2023

Hindcasted bioenergetics modeling of juvenile Chinook salmon (Oncorhynchus tschawytscha) within the Kenai River system to inform future climate projections

Anonymous — Thu, 13 Apr 2023 17:26:48 +0000

Hindcasted bioenergetics modeling of juvenile Chinook salmon (Oncorhynchus tschawytscha) within the Kenai River system to inform future climate projections Anonymous (not verified) Thu, 04/13/2023 - 11:26 Peyton Thomas

The Arctic is one of the fastest warming regions on the planet, yet there is limited data capturing baseline environmental conditions to inform future projections. Likewise, there is limited information regarding the energetic condition and fitness of native fish species with both cultural and consumptive values to Indigenous communities. We used a river routing model (mizuRoute) and a river temperature model (RBM) forced by the Regional Arctic System Model (RASM) to simulate Kenai River flows and river temperature. The RASM produced meteorological forcing data optimized on streamflow and snowpack at a resolution of 4 km. The RBM was optimized using USGS gages for discharge and temperature. Using this hindcast river data and historical biometric data available through colleagues, literature, and publicly accessible databases for the Kenai Peninsula, we estimated historical growth rates during the open water period (May-September) for Age-0 Chinook salmon (Oncorhynchus tschawyscha). The goal of these outputs is to use historical bioenergetic baseline data to estimate future changes in fish growth and survival under mid-century (2035-2065) climatic and hydrological conditions.

Environmental Studies and INSTAAR Postdoctoral Scholar, �鶹��Ѱ��Boulder

Peyton Thomas

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Optimizing a high-resolution river temperature model for Alaskan Rivers

Anonymous — Thu, 13 Apr 2023 17:15:00 +0000

Optimizing a high-resolution river temperature model for Alaskan Rivers Anonymous (not verified) Thu, 04/13/2023 - 11:15 Dylan Blaskey

River temperature is a critical variable that influences the physical, chemical, and biological functions of ecosystems. Climate change is predicted to increase river temperatures worldwide, adding additional stress to these water bodies and the people who depend on them. However, river temperature and discharge observations are spatially and temporally sparse in Alaska, which makes it difficult to understand the impacts of changing river temperature. In this study, we develop a high-resolution river temperature and discharge dataset for rivers in Alaska and the Canadian Yukon River Basin from 1990 to 2021 coupling the physically based river routing (mizuRoute) and river temperature models (River Basin Model) with the 4 km resolution Regional Arctic System Model. We optimize RBM using an adaptive surrogate-based model on eleven sensitive parameters across nine river temperature gages within our study domain. RBM was validated on 18 gages, of which nine were out-of-sample. The mean root-mean-square error of daily temperature decreased in a four-year evaluation, indicating the effectiveness of our optimization. Our model will produce a high-resolution river temperature dataset, which improves the data availability for Alaska that can help inform management and conservation efforts in the region.

Civil, Environmental, and Architectural Engineering Graduate Student, �鶹��Ѱ��Boulder

Dylan Blaskey

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Understanding Arctic Precipitation: How and When Does it Change in CESM2?

Anonymous — Thu, 13 Apr 2023 17:05:14 +0000

Understanding Arctic Precipitation: How and When Does it Change in CESM2? Anonymous (not verified) Thu, 04/13/2023 - 11:05 Sean Leister

The Arctic surface has warmed 2-3x faster than the global mean in recent decades and will continue to see unprecedented warming with continued climate change. Though harder to observe, the Arctic hydrologic cycle is also seeing considerable change. Modeling studies and theory suggest that Arctic mean precipitation increases more than twice as much as global mean precipitation per degree of global warming. Superimposed on top of these mean increases are robust increases in Arctic precipitation variability, increasing the risk of extreme precipitation events and adding to the vulnerability of the already fragile Arctic ecosystem. Understanding the changing Arctic hydrologic cycle under increasing surface warming is an important area of ongoing research. Here, we prescribe sea surface temperatures and sea ice extent in four 50 year atmosphere-only CESM2 simulations to better understand the uncoupled response of the Arctic to atmospheric moisture changes. We then quantify the relative influence that poleward atmospheric moisture transport and evaporation have on Arctic precipitation change. Initial results show that evaporation and moisture transport are sensitive to changes in boundary conditions across our four simulations. Overall, we find that remote moisture transport dominates spring, summer, and fall precipitation change, while local surface evaporation dominates winter precipitation change.

Atmospheric and Oceanic Sciences (ATOC)/Cooperative Institute for Research in Environmental Sciences (CIRES) Graduate Student, �鶹��Ѱ��Boulder

Sean Leister

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Shifts in riverine biofilms induced by WUI-fires and wastewater effluent

Anonymous — Thu, 13 Apr 2023 16:25:42 +0000

Shifts in riverine biofilms induced by WUI-fires and wastewater effluent Anonymous (not verified) Thu, 04/13/2023 - 10:25 William Johnson , Cresten Mansfeldt

The current age is increasingly being described as the pyrocene, where large biogeographic shifts are induced by more intense and frequent wildfires. Concurrently, due in part to the increasing extent of the wildland-urban interface, where people live in close proximity to wildland vegetation, there have been a number of recent wildfires where wildfire has intersected cities and burned homes and other human infrastructure. While it is expected that WUI-fires may generate a different toxicant profile than wildland-fires, the impact of WUI-fires on aquatic systems has been under characterized. This presentation will detail benchtop experiments to determine the effects of WUI-fire ash and wastewater effluent, a common co-occurring anthropogenic input, on microbial community structure.

Presentation by William Johnson, Graduate Student, Civil, Architectural, and Environmental Engineering, �鶹��Ѱ��Boulder

Cresten Mansfeldt, Assistant Professor, Environmental Engineering, �鶹��Ѱ��Boulder

William Johnson

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Atmosphere to surface profiles of water vapor isotopes and meteorological conditions over the northeast Greenland ice sheet reveals the role of sublimation to the ice sheet hydrological cycle

Anonymous — Thu, 13 Apr 2023 16:15:20 +0000

Atmosphere to surface profiles of water vapor isotopes and meteorological conditions over the northeast Greenland ice sheet reveals the role of sublimation to the ice sheet hydrological cycle Anonymous (not verified) Thu, 04/13/2023 - 10:15 Kevin Rozmiarek , Laura Dietrich , Bruce Vaughn , Mike Town , Bradley Markle , Valarie Morris , Hans Christian Steen-Larsen , Xavier Fettweis , Chloe Brashear , Hayley Bennett , Tyler Jones

The isotopic composition of water in ice cores is used as a proxy for past climate. Traditional interpretation of this recorded climate signal is that during formation precipitation captures a snapshot of the column integrated atmosphere. In recent work, observations have documented that the snow isotopic composition changes during the post-depositional interaction with the near-surface atmosphere. To more accurately interpret the climate signal in ice cores an better understand the surface mass balance budget, it is necessary to understand the source of the water vapor in the planetary boundary layer (PBL), as well as the vertical mixing and transportation in the polar atmosphere. However, the dynamics in the polar PBL are poorly constrained in most climate models due to a lack of observations. Here we present insights from the first Arctic in-situ water-vapor isotope record both within and above the PBL up to 1500 meters above the Greenland Ice Sheet (GrIS) from the EastGRIP ice core camp 2022 summer field campaign. A total of 105 flights were performed with a fixed-wing uncrewed aircraft recording high resolution atmospheric profiles. Moreover, air is sampled in glass flasks and brought to the surface for determination of δ18O and δD of water vapor. Based on observed temperature, humidity and isotopic profiles we identify the typical atmospheric structure above the GrIS. We evaluate the vertical atmospheric representation of the polar regional climate model MAR and the isotope-enabled global climate models. Finally, from observations, we provide evidence for the role of sublimated water vapor in determining the isotopic composition of water above the surface.

Presentation by Kevin Rozmiarek, Graduate Student Geological Sciences, �鶹��Ѱ��Boulder

Kevin Rozmiarek

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Understanding how urbanization affects streamflow in the Denver Metro area

Anonymous — Thu, 13 Apr 2023 15:20:47 +0000

Understanding how urbanization affects streamflow in the Denver Metro area Anonymous (not verified) Thu, 04/13/2023 - 09:20 Santiago Ramírez-Núñez

Urban development transforms the natural hydrologic regime and has significant effects on baseflow and storm runoff. Colorado’s population is expected to increase to 7.48 million by 2050. 85% of the population is projected to reside along the Front Range with the Denver Metro area hosting about 45% of this population. Previous studies have analyzed changes in streamflow driven by urban development in the Denver Metro area and have found considerable effects on the magnitude and duration of streamflow and baseflow. We aim to build on this work by developing predictive models for changes in streamflow considering different watershed characteristics. For this, 21 gauged watersheds with different extent of urbanization located in the Denver Metro area will be analyzed. The studied watersheds range in size from 0.73 km2 to 89.61 km2, and in imperviousness from 0.8% to 47.3%. So far, the analysis suggests that the lower values of imperviousness have a linear relationship with the median discharge, but other watershed characteristics should be explored for a better fit in the higher end of imperviousness. These predictive models will help us determine what most affects the streamflow change from an undeveloped watershed to traditionally developed watershed. The results of this project will help decision makers in the urban planning process by providing a tool to explore the potential effects of different future urban development scenarios on streamflow.

Graduate Student Civil, Environmental, and Architectural Engineering, �鶹��Ѱ��Boulder

Santiago Ramírez-Núñez

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Stream Water Quality and Soil Health After Compound Disturbance: A History of Forest Harvesting, Severe Wildfire, and Post-Fire Management in a Western Oregon Watershed

Anonymous — Wed, 12 Apr 2023 21:10:27 +0000

Stream Water Quality and Soil Health After Compound Disturbance: A History of Forest Harvesting, Severe Wildfire, and Post-Fire Management in a Western Oregon Watershed Anonymous (not verified) Wed, 04/12/2023 - 15:10 Katherine McCredie

The impact of large, high severity wildfires on soil health and stream water quality remains poorly understood, in part, due to the lack of tightly controlled, landscape scale experiments that integrate the effects from fire and land use activities. In 2020, the Archie Creek fire burned ~53,230 ha of forested land in Oregon, with ~77% at moderate to high severity. The burn area included the Hinkle Creek watershed, an intensively managed Douglas-fir (Pseudotsuga menziesii) plantation, which was previously studied from 2002–2011 to investigate the effects of forest harvesting on streamflow and water quality. We are leveraging the existing study sites to compare pre-harvest, post-harvest, and post-fire stream water nitrate concentrations (NO3-). We are also quantifying the effect of fire on saturated hydraulic conductivity (Ksat), soil nitrogen (NO3-, NH4+, potentially mineralizable N), and active soil carbon to understand the mechanisms driving in-stream responses. We applied a chronosequence study design across a matrix of forest harvesting to disentangle the potential variability in fire effects. In 2021, we began collecting stream water samples at six of the historic locations. Within the riparian zones, we collected soil cores (0–5 cm) for soil hydraulic properties and soil samples (0–15 cm) for nutrient analysis at ~60 sites. Historically, stream NO3- did not vary substantially in harvested catchments; the average concentrations were 0.15 ± 0.03 (SE) mg L-1 during pre-harvest and 0.18 mg L-1 ± 0.02 during post-harvest. However, preliminary results from our post-fire study indicate a substantial variation among streams, with post-fire concentrations ranging from 0.16 ± 0.04 mg L-1 to 1.46 ± 0.15 mg L-1. We have observed a positive linear relationship between stream NO3- concentrations and the extent of catchment burned at low and moderate severities (r2 = ~0.55, p <0.001). Contrary to findings from other studies (Rhoades et al., 2011), we have observed a negative relationship with high severity burn and stream NO3- (r2 = -0.76, p<0.001), signaling the potential influence of other localized factors. Extractable soil N in year one appears to be elevated by fire. However, by year two, we observed a ~54% reduction in NO3-, ~59% reduction in NH4+, and ~69% increase in potentially mineralizable N. Critical questions remain about the timing and legacy of nutrient pulses after wildfire. Watershed-scale studies, such as this, allow us to evaluate the links between soil properties and water quality following fire disturbance in western forest ecosystems.

Graduate Student Forest Ecosystems & Society, College of Forestry, Oregon State University

Katherine McCredie

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Beaver dams as sites of carbon accretion and sediment storage and implications for river restoration

Anonymous — Wed, 12 Apr 2023 21:00:49 +0000

Beaver dams as sites of carbon accretion and sediment storage and implications for river restoration Anonymous (not verified) Wed, 04/12/2023 - 15:00 Huck Rees

In recent years, land managers, restoration practitioners, and government agencies increasingly have been employing beaver-based restoration techniques in rivers and streams, including reintroduction of beaver populations and construction of beaver dam analogues (BDAs). Beaver-based restoration has the potential beneficial effects of increasing geomorphic heterogeneity, increasing riparian vegetation biomass, storing water on the landscape, creating habitat for biota, and storing fine sediment and associated pollutants, nutrients, and organic carbon (OC). However, the rates sediment and OC accrual within beaver ponds are not adequately quantified. We conducted sediment surveys and radiometric dating of sediment cores within beaver ponds in the southern Rocky Mountains of Colorado at Manitou Experimental Forest and Coal Creek near Crested Butte. Sediment samples and cores were analyzed for OC content (%) and converted to total OC stock per area. Using a time-series of historical aerial imagery coupled with 7Be:210Pb radionuclide dating, we calculated sedimentation and carbon accretion rates. One of our study locations, Trout Creek, is an incised stream impacts by flow regulation and cattle grazing. We compare rates of sediment accumulation in beaver ponds to the amount of sedimentation that would be required to reconnect the channel to the abandoned floodplain in this system. Our study aims to provide insight into the rates at which beaver-based restoration can address human-caused stream incision. Understanding these processes on a variety of timescales, including both short-term (1-10 year) and multidecade (10-100 year), will aid river management decisions.

Graduate Student Geography, �鶹��Ѱ��Boulder

James Rees

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post-MORDM: mapping policies to synthesize optimization and robustness results for decision-maker compromise

Anonymous — Wed, 12 Apr 2023 16:40:11 +0000

post-MORDM: mapping policies to synthesize optimization and robustness results for decision-maker compromise Anonymous (not verified) Wed, 04/12/2023 - 10:40 Nathan Bonham

This paper introduces post-MORDM, a decision-support framework that augments Many Objective Robust Decision Making (MORDM). MORDM often creates an intractable number of environmental management policies, characterized by decision variable, objective, and robustness values. This large number of policies inhibits decision support, causing disagreements among decision-makers. Post-MORDM addresses these challenges via the Self-Organizing Map (SOM), synthesizing MORDM data as layers organized in a map-like coordinate system. It uses the SOM to cluster policies, discover salient characteristics, and assess cause-effect relationships between decision-maker choices (i.e. decision variable values) and performance (objective and robustness values). Overall, the goal of post-MORDM is to create a structured platform that encourages negotiation and compromise. We demonstrate post-MORDM with a case study of two illustrative decision-makers for reservoir operation policy in the Colorado River Basin, USA. Post-MORDM helps communicate tradeoffs between storage and delivery objectives, relate tradeoffs to shortage policies, and identify mutually feasible policies.

Graduate Student Civil Engineering, CU Boulder

Nathan Bonham

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Variability of Residence Time in Arctic Back-Barrier Estuaries

Anonymous — Wed, 12 Apr 2023 04:53:05 +0000

Variability of Residence Time in Arctic Back-Barrier Estuaries Anonymous (not verified) Tue, 04/11/2023 - 22:53 Tina Geller

Along a quarter of the Beaufort Sea coast, back-barrier estuaries modulate the transport and transformation of nitrogen and carbon, impacting food webs and carbon budgets. It is unclear what effect rapid Arctic change will have on coastal biogeochemistry, partly because present-day spatial and temporal variability of residence time in Arctic back-barrier estuaries is unknown, which complicates efforts to predict future change. This study investigates the residence time of water in Arey, Kaktovik, and Jago Lagoons, three back-barrier estuaries along the Beaufort Sea coast of northern Alaska. Estimates of residence time based on the volume of the lagoon and river input suggest that residence time in the model domain range from less than one month to several months, depending on the river discharge. These preliminary results assume the estuary is not frozen and is in steady state. Ongoing work to investigate the spatial and temporal variability in residence time of water in these estuaries includes implementing a hydrodynamic numerical model, the Regional Ocean Modeling System (ROMS). The model accounts for processes including local winds, rivers, and larger scale circulation in 2019, and future work includes accounting for sea ice and waves, as well as validating the model. Analysis will focus on spatial and temporal variations in residence time and other circulation dynamics. Results will inform efforts to predict future coastal Arctic changes to circulation and carbon cycles.

Graduate student Atmospheric and Oceanic Sciences, CU Boulder

Tina Geller

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