Intellectual Merits. Glaciers in Alaska and elsewhere are melting, and glacier meltwater likely induces profound changes in hydrology and the functions of peatland ecosystems. However, we don?t know the magnitude and mechanisms of meltwater impacts at a regional scale nor potential feedbacks from the resulting changes in peatland carbon and water storage. This proposal intends to evaluate the hypothesis that climate-induced glacier melting has accelerated the lateral expansion and vertical growth of peatlands in the Susitna Valley of south-central Alaska.
This interdisciplinary project will document temporal and spatial changes in peatlands at a regional scale over the last 1000 years using field monitoring (interannual resolution), remote sensing (decadal resolution) and paleoecological (decadal to centennial resolution) techniques in paired glacierized and non-glacierized watersheds of the Susitna Basin. We will use modern ecological and hydrological monitoring and geochemical tracers to understand the connection between peatland dynamics and ongoing changes in climate and hydrology. We will reconstruct peatland moisture and C accumulation history to evaluate peatland responses to the Little Ice Age and Medieval Warm Period (past glacier advance and retreat events).
Broader Impacts. This project will bring together 4 junior researchers from diverse fields of ecology and paleoecology, hydroclimatology and low-temperature geochemistry, and remote sensing and ice/snow science to study both long-term ecosystem development and contemporary ecological and hydrologic dynamics. The project will initiate collaboration and interactions among them to bring fresh ideas and multidisciplinary tools together to conduct global change science in high latitudes and high altitudes. The project will include interdisciplinary training of graduate students and research experience for undergraduate students at Lehigh and Ohio State Universities.
An educational specialist at the Byrd Polar Research Center at OSU will use the results from this project to develop an innovative outreach program to improve the delivery of climate change information to middle and high school teachers. Also, the project will contribute materials to a new Polar Frontier exhibit (featuring Frontier Alaska) in the Columbus Zoo.
The results from this study will provide valuable insights into understanding the connections of climate change, glacier dynamics, hydrology, and ecosystems in a changing world. The project will contribute to disciplinary areas in hydrologic sciences, ecosystem studies, and geobiology and low-temperature geochemistry. Furthermore, the project has merited the support by ETBC (Emerging Topics in Biogeochemical Cycles) because it exemplifies interdisciplinary research focused on the tandem investigation of climate-water-carbon dynamics and physical-chemical-biological processes over a range of temporal and spatial scales.
This project investigated the dynamics and responses of carbon-rich peatland ecosystems to climate change in the recent past. The researchers used an interdisciplinary approach to study temporal and spatial changes in peatlands at a regional scale over the last 1000 years using field monitoring (interannual timescale), remote sensing (decadal timescale) and paleoecological (decadal to centennial timescale) techniques in the Susitna Basin of south-central Alaska. The peat-core multiple proxy results from the Kahiltna Valley show that peat accumulation was higher during the warm Medieval time about 800 year ago than the cold Little Ice Age at 600-100 years ago. However, these results also highlight the importance of local-scale controls, such as surficial geology, in mediating the response of peatland hydrology and carbon accumulation to climate change. The detailed analysis of multiple sites near Petersville demonstrate that peat accumulation increased 10-fold over the last 100 years, along with a major shift in the recent decades from highly decomposed sedge peat to rapidly accumulating peat moss (Sphagnum) peat. Once differential decomposition history was considered using three modeling approaches, the expected long-term accumulation rate of the past several decades was still 2–6 times greater than that of the past 4000 years. We propose that recent warming has led to Sphagnum establishment, which rapidly altered the peatland surface chemistry and hydrology, further promoting Sphagnum growth and enhancing the carbon sink capacity of this peatland. Longer and warmer growing seasons could also have stimulated plant growth. Our results imply that accelerated carbon accumulation under global warming in some wet peatlands might offset some of the carbon losses experienced from other peatland types. The integrated analysis using ground penetrating radar (GPR) and peat core analysis shows that local slope and topography have great impact on peatland development and that peatland expansion becomes slope-limited above a slope threshold of 0.5 degrees. Comparison of Landsat satellite images and historical air photos are equivocal about peatland extent change, as most areas in the study basin show barely noticeable changes in peatland extent or areas over the last 50 years. More obvious peatland expansion appears to occur in a low-elevation valley (Yentna Valley), possibly caused by higher temperature at these low elevation sites. We attributed the absence of widespread detectable peatland area change in the last 50 years to (1) low image resolution, especially of the 1950 air photos; (2) some changes occurred before the 1950s (the earliest available photos); and (3) no lateral expansion of peatlands at regional scale, despite higher rate of vertical accumulation (as reconstructed from peat-core analysis). The project so far resulted in five refereed publications, three dissertations and thesis, and 10 abstracts for presentations at national and international scientific conferences. The grant supported the training and education of three young scientists, including two Ph.D. students and one undergraduate student. Results and insights from this project have improved our understanding of geomorphology, hydrology and climate controls on peatland dynamics and carbon sequestration capacity.
