; M.E. Noordeloos; D.L. Taylor

2011-01-01

Current evidence from temperate studies suggests that ectomycorrhizal (ECM) fungi require overland routes for migration because of their obligate symbiotic associations with woody plants. Despite their key roles in arctic ecosystems, the phylogenetic diversity and phylogeography of arctic ECM fungi remains little known. Here we assess the phylogenetic diversity of ECM...

Improving the representation of Arctic photosynthesis in Earth system models

NASA Astrophysics Data System (ADS)

Rogers, A.; Serbin, S.; Ely, K.; Sloan, V. L.; Wyatt, R. A.; Kubien, D. S.; Ali, A. A.; Xu, C.; Wullschleger, S. D.

2015-12-01

The primary goal of Earth System Models (ESMs) is to improve understanding and projection of future global change. In order to do this they must accurately represent the carbon fluxes associated with the terrestrial carbon cycle. Although Arctic carbon fluxes are small - relative to global carbon fluxes - uncertainty is large. As part of a multidisciplinary project to improve the representation of the Arctic in ESMs (Next Generation Ecosystem Experiments - Arctic) we are examining the photosynthetic parameterization of the Arctic plant functional type (PFT) in ESMs. Photosynthetic CO2 uptake is well described by the Farquhar, von Caemmerer and Berry (FvCB) model of photosynthesis. Most ESMs use a derivation of the FvCB model to calculate gross primary productivity. Two key parameters required by the FvCB model are an estimate of the maximum rate of carboxylation by the enzyme Rubisco (Vc,max) and the maximum rate of electron transport (Jmax). In ESMs the parameter Vc,max is usually fixed for a given PFT. Only four ESMs currently have an explicit Arctic PFT and the data used to derive Vc,max for the Arctic PFT in these models relies on small data sets and unjustified assumptions. We examined the derivation of Vc,max and Jmax in current Arctic PFTs and estimated Vc,max and Jmax for 7 species representing both dominant vegetation and key Arctic PFTs growing on the Barrow Environmental Observatory, Barrow, AK. The values of Vc,max currently used to represent Arctic PFTs in ESMs are 70% lower than the values we measured in these species. Examination of the derivation of Vc,max in ESMs identified that the cause of the relatively low Vc,max value was the result of underestimating both the leaf N content and the investment of that N in Rubisco. Contemporary temperature response functions for Vc,max also appear to underestimate Vc,max at low temperature. ESMs typically use a single multiplier (JVratio) to convert Vc,max to Jmax for all PFTs. We found that the JVratio of

Recent climate warming drives ecological change in a remote high-Arctic lake.

PubMed

Woelders, Lineke; Lenaerts, Jan T M; Hagemans, Kimberley; Akkerman, Keechy; van Hoof, Thomas B; Hoek, Wim Z

2018-05-01

The high Arctic is the fastest warming region on Earth, evidenced by extreme near-surface temperature increase in non-summer seasons, recent rapid sea ice decline and permafrost melting since the early 1990's. Understanding the impact of climate change on the sensitive Arctic ecosystem to climate change has so far been hampered by the lack of time-constrained, high-resolution records and by implicit climate data analyses. Here, we show evidence of sharp growth in freshwater green algae as well as distinct diatom assemblage changes since ~1995, retrieved from a high-Arctic (80 °N) lake sediment record on Barentsøya (Svalbard). The proxy record approaches an annual to biennial resolution. Combining remote sensing and in-situ climate data, we show that this ecological change is concurrent with, and is likely driven by, the atmospheric warming and a sharp decrease in the length of the sea ice covered period in the region, and throughout the Arctic. Moreover, this research demonstrates the value of palaeoclimate records in pristine environments for supporting and extending instrumental records. Our results reinforce and extend observations from other sites that the high Arctic has already undergone rapid ecological changes in response to on-going climate change, and will continue to do so in the future.

Future Climate Change Will Favour Non-Specialist Mammals in the (Sub)Arctics

PubMed Central

Hof, Anouschka R.; Jansson, Roland; Nilsson, Christer

2012-01-01

Arctic and subarctic (i.e., [sub]arctic) ecosystems are predicted to be particularly susceptible to climate change. The area of tundra is expected to decrease and temperate climates will extend further north, affecting species inhabiting northern environments. Consequently, species at high latitudes should be especially susceptible to climate change, likely experiencing significant range contractions. Contrary to these expectations, our modelling of species distributions suggests that predicted climate change up to 2080 will favour most mammals presently inhabiting (sub)arctic Europe. Assuming full dispersal ability, most species will benefit from climate change, except for a few cold-climate specialists. However, most resident species will contract their ranges if they are not able to track their climatic niches, but no species is predicted to go extinct. If climate would change far beyond current predictions, however, species might disappear. The reason for the relative stability of mammalian presence might be that arctic regions have experienced large climatic shifts in the past, filtering out sensitive and range-restricted taxa. We also provide evidence that for most (sub)arctic mammals it is not climate change per se that will threaten them, but possible constraints on their dispersal ability and changes in community composition. Such impacts of future changes in species communities should receive more attention in literature. PMID:23285098

Genetic diversity and connectivity within Mytilus spp. in the subarctic and Arctic.

PubMed

Mathiesen, Sofie Smedegaard; Thyrring, Jakob; Hemmer-Hansen, Jakob; Berge, Jørgen; Sukhotin, Alexey; Leopold, Peter; Bekaert, Michaël; Sejr, Mikael Kristian; Nielsen, Einar Eg

2017-01-01

Climate changes in the Arctic are predicted to alter distributions of marine species. However, such changes are difficult to quantify because information on present species distribution and the genetic variation within species is lacking or poorly examined. Blue mussels, Mytilus spp., are ecosystem engineers in the coastal zone globally. To improve knowledge of distribution and genetic structure of the Mytilus edulis complex in the Arctic, we analyzed 81 SNPs in 534 Mytilus spp. individuals sampled at 13 sites to provide baseline data for distribution and genetic variation of Mytilus mussels in the European Arctic. Mytilus edulis was the most abundant species found with a clear genetic split between populations in Greenland and the Eastern Atlantic. Surprisingly, analyses revealed the presence of Mytilus trossulus in high Arctic NW Greenland (77°N) and Mytilus galloprovincialis or their hybrids in SW Greenland, Svalbard, and the Pechora Sea. Furthermore, a high degree of hybridization and introgression between species was observed. Our study highlights the importance of distinguishing between congener species, which can display local adaptation and suggests that information on dispersal routes and barriers is essential for accurate predictions of regional susceptibility to range expansions or invasions of boreal species in the Arctic.

Arctic foxes, lemmings, and canada goose nest survival at cape Churchill, Manitoba

USGS Publications Warehouse

Reiter, M.E.; Andersen, D.E.

2011-01-01

We examined factors influencing Canada Goose (Branta canadensis interior) annual nest success, including the relative abundance of collared lemmings (Dicrostonyx richardsoni), arctic fox (Alopex lagopus) den occupancy, nest density, and spring phenology using data collected during annual Canada Goose breeding area surveys at Cape Churchill, Manitoba. Nest density and arctic fox den occupancy strongly influenced Canada Goose nest success. High nest density resulted in higher nest success and high den occupancy reduced nest success. Nest success was not influenced by lemming abundance in the current or previous year as predicted by the "bird-lemming" hypothesis. Reducing arctic fox abundance through targeted management increased nest survival of Canada Geese; a result that further emphasizes the importance of arctic fox as nest predators in this system. The spatial distribution of nest predators, at least for dispersed-nesting geese, may be most important for nest survival, regardless of the abundance of small mammals in the local ecosystem. Further understanding of the factors influencing the magnitude and variance in arctic fox abundance in this region, and the spatial scale at which these factors are realized, is necessary to fully explain predator-prey-alternative prey dynamics in this system. ?? 2011 by the Wilson Ornithological Society.

Projected changes in diverse ecosystems from climate warming and biophysical drivers in northwest Alaska

Treesearch

Mark Torre Jorgenson; Bruce G. Marcot; David K. Swanson; Janet C. Jorgenson; Anthony R. DeGange

2015-01-01

Climate warming affects arctic and boreal ecosystems by interacting with numerous biophysical factors across heterogeneous landscapes. To assess potential effects of warming on diverse local-scale ecosystems (ecotypes) across northwest Alaska, we compiled data on historical areal changes over the last 25–50 years. Based on historical rates of change relative to time...

A Comprehensive Modeling Approach Towards Understanding and Prediction of the Alaskan Coastal System Response to Changes in an Ice-diminished Arctic

DTIC Science & Technology

2008-01-01

signature of an apparent increased contribution of diazotrophs to Arctic primary production was also recorded in muscle tissue of bowheads, harvested from...Arctic temperatures of the Beaufort Sea need not be invoked. Instead, the diazotrophic marker of particulate nitrogen within bowhead whale baleen...dinoflagellates, microflagellates, and diazotrophs from downstream boreal and subtropical ecosystems. Furthermore, at lower latitudes, Saharan dust plumes in

Changing Arctic snow cover: A review of recent developments and assessment of future needs for observations, modelling, and impacts.

PubMed

Bokhorst, Stef; Pedersen, Stine Højlund; Brucker, Ludovic; Anisimov, Oleg; Bjerke, Jarle W; Brown, Ross D; Ehrich, Dorothee; Essery, Richard L H; Heilig, Achim; Ingvander, Susanne; Johansson, Cecilia; Johansson, Margareta; Jónsdóttir, Ingibjörg Svala; Inga, Niila; Luojus, Kari; Macelloni, Giovanni; Mariash, Heather; McLennan, Donald; Rosqvist, Gunhild Ninis; Sato, Atsushi; Savela, Hannele; Schneebeli, Martin; Sokolov, Aleksandr; Sokratov, Sergey A; Terzago, Silvia; Vikhamar-Schuler, Dagrun; Williamson, Scott; Qiu, Yubao; Callaghan, Terry V

2016-09-01

Snow is a critically important and rapidly changing feature of the Arctic. However, snow-cover and snowpack conditions change through time pose challenges for measuring and prediction of snow. Plausible scenarios of how Arctic snow cover will respond to changing Arctic climate are important for impact assessments and adaptation strategies. Although much progress has been made in understanding and predicting snow-cover changes and their multiple consequences, many uncertainties remain. In this paper, we review advances in snow monitoring and modelling, and the impact of snow changes on ecosystems and society in Arctic regions. Interdisciplinary activities are required to resolve the current limitations on measuring and modelling snow characteristics through the cold season and at different spatial scales to assure human well-being, economic stability, and improve the ability to predict manage and adapt to natural hazards in the Arctic region.

Changing Arctic Snow Cover: A Review of Recent Developments and Assessment of Future Needs for Observations, Modelling, and Impacts

NASA Technical Reports Server (NTRS)

Bokhorst, Stef; Pedersen, Stine Hojlund; Brucker, Ludovic; Anisimov, Oleg; Bjerke, Jarle W.; Brown, Ross D.; Ehrich, Dorothee; Essery, Richard L. H.; Heilig, Achim; Ingvander, Susanne;

Use of a cable-based system for observing the heterogeneity of vegetation communities in arctic tundra

NASA Astrophysics Data System (ADS)

Ahrends, H. E.; Oberbauer, S. F.; Tweedie, C.; Hollister, R. D.

2010-12-01

Knowledge of changing tundra vegetation and its response to climate variability is critical for understanding the land-atmosphere-interactions for the Arctic and the global system. However, vegetation characteristics, such as phenology, structure and species composition, are characterized by an extreme heterogeneity at a small scale. Manual observations of these variables are highly time-consuming, labor intensive, subjective, and disturbing to the vegetation. In contrast, recently developed robotic systems (networked infomechanical systems, NIMS) allow for performing non-intrusive spatially integrated measurements of vegetation communities. Within the ITEX (International Tundra Experiment) AON (Arctic Observation Network) project we installed a cable-based sensor system, running over a transect of approximately 50 m length and 2 m width, at two long-term arctic research sites in Alaska. The trolley was initially equipped with instruments recording the distance to vegetation canopy, up- and downwelling short- and longwave radiation, air and surface temperature and spectral reflection. We aim to study the thermal and spectral response of the vegetation communities over a wide range of ecosystem types. We expect that automated observations, covering the spatial heterogeneity of vegetation and surface characteristics, can give a deeper insight in ecosystem functioning and vegetation response to climate. The data can be used for scaling up vegetation characteristics derived from manual measurements and for linking them to aircraft and satellite data and to carbon, water and surface energy budgets measured at the ecosystem scale. Sampling errors due to cable sag are correctable and effects of wind-driven movements can be offset by repeat measurements. First hand-pulled test measurements during summer 2010 show strong heterogeneity of the observation parameters and a variable spectral and thermal response of the plants within the transects. Differences support the

Seasonal greening of an Arctic ecosystem in response to early snowmelt and climate warming: do plant community responses differ from species responses?

NASA Astrophysics Data System (ADS)

Steltzer, H.; Weintraub, M. N.; Sullivan, P.; Wallenstein, M. D.; Schimel, J.; Darrouzet-Nardi, A.; Shory, R.; Livensperger, C.; Melle, C.; Segal, A. D.; Daly, K.; Tsosie, T.

2011-12-01

In the Arctic and around the world, earlier plant growth and a longer growing season are indications that warmer temperatures or other global changes are changing the seasonality of the Earth's ecosystems. These changes in plant life histories have multi-trophic level consequences that affect food webs and biogeochemical cycles. Both the response of the plant community and of individual species can affect food and habitat resources for animals or nutrient resources for microbes. Our aim was to determine if the response of an Arctic plant community differs from individual species responses to climate change. For two years in an early snowmelt and climate warming experiment in moist acidic tussock tundra, we observed the seasonal greening of the ecosystem through near-surface measurements of surface greenness and through direct observations of the timing of plant life history events for five to eight common species that differ in growth form. In 2010 when snowmelt was accelerated by 4 days, earlier snowmelt alone or in combination with climate warming extended the life history of the dominant graminoids (E. vaginatum and C. bigelowii) and willow (S. pulchra) by 3 to 4 days. For these species, new leaf production began earlier, while the timing of senescence was similar to the controls. The effect of earlier snowmelt on the life histories of birch (B. nana) and cranberry (V. vitis-idaea) was less, but warming alone tended to increase life history duration. Warming led to earlier leaf expansion for birch and delayed senescence for cranberry. We found that the onset of greening for the plant community began four days earlier, due to the earlier loss of snow cover, and that warming accelerated the rate of greening. Peak season ended 4 days earlier in response to earlier snowmelt and climate warming, due to earlier senescence by birch. In 2011, our manipulation of the snowpack by increasing energy absorption accelerated snowmelt by 15 days and control plots were snowfree

Response of an arctic predator guild to collapsing lemming cycles

PubMed Central

Schmidt, Niels M.; Ims, Rolf A.; Høye, Toke T.; Gilg, Olivier; Hansen, Lars H.; Hansen, Jannik; Lund, Magnus; Fuglei, Eva; Forchhammer, Mads C.; Sittler, Benoit

2012-01-01

Alpine and arctic lemming populations appear to be highly sensitive to climate change, and when faced with warmer and shorter winters, their well-known high-amplitude population cycles may collapse. Being keystone species in tundra ecosystems, changed lemming dynamics may convey significant knock-on effects on trophically linked species. Here, we analyse long-term (1988–2010), community-wide monitoring data from two sites in high-arctic Greenland and document how a collapse in collared lemming cyclicity affects the population dynamics of the predator guild. Dramatic changes were observed in two highly specialized lemming predators: snowy owl and stoat. Following the lemming cycle collapse, snowy owl fledgling production declined by 98 per cent, and there was indication of a severe population decline of stoats at one site. The less specialized long-tailed skua and the generalist arctic fox were more loosely coupled to the lemming dynamics. Still, the lemming collapse had noticeable effects on their reproductive performance. Predator responses differed somewhat between sites in all species and could arise from site-specific differences in lemming dynamics, intra-guild interactions or subsidies from other resources. Nevertheless, population extinctions and community restructuring of this arctic endemic predator guild are likely if the lemming dynamics are maintained at the current non-cyclic, low-density state. PMID:22977153

Response of an arctic predator guild to collapsing lemming cycles.

PubMed

Schmidt, Niels M; Ims, Rolf A; Høye, Toke T; Gilg, Olivier; Hansen, Lars H; Hansen, Jannik; Lund, Magnus; Fuglei, Eva; Forchhammer, Mads C; Sittler, Benoit

2012-11-07

Alpine and arctic lemming populations appear to be highly sensitive to climate change, and when faced with warmer and shorter winters, their well-known high-amplitude population cycles may collapse. Being keystone species in tundra ecosystems, changed lemming dynamics may convey significant knock-on effects on trophically linked species. Here, we analyse long-term (1988-2010), community-wide monitoring data from two sites in high-arctic Greenland and document how a collapse in collared lemming cyclicity affects the population dynamics of the predator guild. Dramatic changes were observed in two highly specialized lemming predators: snowy owl and stoat. Following the lemming cycle collapse, snowy owl fledgling production declined by 98 per cent, and there was indication of a severe population decline of stoats at one site. The less specialized long-tailed skua and the generalist arctic fox were more loosely coupled to the lemming dynamics. Still, the lemming collapse had noticeable effects on their reproductive performance. Predator responses differed somewhat between sites in all species and could arise from site-specific differences in lemming dynamics, intra-guild interactions or subsidies from other resources. Nevertheless, population extinctions and community restructuring of this arctic endemic predator guild are likely if the lemming dynamics are maintained at the current non-cyclic, low-density state.

Aquatic Ecosystems, Water Quality, and Global Change: Challenges of Conducting Multi-Stressor Vulnerability Assessments (Final Report)

EPA Science Inventory

EPA announced the availability of the final report, Aquatic Ecosystems and Global Change: The Challenges of conducting Multi-Stressor Global Change Vulnerability Assessments. This report investigates the issues and challenges associated with identifying, calculating, and ...

Comparing pristine and depleted ecosystems: The Sørfjord, Norway versus the Gulf of St. Lawrence, Canada. Effects of intense fisheries on marine ecosystems

NASA Astrophysics Data System (ADS)

Morissette, Lyne; Pedersen, Torstein; Nilsen, Marianne

2009-04-01

The Sørfjord, Norway, and the Gulf of St. Lawrence, Canada, are two sub-arctic ecosystems with similar trophic structure. However, in the Gulf of St. Lawrence, severe exploitation of groundfish stocks has lead to important shifts in the trophic structure. In the Sørfjord, the situation is different: fishing pressure is much lighter. Our hypothesis is that overexploitation leads to changes in the trophic structure and severely alters the resilience of ecosystems. Based on the same modelling approach ( Ecopath with Ecosim) the food web structure was compared, using different ecosystem indicators. Patterns of food web structure and trophodynamics were contrasted. Cod was the keystone species in both ecosystems, and forage fish were also important. Even after similar environmental changes in both ecosystems, and after a reduction of fishing pressure in the Gulf of St. Lawrence, there is no recovery of cod stocks in this ecosystem. In the Sørfjord, after different perturbations (but not from the fishery), the ecosystem seems to return to its equilibrium.

Will the Arctic Land Surface become Wetter or Drier in Response to a Warming Climate

NASA Astrophysics Data System (ADS)

Hinzman, L. D.; Rawlins, M.; Serreze, M.; Vorosmarty, C. J.; Walsh, J. E.

2015-12-01

There is much concern about a potentially "accelerated" hydrologic cycle, with associated extremes in weather and climate-related phenomena. Whether this translates into wetter or drier conditions across arctic landscapes remains an open question. Arctic ecosystems differ substantially from those in temperate regions, largely due to the interactions of extremes in climate and land surface characteristics. Ice-rich permafrost prevents percolation of rainfall or snowmelt water, often maintaining a moist to saturated active layer where the permafrost table is shallow. Permafrost may also block the lateral movement of groundwater, and act as a confining unit for water in sub- or intra-permafrost aquifers. However, as permafrost degrades, profound changes in interactions between groundwater and surface water occur that affect the partitioning among the water balance components with subsequent impacts to the surface energy balance and essential ecosystem processes. Most simulations of arctic climate project sustained increases in temperature and gradual increases in precipitation over the 21st century. However, most climatic models do not correctly represent the essential controls that permafrost exerts on hydrological, ecological, and climatological processes. If warming continues as projected, we expect large-scale changes in surface hydrology as permafrost degrades. Where groundwater gradients are downward (i.e. surface water will infiltrate to subsurface groundwater), as in most cases, we may expect improved drainage and drier soils, which would result in reduced evaporation and transpiration (ET). In some special cases, where the groundwater gradient is upward (as in many wetlands or springs) surface soils may become wetter or inundated as permafrost degrades. Further, since soil moisture is a primary factor controlling ecosystem processes, interactions between ecosystems, GHG emissions, and high-latitude climate must also be considered highly uncertain. These inter

Poles apart: the "bipolar" pteropod species Limacina helicina is genetically distinct between the Arctic and Antarctic oceans.

PubMed

Hunt, Brian; Strugnell, Jan; Bednarsek, Nina; Linse, Katrin; Nelson, R John; Pakhomov, Evgeny; Seibel, Brad; Steinke, Dirk; Würzberg, Laura

2010-03-23

The shelled pteropod (sea butterfly) Limacina helicina is currently recognised as a species complex comprising two sub-species and at least five "forma". However, at the species level it is considered to be bipolar, occurring in both the Arctic and Antarctic oceans. Due to its aragonite shell and polar distribution L. helicina is particularly vulnerable to ocean acidification. As a key indicator of the acidification process, and a major component of polar ecosystems, L. helicina has become a focus for acidification research. New observations that taxonomic groups may respond quite differently to acidification prompted us to reassess the taxonomic status of this important species. We found a 33.56% (+/-0.09) difference in cytochrome c oxidase subunit I (COI) gene sequences between L. helicina collected from the Arctic and Antarctic oceans. This degree of separation is sufficient for ordinal level taxonomic separation in other organisms and provides strong evidence for the Arctic and Antarctic populations of L. helicina differing at least at the species level. Recent research has highlighted substantial physiological differences between the poles for another supposedly bipolar pteropod species, Clione limacina. Given the large genetic divergence between Arctic and Antarctic L. helicina populations shown here, similarly large physiological differences may exist between the poles for the L. helicina species group. Therefore, in addition to indicating that L. helicina is in fact not bipolar, our study demonstrates the need for acidification research to take into account the possibility that the L. helicina species group may not respond in the same way to ocean acidification in Arctic and Antarctic ecosystems.

Long-term Nutrient Fertilization Increases CO2 Loss in Arctic Tundra

NASA Astrophysics Data System (ADS)

Graham, L. M.; Natali, S.; Rastetter, E. B.; Shaver, G. R.; Risk, D. A.; Loranty, M. M.; Jastrow, J. D.

2015-12-01

As anthropogenic climate change warms the Arctic, organic carbon (C) trapped in permafrost is at an increased risk of being released to the atmosphere as carbon dioxide (CO2). At the same time, higher rates of decomposition may increase nutrient availability and enhance plant growth, leading to an uptake of C that may offset respiratory losses. Arctic tundra ecosystems are highly nitrogen (N) limited, and the indirect effects of warming on nutrient availability will be the most likely outcome of increased temperature on plant productivity. This study aims to understand the effects of nutrient addition on arctic CO2 and H2O exchange in a tundra ecosystem at Toolik Lake Field Station, Alaska. The nutrient addition experiment, which began in 2006, is comprised of 7 fertilization treatments: 0.5, 1, 2, 5, and 10 g m-2 of N as NO3- and NH4+ (1:1) with 0.25, 0.5, 1, 2.5, and 5 g m-2 of phosphorus as PO43-; 5 g m-2 of N as NO3-; 5 g m-2 of N as NH4+, and one control plot. Plot-level CO2 and H2O exchange was measured at 5 light levels 7 times over a four-week period in June and July 2015. We measured ecosystem CO2 and H2O exchange using a rectangular plexiglass chamber (0.49 m2) that was connected to an infrared gas analyzer (LI-840). Other ecosystem variables measured include thaw depth, soil moisture and temperature, and normalized difference vegetation index. After 10 years of nutrient addition, fertilization significantly altered ecosystem C cycling. Soil respiration was greatest in the highest fertilization treatment (2.97 μmol m-2 s-1), increasing linearly with nutrient level at a rate of 0.133 μmol m-2 s-1 per g m-2 of N added (R2=0.914). Net CO2 uptake was greatest under highest fertilization (-2.06 μmol m-2 s-1), decreasing linearly with nutrient addition at a rate of -0.068 μmol m-2 s-1 per g m-2 of N added (R2=0.687). These results suggest that as nutrients become more available under a warmer climate, plant productivity increases may not offset respiratory

Atmospheric mercury in the Canadian Arctic. Part II: insight from modeling.

PubMed

Dastoor, Ashu; Ryzhkov, Andrew; Durnford, Dorothy; Lehnherr, Igor; Steffen, Alexandra; Morrison, Heather

2015-03-15

A review of mercury in the Canadian Arctic with a focus on field measurements is presented in part I (see Steffen et al., this issue). Here we provide insights into the dynamics of mercury in the Canadian Arctic from new and published mercury modeling studies using Environment Canada's mercury model. The model simulations presented in this study use global anthropogenic emissions of mercury for the period 1995-2005. The most recent modeling estimate of the net gain of mercury from the atmosphere to the Arctic Ocean is 75 Mg year(-1) and the net gain to the terrestrial ecosystems north of 66.5° is 42 Mg year(-1). Model based annual export of riverine mercury from North American, Russian and all Arctic watersheds to the Arctic Ocean are in the range of 2.8-5.6, 12.7-25.4 and 15.5-31.0 Mg year(-1), respectively. Analysis of long-range transport events of Hg at Alert and Little Fox Lake monitoring sites indicates that Asia contributes the most ambient Hg to the Canadian Arctic followed by contributions from North America, Russia, and Europe. The largest anthropogenic Hg deposition to the Canadian Arctic is from East Asia followed by Europe (and Russia), North America, and South Asia. An examination of temporal trends of Hg using the model suggests that changes in meteorology and changes in anthropogenic emissions equally contribute to the decrease in surface air elemental mercury concentrations in the Canadian Arctic with an overall decline of ~12% from 1990 to 2005. A slow increase in net deposition of Hg is found in the Canadian Arctic in response to changes in meteorology. Changes in snowpack and sea-ice characteristics and increase in precipitation in the Arctic related with climate change are found to be primary causes for the meteorology-related changes in air concentrations and deposition of Hg in the region. The model estimates that under the emissions reduction scenario of worldwide implementation of the best emission control technologies by 2020, mercury

A HYPOTHESIS-DRIVEN FRAMEWORK FOR ASSESSING CLIMATE INDUCED CHANGES IN COASTAL FINAL ECOSYSTEM GOODS AND SERVICES

EPA Science Inventory

Understanding how climate change will alter the availability of coastal final ecosystem goods and services (FEGS; such as food provisioning from fisheries, property protection, and recreation) has significant implications for coastal planning and the development of adaptive manag...

Production and Cycling of Methylmercury in High Arctic Wetland Ponds

NASA Astrophysics Data System (ADS)

Lehnherr, I.; St. Louis, V. L.

2010-12-01

Some species of freshwater fish in the Canadian high Arctic contain levels of methylmercury (MeHg) that pose health risks to the northern Inuit peoples that harvest these species as a traditional food source. In temperate regions, wetlands are known natural sites of MeHg production and hence significant MeHg sources to downstream ecosystems. However, the importance of wetlands to Hg methylation in the Arctic is unclear and the sources of MeHg to arctic freshwater ecosystems are still largely unidentified. Our research is demonstrating that some shallow and warm wetland ponds on the Arctic landscape contain high MeHg concentrations compared to nearby deep and cold lakes. We used a mass-balance approach to measure the net in-pond production of MeHg in two warm wetland ponds (Ponds 1 and 2) near Lake Hazen, Ellesmere Island, Nunavut (81° N latitude). We quantified external inputs and outputs of MeHg to and from the ponds, as well as the accumulation of MeHg in the water column during the summers of 2005 and 2008. Any changes in water column MeHg concentrations that could not be accounted for by external inputs or sinks were attributed to in-pond production. The principal external input and sink of MeHg was, respectively, wet atmospheric deposition and water-column MeHg photodemethylation. For 2005, we estimate that the net flux of MeHg from sediments into the water column was 0.015 μg m-2 d-1 in Pond 1 and 0.0016 μg m-2 d-1 in Pond 2. Compared to sediment-water MeHg fluxes measured in Alaskan tundra lakes (0.0015-0.0045 μg m-2 d-1), Pond 1 sediments are a greater source of MeHg while Pond 2 is similar to the Alaskan lakes. Furthermore, the accumulation of MeHg in the water column of Pond 1 (0.0061 μg m-2 d-1) was similar to the net yield of MeHg from temperate boreal wetlands (0.0005-0.006 μg m-2 d-1), demonstrating that these Arctic wetlands are important sites of MeHg production. In addition, we used mercury stable-isotope tracers to quantify methylation and

Defining ecospace of Arctic marine food webs using a novel quantitative approach

NASA Astrophysics Data System (ADS)

Gale, M.; Loseto, L. L.

2011-12-01

The Arctic is currently facing unprecedented change with developmental, physical and climatological changes. Food webs within the marine Arctic environment are highly susceptible to anthropogenic stressors and have thus far been understudied. Stable isotopes, in conjunction with a novel set of metrics, may provide a framework that allows us to understand which areas of the Arctic are most vulnerable to change. The objective of this study was to use linear distance metrics applied to stable isotopes to a) define and quantify four Arctic marine food webs in ecospace; b) enable quantifiable comparisons among the four food webs and with other ecosystems; and, c) evaluate vulnerability of the four food webs to anthropogenic stressors such as climate change. The areas studied were Hudson Bay, Beaufort Sea, Lancaster Sound and North Water Polynya. Each region was selected based on the abundance of previous research and published and available stable isotope data in peer-review literature. We selected species to cover trophic levels ranging from particulate matter to polar bears with consideration of pelagic, benthic and ice-associated energy pathways. We interpret higher diversity in baseline carbon energy as signifying higher stability in food web structure. Based on this, the Beaufort Sea food web had the highest stability; the Beaufort Sea food web occupied the largest isotopic niche space and was supported by multiple carbon sources. Areas with top-down control system, such as Lancaster Sound and North Water Polynya, would be the first to experience an increase in trophic redundancy and possible hardships from external stressors, as they have fewer basal carbon sources and greater numbers of mid-high level consumers. We conclude that a diverse carbon energy based ecosystem such as the Beaufort Sea and Hudson Bay regions are more resilient to change than a top down control system.

A new Arctic 25-year Altimetric Sea-level Record (1992-2016) and Initial look at Arctic Sea Level Budget Closure

NASA Astrophysics Data System (ADS)

Andersen, O. B.; Passaro, M.; Benveniste, J.; Piccioni, G.

2016-12-01

A new initiative within the ESA Sea Level Climate Change initiative (SL-cci) framework to improve the Arctic sea level record has been initiated as a combined effort to reprocess and retrack past altimetry to create a 25-year combined sea level record for sea level research studies. One of the objectives is to retracked ERS-2 dataset for the high latitudes based on the ALES retracking algorithm through adapting the ALES retracker for retracking of specular surfaces (leads). Secondly a reprocessing using tailored editing to Arctic Conditions will be carried out also focusing on the merging of the multi-mission data. Finally an effort is to combine physical and empirical retracked sea surface height information to derive an experimental spatio-temporal enhanced sea level product for high latitude. The first results in analysing Arctic Sea level variations on annual inter-annual scales for the 1992-2015 from a preliminar version of this dataset is presented. By including the GRACE water storage estimates and NOAA halo- and thermo-steric sea level variatios since 2002 a preliminary attempt to close the Arctic Sea level budget is presented here. Closing the Arctic sea level budget is by no mean trivial as both steric data and satellite altimetry is both sparse temporally and limited geographically.

Arctic Riverine CDOM and its effects on the Polar Marine Light Field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orandle, Zoe Ann; Weijer, Wilbert; Elliott, Scott M.

2016-09-28

It is well-known that CDOM (Chromophoric Dissolved Organic Matter) can have a significant effect on biological activity in the photic zones of aquatic ecosystems. However, the extent of CDOM’s interference with biological activity is not well-known. We examined this issue in great detail in the mixed surface layer of the Arctic Ocean. We studied the impacts of CDOM’s light attenuation on Arctic phytoplankton populations to discover if riverine CDOM’s presence in the Arctic ocean could inhibit and possibly prevent local phytoplankton populations from performing photosynthesis. We incorporated biogeochemistry concepts and data with oceanographic models and calculations to approach the problem.more » The results showed that riverine CDOM can indeed significantly impact the productivity of phytoplankton populations during the spring and summer months near the major Arctic river mouths we chose to examine. Although our study was detailed and inclusive of many variables, the issue of CDOM’s light attenuation and its effects on phytoplankton populations must be explored on a global scale to help understand if riverine CDOM could prove disastrous for phytoplankton populations.« less

Networking 2.0: Expanding your collaboration circles through the Interagency Arctic Research Policy Committee (IARPC)

NASA Astrophysics Data System (ADS)

Rohde, J. A.; Bowden, S.; Stephenson, S. N.; Starkweather, S.

2015-12-01

The Interagency Arctic Research Policy Committee (IARPC) envisions a prosperous, sustainable, and healthy Arctic understood through innovative and collaborative research coordinated among Federal agencies and domestic and international partners. IARPC's approach is to harnesses the talent of the scientific and stakeholder community through Federally-run but broadly open collaboration teams, and an innovative website that expands the frontiers of collaborative research. The Obama Administration released the five-year Arctic Research Plan: FY2013-2017 in February 2013. The Plan focuses on advancing knowledge and sustainability of the Arctic by improving collaboration in seven priority research areas: sea ice and marine ecosystems, terrestrial ice and ecosystems, atmospheric studies, observing systems, regional climate models, human health studies, and adaptation tools for communities. From these seven research areas, 12 collaboration teams were formed to respond to the 145 milestones laid out in the Plan. The collaboration teams are charged with enhancing inter-institutional and interdisciplinary implementation of scientific research on local, regional, and circumpolar environmental and societal issues in the Arctic. The collaboration teams are co-chaired by Federal program managers, and, in some cases, external partners and are open to research and stakeholder communities. They meet on a regular basis by web- or teleconference to inform one another about ongoing and planned programs and new research results, as well as to inventory existing programs, identify gaps in knowledge and research, and address and implement the Plan's milestones. In-between meetings, team members communicate via our innovative, user-driven, collaboration website. Members share information about their research activities by posting updates, uploading documents, and including events on our calendar, and entering into dialogue about their research activities. Conversations taking place on the

Remote sensing of the Canadian Arctic: Modelling biophysical variables

NASA Astrophysics Data System (ADS)

Liu, Nanfeng

It is anticipated that Arctic vegetation will respond in a variety of ways to altered temperature and precipitation patterns expected with climate change, including changes in phenology, productivity, biomass, cover and net ecosystem exchange. Remote sensing provides data and data processing methodologies for monitoring and assessing Arctic vegetation over large areas. The goal of this research was to explore the potential of hyperspectral and high spatial resolution multispectral remote sensing data for modelling two important Arctic biophysical variables: Percent Vegetation Cover (PVC) and the fraction of Absorbed Photosynthetically Active Radiation (fAPAR). A series of field experiments were conducted to collect PVC and fAPAR at three Canadian Arctic sites: (1) Sabine Peninsula, Melville Island, NU; (2) Cape Bounty Arctic Watershed Observatory (CBAWO), Melville Island, NU; and (3) Apex River Watershed (ARW), Baffin Island, NU. Linear relationships between biophysical variables and Vegetation Indices (VIs) were examined at different spatial scales using field spectra (for the Sabine Peninsula site) and high spatial resolution satellite data (for the CBAWO and ARW sites). At the Sabine Peninsula site, hyperspectral VIs exhibited a better performance for modelling PVC than multispectral VIs due to their capacity for sampling fine spectral features. The optimal hyperspectral bands were located at important spectral features observed in Arctic vegetation spectra, including leaf pigment absorption in the red wavelengths and at the red-edge, leaf water absorption in the near infrared, and leaf cellulose and lignin absorption in the shortwave infrared. At the CBAWO and ARW sites, field PVC and fAPAR exhibited strong correlations (R2 > 0.70) with the NDVI (Normalized Difference Vegetation Index) derived from high-resolution WorldView-2 data. Similarly, high spatial resolution satellite-derived fAPAR was correlated to MODIS fAPAR (R2 = 0.68), with a systematic

Global W`o'rming and Darwin Revisited: Quantifying Soil Mixing Rates by Non-native Earthworms in Fennoscandian Boreal and Arctic Ecosystems

NASA Astrophysics Data System (ADS)

Wackett, A. A.; Yoo, K.; Cameron, E. K.; Olid, C.; Klaminder, J.

2017-12-01

Fennoscandian boreal and arctic ecosystems represent some of the most pristine environments in Europe and store sizeable quantities of soil carbon. Both ecosystems may have evolved without native earthworms since the last glaciation, but are now increasingly subject to arrivals of novel geoengineering earthworm species due to human activities. As a result, invaded areas are devoid of the typical thick organic horizon present in earthworm free forest soils and instead contain carbon-rich mineral (A-horizon) soils at the surface. How rapidly this transition occurs and how it affects the fate of soil organic carbon (SOC) pools is not well known. In this study, we quantify the rates at which earthworm-mediated mixing of forest soils proceeds in these formerly glaciated landscapes. We infer soil mass fluxes using the vertical distribution of 210Pb in soils from Fennoscandia (N=4) and North America (N=1) and quantify annual mixing velocities as well as vertical fluxes of organic and mineral matter throughout the upper soil profiles. Across the sites, mixing velocities generally increase with increasing earthworm biomass and functional group diversity, and our annual mixing rates closely align with those predicted by Darwin for earthworm-engineered ecosystems in the UK 130 years earlier. Reduction of the O-horizon is concomitant with a decrease in surface SOC contents. However, we observe minimal changes to SOC inventories with earthworm invasion across the sites, reflecting the upward translocation of mineral soil and accompanying increase in soil bulk densities. Thus, the reduction or depletion of organic horizon by exotic earthworms does not necessarily involve loss of SOC via earthworm-accelerated decomposition, but is rather compensated for by physical mixing of organic matter and minerals, which may facilitate stabilizing organo-mineral interactions. This work constitutes an important step to elucidate how non-native earthworms impact SOC inventories and potentially

Multidecadal Rates of Disturbance- and Climate Change-Induced Land Cover Change in Arctic and Boreal Ecosystems over Western Canada and Alaska Inferred from Dense Landsat Time Series

NASA Astrophysics Data System (ADS)

Wang, J.; Sulla-menashe, D. J.; Woodcock, C. E.; Sonnentag, O.; Friedl, M. A.

2017-12-01

Rapid climate change in arctic and boreal ecosystems is driving changes to land cover composition, including woody expansion in the arctic tundra, successional shifts following boreal fires, and thaw-induced wetland expansion and forest collapse along the southern limit of permafrost. The impacts of these land cover transformations on the physical climate and the carbon cycle are increasingly well-documented from field and model studies, but there have been few attempts to empirically estimate rates of land cover change at decadal time scale and continental spatial scale. Previous studies have used too coarse spatial resolution or have been too limited in temporal range to enable broad multi-decadal assessment of land cover change. As part of NASA's Arctic Boreal Vulnerability Experiment (ABoVE), we are using dense time series of Landsat remote sensing data to map disturbances and classify land cover types across the ABoVE extended domain (spanning western Canada and Alaska) over the last three decades (1982-2014) at 30 m resolution. We utilize regionally-complete and repeated acquisition high-resolution (<2 m) DigitalGlobe imagery to generate training data from across the region that follows a nested, hierarchical classification scheme encompassing plant functional type and cover density, understory type, wetland status, and land use. Additionally, we crosswalk plot-level field data into our scheme for additional high quality training sites. We use the Continuous Change Detection and Classification algorithm to estimate land cover change dates and temporal-spectral features in the Landsat data. These features are used to train random forest classification models and map land cover and analyze land cover change processes, focusing primarily on tundra "shrubification", post-fire succession, and boreal wetland expansion. We will analyze the high resolution data based on stratified random sampling of our change maps to validate and assess the accuracy of our model

Climate Effects on Methylmercury Bioaccumulation Along a Latitudinal Gradient in the Eastern Canadian Arctic

NASA Astrophysics Data System (ADS)

Chetelat, J.; Richardson, M.; MacMillan, G. A.; Amyot, M.; Hintelmann, H.; Crump, D.

2014-12-01

Recent evidence indicates that inorganic mercury (Hg) loadings to Arctic lakes decline with latitude. However, monomethylmercury (MMHg) concentrations in fish and their prey do not decline in a similar fashion, suggesting that higher latitude lakes are more vulnerable to Hg inputs. Preliminary results will be presented from a three-year study (2012-2015) of climate effects on MMHg bioaccumulation in lakes of the eastern Canadian Arctic. We have investigated mercury transport and accumulation processes in lakes and ponds from three study regions along a latitudinal gradient in climate-controlled ecosystem types in the Canadian Arctic, specifically sub-Arctic taiga, Arctic tundra and polar desert. In each water body, we measured key aspects of MMHg bioaccumulation—MMHg bioavailability to benthic food webs and organism growth rates—as well as how watershed characteristics affect the transport of Hg and organic carbon to lakes. Novel approaches were incorporated including the use of passive samplers (Diffusive Gradient in Thin Film samplers or DGTs) to estimate sediment bioavailable MMHg concentrations and tissue RNA content to compare organism short-term growth rates. A comparison of Arctic tundra and sub-Arctic taiga lakes showed that surface water concentrations of MMHg were strongly and positively correlated to total Hg concentrations both within and among study regions, implying strong control of inorganic Hg supply. Sediment concentrations of bioavailable MMHg were highly variable among lakes, although average concentrations were similar between study regions. Local environmental conditions appear to have a strong influence on sediment potential for MMHg supply. Lake-dwelling Arctic char from tundra lakes had similar or higher total Hg concentrations compared with brook trout from sub-Arctic lakes that were exposed to higher water MMHg concentrations. Potential environmental drivers of these patterns will be discussed. This latitudinal study will provide new

Consistency and discrepancy in the atmospheric response to Arctic sea-ice loss across climate models

NASA Astrophysics Data System (ADS)

Screen, James A.; Deser, Clara; Smith, Doug M.; Zhang, Xiangdong; Blackport, Russell; Kushner, Paul J.; Oudar, Thomas; McCusker, Kelly E.; Sun, Lantao

2018-03-01

The decline of Arctic sea ice is an integral part of anthropogenic climate change. Sea-ice loss is already having a significant impact on Arctic communities and ecosystems. Its role as a cause of climate changes outside of the Arctic has also attracted much scientific interest. Evidence is mounting that Arctic sea-ice loss can affect weather and climate throughout the Northern Hemisphere. The remote impacts of Arctic sea-ice loss can only be properly represented using models that simulate interactions among the ocean, sea ice, land and atmosphere. A synthesis of six such experiments with different models shows consistent hemispheric-wide atmospheric warming, strongest in the mid-to-high-latitude lower troposphere; an intensification of the wintertime Aleutian Low and, in most cases, the Siberian High; a weakening of the Icelandic Low; and a reduction in strength and southward shift of the mid-latitude westerly winds in winter. The atmospheric circulation response seems to be sensitive to the magnitude and geographic pattern of sea-ice loss and, in some cases, to the background climate state. However, it is unclear whether current-generation climate models respond too weakly to sea-ice change. We advocate for coordinated experiments that use different models and observational constraints to quantify the climate response to Arctic sea-ice loss.

Herbivore impacts to the moss layer determine tundra ecosystem response to grazing and warming.

PubMed

Gornall, Jemma L; Woodin, Sarah J; Jónsdóttir, Ingibjörg S; Van der Wal, Rene

2009-10-01

Herbivory and climate are key environmental drivers, shaping ecosystems at high latitudes. Here, we focus on how these two drivers act in concert, influencing the high arctic tundra. We aim to investigate mechanisms through which herbivory by geese influences vegetation and soil processes in tundra ecosystems under ambient and warmed conditions. To achieve this, two grazing treatments, clipping plus faecal additions and moss removal, were implemented in conjunction with passive warming. Our key finding was that, in many cases, the tundra ecosystem response was determined by treatment impacts on the moss layer. Moss removal reduced the remaining moss layer depth by 30% and increased peak grass biomass by 27%. These impacts were probably due to observed higher soil temperatures and decomposition rates associated with moss removal. The positive impact of moss removal on grass biomass was even greater with warming, further supporting this conclusion. In contrast, moss removal reduced dwarf shrub biomass possibly resulting from increased exposure to desiccating winds. An intact moss layer buffered the soil to increased air temperature and as a result there was no response of vascular plant productivity to warming over the course of this study. In fact, moss removal impacts on soil temperature were nearly double those of warming, suggesting that the moss layer is a key component in controlling soil conditions. The moss layer also absorbed nutrients from faeces, promoting moss growth. We conclude that both herbivory and warming influence this high arctic ecosystem but that herbivory is the stronger driver of the two. Disturbance to the moss layer resulted in a shift towards a more grass-dominated system with less abundant mosses and shrubs, a trend that was further enhanced by warming. Thus herbivore impacts to the moss layer are key to understanding arctic ecosystem response to grazing and warming.

Detecting regional carbon-climate feedbacks in the Arctic

NASA Astrophysics Data System (ADS)

Parazoo, N.; Koven, C.; Miller, C. E.; Commane, R.; Wofsy, S.; Frankenberg, C.; Luus, K. A.

2016-12-01

The Arctic Boreal Zone (ABZ) is one of the most important and sensitive regions on Earth in the context of climate change. Recent evidence points to ongoing changes to ecosystem metabolism and permafrost that have potential to significantly feed back to global climate processes. Our ability to detect and quantify carbon-climate feedbacks in the ABZ requires methods to measure long term changes in the rate of ecosystem carbon exchange across geographical regions and over seasonal timescales, disentangle fluxes from permafrost thaw and biosphere uptake, and resolve functional and structural characteristics of diverse ABZ ecosystems. In this study, we analyze satellite and airborne observations of atmospheric CO2 and solar induced chlorophyll fluorescence with climatically forced CO2 flux simulations to assess the detectability of Alaskan biosphere carbon cycle signals in current and future climates. A key finding is that current airborne and satellite measurements of CO2 in Alaska can accurately quantify interannual and long term changes in peak summer uptake, but are insufficient to capture regional changes in cold season emissions. As the potential for Arctic carbon budgets to become impacted by permafrost thaw and cold season emissions increases, strategies focused on year-round vertical profiles and improved spatial sampling will be needed to track carbon balance changes. We also present evidence that measurements of chlorophyll fluorescence, a variable tightly linked to terrestrial vegetation photosynthesis, provide critical information on the timing of spring photosynthetic onset and duration of growing season carbon uptake in tundra and boreal ecosystems. Comparisons to vegetation indices such as NDVI have shed light on structural and functional controls of seasonal carbon fluxes, and helped refine estimates of the overall carbon balance of the ABZ. A key theme in this study is emphasis of strategies that combine satellite, airborne, and ground based platforms

Building International Research Partnerships in the North Atlantic-Arctic Region

NASA Astrophysics Data System (ADS)

Benway, Heather M.; Hofmann, Eileen; St. John, Michael

2014-09-01

The North Atlantic-Arctic region, which is critical to the health and socioeconomic well being of North America and Europe, is susceptible to climate-driven changes in circulation, biogeochemistry, and marine ecosystems. The need for strong investment in the study of biogeochemical and ecosystem processes and interactions with physical processes over a range of time and space scales in this region was clearly stated in the 2013 Galway Declaration, an intergovernmental statement on Atlantic Ocean cooperation (http://europa.eu/rapid/press-release_IP-13-459_en.htm). Subsequently, a workshop was held to bring together researchers from the United States, Canada, and Europe with expertise across multiple disciplines to discuss an international research initiative focused on key features, processes, and ecosystem services (e.g., Atlantic Meridional Overturning Circulation, spring bloom dynamics, fisheries, etc.) and associated sensitivities to climate changes.

Potential influence of birds on soil testate amoebae in the Arctic

NASA Astrophysics Data System (ADS)

Mazei, Yuri A.; Lebedeva, Natalia V.; Taskaeva, Anastasia A.; Ivanovsky, Alexander A.; Chernyshov, Viktor A.; Tsyganov, Andrey N.; Payne, Richard J.

2018-06-01

Birds can be an important agent of environmental change in High Arctic ecosystems, particularly due to the role of seabirds as a vector transferring nutrients from the marine to terrestrial realms. The soils of bird nesting sites are known to host distinct plant communities but the consequences of bird modification for microorganisms are much less clear. Our focus here is testate amoebae: a widely-distributed group of protists with significant roles in many aspects of ecosystem functioning. We compared the testate amoeba assemblages of a site on Spitsbergen (Svalbard archipelago) affected by nesting birds, with nearby control sites. We found differences in assemblage between sites, typified by reduced relative abundance of Phryganella acropodia and Centropyxis aerophila in bird-modified soils. These changes may reflect a reduced availability of fungal food sources. We found no evidence for differences in assemblage diversity or test concentration between bird-modified and control soils. Our dataset is small but results provide the first evidence for the potential effect of bird modification of soils on testate amoebae in the Arctic. Results show only limited similarity to experimental studies of nutrient addition, implying that response mechanisms may be more complicated than simply additional nutrient supply.

Scenarios Creation and Use in the Arctic Council's Arctic Marine Shipping Assessment

NASA Astrophysics Data System (ADS)

Brigham, L. W.

2016-12-01

The Arctic Council's Arctic Marine Shipping Assessment (AMSA), conducted 2004-2009, used a scenarios-based approach to reveal the complexity of future Arctic marine navigation and to develop a set of plausible futures. The initial task was to use experts and stakeholders in brainstorming sessions to identify the key drivers and uncertainties for Arctic marine navigation. AMSA scenario participants identified 120 driving forces or factors that may influence future levels of marine activity. This effort illustrated the broad, global connections that can impact future use of the Arctic Ocean. Two primary factors were selected to anchor, as axes of uncertainty, the scenarios matrix: resources and trade (the level of demand for Arctic natural resources and trade); and, governance (the degree of relative stability of rules and standards for marine use both within the Arctic and internationally). Four scenarios were created by crossing the two primary drivers: a Polar Lows scenario (low demand and unstable governance); an Arctic Race scenario (high demand and unstable governance); a Polar Preserve scenario (low demand and stable governance); and, an Arctic Saga scenario (high demand and stable governance). The AMSA scenarios effort proved to be an effective and powerful way to communicate to the Arctic Council diplomats, Arctic indigenous peoples, maritime stakeholders and many other actors in the global community the complexities influencing the future of Arctic shipping and marine operations. The scenarios approach facilitated unconstrained thinking and identified the many plausible linkages of the Arctic to the global economic system. The AMSA scenarios work was influential in the Arctic ministers' approval of the framework set of AMSA recommendations that are being implemented today to enhance Arctic marine safety and environmental protection.

Reduced arctic tundra productivity linked with landform and climate change interactions.

PubMed

Lara, Mark J; Nitze, Ingmar; Grosse, Guido; Martin, Philip; McGuire, A David

2018-02-05

Arctic tundra ecosystems have experienced unprecedented change associated with climate warming over recent decades. Across the Pan-Arctic, vegetation productivity and surface greenness have trended positively over the period of satellite observation. However, since 2011 these trends have slowed considerably, showing signs of browning in many regions. It is unclear what factors are driving this change and which regions/landforms will be most sensitive to future browning. Here we provide evidence linking decadal patterns in arctic greening and browning with regional climate change and local permafrost-driven landscape heterogeneity. We analyzed the spatial variability of decadal-scale trends in surface greenness across the Arctic Coastal Plain of northern Alaska (~60,000 km²) using the Landsat archive (1999-2014), in combination with novel 30 m classifications of polygonal tundra and regional watersheds, finding landscape heterogeneity and regional climate change to be the most important factors controlling historical greenness trends. Browning was linked to increased temperature and precipitation, with the exception of young landforms (developed following lake drainage), which will likely continue to green. Spatiotemporal model forecasting suggests carbon uptake potential to be reduced in response to warmer and/or wetter climatic conditions, potentially increasing the net loss of carbon to the atmosphere, at a greater degree than previously expected.

Reduced arctic tundra productivity linked with landform and climate change interactions

USGS Publications Warehouse

Lara, Mark J.; Nitze, Ingmar; Grosse, Guido; Martin, Philip; McGuire, A. David

2018-01-01

Arctic tundra ecosystems have experienced unprecedented change associated with climate warming over recent decades. Across the Pan-Arctic, vegetation productivity and surface greenness have trended positively over the period of satellite observation. However, since 2011 these trends have slowed considerably, showing signs of browning in many regions. It is unclear what factors are driving this change and which regions/landforms will be most sensitive to future browning. Here we provide evidence linking decadal patterns in arctic greening and browning with regional climate change and local permafrost-driven landscape heterogeneity. We analyzed the spatial variability of decadal-scale trends in surface greenness across the Arctic Coastal Plain of northern Alaska (~60,000 km²) using the Landsat archive (1999–2014), in combination with novel 30 m classifications of polygonal tundra and regional watersheds, finding landscape heterogeneity and regional climate change to be the most important factors controlling historical greenness trends. Browning was linked to increased temperature and precipitation, with the exception of young landforms (developed following lake drainage), which will likely continue to green. Spatiotemporal model forecasting suggests carbon uptake potential to be reduced in response to warmer and/or wetter climatic conditions, potentially increasing the net loss of carbon to the atmosphere, at a greater degree than previously expected.

The Arctic Research Consortium of the United States (ARCUS): Connecting Arctic Research

NASA Astrophysics Data System (ADS)

Rich, R. H.; Wiggins, H. V.; Creek, K. R.; Sheffield Guy, L.

2015-12-01

This presentation will highlight the recent activities of the Arctic Research Consortium of the United States (ARCUS) to connect Arctic research. ARCUS is a nonprofit membership organization of universities and institutions that have a substantial commitment to research in the Arctic. ARCUS was formed in 1988 to serve as a forum for planning, facilitating, coordinating, and implementing interdisciplinary studies of the Arctic; to act as a synthesizer and disseminator of scientific information on arctic research; and to educate scientists and the general public about the needs and opportunities for research in the Arctic. ARCUS, in collaboration with the broader science community, relevant agencies and organizations, and other stakeholders, coordinates science planning and educational activities across disciplinary and organizational boundaries. Examples of ARCUS projects include: Arctic Sea Ice Outlook - an international effort that provides monthly summer reports synthesizing community estimates of the expected sea ice minimum. Sea Ice for Walrus Outlook - a resource for Alaska Native subsistence hunters, coastal communities, and others that provides weekly reports with information on sea ice conditions relevant to walrus in Alaska waters. PolarTREC (Teachers and Researchers Exploring and Collaborating) - a program whereby K-12 educators and researchers work together in hands-on field experiences in the Arctic and Antarctic to advance polar science education. ArcticInfo mailing list, Witness the Arctic newsletter, and the Arctic Calendar - communication tools for the arctic science community to keep apprised of relevant news, meetings, and announcements. Coordination for the Study of Environmental Arctic Change (SEARCH) program, which aims to provide scientific understanding of arctic environmental change to help society understand and respond to a rapidly changing Arctic. More information about these and other ARCUS activities can be found at the ARCUS website at

Climate-induced behavioral changes influence exposure of an Arctic apex predator to pathogens and contaminants

USDA-ARS?s Scientific Manuscript database

Polar bears (Ursus maritimus) may serve as sentinels for pathogens and contaminants, providing insight into changing Arctic ecosystems and health risks to wildlife and humans. Recent changes in the availability of sea ice habitat have coincided with increased use of land by polar bears from the sout...

Was the Eocene Arctic a Source Area for Exotic Plants and Mammals? (Invited)

NASA Astrophysics Data System (ADS)

Eberle, J. J.; Harrington, G. J.; Fricke, H. C.; Humphrey, J.; Hackett, L.; Newbrey, M.; Hutchison, J. H.

2010-12-01

Today’s High Arctic is undergoing rapid warming, but the impact on its animal and plant communities is not clear. As a deep time analog to better understand and predict the impacts of global warming on the Arctic biota, early Eocene (52-53 Ma) rocks on Ellesmere Island, Nunavut in Canada’s High Arctic (~79°N latitude) preserve evidence of diverse terrestrial ecosystems that supported dense forests inhabited by turtles, alligators, snakes, primates, tapirs, brontotheres, and hippo-like Coryphodon. The fossil localities were just a few degrees further south and still well above the Arctic Circle during the early Eocene; consequently, the biota experienced months of continuous sunlight as well as darkness, the Arctic summer and winter, respectively. The flora and fauna of the early Eocene Arctic imply warmer, wetter conditions than at present, and recently published analyses of biogenic phosphate from fossil fish, turtle, and mammal estimate warm summers (19 - 20 C) and mild, above-freezing winters. In general, temperature estimates for the early Eocene Arctic can be compared to those found today in temperate rainforests in the Pacific Northwest of the United States. The early Eocene Arctic mammalian fauna shares most genera with coeval mid-latitude faunas thousands of kilometers to the south in the US Western Interior, and several genera also are shared with Europe and Asia. Recent analyses suggest that the large herbivores such as hippo-like Coryphodon were year-round inhabitants in the Eocene Arctic forests. Although several of the Eocene Arctic mammalian taxa are hypothesized to have originated in either mid-latitude North America or Asia, the earlier occurrence of certain clades (e.g., tapirs) in the Arctic raises the possibility of a northern high-latitude origin. Analysis of the early Eocene Arctic palynoflora indicates comparable richness to early Eocene plant communities in the US Western Interior, but nearly 50% of its species (mostly angiosperms) are

Explore Arctic Health.

PubMed

Lebow, Mahria

2014-04-01

The Arctic Health web site is a portal to Arctic-specific, health related content. The site provides expertly organized and annotated resources pertinent to northern peoples and places, including health information, research publications and environmental information. This site also features the Arctic Health Publications Database, which indexes an array of Arctic-related resources.

Changes in the Arctic: Background and Issues for Congress

DTIC Science & Technology

2012-08-01

selection of individuals within the population more suited to the changed environment) may not be able to occur fast enough, leaving migration and death...species in an ecosystem (e.g., host plants might not move north (or up) as fast as their moth herbivores, nor as fast as the birds that depend on the...Cold Response 2012, Norwegian Armed Forces web page: http://mil.no/ excercises /coldresponse2012/pages/default.aspx 185 “The Arctic: Special Report

Volatile organic compound emission profiles of four common arctic plants

NASA Astrophysics Data System (ADS)

Vedel-Petersen, Ida; Schollert, Michelle; Nymand, Josephine; Rinnan, Riikka

2015-11-01

The biogenic volatile organic compound (BVOC) emissions from plants impact atmosphere and climate. The species-specific emissions, and thereby the atmospheric impact, of many plant species are still unknown. Knowledge of BVOC emission from arctic plants is particularly limited. The vast area and relatively high leaf temperature give the Arctic potential for emissions that cannot be neglected. This field study aimed to elucidate the BVOC emission profiles for four common arctic plant species in their natural environment during the growing season. BVOCs were sampled from aboveground parts of Empetrum hermaphroditum, Salix glauca, Salix arctophila and Betula nana using the dynamic enclosure technique and collection of volatiles in adsorbent cartridges, analyzed by gas chromatography-mass spectrometry. Sampling occurred three times: in late June/early July, in mid-July and in early August. E. hermaphroditum emitted the least BVOCs, dominated by sesquiterpenes (SQTs) and non-isoprenoid BVOCs. The Salix spp. emitted the most, dominated by isoprene. The emissions of B. nana were composed of about two-thirds non-isoprenoid BVOCs, with moderate amounts of monoterpenes (MTs) and SQTs. The total B. nana emissions and the MT and SQT emissions standardized to 30 °C were highest in the first measurement in early July, while the other species had the highest emissions in the last measurement in early August. As climate change is expected to increase plant biomass and change vegetation composition in the Arctic, the BVOC emissions from arctic ecosystems will also change. Our results suggest that if the abundance of deciduous shrubs like Betula and Salix spp. increases at the expense of slower growing evergreens like E. hermaphroditum, there is the potential for increased emissions of isoprene, MTs and non-isoprenoid BVOCs in the Arctic.

The great 2012 Arctic Ocean summer cyclone enhanced biological productivity on the shelves

PubMed Central

Zhang, Jinlun; Ashjian, Carin; Campbell, Robert; Hill, Victoria; Spitz, Yvette H; Steele, Michael

2014-01-01

[1] A coupled biophysical model is used to examine the impact of the great Arctic cyclone of early August 2012 on the marine planktonic ecosystem in the Pacific sector of the Arctic Ocean (PSA). Model results indicate that the cyclone influences the marine planktonic ecosystem by enhancing productivity on the shelves of the Chukchi, East Siberian, and Laptev seas during the storm. Although the cyclone's passage in the PSA lasted only a few days, the simulated biological effects on the shelves last 1 month or longer. At some locations on the shelves, primary productivity (PP) increases by up to 90% and phytoplankton biomass by up to 40% in the wake of the cyclone. The increase in zooplankton biomass is up to 18% on 31 August and remains 10% on 15 September, more than 1 month after the storm. In the central PSA, however, model simulations indicate a decrease in PP and plankton biomass. The biological gain on the shelves and loss in the central PSA are linked to two factors. (1) The cyclone enhances mixing in the upper ocean, which increases nutrient availability in the surface waters of the shelves; enhanced mixing in the central PSA does not increase productivity because nutrients there are mostly depleted through summer draw down by the time of the cyclone's passage. (2) The cyclone also induces divergence, resulting from the cyclone's low-pressure system that drives cyclonic sea ice and upper ocean circulation, which transports more plankton biomass onto the shelves from the central PSA. The simulated biological gain on the shelves is greater than the loss in the central PSA, and therefore, the production on average over the entire PSA is increased by the cyclone. Because the gain on the shelves is offset by the loss in the central PSA, the average increase over the entire PSA is moderate and lasts only about 10 days. The generally positive impact of cyclones on the marine ecosystem in the Arctic, particularly on the shelves, is likely to grow with increasing

The great 2012 Arctic Ocean summer cyclone enhanced biological productivity on the shelves.

PubMed

Zhang, Jinlun; Ashjian, Carin; Campbell, Robert; Hill, Victoria; Spitz, Yvette H; Steele, Michael

2014-01-01

[1] A coupled biophysical model is used to examine the impact of the great Arctic cyclone of early August 2012 on the marine planktonic ecosystem in the Pacific sector of the Arctic Ocean (PSA). Model results indicate that the cyclone influences the marine planktonic ecosystem by enhancing productivity on the shelves of the Chukchi, East Siberian, and Laptev seas during the storm. Although the cyclone's passage in the PSA lasted only a few days, the simulated biological effects on the shelves last 1 month or longer. At some locations on the shelves, primary productivity (PP) increases by up to 90% and phytoplankton biomass by up to 40% in the wake of the cyclone. The increase in zooplankton biomass is up to 18% on 31 August and remains 10% on 15 September, more than 1 month after the storm. In the central PSA, however, model simulations indicate a decrease in PP and plankton biomass. The biological gain on the shelves and loss in the central PSA are linked to two factors. (1) The cyclone enhances mixing in the upper ocean, which increases nutrient availability in the surface waters of the shelves; enhanced mixing in the central PSA does not increase productivity because nutrients there are mostly depleted through summer draw down by the time of the cyclone's passage. (2) The cyclone also induces divergence, resulting from the cyclone's low-pressure system that drives cyclonic sea ice and upper ocean circulation, which transports more plankton biomass onto the shelves from the central PSA. The simulated biological gain on the shelves is greater than the loss in the central PSA, and therefore, the production on average over the entire PSA is increased by the cyclone. Because the gain on the shelves is offset by the loss in the central PSA, the average increase over the entire PSA is moderate and lasts only about 10 days. The generally positive impact of cyclones on the marine ecosystem in the Arctic, particularly on the shelves, is likely to grow with increasing

Optical properties of melting first-year Arctic sea ice

NASA Astrophysics Data System (ADS)

Light, Bonnie; Perovich, Donald K.; Webster, Melinda A.; Polashenski, Christopher; Dadic, Ruzica

2015-11-01

The albedo and transmittance of melting, first-year Arctic sea ice were measured during two cruises of the Impacts of Climate on the Eco-Systems and Chemistry of the Arctic Pacific Environment (ICESCAPE) project during the summers of 2010 and 2011. Spectral measurements were made for both bare and ponded ice types at a total of 19 ice stations in the Chukchi and Beaufort Seas. These data, along with irradiance profiles taken within boreholes, laboratory measurements of the optical properties of core samples, ice physical property observations, and radiative transfer model simulations are employed to describe representative optical properties for melting first-year Arctic sea ice. Ponded ice was found to transmit roughly 4.4 times more total energy into the ocean, relative to nearby bare ice. The ubiquitous surface-scattering layer and drained layer present on bare, melting sea ice are responsible for its relatively high albedo and relatively low transmittance. Light transmittance through ponded ice depends on the physical thickness of the ice and the magnitude of the scattering coefficient in the ice interior. Bare ice reflects nearly three-quarters of the incident sunlight, enhancing its resiliency to absorption by solar insolation. In contrast, ponded ice absorbs or transmits to the ocean more than three-quarters of the incident sunlight. Characterization of the heat balance of a summertime ice cover is largely dictated by its pond coverage, and light transmittance through ponded ice shows strong contrast between first-year and multiyear Arctic ice covers.