Hood, Eran
http://hdl.handle.net/11122/12159
2024-03-29T07:40:44ZBig avalanches in a changing climate: Using tree-ring Derived avalanche chronologies to examine avalanche frequency across multiple climate types
http://hdl.handle.net/11122/14924
Big avalanches in a changing climate: Using tree-ring Derived avalanche chronologies to examine avalanche frequency across multiple climate types
Peitzsch, Erich H.; Pederson, Gregory; Martin, Justin; Hood, Eran; Greene, Ethan; Birkeland, Kelly Elder; Wolken, Gabriel; Kichas, Nick; Stahle, Daniel; Harley, John R.
Large-magnitude snow avalanches pose a hazard to humans and infrastructure worldwide. Analyzing the spatiotemporal behavior of avalanches and the contributory climate factors is important for understanding historical variability in climate-avalanche relationships as well as improving avalanche forecasting. This study uses established dendrochronological methods to develop long-term regional avalanche chronologies for three different climate types: high-latitude maritime climate of southeast Alaska, intermountain climate of the northern Rocky Mountains, and continental climate of Colorado. In the maritime study area, we collected 434 cross sections throughout six avalanche paths near Juneau, Alaska. This resulted in 2706 identified avalanche growth disturbances between year 1720 and 2018 Common Era (CE), which allowed us to reconstruct 82 years with large magnitude avalanche activity across three sub-regions. By combining this tree-ring derived avalanche dataset with a suite of climate and atmospheric variables and applying a generalized linear model to fit a binomial regression, we found February and March precipitation and the Oceanic Niño Index (ONI) were significant predictors of large magnitude avalanche activity in the southeast Alaska study area. In the intermountain climate study area, tree-rings from 647 trees exhibited 2134 avalanche-related growth disturbances in the northern Rocky Mountains of northwest Montana from 1867 to 2019. The data show that the amount of snowpack across the northern Rocky Mountain region is directly related to avalanche probability. Coincident with warming and regional snowpack reductions, a decline of ~ 14% (~ 2% per decade) in overall large magnitude avalanche probability is apparent through the period 1950–2017 CE. In the continental climate of Colorado, we sampled 24 avalanche paths throughout the state and collected 1188 total samples with 4135 identified growth disturbances from 1698 to 2019. Preliminary results suggest years with large magnitude avalanche activity across the sub-regions of this study area are generally characterized by stormy winters with above average snowpack development but that early and late winter temperature and precipitation also play an important role in large avalanche activity. Characterizing historical climate-avalanche relationships across different climate types provides a broad baseline for understanding potential future changes in avalanche activity. Overall, this work helps forecasters and planners better understand the influence of climate on large magnitude avalanche frequency, and how potential changes in avalanche character and occurrence will affect their operations in the context of a warming climate.
2023-10-08T00:00:00ZHydroclimate drives seasonal riverine export across a gradient of glacierized high-latitude coastal catchments
http://hdl.handle.net/11122/14910
Hydroclimate drives seasonal riverine export across a gradient of glacierized high-latitude coastal catchments
Jenckes, J.; Munk, L. A.; Ibarra, D. E.; Boutt, D. F.; Fellman, Jason; Hood, Eran
Glacierized coastal catchments of the Gulf of Alaska (GoA) are undergoing rapid hydrologic fluctuations in response to climate change. These catchments deliver dissolved and suspended inorganic and organic matter to nearshore marine environments, however, these glacierized coastal catchments are relatively understudied and little is known about total solute and particulate fluxes to the ocean. We present hydrologic, physical, and geochemical data collected during April–October 2019–2021 from 10 streams along gradients of glacial fed to non-glacial (i.e., precipitation) fed, in one Southcentral and one Southeast Alaska region. Hydrologic data reveal that glaciers drive the seasonal runoff patterns. The ẟ18O signature and specific conductance show distinctive seasonal variations in stream water sources between the study regions apparently due to the large amounts of rain in Southeast Alaska. Total dissolved solids concentrations and yields were elevated in the Southcentral region, due to lithologic influence on dissolved loads, however, the hydroclimate is the primary driver of the timing of dissolved and suspended yields. We show the yields of dissolved organic carbon is higher and that the δ13CPOC is enriched in the Southeast streams illustrating contrasts in organic carbon export across the GoA. Finally, we illustrate how future yields of solutes and sediments to the GoA may change as watersheds evolve from glacial influenced to precipitation dominated. This integrated analysis provides insights into how watershed characteristics beyond glacier coverage control properties of freshwater inputs to the GoA and the importance of expanding study regions to multiple hydroclimate regimes.
2023-04-14T00:00:00ZRiverine dissolved inorganic carbon export from the Southeast Alaskan Drainage Basin with implications for coastal ocean processes
http://hdl.handle.net/11122/14904
Riverine dissolved inorganic carbon export from the Southeast Alaskan Drainage Basin with implications for coastal ocean processes
Harley, John R.; Biles, Frances E.; Brooks, Mariela K.; Fellman, Jason M.; Hood, Eran; D'Amore, David V.
Dissolved inorganic carbon (DIC) represents an important but poorly constrained form of lateral carbon flux to the oceans. With high precipitation rates, large glaciers, and dense temperate rainforest, Southeast Alaska plays a critical role in the transport of carbon to the Gulf of Alaska (GOA). Previous estimates of DIC flux across the Southeast Alaska Drainage Basin (SEAKDB) are poorly constrained in space and time. Our goal was to incorporate recent measurements of DIC concentrations with previous measurements from the U.S. Geological Survey in order to model the spatial and temporal patterns of riverine DIC transport from SEAK to the GOA. We aggregated DIC concentration measurements from 1957 to 2020 and associated measurements of mean daily discharge. We then constructed load estimation models to generate concentration predictions across 24 watersheds. By spatially matching measurements of DIC with SEAKDB watersheds, we extrapolated concentration predictions across 2,455 watersheds encompassing approximately 190,000 km2. Models were aggregated according to two factors, the presence of karst and the discharge regime. Finally, monthly flux predictions were generated for each watershed using predicted concentrations and runoff estimates from the Distributed Climate Water Balance Model. Mean annual DIC flux from the SEAKDB was 2.36 Tg C with an average yield of 12.52 g C m−2. Both karst presence and flow regimes modified DIC flux and speciation across coastal marine areas. The high resolution of DIC flux estimates will provide useful inputs for describing seasonal C dynamics, and further refines our understanding of C budgets in the Pacific temperate rainforest and the surrounding marine environment.
2023-10-16T00:00:00ZA tropical cocktail of organic matter sources: Variability in supraglacial and glacier outflow dissolved organic matter composition and age across the Ecuadorian Andes
http://hdl.handle.net/11122/14837
A tropical cocktail of organic matter sources: Variability in supraglacial and glacier outflow dissolved organic matter composition and age across the Ecuadorian Andes
Holt, Amy D.; Kellerman, Anne M.; Battin, Tom I.; McKenna, Amy M.; Hood, Eran; Andino, Patricio; Crespo-Perez, Veronica; Peter, Hannes; Schon, Martina; De Staercke, Vincent; Styllas, Michail; Tolosano, Matteo; Spencer, Robert G. M.
The biogeochemistry of rapidly retreating Andean glaciers is poorly understood, and Ecuadorian glacier dissolved organic matter (DOM) composition is unknown. This study examined molecular composition and carbon isotopes of DOM from supraglacial and outflow streams (n = 5 and 14, respectively) across five ice capped volcanoes in Ecuador. Compositional metrics were paired with streamwater isotope analyses (δ18O) to assess if outflow DOM composition was associated with regional precipitation gradients and thus an atmospheric origin of glacier DOM. Ecuadorian glacier outflows exported ancient, biolabile dissolved organic carbon (DOC), and DOM contained a high relative abundance (RA) of aliphatic and peptide-like compounds (≥27%RA). Outflows were consistently more depleted in Δ14C-DOC (i.e., older) compared to supraglacial streams (mean −195.2 and −61.3‰ respectively), perhaps due to integration of spatially heterogenous and variably aged DOM pools across the supraglacial environment, or incorporation of aged subglacial OM as runoff was routed to the outflow. Across Ecuador, Δ14C-DOC enrichment was associated with decreased aromaticity of DOM, due to increased contributions of organic matter (OM) from microbial processes or atmospheric deposition of recently fixed and subsequently degraded OM (e.g., biomass burning byproducts). There was a regional gradient between glacier outflow DOM composition and streamwater δ18O, suggesting covariation between regional precipitation gradients and the DOM exported from glacier outflows. Ultimately, this highlights that atmospheric deposition may exert a control on glacier outflow DOM composition, suggesting regional air circulation patterns and precipitation sources in part determine the origins and quality of OM exported from glacier environments.
2023-05-09T00:00:00Z