The Aspen FACE experiment was established near Rhinelander, Wisconsin in 1997 to examine the impacts of elevated atmospheric CO2 and/or O3 on the structure and functioning of model aspen/birch/maple ecosystems. Recently, we completed our eighth fumigation season at this Department of Energy User Facility which has been called the world opposite manners and we will examine some curious long-term interactions that were unpredicted at the onset of the experiment. Finally, we will explore remaining research questions that have arisen.
More information on Aspen FACE

Carmen Sandiego is the famous crimer solver, who's work often takes her to mysterious and remote parts of the world. Sometime solving a scientific problem is a bit like Carmen's detective work. You have to take the available data and piece together an explanation. Then you have to try to convince the jury (peer reviewers) that your story is correct.

In this case, the problem is the observed increase in surface ozone in the western U.S. Ozone is an important gas in tropospheric chemistry and is also damaging to humans and vegetation at elevated concentrations. To quantify the changes in background O3 in the US, we evaluated O3 data from 12 relatively unpolluted sites in the western U.S., including 2 sites in Alaska, for the period 1987-2004. At the 2 sites in Alaska, no trend was present. At 9 out of 10 sites in the continental U.S. there is a statistically significant increase in O3 with a mean trend of 0.35 ppbv/year. This trend is similar to surface ozone trends reported for background sites in Europe and Asia.

We propose several possible explanations for this trend including increasing western US NOx emissions, increasing global NOx emissions and/or increasing biomass burning (due to climate change). I have evaluated these hypotheses using a variety of data including emission data, observations from the Mt.Bachelor and Pico-Azores Observatories, fire data from around the world and global observations of Carbon Monoxide from the MOPITT satellite instrument. Based on this analysis, I believe that increasing global NOx emissions and increasing biomass burning are the most likely causes for the ozone increase. Carmen solves another one. Case closed.... I wish.

A mass-balance model for Lake Superior was applied to polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and mercury to determine the major routes of entry and the major mechanisms of loss from this ecosystem as well as the time required for each contaminant class to approach steady state. A two-box model (water column, surface sediments) incorporating seasonally adjusted environmental parameters was used. Both numerical (forward Euler) and analytical solutions were employed and compared. For validation, the model was compared with current and historical concentrations and fluxes in the lake and sediments. Results for PCBs were similar to prior work showing that air-water exchange is the most rapid input and loss process. The model indicates that mercury behaves similarly to a moderately-chlorinated PCB, with air-water exchange being a relatively rapid input and loss process. Modeled accumulation fluxes of PBDEs in sediments agreed with measured values reported in the literature. Wet deposition rates were about three times greater than dry particulate deposition rates for PBDEs. Gas deposition was an important process for tri- and tetra-BDEs (BDEs 28 and 47), but not for higher-brominated BDEs. Sediment burial was the dominant loss mechanism for most of the PBDE congeners while volatilization was still significant for tri- and tetra-BDEs. Because volatilization is a relatively rapid loss process for both mercury and the most abundant PCBs (tri- through penta-), the model predicts that similar times (from 2 - 10 yr) are required for the compounds to approach steady state in the lake. The model predicts that if inputs of Hg(II) to the lake decrease in the future then concentrations of mercury in the lake will decrease at a rate similar to the historical decline in PCB concentrations following the ban on production and most uses in the U.S. In contrast, PBDEs are likely to respond more slowly if atmospheric concentrations are reduced in the future because loss by volatilization is a much slower process for PBDEs, leading to lesser overall loss rates for PBDEs in comparison to PCBs and mercury. Uncertainties in the chemical degradation rates and partitioning constants of PBDEs are the largest source of uncertainty in the modeled times to steady-state for this class of chemicals. The modeled organic PBT loading rates are sensitive to uncertainties in scavenging efficiencies by rain and snow, watershed runoff concentrations, and uncertainties in air-water exchange such as the effect of atmospheric stability.

Clouds are profoundly influenced by the seemingly-simple process of water droplets freezing to form ice: the formation of ice can accelerate the formation of precipitation, it alters the interaction of clouds with solar and infrared radiation, and it increases the cloud buoyancy and therefore the very dynamics of motion. Nevertheless, the formation of ice not well understood. For example, in many instances much more ice forms in clouds than can be accounted for with known nucleation mechanisms. With this in mind, we carried out laboratory experiments aimed at understanding the mechanisms for ice formation by a catalyst (heterogeneous nucleation). During the course of our experiments we chanced upon an unexpected observation: freezing rates were much higher when an ice-forming nucleus is near the surface of an undercooled water drop than when the nucleus is immersed in the drop (the nucleation rate at the water surface is a factor of 10^10 greater than in bulk water). This "surface crystallization" has important implications for ice formation in clouds, and may even provide insight on the fundamental behavior of water at interfaces.

Trapping of deep convective pollution by upper level anticyclones: Implications for global change

Dr. Qinbin Li, NASA JPL

Convective outflow of pollution and its subsequent long-range transport plays an important role
in linking regional air pollution and global change. Deep convection associated with summer
monsoons effectively ventilates two monsoon regions with large surface emissions, the southern
United States and South Asia. The semi-permanent anticyclones centered in the upper
troposphere over these regions can circulate (hence 'trap') the convective outflows from
these regions for days.
Over the southern U.S., an ozone maximum in the upper troposphere in summer is predicted by
the GEOS-CHEM global 3D model of tropospheric chemistry and transport, a prediction confirmed
by observations from the ICARTT aircraft campaign. Model results indicate that rapid ozone
production (up to 10 ppb/day) takes place in the circulating outflow. We find that this production
is driven in part by anthropogenic and lightning NOx, and in part by reactive radicals produced
from convectively lifted formaldehyde produced from biogenic isoprene emissions. (The ozone
production takes place near the transition between NOx-limited and NOx-saturated regimes
for ozone production.)
Over South Asia, observations during 25 August-6 September 2004 from the
Microwave Limb Sounder (MLS) instrument aboard the Aura satellite reveal
elevated CO concentrations and dense high-altitude clouds in the upper troposphere,
collocated with the upper-level Tibetan anticyclone. The observed dense high-altitude
clouds are accompanied with relatively little precipitation. GEOS-CHEM simulations
indicate the transport of boundary layer pollution including aerosols by Asian summer monsoon
convection to the upper troposphere over South Asia. Analysis of simulated CO and aerosols
indicate that the upper-level Tibetan anticyclone effectively ‘traps’ anthropogenic emissions
lifted from northeast India and southwest China. These aerosols may be responsible for the
formation of some of the dense high clouds.

Where does all the dirty air go? Insights from MTU and INSTAAR's research at the PICO-NARE (Azores/Portugal) observatory

Dr. Detlev Helmig, University of Colorado

Emissions and transport of air pollution from continents bordering the North Atlantic have been studied on top of Pico Mountain in the Azores, Portugal. A remotely controlled analytical system for the continuous, unattended monitoring of non-methane hydrocarbons (NMHCs) was developed. This instrument has some unique technical features that allow operation at this site under the challenging power, space and access conditions. Ten 10 different C2-C6 NMHCs have been monitored at this site for more than a year. Data from these measurements are used to research source regions and photochemical processing of air reaching the station. Particular areas of interest are the investigation of anthropogenic pollution transport and boreal biomass burning events, as forest fires have been shown and are predicted to further increase due to the warming and summertime drying of high northern latitude ecosystems. Air transported from biomass burning events is frequently observed at Pico during the summer. Ozone production in both the anthropogenic outflow and in boreal biomass burning plumes has been found to be higher than model predictions, which is of high interest and concern, as an increase in tropospheric ozone constitutes an important climate feedback. The value of the Pico Mountain observatory for atmospheric and climate research has been increasingly recognized and has motivated new initiatives for incorporating this station in the World Meteorological Organization (WMO) - Global Atmospheric Watch (GAW) network.

Everglades Restoration: Coupling Science and Engineering to Ensure Success

Dr. Scot Hagerthy, Southern Waterways Management Agency, Florida

The Everglades was once a large subtropical wetland that encompassed more than 1.2 million hectares of south Florida. Over the past century, more than 2700 km of canals and levees and hundreds of water control structures have been constructed to drain the wetlands for development, to serve as a water supply, and to protect the residents from flood waters. What remains today of the Everglades bears little resemblance to predrainage conditions. Less than half of the wetland still exists. The canal and levee network has compartmentalized this once free-flowing system and reduced flow volumes by an estimated 70%. Water control structures discharge nutrient enriched runoff into the wetland resulting in eutrophication. Two major initiatives by the South Florida Water Management District, the Army Corp of Engineers, and many other agencies are underway to restore the Everglades. The Long-Term Plan is mandated by the Everglades Forever Act to improve water quality and to accelerate the recovery of nutrient impacted areas. The Comprehensive Everglades Restoration Plan (CERP) focuses on restoring Everglades hydrology. The two programs are not mutually exclusive. In this seminar, I will present how science and engineering are being used to ensure restoration success.

Resurrection Ecology:
Chasing Van Valen’s Red Queen Hypothesis

Charles Kerfoot

Department of Biological Sciences, Michigan Tech

Testing modern communities for reaction to change involves a dilemma of dimension. How can you test responses that presumably occur over generations? Caught between fossils and genetic reconstructions of phylogenies based on modern organisms, we advocated taking an experimental approach to paleoecology. We found that one can evaluate the prey portion of Van Valen’s Red Queen hypothesis, that species “must continually evolve just to stay in place”, by retrieving diapausing eggs from lake sediments for laboratory tests of evolutionary responses. In one of the original studies, the sediments consisted of core samples from Portage Lake, which were dated by a combination of varve counts and radioisotope (137Cs and 210Pb) techniques. Predators and prey were followed for nearly a century. The technique is now being refined to address how many partners are in the evolutionary “dance”, quantifying how fast communities are changing, and inspecting “transitional series” and speciation.