Larry Hinzman

The annually averaged Arctic Oscillation index (AO, a measure of the strength of circumpolar winds) was slightly positive in 2006, continuing the trend of a relatively low and fluctuating index which began in the mid-1990s (Figure A1). This follows a strong, persistent positive pattern from 1989 to 1995. The current characteristics of the AO are more consistent with the characteristics of the period from the 1950s to the 1980s, when the AO switched frequently between positive and negative phases. Initial data from 2007 shows a positive AO pattern

ABSTRACT The Arctic, including Alaska, is currently experiencing an unprecedented degree of environmental change. Increases in both the mean annual surface temperature and precipitation have been observed. The combination of the recent increase in air temperature and precipitation have led to "unstable" or "warm" permafrost conditions. This warm and unstable permafrost condition is particularly sensitive to changes in both the surface energy and water balances. The observed climatic changes are expected to continue into the next century. As such, most of the current or expected changes (related to climate, permafrost, and vegetation distributions) will be experienced in areas underlain with warm, unstable permafrost. Themokarst topography forms whenever ice-rice permafrost thaws and the ground subsides into the resulting voids. Extensive areas of active thermokarst activity are currently being observed in these warm, unstable permafrost environments. The important processes involved with thermokarsting include surface ponding, surface subsidence, changes in drainage patterns and related erosion. In this study, we will present a conceptual model of the development of thermokarst features, emphasizing the resulting feedbacks and connections between hydrologic processes and a dynamic surface topography.

Permafrost temperatures in boreholes displayed a 2 4◦C increase over the last 50-100 years on the North Slope of Alaska and there was a concurrent warming of discontinuous permafrost. Long-term monitoring of deep wells in a north/south transect across the North Slope of Alaska reveals variable warming with some cooling periods, over the last twenty five years; this is consistent with the broader-scale trends in air temperatures observed in northern Alaska. Discontinuous permafrost is warming and thawing and extensive areas of thermokarst terrain (marked subsidence of the surface resulting from thawing of ice-rich permafrost) are now developing as a result of climatic change. Thawing permafrost and thermokarst have been observed at several sites in Interior Alaska. Thermokarst is developing in the boreal forests of Alaska where ice-rich discontinuous permafrost is thawing. Thawing destroys the physical foundation (ice-rich soil) on which forests develop, causing dramatic changes in t...

A valuable input to crop growth and yield models would be estimates of current crop condition. If multispectral reflectance indicates crop condition, then remote sensing may provide an additional tool for crop assessment. The effects of nitrogen fertilization on the spectral reflectance and agronomic characteristics of winter wheat (Triticum aestivum L.) were determined through field experiments. Spectral reflectance was measured during the 1979 and 1980 growing seasons with a spectroradiometer. Agronomic data included total leaf N concentration, leaf chlorophyll concentration, stage of development, leaf area index (LAI), plant moisture, and fresh and dry phytomass. Nitrogen deficiency caused increased visible, reduced near infrared, and increased middle infrared reflectance. These changes were related to lower levels of chlorophyll and reduced leaf area in the N-deficient plots. Green LAI, an important descriptor of wheat canopies, could be reliably estimated with multispectral dat...

Lakes are important water resources on the North Slope of Alaska. Oilfield exploration and production requires water for facility use as well as transportation. Ice road construction requires winter extraction of fresh water. Since most North Slope lakes are relatively shallow, the quantity and quality of the water remaining under the ice by the end of the winter are important

ABSTRACT Area underlain by permafrost in Alaska varies from continuous in the north through sporadic and warmer ground in the south. A changing climate makes estimating thermal response and predicting changes in extent in the transitional areas valuable for wildlife management as well as human infrastructure resiliency. Out recent research has focused on the Seward Peninsula of Alaska. Where average air temperatures are just below freezing and the permafrost is very warm, an area susceptible to dramatic change in response to a warming climate. In this paper the focus expands to the state of Alaska using two methods of estimating extent: the Geophysical Institute Permafrost Lab method (GIPL model is based on the modified Kudryavtsev approach) and the TTOP method originally derived by Smith and Riseborough. Current meteorological data is based on the present observational record.

ABSTRACT The soil moisture regime in the sub-arctic environment plays an important role in a number of processes related to climate change including soil respiration, permafrost distribution, and the frequency and severity of wildfires. In order to understand and predict ecosystem response to a changing climate and resulting feedbacks, it is critical to quantify the interaction of soil moisture and meteorology as a function of climatic processes, landscape type, and vegetation. The primary of goal of our research is to develop/modify a numerical model, which is able to describe, simulate, and predict soil moisture dynamics and all other hydrologic processes everywhere throughout a sub-arctic watershed. This model will be used as a tool to better understand the effects of vegetation and soil type, presence of permafrost, amount and timing of precipitation, and disturbance (such as wildfire) on soil moisture dynamics. The area selected for this research is the Caribou-Poker Creeks Research Watershed (CPCRW), located 48 km north of Fairbanks, Alaska (65° 10'N, 147° 30'W) and encompasses and area of 101.5 km2. Permafrost in CPCRW is discontinuous, generally found along north facing slopes and valley bottoms. Three small sub-basins of CPCRW, which are underlain with approximately 3, 19, and 53% permafrost, are simulated to explore differences in permafrost vs. non-permafrost dominated areas. The Arctic Hydrological and Thermal Process Model (ARHYTHM) is a process based, physically distributed numeric model will be modified to simulate the hydrologic processes throughout a watershed underlain by discontinuous permafrost. The model can be used as a tool to simulate spatially distributed processes, such as soil moisture dynamics or snowmelt, as well as point measurements such as streamflow at any point within the model domain. ARHYTHM was developed to simulate energy and mass transfer processes in the Alaskan arctic regions. Modifications made to the ARHYTHM model will be made to reflect the differences between the sub-arctic and arctic environments. Changes to the model will include the representation of discontinuous permafrost, distributed vegetation types, and the incorporation of a deep groundwater component. The model domain is based upon a 100-meter digital elevation model (DEM) that encompasses CPCRW. Parameters such as soil type and depth, vegetation type, and permafrost distribution (as well as their hydrologic properties) will be spatially distributed throughout the model domain. Meteorologic data (radiation components, relative humidity, air and ground temperature, precipitation, and wind speed) are used to drive the model. This paper will present up-to-date results of this on-going research.

ABSTRACT Much of the Alaskan Arctic and Subarctic receives a minimal amount of annual precipitation. Changes to regional precipitation patterns and the general transient warming expected in the next century's lake hydrology and the associated wetlands place the risk of lakes perforating the permafrost boundary on the forefront. Lake change on the Alaskan landscape due to permafrost degradation is going to be important to local ecosystems and in, for example, providing habitat for migratory waterfowl in the next decades and centuries. Permafrost presence, absence, and thickness are interconnected in the deciphering of groundwater gradients and projection of surface water presence, absence, disappearance, and appearance on the Alaskan landscape. Detailed efforts have been made to produce datasets of presence or absence of the permafrost on the Seward Peninsula and further efforts are in place to do the same for the entire state. Continuous permafrost can provide an impervious barrier to groundwater movement and most groundwater-surface water interaction occurs in areas of discontinuous permafrost. With permafrost thawing and open talik formation in discontinuous permafrost regions, surface water formerly perched above the permafrost can drain into the subpermafrost groundwater. In contrast, in areas where the local hydraulic gradient is upwards, subpermafrost groundwater may discharge at the surface as the confining layer of permafrost degrades and an open talik forms. Lake change, in the absence of changes in evaporation and surface flow, are governed by the local vertical flux of water. In this study we compile observations of surface water storage change in Alaska and conjecture that shrinking/ disappearing lakes are evidence of supra-permafrost groundwater downwelling. The resulting dataset serves as verification for our model of groundwater dynamics. The planned method for determining the ground water gradient and degree to which vertical percolation will be restricted is to analyze digital terrain information with hydrology, permafrost, soils, geology, and current climate data. To start the groundwater gradient computations we will focus on areas with known hydrologic phenomena and elaborate on a vector based gradient map referencing the steepness of the terrain and the precipitation on the surrounding higher elevations. Once the present groundwater and surface water situation is captured, based on the future subsidence of the permafrost in areas on the landscape, we propose to forecast the wetness and dryness across Alaska, capturing the uniqueness of each watershed's turn toward wetter and then drier over the next decades and centuries.

ABSTRACT The Water Balance Simulation Model ETH, WaSiM-ETH, is a deterministic, spatially distributed hydrological model that has been successfully applied to numerous basins ranging from tropical rainforests in Asia to Alpine regions in Europe. This is the first time WaSiM-ETH is applied to the Arctic. Until now, the model has been lacking an active layer algorithm that is essential to successfully simulate the hydrologic regime in permafrost regions. Although the long-term goal of WaSiM-ETH is to dynamically couple the thermal and hydrological regimes, we implemented a simple empiric formula alpha*sqrt(snowfreedays) to represent the seasonal freezing and thawing of the active layer. The count of snow-free-days starts as soon as the snow water equivalent decreases below a defined value. If fresh snow falls, then two things can happen: 1) increasing the counter for snow free days will be paused until the snow melts away within a defined period. The snow free days are increased normally once the snow cover is ablated. 2) If the snow cover lasts for more than a specified time, the snow-free-days counter is reset to zero thus setting the thaw depth to zero. The latter is the simple refreezing model. We applied the model to an intensively studied wetland in northern Alaska that has all portions of the water balance measured. The watershed is mainly represented by a drained thaw lake basin and hence, exhibit low hydraulic gradients with the main topographical features formed by high and low centered polygons. Evapotranspiration (ET) represents the major pathway of water loss from the wetland despite several ET-limiting factors. Through its dynamic linkage between soil moisture and evaporation, WaSiM-ETH allows for a realistic representation of evaporation from the moss dominated wetland that experiences increased canopy resistance in late summer. WaSiM-ETH has a surface routing scheme that takes into account ponds as well as small scale topography that are typical features in the area. Lateral flows exhibit a strong seasonal variation with peak flow during snowmelt. The modeling of lateral flow is complicated by the disconnection of the early season flow paths, leaving most low centered polygons as individual hydrologic units a week after snow melt. We present a validation of the modified WaSiM-ETH on measured runoff, evapotranspiration and spatially distributed water table elevations from an arctic watershed underlain by permafrost. Our aim is to reduce the uncertainty in water table projections at finer scales (

ABSTRACT The framework of the International Polar Decade (IPD) could support cooperation, data sharing and collaboration needed to understand the rapidly changing polar environment. The Arctic is experiencing rapid transitions in the atmosphere, the terrestrial regions and in the Arctic Ocean, perhaps greater than has been observed in recorded history. We were fortunate to convene the beginning of the Fourth International Polar Year (IPY) at the same time we experienced a record low in summer sea ice extent in the Arctic Ocean. This serendipitous occurrence of enhanced and coordinated observations at a time when a record minimum occurred focused public attention on the polar regions and permitted higher level system analyses that would not otherwise have been possible. The international commitment towards dense observations of the Arctic Ocean during IPY led to comprehensive documentation of the record sea ice minimum and its aftermath and repercussions throughout the Arctic system. Many other cryospheric processes are also changing on relatively rapid time scales, but these may not be statistically significant or even consistent over the short time frame of the IPY. In order to document and understand the system-scale changes occurring in high latitudes, it is necessary to engage in longer-term observations and analyses. Many of these processes display a very small or subtle signal of climate warming amidst the noise of large inherent variability. Although precipitation in the form of snow is projected to increase, that change is difficult to document due to very large year to year variability. Permafrost is warming in most places throughout the Arctic, but in many cases that change is on the order of tenths of a degree per decade. Although we can project trends in variables, the consequences and interactions between variables are more difficult to reliably document. In order to more confidently predict interactions between processes, and to quantitatively describe the mechanisms associated with critically important feedback processes, we must invest in long-term monitoring. We must maintain observations and conduct synthetic analyses on the many inter-dependent processes that collectively comprise the polar systems. Defined intensive observation periods with agreed-upon temporal and spatial extent during the IPD is appropriate to help focus these efforts. Regional studies, such as comparative analyses of the Barents and Bering Seas would provide a contextual framework for promoting international collaboration. Thematic studies, such as quantifying changes in circumpolar precipitation regimes, would focus efforts upon particularly problematic challenges.

... Title;Characteristics of the water cycle in the discontinuous permafrost region in interior Alaska. Author; ISHIKAWA N (Hokkaido Univ., Sapporo) SATO N (Hokkaido Univ., Sapporo) KAWAUCHI K (Muroran Inst. Technol., Muroran) YOSHIKAWA K (Univ. ...

ABSTRACT The Arctic is experiencing changes never before seen in historic times. The physical, chemical, biological, and social components of the Arctic System are interrelated, and therefore a holistic perspective is needed to understand and quantify their connections and predict future system changes. A regional Arctic System Model (ASM) will strengthen our understanding of these components. It will advance scientific investigations and provide a framework for improving predictive capabilities, thereby helping society to prepare for environmental change and its impacts on humans, ecosystems, and the global climate system. It will be a vehicle for harnessing the resources of the many sub-disciplines of arctic research for the benefit of planners and policymakers. An ASM will build on previous modeling and observations, and it will benefit from ongoing studies of component models that are in varying stages of development. The initial core model will include atmosphere, ocean, sea ice, and selected land components and will be constructed in a manner that allows investigators to add or exchange components as the ASM project progresses. These will include ice sheets, mountain glaciers, dynamic vegetation, biogeochemistry, terrestrial and marine ecosystems, coastal systems, atmospheric chemistry, and human and social dimension modules. The core focus of the proposed ASM program will be to understand complexity and adaptation in the Arctic System as well as society’s role and response in the evolution of that system. The program is designed to complement and work with global Earth System Modeling programs to create reliable probabilistic forecasts of the state of the Arctic on seasonal to decadal timescales. Therefore, the modeling program must work toward quantifying and reducing uncertainties related to variability of the Arctic System, uncertainty in the models themselves, and uncertainty in society’s response and adaptation to arctic change. Basic model development within the ASM program should be focused on improving simulations of the arctic biosphere and anthroposphere. The ASM program will require coordination of diverse segments of the research community and support for computing infrastructure and software. The coordination function should be guided by a number of working groups and a scientific steering committee. A central facility will fulfill the functions of a project office, data center, and point of international liaison to be shaped and overseen by the steering committee. Dedicated personnel at this facility should provide documentation, testing, and support for the ASM. Proposals for providing these core functions should be sought at the outset of the program. The program should be approached in stages to make sure it is meeting the overarching goals mentioned above. Stage One will be to fund small pilot projects that allow researchers to demonstrate the capacity of limited-area coupled models to improve understanding of the role of the Arctic in global environmental change. These projects would use high-resolution, Arctic-focused simulations to understand the physics, chemistry, and biology of the Arctic as it undergoes rapid change. If successful, this stage will be expanded to construct a basic regional ASM climate model core. Stage Two incorporates coupled biogeochemical and ecological components into the ASM. Stage Three targets the coupling of those components least ready for integration into the ASM; these include components related to human interaction with the environment. Each stage requires close interaction between ASM model developers and the global modeling and observation communities, and each should be focused on understanding the Arctic as a complex adaptive system.

This study examines the water balance components from three small sub-arctic watersheds near Fairbanks, Alaska, USA, which vary in permafrost coverage from 3 to 53%. The results show that the presence or absence of permafrost affects many of the water balance ...

... Title;Characteristics of the water cycle in the discontinuous permafrost region in interior Alaska. Author; ISHIKAWA N (Hokkaido Univ., Sapporo) SATO N (Hokkaido Univ., Sapporo) KAWAUCHI K (Muroran Inst. Technol., Muroran) YOSHIKAWA K (Univ. ...

... Elizabeth K. Lilly, University of Alaska Fairbanks; Douglas L. Kane; Larry D. Hinzman; Robert E. Gieck Page 61. ... There are very high densities of clams southwest of the polynya, resulting from high supply of organic matter (OM) to the benthos in a rather well-defined area. ...

The Arctic constitutes a unique and important environment that is central to the dynamics and evolution of the Earth system. The Arctic water cycle, which controls countless physical, chemical, and biotic processes, is also unique and important. These processes, in turn, ...

To examine the possibilities of reducing fertilizer levels and losses of nitrogen, we studied the effects of amount and timing of nitrogen fertilization on growth parameters and on soil nitrogen depletion in cauliflower. A higher nitrogen supply, calculated as the sum of ...

ABSTRACT Permafrost study has received great attention worldwide in recent decades because changes in permafrost conditions have profound influence on hydrological cycle, plant growth and ecosystem productivity, carbon exchange between the atmosphere and the land surface, and engineering implications in cold regions. Soil temperature has been measured up to 3.20 m from more than 30 hydro-meteorological stations in area underlain by permafrost across the Russian Arctic and Subarctic for the period from the mid-1950s through 2000. We found that mean annual temperature at the top of permafrost has increased by greater than 1.0oC. The thickness of the active layer has increased by more than 20 cm. More importantly, for the first time, we found that talik, a thawed layer between the maximum depth of seasonal freeze and the top of permafrost, might have formed at various sites over Siberia in the past few decades. Increase in permafrost temperature and active layer thickness and talik formation are clearly indicators of permafrost degradation over the study area. Increase in winter air temperature and changes in snow cover conditions may be responsible for permafrost temperature increase, while increase in active layer thickness may be controlled by increase in summer air temperature. Although talik formation is a complicated process, changes in air temperature and precipitation, especially snowfall, may account for a deeper thaw in summer and a shallow freeze in winter, resulting in taliks over the study area. We will also discuss the potential environmental impacts due to changes in permafrost conditions across the Russian Arctic and Subarctic.

While spring snowmelt floods are common annually in the Arctic, rainfall generated floods are rare or at least seldom documented. Since 1999, we have documented two rainfall events in the Upper Kuparuk River where the total precipitation for each storm approached 100 mm. These two floods (July 1999 and August 2002) produced flows that exceeded the maximum snowmelt runoff by a factor of three to four. It is these large events that shape the drainage network. Passive and active tracer rocks, scour chains and pre- and post-storm surveyed cross-sections were used to quantify bedload transport. The August 2002 event mobilized the entire bed. All of the tracer rocks moved and those that were recovered after the flood traveled an average of 72.8 m, with those in pools traveling farther than those in riffles. Lateral bank erosion exceeded 10 m in many areas; the bed degraded and aggraded more than 1 m. It is estimated that 870 cubic meters of bed material passed through the study area.

Numerous studies (Billings et al. 1982; Peterson et al. 1984; Oberbauer et al. 1991; Funk et al., 1994; Oechel et al., 1998) have demonstrated that decreasing soil moisture and increasing soil oxygen increase respiration loss in the Arctic tundra. Warming and drying of tundra soils due to climate change are assumed to increase greenhouse gas emissions and the potential for strong positive feedbacks on the climate of the Arctic. However, here we show that an increase in the water table can lead to the same result, increasing respiration. In the largest scale water table manipulation experiment ever performed in the Arctic tundra, we showed that increasing the water table to 7.5 cm above the surface caused the ecosystem to more than half its net C uptake (9 gCm-2season-1) compared to the 23 gCm-2season-1 of a control site where water table was about 2 cm below the surface. Standing water saturated the moss layer, increased the heat conduction into the soil, and lead to higher soil temperature, deeper thaw and, surprisingly, to higher respiration rates in the most anaerobic area of the manipulation experiment. Probably, the increase in thaw depth increased substrate availability and freed sufficient Fe(III) to act as an electron acceptor in place of oxygen for respiration and CO2 production in these anaerobic soils (Zehnder and Stumm 1988, Kappler et al. 2004, Lipson et al. in review). In contrast to the general assumption that aerobic peat soils release more CO2 than soils under anaerobic conditions (Billing et al., 1982; Funk et al., 1994; Bridgham et al., 1998), here we show that this is not always the case. That the increase in the water table can result in increased respiration, even under nearly fully anaerobic conditions, through previously underestimated pathways, highlights yet another unexpected positive feedback on climate change of carbon exchange in the Arctic. That anaerobic conditions do not necessarily prevent CO2 loss in permafrost areas has major implications on current and future estimates of the carbon balance, especially considering the very large amount of C stored in the Arctic soils as soil organic matter. These finding suggest a significant re-evaluation of possible carbon loss from Arctic ecosystems under warmer and wetter conditions.

Permafrost imparts strong controls on the pathways that precipitation takes through watersheds, which change as the seasonal thaw increases through the summer. For example, the composition of storm hydrographs becomes progressively dominated by old water as soil thaw depths increase, and hyporheic exchange flow can potentially be altered as thaw bulbs grow beneath streams. Can the changes that occur in the hydrology of permafrost-dominated watersheds within a thaw season be used as analogs for the potential changes that may occur due to projected climate warming? In this talk we present examples of how seasonal thawing within a summer season imposes changes in hillslope and channel hydrologic pathways, illustrate the consequences of changing hydrologic pathways on catchment biogeochemistry, and speculate on the implications of these short-term changes due to summer warming for understanding long-term climate warming.