Quantification of Compound and Cascading Hydroclimatic Extreme Events

Compound and cascading hydroclimatic extreme events have garnered much attention in recent studies. The combined effects of interconnected extremes can cause widespread damage, with a higher potential impact than individual extremes. Both anthropogenic warming and natural climate variability affect these extremes, which is why detecting past extreme events, understanding the underlying mechanisms, and assessing their future impacts can aid in mitigation efforts to reduce their overall impact. However, thus far, identifying such events is oversimplified and the propagation of their impact as cascades from the physical to human systems remains partly explored. The overreaching goal of this thesis is to develop robust methodologies to quantify the compound and cascading extreme events, such as drought and heatwaves, extreme precipitation and atmospheric rivers, extreme heat and humidity, and flash droughts in the past and future climate. A suite of advanced statistical methods, system dynamics, and causality approaches are implemented to achieve the research goal. This thesis consists of ten chapters, and the objective of each chapter are summarized as follows. (1) Chapter 1 provides a brief introduction and examples of various compound and cascading hydroclimatic extremes. (2) Chapter 2 provides a perspective of drought indices and highlights the challenges in the context of climate change. (3) The objective of chapter 3- chapter 5 is to quantify the compound drought and heatwave characteristics (frequency, duration, and severity) and investigate their association with natural climate variability, anthropogenic warming, land-climate feedback, and background aridity across the globe. (4) Chapter 6 is dedicated to quantifying the future changes in the potential impact of heat-stress (combination of extreme heat and humidity) on the human population. (5) The cascading influence of meteorological forcing on the moisture advection processes associated with extreme precipitation related to atmospheric rivers is discussed in chapter 7. (6) The objective of chapter 8 is to investigate and quantify the compound and cascading influence of different spatial drivers, such as precipitation, temperature, surface-energy portioning, soil moisture-temperature coupling strength, and vapor pressure deficit on the evolution and intensification of global flash droughts. (7) Chapter 9 proposes a methodology to quantify the compound and cascading effects in a dry-hot event network using a system dynamics approach. Finally, the conclusion and recommendations are provided in chapter 10

HIGH-RESOLUTION STABLE ISOTOPE ANALYSIS OF BIOGENIC CARBONATES AS PROXY EVIDENCE FOR HOLOCENE ENVIRONMENTAL CHANGE: EXAMPLES FROM AUTHIGENIC LAKE CARBONATE AND BIVALVE ISOTOPE PROFILES

Biogenic carbonates are valuable archives of paleoenvironmental information because they record chemical signatures of ambient environmental conditions during their formation. Therefore, long-term records of biogenic carbonates provide long-term records of environmental conditions that can be utilized to develop climate histories for specific regions to explore past climatic change. Traditionally, these studies have been conducted with low temporal resolution owing to analytical or economical restrictions. Although these records provide valuable information surrounding long-term climatic change, they lack the resolution to resolve the short-term climatic oscillations such as the Pacific Decadal Oscillation and El Niño Southern Oscillation that drive environmental change. This dissertation focuses on using high-resolution stable isotope analysis of biogenic carbonates for paleoenvironmental reconstruction and associated applications. Three studies are presented herein, applying increasing sampling resolution from sub-centennial, to sub-decadal, to sub-seasonal, that illustrate the diversity of paleoenvironmental information gained with each increase in resolution. The first study uses sub-centennial oxygen isotope analysis of authigenic lake carbonate to assess how climate change has affected precipitation patterns in the southern Yukon Territory from the end of the last glacial to the present day. Large changes in atmospheric circulation patterns associated with changes in the strength of the North Pacific High and the Aleutian Low pressure systems lead to variations in the oxygen isotope value of precipitation in the southwest Yukon Territory recorded in the oxygen isotope values of lake carbonate. The degradation of a glacial anticyclone led to a reduction in strength of the Aleutian Low coupled with an increase in the strength of the North Pacific High resulting in an increase in summer precipitation to the southwest Yukon represented by an increase in effective moisture following the transition from the Late Pleistocene to the Early Holocene. The second study is a sub-decadal oxygen isotope record of lacustrine carbonate stretching back 8,000 years to quantify the strength and state of the Pacific/North American (PNA) Index through time. This study relies on the relationship between the PNA Index and the oxygen isotope values of precipitation from central Canada (Birks and Edwards, 2009), and the ability of Sturgeon Lake to accurately represent 18O values of precipitation. Results show that the strength of the PNA varied through time. The Early to Mid-Holocene (8,000- 4,200 years BP) is characterized by large fluctuations between PNA+ and PNA– phases; PNA–-like conditions dominate the period after 4,200 years BP; and ~1,800 years BP PNA+-like conditions resume. Changes in the Holocene PNA pattern are shown to be contemporaneous with similar changes in Holocene records of El Niño illustrating the intrinsic relationship between Pacific climate patterns. The final study uses sub-seasonal oxygen isotope records from bivalves derived from an overwash deposit to define the seasonality of the deposit. Data indicate a late spring to early summer timing of deposition that presents an alternative interpretation to the previous late fall tsunami origin hypothesis. In conclusion, this dissertation focused on improving our understanding of how paleoenvironmental information is archived in biogenic carbonates by focusing on the use of high-resolution sampling strategies. Modifying the sampling resolution resulted in an enhanced understanding of how short-term climate oscillations drive climate and illustrates how the type of paleoenvironmental information generated varies with sampling resolution

Earth Observations for Addressing Global Challenges

"Earth Observations for Addressing Global Challenges" presents the results of cutting-edge research related to innovative techniques and approaches based on satellite remote sensing data, the acquisition of earth observations, and their applications in the contemporary practice of sustainable development. Addressing the urgent tasks of adaptation to climate change is one of the biggest global challenges for humanity. As His Excellency António Guterres, Secretary-General of the United Nations, said, "Climate change is the defining issue of our time—and we are at a defining moment. We face a direct existential threat." For many years, scientists from around the world have been conducting research on earth observations collecting vital data about the state of the earth environment. Evidence of the rapidly changing climate is alarming: according to the World Meteorological Organization, the past two decades included 18 of the warmest years since 1850, when records began. Thus, Group on Earth Observations (GEO) has launched initiatives across multiple societal benefit areas (agriculture, biodiversity, climate, disasters, ecosystems, energy, health, water, and weather), such as the Global Forest Observations Initiative, the GEO Carbon and GHG Initiative, the GEO Biodiversity Observation Network, and the GEO Blue Planet, among others. The results of research that addressed strategic priorities of these important initiatives are presented in the monograph

Integration Frameworks for Merging Satellite Remote Sensing Observations with Hydrological Model Outputs

With a growing number of available datasets especially from satellite remote sensing, there is a great opportunity to improve our knowledge of hydrological processes by integrating them with hydrological models. In this regard, data assimilation technique can be used to constrain the dynamic of a model with available observations in order to improve its estimates. In this thesis, a comprehensive data assimilation framework containing multiple stages is proposed and tested over various areas

Annual Report: 2008

I submit herewith the annual report from the Agricultural and Forestry Experiment Station, School of Natural Resources and Agricultural Sciences, University of Alaska Fairbanks, for the period ending December 31, 2008. This is done in accordance with an act of Congress, approved March 2, 1887, entitled, “An act to establish agricultural experiment stations, in connection with the agricultural college established in the several states under the provisions of an act approved July 2, 1862, and under the acts supplementary thereto,” and also of the act of the Alaska Territorial Legislature, approved March 12, 1935, accepting the provisions of the act of Congress. The research reports are organized according to our strategic plan, which focuses on high-latitude soils, high-latitude agriculture, natural resources use and allocation, ecosystems management, and geographic information. These areas cross department and unit lines, linking them and unifying the research. We have also included in our financial statement information on the special grants we receive. These special grants allow us to provide research and outreach that is targeted toward economic development in Alaska. Research conducted by our graduate and undergraduate students plays an important role in these grants and the impact they make on Alaska.Financial statement -- Grants -- Students -- Research reports: Partners, Facilities, and Programs; Geographic Information; High-Latitude Agriculture; High-Latitude Soils, Management of Ecosystems; Natural Resources Use and Allocation; Index to Reports -- Publications -- Facult