Media Advisory: Highlights of CIRES science at AGU

Scientists from the Cooperative Institute for Research in Environmental Sciences (CIRES) will present new research at next week’s American Geophysical Union (AGU) Fall Meeting in San Francisco.

Reporters are invited to attend our scientists’ scheduled talks and poster presentations. Among the issues our scientists will be focusing on are:

  • Air-quality impacts of oil and gas operations in Utah and Colorado
  • Postwildfire land erosion
  • Mountain pine beetle impacts on water resources
  • Regional vulnerability to water scarcity
  • Changes to the Greenland and Antarctic ice sheets

Scientists from the National Snow and Ice Data Center (NSIDC), which is part of CIRES, will also present new research on permafrost, Arctic sea ice, ice sheet mass balance in Antarctica, glaciers in High Asia’s Himalaya-Karakoram region, and dust on snow cover. 

For NSIDC press highlights for the meeting, view
and for updates from the meeting, follow @NSIDC on Twitter. For a full list of presentations by NSIDC scientists and staff, see the NSIDC Events Web page

Below, find highlights of potential interest to journalists:

Tuesday, Dec. 4

Source signature of volatile organic compounds (VOCs) associated with oil and natural gas operations in Utah and Colorado (Invited)

Jessica Gilman, CIRES scientist working at NOAA's Earth System Research Laboratory
Presentation A21J-07
9:40 a.m.–10:00 a.m.; 3008 (Moscone West)

The U.S. Energy Information Administration has reported a sharp increase in domestic oil and natural gas production from “unconventional” reserves (e.g., shale and tight sands) between 2005 and 2012. The recent growth in drilling and fossil fuel production has led to environmental concerns regarding local air quality. Severe wintertime ozone events (greater than 100 ppb ozone) have been observed in Utah’s Uintah Basin and Wyoming’s Upper Green River Basin, both of which contain large natural gas fields. Raw natural gas is a mixture of approximately 60-95 mole percent methane while the remaining fraction is composed of volatile organic compounds (VOCs) and other non-hydrocarbon gases. We measured an extensive set of VOCs and other trace gases near two highly active areas of oil and natural gas production in Utah’s Uintah Basin and Colorado’s Denver-Julesburg Basin in order to characterize primary emissions of VOCs associated with these industrial operations and identify the key VOCs that are precursors for potential ozone formation. UBWOS (Uintah Basin Winter Ozone Study) was conducted in Uintah County located in northeastern Utah in January-February 2012. Two Colorado studies were conducted at NOAA’s Boulder Atmospheric Observatory in Weld County in northeastern Colorado in February-March 2011 and July-August 2012 as part of the NACHTT (Nitrogen, Aerosol Composition, and Halogens on a Tall Tower) and SONNE (Summer Ozone Near Natural gas Emissions) field experiments, respectively. The C2-C6 hydrocarbons were greatly enhanced for all of these studies. For example, the average propane mixing ratio observed during the Utah study was 58 ppb (median = 35 ppb, minimum = 0.8, maximum = 520 ppb propane) compared to urban averages which range between 0.3 and 6.0 ppb propane. We compare the ambient air composition from these studies to urban measurements in order to show that the VOC source signature from oil and natural gas operations is distinct and can be clearly distinguished from typical urban emissions associated with on-road combustion sources. We show that each geologic basin has a unique VOC source signature. We will examine the effects of photochemical processing of the primary VOC emissions by comparing the composition and OH reactivity for the wintertime studies to the summertime when there is active photochemistry occurring.

Emissions from oil and natural gas operations in northeastern Utah

Gabrielle Petron, CIRES scientist working at NOAA's Earth System Research Laboratory
Poster Presentation A23B-0214
1:40 p.m.–6:00 p.m.; Hall A-C (Moscone South)

The Uintah oil and natural gas Basin in Northeastern Utah experienced several days of high ozone levels in early 2011 during cold temperature inversions. To study the chemical and meteorological processes leading to these wintertime ozone pollution events, the State of Utah, EPA region 8 and oil and gas operators pulled together a multi-agency research team, including NOAA ESRL/CIRES scientists. The data gathering took place between January 15 and February 29, 2012.To document the chemical signature of various sources in the Basin, we outfitted a passenger van with in-situ analyzers (Picarro: CH4, CO2, CO, H2O, 13CH4; NOxCaRD: NO, NOx, 2B & NOxCaRD: O3) meteorological sensors, GPS units, discrete flask sampling apparatus, as well as a data logging and “real-time” in-situ data visualization system. The instrumented van, called Mobile Lab, also hosted a KIT Proton Transfer Reaction Mass Spectrometer (suite of VOCs in situ measurements) for part of the campaign. For close to a month, the Mobile Lab traveled the roads of the oil and gas field, documenting ambient levels of several tracers. Close to 180 valid air samples were collected in February by the Mobile Lab for future analysis in the NOAA and CU/INSTAAR labs in Boulder. At the same time as the surface effort was going on, an instrumented light aircraft conducted transects over the Basin collecting air samples mostly in the boundary layer and measuring in situ the following species CH4, CO2, NO2, O3. We will present some of the data collected by the Mobile Lab and the aircraft and discuss analysis results.

Emissions of volatile organic compounds (VOCs) associated with natural gas production in the Uintah Basin, Utah

Carsten Warneke, CIRES scientist working at NOAA's Earth System Research Laboratory
Presentation A23H-04
2:25 p.m.–2:40 p.m.; 3022 (Moscone West)

Technological advances such as hydraulic fracturing have led to a rapid increase in the production of natural gas from several basins in the Rocky Mountain West, including the Denver-Julesburg basin in Colorado, the Uintah basin in Utah and the Upper Green River basin in Wyoming. There are significant concerns about the impact of natural gas production on the atmosphere, including (1) emissions of methane, which determine the net climate impact of this energy source, (2) emissions of reactive hydrocarbons and nitrogen oxides, and their contribution to photochemical ozone formation, and (3) emissions of air toxics with direct health effects. The Energy & Environment – Uintah Basin Wintertime Ozone Study (UBWOS) in 2012 was focused on addressing these issues. During UBWOS, measurements of volatile organic compounds (VOCs) were made using proton-transfer-reaction mass spectrometry (PTR-MS) instruments from a ground site and a mobile laboratory.

Measurements at the ground site showed mixing ratios of VOCs related to oil and gas extraction were greatly enhanced in the Uintah basin, including several days long periods of elevated mixing ratios and concentrated short term plumes. Diurnal variations were observed with large mixing ratios during the night caused by low nighttime mixing heights and a shift in wind direction during the day. The mobile laboratory sampled a wide variety of individual parts of the gas production infrastructure including active gas wells and various processing plants. Included in those point sources was a new well that was sampled by the mobile laboratory 11 times within two weeks. This new well was previously hydraulically fractured and had an active flow-back pond. Very high mixing ratios of aromatics were observed close to the flow-back pond.

The measurements of the mobile laboratory are used to determine the source composition of the individual point sources and those are compared to the VOC enhancement ratios observed at the ground site. The source composition of most point sources was similar to the typical enhancement ratios observed at the ground site, whereas the new well with the flow-back pond showed a somewhat different composition.

Interpreting changes to Upper Colorado River Basin hydrologic response via alternate climatic and land-cover scenarios

Ben Livneh, CIRES scientist
Presentation C43D-0636
3:25 p.m.–3:40 p.m.; 3022 (Moscone West)

The Colorado River Basin is an essential freshwater resource for the southern Rocky Mountains and U.S. Southwest, providing water supply to 7 states and over 30 million people, and irrigation to roughly 3 million acres of farmland. The majority of water originates in the headwaters region and hence changes to this region will impact downstream water availability. Numerous studies have predicted future reductions in streamflow, predominantly focusing on climatic warming as the chief driver for change. More recently, the northern headwaters region has suffered widespread tree kills due to Mountain Pine Beetle (MPB) infestation across a range of forest types, elevation, and latitude. In this study, we investigate the relative impacts of competing streamflow alteration drivers through assessing system sensitivities to individual and combined disturbances. The preliminary analysis is geared towards training a hydrologic model over the historical period as a baseline for sensitivities. The Distributed Hydrology and Vegetation Model (DHSVM) was selected to simulate hydrologic conditions over a set of 4 candidate catchments within the headwaters region that offer a gradient in MPB impacts, elevation, and forest coverage. The observational data sets include meteorological forcings of precipitation, maximum and minimum temperature, time series maps of leaf area index (LAI), as well as other ecological indices derived from MODIS forest phenology products. Experiments are focused on examining the impacts of changing LAI (from MPB) and phenology cycles under different climate scenarios on streamflow and hydrologic fluxes, such as evapotranspiration. It is expected that these results will lead to a clearer understanding of system components and to better inform mitigation strategies and planning efforts.

Wednesday, Dec. 5

A group intercomparison of GRACE Antarctic and Greenland ice loss estimates, as part of the Ice Mass Balance Inter-comparison Exercise (IMBIE)

John Wahr, CIRES Fellow Affiliate
Presentation G31C-03
8:00 a.m.–8:45 a.m.; 3009 (Moscone West)
The ICE Mass Balance Inter-comparison Exercise (IMBIE), under the overall direction of Andrew Shepherd and Erik Ivins, was initiated in the fall of 2011 to try to come to a consensus agreement about the present-day rates of Antarctic and Greenland mass loss as inferred from various geodetic techniques: GRACE, radar and laser altimetry, and InSAR observations combined with surface mass balance model output. This talk will focus on the intercomparison of GRACE results obtained by the individual GRACE IMBIE participants. Results from the different GRACE groups are in good agreement. For January, 2003 through December, 2010, they average to -230 ± 27 Gt/yr for Greenland, and to -81 ± 33 Gt/yr for Antarctica. The Antarctic results were obtained using two new models of Antarctic Glacial Isostatic Adjustment (GIA), to remove GIA effects from GRACE. The use of those models reduces the Antarctic mass loss estimates by about 60-80 Gt/yr over that obtained with older ICE5G–based GIA models.

Quantifying post-wildfire erosion patterns using terrestrial LiDAR

Francis Rengers, CIRES graduate student  
Poster Presentation EP31C-0832
8:00 a.m.–12:20 Pp.m.; Hall A-C (Moscone South)

Wildfires are becoming increasingly frequent in the western United States. In burned landscapes, geomorphic change can take place rapidly during rainstorms following a wildfire. Rainfall over a burned area tends to mobilize more sediment than in unburned basins because the wildfire changes soil properties, creating more overland flow. A dearth of ground debris allows for deeper and faster flow that can entrain sediment. We apply terrestrial LiDAR to post-wildfire geomorphic change analysis to determine the pattern and magnitude of erosion following rain storms. By differencing digital elevation models created from terrestrial LiDAR surveys, we can measure post-wildfire geomorphic change. Topographic analysis with LiDAR allows us to monitor landscape recovery and evolution following a wildfire.

Traditional methods of post-wildfire erosion analysis have focused on measurements such as erosion pins and silt fences. These capture erosion or deposition at a point or cumulative deposition of the sediment from some unknown contributing area upstream of the silt fence. This requires researchers to integrate measurements over a large area to determine basin-wide erosion. By contrast, successive terrestrial LiDAR surveys allow us to map changes in topography over an entire basin or hillslope to determine the spatial distribution of erosion within a basin or on a hillslope and to correlate the erosion with the hydrologic processes between surveys.

Our study site is a high-severity burn hillslope, burned by the 2010 Fourmile Canyon fire about 15 km west of Boulder, CO. The wildfire was contained on 16 September 2010 and the first LiDAR survey was on 7 October 2010 prior to any significant rain storms. Following this baseline survey, we have used terrestrial LiDAR to capture the landscape state before and after unique hydrologic events such as: low-intensity rain storms, winter snowmelt, and summer convective thunderstorms. Comparing the landscape topography before and after these hydrologic events allows us to quantify the topographic change due to specific hydrologic processes. The results of our LiDAR survey reveal that at the hillslope scale, erosion is not uniform across the burned hillslope. The maximum erosion on a hillslope area of 1900 m2 showed detectable change on only 4% of the total area, but 4 m3 of erosion. The centimeter scale LiDAR topography reveals that most of the erosion is concentrated in concave portions of the hillslope where water concentrates, and relatively little inter-rill erosion was observed. Moreover, the majority of erosion occurs during high-intensity short duration summer convective thunderstorms.

We saw a mean depth of erosion of 7 cm in a hillslope swale following storms with rainfall intensities greater than 30 mm/hr. However, in the same swale there was a mean erosion depth of 9 mm after a storm with only 10 mm/hr of precipitation. In general, low-intensity long duration rain storms and snowmelt events have had very little effect on our burned hillslope. The change in erosion with changing rainfall intensity is likely linked to switching between saturation-excess overland flow to infiltration-excess overland flow with increasing rainfall intensity.

The combined use of GPS horizontal and vertical crustal motion measurements to study mass loss from glaciers in southeast Greenland (Invited)

John Wahr, CIRES Fellow Affiliate
Presentation T331-02
1:55 p.m.–2:10 p.m.; 308 (Moscone South)

A change in the distribution of ice and snow on an ice sheet or mountain glacier causes the underlying Earth to deform. By monitoring the crustal deformation with nearby GPS receivers, it is possible to place constraints on the change in mass. Virtually all previous GPS loading studies have focused on vertical displacements. Here, we describe how observations of horizontal motion can be incorporated into these types of studies. Basically, the horizontals provide information about the location of the mass change, while the verticals place constraints on the total amount of mass change. We apply these ideas to data from the GPS site KULU in southeast Greenland (installed in 1996), to help determine changes in mass of nearby outlet glaciers. The results imply that Helheim Glacier (located ~90 km from KULU) began losing mass at a rapid rate in 2003, but that the rate decreased dramatically in 2006, followed by a modest increase again in 2009-2010. The results also imply that nearby glaciers to the east of Helheim have been losing mass at a more-or-less steady rate since 2003.

Thursday, Dec. 6

Integrating satellite, airborne, and in situ observations to assess the stability of the Larsen C Ice Shelf, Antarctica

Daniel McGrath, CIRES Graduate Student 
Presentation C43D-0636
1:40 p.m.–6:00 p.m.; Hall A-C (Moscone South)

The collapse of the Larsen A and B ice shelves has been attributed to meltwater driven crevasse propagation, rendering the ice shelf into numerous, elongate icebergs which rapidly overturned during the final disintegration. The rapid nature of this style of disintegration overshadows the role structural features, such as crevasses and rifts, and processes, such as thinning and firn densification, play in ‘pre-conditioning’ the ice shelf in the years and decades preceding these events, whereby making it increasingly susceptible to collapse. We assess the stability of the Larsen C ice shelf, which, at ~50,000 km2, is the largest remaining ice shelf on the Antarctic Peninsula (AP). We examine, in detail, three specific structural features of the ice shelf: marine ice, basal crevasses, and ice rises, through the integration of historic defense, moderate and high-resolution satellite imagery, NASA IceBridge airborne altimetry, and in situ ground penetrating radar (GPR). In particular, (1) we examine the termination of rift tips along coherent flow domains, assumed to be of marine provenance, and assess the properties of these domains with GPR, (2) highlight the prevalence of basal crevasses across the ice shelf, and consider how these features, by inducing both surface crevassing and depressions, may play an important role in hydrofracture, and (3) assess the two primary ice rises, the Bawden and Gipps, and their role in past and potentially future calving events. Lastly, we calculate current grounding line ice fluxes delineated by ice shelf domain, and compare this flux to the total ice volume within each domain, thereby calculating a “replacement time.” We consider, based on observed grounding line flux increases following the collapse of Larsen B, the potential future contribution to sea level rise if the Larsen C ice shelf were to collapse.

Sectoral vulnerabilities to changing water resources: Current and future tradeoffs between supply and demand in the conterminous U.S.

James Meldrum, CIRES graduate student
Poster Presentation PA43A-1967
1:40 p.m.–6:00 p.m.; Hall A-C (Moscone South)

Assessing the sustainability of human activities depends, in part, on the availability of water supplies to meet the demands of those activities. Thermoelectric cooling, agriculture, and municipal uses all compete for water supplies, but each sector differs in its characteristic ratio of water consumption versus withdrawals. This creates different implications for contributing to water supply stress and, conversely, vulnerabilities within each sector to changing water supplies. In this study, we use two measures of water stress, relating to water withdrawals and to water consumption, and calculate the role of each of these three sectors in contributing to the two different measures. We estimate water stress with an enhanced version of the Water Supply Stress Index (WaSSI), calculating the ratio of water demand to water supply at the 8-digit Hydrologic Unit Code (HUC) scale (Sun et al. 2008, 2011; Caldwell et al. 2011). Current water supplies are based on an integrated water balance and flow routing model of the conterminous United States, which accounts for surface water supply, groundwater supply, and major return flows. Future supplies are based on simulated regional changes in streamflow in 2050 from an ensemble of 12 climate models (Milly et al. 2005). We estimate water demands separately for agriculture, municipal uses, and thermoelectric cooling, with the first two based on Kenny et al. (2005) and the last on the approach of Averyt et al. (2011). We find substantial regional variation not only in the overall WaSSI for withdrawals and consumption but also in contribution of the three water use sectors to that total. Results suggest that the relative vulnerabilities of different sectors of human activity to water supply stress vary spatially and that policies for alleviating that stress must consider the specific, regional context of the tradeoffs between competing water demands.

Friday, Dec. 7

Wildfire and Hillslope Aspect Impacts on Subsurface Hydrologic Response

Brian Ebel, CIRES scientist
Oral Presentation H54D-01
4:00 p.m–4.20 p.m.; 3020 (Moscone West)

Wildfire is one of the most prevalent disturbance events in the disturbance regime of mountainous terrain and can substantially impact hydrologic processes. Recent evidence suggests wildfire incidence, susceptibility, and synchrony are increasing in some regions. The interactions between wildfire disturbance and pre-existing landscape-scale controls on hydrology such as hillslope aspect are not well quantified, but are important for understanding the long term impacts of wildfire on ecological and geomorphic processes. We monitored subsurface hydrologic response to rainfall at the plot-scale for north- and south-facing hillslope aspects in burned and unburned conditions within the area impacted by the 2010 Fourmile Canyon Fire near Boulder, Colorado, USA. Our observations documented that the combustion of the litter/duff and forest canopy had the largest hydrologic impact on north-facing hillslopes, resulting in the loss of the “hydrologic buffering” capacity present in the unburned state. In contrast, unburned south-facing hillslopes did not have a robust pre-fire vegetation canopy or litter/duff layer and post-fire changes in hydrologic response were primarily the result of decreases in soil-water retention resulting from soil organic matter reduction. Overall, subsurface hydrologic response had greater variability and more rapid dynamics in wildfire-impacted soils. Furthermore, wildfire homogenized pre-fire hillslope aspect-driven differences in hydrologic response thus “clearing the slate” of some pre-fire landscape-scale controls on subsurface hydrologic conditions. The timescale of altered hydrologic and accompanying ecologic and geomorphologic processes likely depends on re-establishment of vegetation communities and soil recovery. Quantifying this timescale is an important direction for future research.