Effects of climatic variability on the active layer and permafrost

Thesis (Ph.D.) University of Alaska Fairbanks, 1996This thesis represents a collection of papers on the response of the active layer and permafrost to climatic variations on different time scales. Quantitative estimates of the amplitudes of the Milankovich rhythms in several regions of the Russian permafrost zone were used in numerical simulations of permafiost dynamics. The results of modeling explained many aspects of the permafrost distribution and its vertical structure within Russia. Spatial and temporal variability of the air, ground surface and permafrost temperatures were also analyzed using daily temperature data (upper 0.9 m) from 1986-1993 and results of annual temperature measurements in boreholes (nominally 60 m) from 1983-1995 at three sites in the Prudhoe Bay region of Alaska. Three numerical models which are based on different numerical methods and are used for calculations of the ground thermal regime were compared with each other, with analytical solutions, and with temperature data. Several approximate analytical solutions for the temperature regime and thickness of the active layer were introduced. The calculations were used to estimate the interannual variability of the thermal properties of soils which appear to be a result of interannual variations of the average water content during the summer in the upper part of the active layer. Precise temperature data together with computer modeling provided essential new information on dynamics of unfrozen water content in the ground in natural undisturbed conditions during freezing and the subsequent cooling of the active layer. A layer with unusually large unfrozen water content was found to exist at the depth of freeze-up. The same set of data was used to reconstruct daily permafrost temperatures from 1986-1993 for all depths down to 55 m. Mean annual temperature profiles for each year of 1987-1992 show significant interannual variations within the upper 40 m in a good agreement with published data. A numerical model of the temperature field in permafrost near its southern limits was developed to study the influence of short-term climatic variations (with periods of 300 and 90 years) on permafrost dynamics

Recent and Possible Future Changes in Permafrost

Recent observations indicate a warming of permafrost in many northern regions with the resulting degradation of ice-rich and carbon rich permafrost. Permafrost temperature has increased by 0.5°C to 3°C in the northern Hemisphere during the last 30-40 years (Romanovsky et al., 2010)

Scaling-up permafrost thermal measurements in western Alaska using an ecotype approach

Permafrost temperatures are increasing in Alaska due to climate change and in some cases permafrost is thawing and degrading. In areas where degradation has already occurred the effects can be dramatic, resulting in changing ecosystems, carbon release, and damage to infrastructure. However, in many areas we lack baseline data, such as subsurface temperatures, needed to assess future changes and potential risk areas. Besides climate, the physical properties of the vegetation cover and subsurface material have a major influence on the thermal state of permafrost. These properties are often directly related to the type of ecosystem overlaying permafrost. In this paper we demonstrate that classifying the landscape into general ecotypes is an effective way to scale up permafrost thermal data collected from field monitoring sites. Additionally, we find that within some ecotypes the absence of a moss layer is indicative of the absence of near-surface permafrost. As a proof of concept, we used the ground temperature data collected from the field sites to recode an ecotype land cover map into a map of mean annual ground temperature ranges at 1 m depth based on analysis and clustering of observed thermal regimes. The map should be useful for decision making with respect to land use and understanding how the landscape might change under future climate scenarios

Arctic–CHAMP: A program to study Arctic hydrology and its role in global change

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, regulate the climate, habitat, and natural resources that are of great importance to both native and industrial societies. Comprehensive understanding of water cycling across the Arctic and its linkage to global biogeophysical dynamics is a scientific as well as strategic policy imperative

Arctic–CHAMP: A program to study Arctic hydrology and its role in global change

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, regulate the climate, habitat, and natural resources that are of great importance to both native and industrial societies. Comprehensive understanding of water cycling across the Arctic and its linkage to global biogeophysical dynamics is a scientific as well as strategic policy imperative

Landsat-based lake distribution and changes in western Alaska permafrost regions between the 1970s and 2010s

Lakes are an important ecosystem component and geomorphological agent in northern high latitudes and it is important to understand how lake initiation, expansion and drainage may change as high latitudes continue to warm. In this study, we utilized Landsat Multispectral Scanner System (MSS) images from the 1970s (1972, 1974, and 1975) and Operational Land Imager (OLI) images from the 2010s (2013, 2014, and 2015) to assess broad-scale distribution and changes of lakes larger than 1 ha across the four permafrost zones (continuous, discontinuous, sporadic, and isolated extent) in western Alaska. Across our ca 70,000 km2study area, we saw a decline in overall lake coverage across all permafrost zones with the exception of the sporadic permafrost zone. In the continuous permafrost zone lake area declined by -6.7 % (-65.3 km2), in the discontinuous permafrost zone by -1.6 % (-55.0 km2), in the isolated permafrost zone by -6.9 % (-31.5 km2) while lake cover increased by 2.7 % (117.2 km2) in the sporadic permafrost zone. Overall, we observed a net drainage of lakes larger than 10 ha in the study region. Partial drainage of these medium to large lakes created an increase in the area covered by small water bodies <10 ha, in the form of remnant lakes and ponds by 7.1 % (12.6 km2) in continuous permafrost, 2.5 % (15.5 km2) in discontinuous permafrost, 14.4 % (74.6 km2) in sporadic permafrost, and 10.4 % (17.2 km2) in isolated permafrost. In general, our observations indicate that lake expansion and drainage in western Alaska are occurring in parallel. As the climate continues to warm and permafrost continues to thaw, we expect an increase in the number of drainage events in this region leading to the formation of higher numbers of small remnant lakes

Landsat-Based Lake Distribution and Changes in Western Alaska Permafrost Regions Between 1972 and 2014

Lakes are an important landscape and ecosystem component in the high northern latitudes and they are hotspots for biogeochemical processes in permafrost regions. In this study, we utilized Landsat MSS and OLI images from the 1970s and 2014 to assess broad-scale distribution and changes of lakes larger than 1 ha in 6 major lake districts from various permafrost zones (continuous, discontinuous, sporadic and isolated) located in western Alaska. The lake districts that we included are Beringia, Baldwin Peninsula, Kobuk Delta, Selawik, Central Seward Peninsula, and Yukon-Kuskokwim Delta covering a total area of 68,831.41 km2. These regions encompass various types of lakes; thermokarst lakes are the most common type, while oxbow and delta lakes are also widely distributed in the river floodplains and delta regions. Additional lake types include maar lakes. The highest density of lakes is found in Yukon-Kuskokwim Delta with approximately 16% of the mapped area covered with lakes. The least number of lakes are found in Baldwin Peninsula with only about 2.5% of the mapped area covered with lakes. The lake districts in river deltas have the highest lake coverage (limnicity) with all three deltas (Kobuk Delta, Selawik and YK Delta) having above 10% lake area. For 3 study regions (Baldwin Peninsula, Kobuk, and Yukon-Kuskokwim Delta) an increase in total lake area by less than 4% was observed, while the other 3 regions (Beringia, Central Seward Peninsula, and Selawik) showed lake area decrease ranging between 4 -15%. The most significant change was noticed in Beringia and Central Seward Peninsula due to drainage of very large lakes. We found net lake area loss of about 15.3% (6318.1 ha or 108.1 ha/100 km2 net loss) and 12.4% (6542.1 ha or 110.2 ha/100 km2 net loss) since the 1970s in Beringia and Central Seward Peninsula, respectively. We noticed that 20 lakes larger than 100 ha drained in Beringia that contributed a total lake area loss of 4471.8 ha whereas 2 lakes larger than 100 ha drained in Central Seward Peninsula that contributed a total lake area loss of 6391.1 ha. Selawik experienced the highest number of drainage events but because most of the lakes that drained were small, the net lake area loss in Selawik is the smallest among all. Draining lakes in the 1-50 ha category in Selawik contributed an area loss of 5021.1 ha, which is about 81% of the total drainage area (6171.2 ha) in the region. Additionally, we saw expansion of lakes larger than 100 ha in Selawik by 7% (2812.3 ha) due to creation of water channels that coalesced multiple large lakes in the delta region. Hence, we observed a net lake area loss of 3.9% (3358.9 ha or 52.9 ha/100 km2 net loss) in Selawik. total lake surface area by 3.9% (204 ha or 9.7 ha/100 km2 net gain) due to expansion and coalescence of smaller lakes. In Kobuk, we observed formation of water channels fusing multiple large lakes in the delta region that contributed to a net lake area increase of 1.4% (383 ha or 19.9 ha/100 km2 net gain). Complex hydrological and landscape characteristics of the Yukon-Kuskokwim Delta region as well as shifting precipitation patterns could have played an important role influencing lake area change variability across this large lake district. Therefore, despite numerous large drainage events in Yukon-Kuskokwim Delta, we observed only a slight change in total lake area by 0.5% (3922.8 ha or 8.4 ha/100 km2 net gain). Our assessment shows that lake drainage is widespread in the western Alaska study region. Overall, we found that a large number of lakes in the 10 -100 ha size category drained with an estimated drainage rate of 11 lakes/year that contributed to an area loss of 304.6 ha/year. Not surprisingly, partial drainage of large lakes created numerous remnant pond and hence, lakes smaller than 10 ha increased at a rate of 115 lakes/year and 290 ha/year. Regional permafrost ice content in the lake districts dictated lake change patterns even though there was no direct relationship between permafrost extent and direction of lake change. We observed that lake change patterns transitioned from net area gain due to lake expansion to net area loss in the ice-rich continuous permafrost region, whereas net lake area loss dominated most of the regions with non-continuous permafrost types. Thus, as climate gets warmer and permafrost continues to thaw, we expect increased numbers of drainage events in the continuous permafrost zone of the western Alaska study region. Additionally, as permafrost becomes less stable, influence of other factors such as surficial geology and landscape characteristics likely will magnify the variability of lake area change. Since high spatial and temporal resolution imageries are readily available, assessment of lake area change in high northern latitudes should be continued to quantify the feedbacks associated with lake changes in a warming climate as well as to assist in future planning and decision-making for land and resource management issues related to lakes. References: Jorgenson, T. M., Yoshikawa, K., Kanevskiy, M., Shur, Y. L., Romanovsky, V., Marchenko, S., Grosse, G., Brown, J., Jones, B. 2008. Permafrost characteristics of Alaska. In Proceedings of the Ninth International Conference on Permafrost, Kane DL, Hinkel KM (eds). Fairbanks, AK; 121–122

Application of Graph-Analytical Method of Risk Analysis "The Tree Structures" For the Study of Complex Systems Survivability by the Example of Liquid Rocket Thrusters

The article is devoted to an important topic - the assessment of survivability of complex technical systems, discusses the need to develop a methodology of forecasting reliability of complex systems on the example of liquid rocket thrusters with running a part of composite materials under actual operating conditions for their successful practical use in the propulsion systems. It is proposed to use graph-analytical method of risk analysis "tree structures" (a method of prof. Romanovsky) to predict the behavior of such systems

Long-term release of carbon dioxide from Arctic tundra ecosystems in Alaska

Author Posting. © The Author(s), 2016. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Ecosystems 20 (2017): 960–974, doi:10.1007/s10021-016-0085-9.Releases of the greenhouse gases carbon dioxide (CO2) and methane (CH4) from thawing permafrost are expected to be among the largest feedbacks to climate from arctic ecosystems. However, the current net carbon (C) balance of terrestrial arctic ecosystems is unknown. Recent studies suggest that these ecosystems are sources, sinks, or approximately in balance at present. This uncertainty arises because there are few long-term continuous measurements of arctic tundra CO2 fluxes over the full annual cycle. Here, we describe a pattern of CO2 loss based on the longest continuous record of direct measurements of CO2 fluxes in the Alaskan Arctic, from two representative tundra ecosystems, wet sedge and heath tundra. We also report on a shorter time series of continuous measurements from a third ecosystem, tussock tundra. The amount of CO2 loss from both heath and wet sedge ecosystems was related to the timing of freeze-up of the soil active layer in the fall. Wet sedge tundra lost the most CO2 during the anomalously warm autumn periods of September – December 2013 - 2015, with CH4 emissions contributing little to the overall C budget. Losses of C translated to approximately 4.1% and 1.4% of the total soil C stocks in active layer of the wet sedge and heath tundra, respectively, from 2008 – 2015. Increases in air temperature and soil temperatures at all depths may trigger a new trajectory of CO2 release, which will be a significant feedback to further warming if it is representative of larger areas of the Arctic.This work was funded by the National Science Foundation Division of Polar Programs Arctic Observatory Network grant numbers 856864, 1304271, 0632264, and 1107892. This study was also partially funded by the NSF Alaska Experimental Program to Stimulate Competitive Research award number OIA-1208927.2017-11-2