• Stem Respiration of Black Spruce (Picea mariana), Interior Alaska

      Kim, Yongwon; Kim, S.-D. (2011-10)
      This stem respiration, that is equipped with a control system that consists of data-logger (CR10X), NDIR CO2 analyzer, and pump, a compressor, and seven stem chambers, was conducted in parallel with the flux-measurement of soil respiration in different-sized black spruce of 4.3 cm to 13.5 cm in DBH (diameter at breast height), interior Alaska during the growing season of 2007 to 2009. The average stem respirations were 0.011±0.005 mgCO2/m3/s (range 0.005±0.002 to 0.015±0.008 mgCO2/m3/s, CV 45%) in black spruce forests, which the DBH (Diameter at Breast Height) of black spruce ranges from 4.3 to 13.5 cm. The stem respiration in different-sized black spruce forest soils has temporally varied during the growing season of 2007-9. This suggests that the young black spruce has 3-fold higher metabolism than the old. Temperature is one of critical roles in determining stem respiration rate. Q10 values on air temperature and average stem respiration rates are 2.02 in 2007, 2.00 in 2008, and 2.37 in 2009 during the growing season, respectively. However, during the dormant season, measurement of stem respiration was failed and especially the diaphragm pump was damaged by input of the extremely cold air of 35 °C below the zero. Interestingly, the lagging effect of stem respiration on temperature and PAR (photosynthetically active radiation) was found during the clear sky, indicating lagging time of 1-2 hours on temperature and of 4-5 hours on PAR, respectively. Based on the Q10 equation on air temperature, annual variation of stem respiration rate was estimated, suggesting that the relationship between measured and simulated daily stem respiration was a good linear for the better understanding of interannual variation of stem respiration rates during 2007-9. The contribution of simulated monthly stem respiration to the ecosystem respiration (Re) by the eddy covariance method was 4.2±2.1 % in 2007, 2.5±0.9 % in 2008, and 5.7±4.3 % in 2009, respectively. The suggests that the higher contribution during 2009 may be due to much higher temperature in late winter and early spring.
    • Seasonal Variation in Fraction of Absorbed Photosynthetically Actic Radiation and Vegetation Properties in Burned Forests in Interior Alaska

      Iwata, Hiroki; Harazono, Yoshinobu; Iwama, Chic; Ueyama, Masahito (2011-12)
      Fraction of absorbed photosynthetically active radiation (FAPAR) is an important ecophysiological parameter for carbon and water exchange modeling. However, validation studies of FAPAR are scarce, especially for disturbance area. One study (Steinberg et al., 2006) revealed that the MODIS FAPAR product is overestimated for burned boreal forests. Wildfire is a major disturbance in boreal forest ecosystems, and it significantly influences carbon and water exchange processes. It is important to explicitly incorporate burned areas in estimating regional exchanges. This study aims to provide a validation data for FAPAR by collecting data regarding absorption of photosynthetically active radiation (PAR) in burned boreal forests. It also focuses on obtaining an empirical relationship to estimate seasonal and interannual variations in FAPAR from vegetation indices in the early stage of recovery after wildfire.
    • Ebullition-Driven Fluxes of Methane from Shallow Hot Spots in the East Siberian Arctic Shelf

      Shakhova, Natalia; Semiletov, Igor; Salyuk, Anatoly; Stubbs, Chris; Kosmach, Denis (2011-12)
      The maximum concentration of atmospheric methane (CH4) occurs over the Arctic: the value of CH4 over Greenland exceeds that over Antarctica by 8-10%; an absolute maximum is measured during wintertime (Steel et. al., 1987; Fung et. al., 1991). Geologic evidence provides insight into possible climate change effects from a warmer Arctic, suggesting that enhanced Arctic CH4 emissions during warm periods played a key role in past rapid climate change.
    • Using local knowledge, hydrologic, and climate data to develop a driftwood harvest model in interior Alaska

      Jones, Chas; Hinzman, Larry D.; Kielland, Knut (2011-12)
      Rural Alaskan residents are concerned that the character of the summer discharge in the Yukon River is changing, which is affecting their ability to harvest driftwood. The Yukon River flows northwesterly through British Columbia and the Yukon Territory before flowing southwest through Alaska. In most summers, residents of Tanana, Alaska harvest driftwood from the Yukon River during two different periods. Typically, driftwood accompanies high flows on the Yukon River associated with spring break‐up. A few weeks later, a second series of driftwood appears, associated with the “2nd rise,” which is reported to occur during early June. This study examines the nature of the differential timing of high flow events in the Yukon River. Many communities in interior Alaska have grown to rely upon driftwood as an important source of wood, which is used in construction, carving, and as a fuel source. Increasingly, villages in rural Alaska are trying to lessen their dependence upon expensive fossil fuels. To achieve this goal, a number of Alaskan villages have recently installed wood chip‐fired boilers to generate heat and/or electricity and additional boilers are slated to be installed in rural Alaska in the near future. These boilers are largely fed by driftwood, a cheap and easily processed wood source. Some Tanana residents have expressed concern that in recent years, driftwood was not readily available because the “2nd rise” flood event was absent. This is disconcerting for rural Alaskans that are becoming increasingly reliant upon the driftwood flows. Our goal is to determine if the perceived changes in driftwood availability are related to changes in river hydrology and if predicted changes in hydrology may affect driftwood flows and the livelihoods of rural Alaskans.
    • Using Local Knowledge, Hydrologic, and Climate Data to Develop a Driftwood Harvest Model in Interior Alaska

      Jones, Chas; Hinzman, Larry D.; Kielland, Knut; Schneider, Bill (2012-03)
      Many rural Alaska residents rely on harvested driftwood from the Yukon River for fuel and construction materials, however they have stated that the character of the summer discharge in the Yukon River is changing and affecting their ability to harvest this resource. We examined whether the perceived changes in driftwood availability are related to changes in river hydrology and how changes in hydrology may affect future driftwood flows and the livelihoods of rural Alaskans.
    • On-Shelf Transport of Oceanic Zooplankton in the Bering Sea

      Gibson, Georgina; Coyle, Ken; Hedstrom, Kate; Curchitser, Enrique (2012-10)
      A poster about a project to determine the most significant factors affecting timing, location, and intensity of on-shelf zooplankton transport in the Eastern Bering Sea.
    • On-shelf transport of oceanic zooplankton in the Bering Sea.

      Gibson, Georgina; Coyle, Ken; Hedstrom, Kate; Curchitser, Enrique (2012-10)
      Neocalanus are zooplankton that require deep water to successfully reproduce so tend to occur in oceanic and shelf-break habitats. Shelf-break fronts in the Eastern Bering Sea reduce cross-shelf advection over the outer-shelves potentially retarding on-shelf transport of the oceanic copepods. South-Easterly winds October-May are thought to increase on-shelf flow over the southern shelf. Because Neocalanus are large-bodied with a high energy content they are an important food source for juvenile stages of commercially important fish such as pollock, capelin and salmon in the Bering Sea. Annual differences in forage and commercial fish stocks in the Bering Sea may depend on climatic and oceanographic conditions promoting on- shelf transport of Neocalanus. Timing of on-shelf transport of Neocalanus, and the key physical processes determining the degree and extent of this transport are unclear.
    • Modeling Investigation of Atmospheric Moisture Transport over the North Pacific Ocean: Role of Pacific Decadal Oscillation

      Borries, Cecilia; Zhang, Xiangdong (2012-12)
      Atmospheric moisture content over the North Pacific Ocean can fluctuate under the influence of the Pacific Decadal Oscillation (PDO). For a better understanding of the role which the PDO plays in the North Pacific water budgets and pathways, we conducted sensitivity experiments to examine how atmospheric moisture transport responds to sea surface temperature (SST) anomalies associated with the PDO phases transitions. This study has important implications for improving understanding of precipitation events in areas surrounding the North Pacific.
    • Improve ocean mixing caused by subgrid-scale brine rejection using multi-column ocean grid in a climate model

      Jin, Meibing; Hutchings, Jennifer; Kawaguchi, Yusuke; Kikuchi, Takashi (2012-12)
      Heterogeneous ice pack with sporadic narrow but long leads in the polar oceans was unresolved in typical climate model grid. Although multi-category sea ice thickness distribution was used in one sea ice model grid to calculate separate heat, salt and tracer fluxes through each category, the ocean models use only single-column grid to communicate with the averaged fluxes from all categories. When the lead is resolved by the grid, the added salt at the sea surface will sink to the base of the mixed layer and then spread horizontally. When averaged at a climate-model grid size, this vertical distribution of added salt is lead-fraction dependent. When the lead is unresolved, the model errors were systematic leading to greater surface salinity and deeper mixed-layer depth (MLD). An empirical function was developed to revise the added-salt-related parameter n from being fixed to lead-fraction dependent. Application of this new scheme in climate model showed significant improvement in modeled wintertime salinity and MLD as compared to series of CTD data sets in 1997/1998 and 2006/2007. The results showed the most evident improvement in modeled MLD in the Arctic Basin, similar to that using a fixed n = 5, as recommended by the previous Arctic regional model study, in which the parameter n obtained is close to 5 due to the small lead fraction in the Arctic Basin in winter.
    • Dynamic Interactions of Snow and Plants in the Boreal Forest, Winter 2011-2012 Revealed by Time-Lapse Photography and LiDAR

      Filhol, Simon; Sturm, Matthew (2012-12)
      As winter progresses, snow accumulates on the ground and plants of the boreal forest. On their passage to the ground, the falling snowflakes encounter physical obstacles like the complex structure of tree branches and shrubs. These cause the fall trajectories to deviate, and in some cases even stop, before a snowflake reaches the forest floor. After deposition, wind and gravitational settlement further affect the snow distribution. Because of these snow-vegetation interactions, snow gets distributed in the forest along vertical and the horizontal directions in a complex way. To better understand these interactions between snow and plants, we designed an experiment, in the boreal forest near Fairbanks, Alaska (see panorama below) where we used a ground-based LiDAR (Light Detection And Ranging) to record the 3D geometrical evolution of the snowpack, the flexure of vegetation under snow loads, and the snow deposition on the ground during the winter of 2011-2012. In parallel, we set up a time-lapse camera to record loading and unloading of tree branches, and a weather station to record atmospheric conditions.
    • Sensitivity Analysis of Arctic Sea Ice in CMIP5 Climate Model Simulations

      Zhang, Xiangdong; Lu, Chuhan (2012-12)
      The representative characteristics of the simulated 20th century North Hemisphere sea ice by the CMIP5 models have been evaluated against available observations and compared with those by the CMIP3 models. In addition to the analysis of conventional parameters, such as climatological mean and seasonal cycle of sea ice area (SIA), a transient sensitivity analysis of summer SIA to the changes in Arctic regionally averaged melting season surface air temperatures (SAT) was conducted to better understand physics behind model uncertainties (e.g., Gregory et al. 2004; Zhang 2010).
    • Overview of Bering/Chukchi Sea Wave States for Selected Severe Storms

      Pingree-Shippee, Katherine A.; Shippee, Norman J.; Atkinson, David E. (2012-12)
      Strong storms are regular features over the ocean west of Alaska. These systems often loiter, generating moderate to severe marine states which can exhibit persistence, maximizing damage and hazard potential. This analysis presents the wave states associated with selected storms over the Bering and Chukchi Seas. These include the damaging events of October 2004, September 2005, and November 2009, along with a strong event from September 2011 that exhibited north winds. For each event a brief synoptic overview is presented followed by consideration of the resultant wave state, including parameters such as wave steepness. Wave data come from NOAA’s WAVEWATCH III operational global ocean wave model, implemented locally on the Arctic Region Supercomputing Center at University of Alaska Fairbanks. Comparison with observational data gathered by a wave buoy, funded by the US Environmental Protection Agency/NOAA and deployed in 2011, is also undertaken.
    • Climate Divisions for Alaska Based on Objective Methods

      Bieniek, Peter A.; Bhatt, Uma S.; Thoman, Richard L.; Angeloff, Heather; Partain, James; Papineau, John; Fritsch, Frederick; Holloway, Eric; Walsh, John E.; Daly, Chris; et al. (2012-12)
      Alaska climate regions first drawn by Fitton (1930) [Fitton]. Divisions outlined by Searby (1968) currently used by the National Climatic Data Center [NCDC]. Climate regions updated by Shulski and Wendler (2007) [ACRC]. None are based on primarily objective methods. Useful for seasonal forecasting and many other research applications.
    • CO2 Flux from Tundra Lichen, Moss, and Tussock, Council, Alaska: Assessment of Spatial Representativeness

      Kim, Yongwon; Chae, Namyi; Lee, Bangyong (2012-12)
      CO2 flux-measurement in dominant tundra vegetation on the Seward Peninsula of Alaska was examined for spatial representativeness, using a manual chamber system. In order to assess the representativeness of CO2 flux, a 40 m × 40 m (5-m interval; 81 total points) plot was used in June, August, and September of 2011. Average CO2 fluxes in lichen, moss, and tussock tundra were 3.4 ± 2.7, 4.5 ± 2.9, and 7.2 ± 5.7 mgCO2/m2/m during growing season, respectively, suggesting that tussock tundra is a significant CO2 source, especially considering the wide distribution of tussock tundra in the circumpolar region. Further, soil temperature, rather than soil moisture, held the key role in regulating CO2 flux at the study site: CO2 flux from tussock increased linearly as soil temperature increased, while the flux from lichen and moss followed soil temperature nearly exponentially, reflecting differences in surface area covered by the chamber system. Regarding sample size, the 81 total sampling points over June, August, and September satisfy an experimental average that falls within ±10% of full sample average, with a 95% confidence level. However, the number of sampling points for each variety of vegetation during each month must provide at least ±20%, with an 80% confidence level. In order to overcome the logistical constraints, we were required to identify the site’s characteristics with a manual chamber system over a 40 m × 40 m plot and to subsequently employ an automated chamber for spatiotemporal representativeness.
    • Modeling the Thermal Balance Between Groundwater Springs and River Ice

      Jones, Chas; Kielland, Knut; Hinzman, Larry (2012-12)
      We modeled the thermal balance between groundwater discharge and ice-free areas in the Tanana River near Fairbanks, Alaska, a region that is characterized by discontinuous permafrost. Under degrading permafrost conditions, these areas have been hypothesized to have increased winter discharge due to increasing contributions from groundwater flow. In the winter, interior Alaskan rivers are fed almost entirely by groundwater, which also serves as an external source of heat energy to the system. Several reaches of the river fed by groundwater springs remain ice-free or have dangerously thin ice throughout the winter despite air temperatures that dip below -40° C. These areas are dangerous for winter travelers who regularly use Alaskan rivers for wintertime travel. Our model allows us to explore the relationship between seasonal groundwater flows and ice thickness under changing atmospheric conditions. Our model results explore how local and regional changes in groundwater flow can affect ice thickness by addressing two primary research questions: 1) What physical factors influence seasonal ice dynamics on the Tanana River? 2) How is the thermal balance maintained between changing groundwater flow and cold air temperatures?
    • Modeling Investigation of Atmospheric Moisture Transport over the North Pacific Ocean: Role of Pacific Decadal Oscillation

      Borries, Cecilia; Zhang, Xiangdong (2012-12)
      Atmospheric moisture content over the North Pacific Ocean can fluctuate under the influence of the Pacific Decadal Oscillation (PDO). For a better understanding of the role which the PDO plays in the North Pacific water budgets and pathways, we conducted sensitivity experiments to examine how atmospheric moisture transport responds to sea surface temperature (SST) anomalies associated with the PDO phases transitions. This study has important implications for improving understanding of precipitation events in areas surrounding the North Pacific.
    • Propagation of tsunami-induced acoustic-gravity waves in the atmosphere

      Alexeev, Vladimir A.; Nicolsky, Dmitry J. (2012-12)
      A dynamical core of an atmospheric GCM is utilized for assessing the qualitative picture of propagation of atmospheric acoustic-gravity waves in response to perturbations generated by tsunami waves at the surface. Both resting isothermal atmosphere and model- generated atmosphere with realistic stratification and circulation features were considered. Shallow water tsunami model was run in two different configurations: ocean of equal depth of 4 km and ocean with realistic continents and bottom topography. Amplitude and timing of atmospheric response is analyzed as a function of vertical stratification and configuration of atmospheric jets. This approach has a potential for early tsunami detection by measuring changes in electric properties of the upper atmosphere in response to acoustic-gravity waves generated by tsunami.
    • Uncertainties in Arctic Precipitation

      Majhi, Ipshita; Alexeev, Vladimir; Cherry, Jessica; Groisman, Pavel; Cohen, Judah (2012-12)
      It is crucial to measure precipitation accurately to predict future water budget with confidence. In our study, we aim to understand and compare precipitation datasets and discrepancies associated with them. We divide our datasets into three classes-raw data (data that have only been preprocessed to minimum quality control);corrected products (data that have been adjusted by their respective authors); finally, a reanalysis dataset (a combination of observed data and model output).
    • Carbon exchange rates in Polytrichum juniperinum moss of burned black spruce forest in interior Alaska

      Kim, Yongwon; Kodama, Y.; Iwata, H.; Kim, S.-D.; Shim, C.; Kushida, K.; Harazono, Y. (2013-01)
      Boreal black spruce forest is highly susceptible to wildfire, and postfire changes in soil temperature and substrates have the potential to shift large areas of such ecosystem from a net sink to a net source of carbon. In this paper, we examine CO2 exchange rates (e.g., NPP and Re) in juniper haircap moss (Polytrichum juniperinum) and microbial respiration in no-vegetation conditions using an automated chamber system at 5-year burned black spruce forest in interior Alaska during the fall season of 2009. Mean microbial respiration and NEP (net ecosystem productivity) of juniper haircap moss were 0.73 ± 0.36 and 0.75 ± 1.04 mgC/m2/min, respectively. CO2 exchange rates and microbial respiration showed temporal variations with fluctuation in air temperature during the fall season, suggesting the temperature sensitivity of juniper haircap moss and soil microbes after fire. During the 45-day fall period, mean NEP of P. juniperinum moss was 0.49 ± 0.28 MgC/ha after 5-year-old forest fire. On the other hand, simulated microbial respiration normalized to a 10 °C temperature might be stimulated by as much as 0.40 ± 0.23 MgC/ha. These findings demonstrate that fire-pioneer species juniper haircap moss is a net C sink in burned black spruce forest of interior Alaska.
    • Ocean heat effect on the observed and predicted reduction of the Arctic sea ice: results of the AARI contribution to ACCESS WP1

      Ivanov, Vladimir; Ashik, Igor (2013-03)
      Under conditions of reducing ice cover the influence of ocean heat on Arctic sea ice is expected to increase. We are identifying several ways how the ocean heat may be transferred towards the ice contributing to the existent ice thinning and/or impeding new ice formation. They include: Direct impact of sensible heat, stored in the ocean on the ice cover in the locations close to the warm inflow of Atlantic Water (AW) and Pacific Water (PW); Vertical heat flux via double diffusion convection from AW layer in the central Arctic Basin Increased upward heat flux from AW over continental slope and outer shelf, where AW upwells the shelf, and vertical mixing is enhanced due to strong shear, tidal currents, and shelf intrusions; Atmospheric heat accumulation in the melted water, which enhances lateral ice erosion.