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From a distance, Anne has been watching an incredibly unusual summer play out in the Pacific Northwest, following a winter with far less snow (but more rain) than usual. Folks on the ground in Oregon have been collecting data on the response of the Oregon Cascades streams to “no snow, low flow” conditions. Anne is making minor contributions to the following poster, to be presented in Session No. 291, Geomorphology and Quaternary Geology (Posters) at Booth# 101 on Wednesday, 4 November 2015: 9:00 AM-6:30 PM.
HOW LOW WILL THEY GO? THE RESPONSE OF HEADWATER STREAMS IN THE OREGON CASCADES TO THE 2015 DROUGHT
LEWIS, Sarah L.1, GRANT, Gordon E.2, NOLIN, Anne W.1, HEMPEL, Laura A.1, JEFFERSON, Anne J.3 and SELKER, John S.4, (1)College of Earth Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, (2)Pacific Northwest Research Station, USDA Forest Service, 3200 SW Jefferson Way, Corvallis, OR 97331-8550, (3)Department of Geology, Kent State University, Kent, OH 44242, (4)Biological & Ecological Engineering, Oregon State University, Corvallis, OR 97331, firstname.lastname@example.org
Larger rivers draining the Oregon Cascades are sourced from headwater systems with two distinct runoff regimes: surface-flow dominated watersheds with flashy hydrographs, rapid baseflow recession, and very low summer flows; and spring-fed systems, with slow-responding hydrographs, long baseflow recession, and summer flow sustained by deep groundwater fed coldwater springs. Our previous research has explored these differences on both the wet west-side and dry east-side of the Cascade crest, as expressed in contrasting discharge and temperature regimes, drainage efficiency, low and peak flow dynamics, and sensitivity to snowpack and climate change scenarios. In 2015, record low winter snowpack combined with an anomalously dry spring resulted in historically low flows across our research sites and throughout Oregon. These extreme meteorological conditions, equivalent to a 4°C warming scenario, offer an exceptional opportunity to witness how these contrasting stream networks might respond to anticipated changes in amount and timing of recharge.
Conceptually, channel network response to decreasing discharge may involve both lateral and longitudinal contraction. Lateral contraction, the decrease of wetted channel width and depth, occurs in both surface-flow and spring-fed streams as flows diminish. Longitudinal contraction may be expressed as (a) a gradual drying of the stream channel and downstream retreat of the channel head, (b) a “jump” of the channel head downstream to the next spring when an upper spring goes dry, or (c) no change in channel head despite diminishing flows. We hypothesize that while individual stream channels may display a combination of these dynamics, surface-flow and spring-fed watersheds will have distinctive and different behaviors. We field test our hypothesis by monitoring channel head locations in 6 watersheds during the low flow recession of 2015, and repeatedly measuring discharge, water quality and hydraulic geometry at a longitudinal array of sites along each surface-flow or spring-fed channel. The resulting data set can be used to explore the fundamental processes by which drainage networks accommodate decreasing flows.
The Watershed Hydrology lab will be out in force for the Geological Society of America annual meeting in Vancouver in October. Over the next few days, we’ll be sharing the abstracts of the work we are presenting there.
SENSITIVITY OF PRECIPITATION ISOTOPE METEORIC WATER LINES AND SEASONAL SIGNALS TO SAMPLING FREQUENCY AND LOCATION
REYNOLDS, Allison R., Department of Geology, Kent State University, 221 McGilvrey Hall, Kent, OH 44242, email@example.com and JEFFERSON, Anne J., Department of Geology, Kent State University, 221 McGilvrey Hall, Kent, OH 44240
Every precipitation event has its own isotopic signature, making it useful for hydrology purposes, like estimating transit time or identifying seasonality of groundwater recharge. Our purpose is to compare the seasonal signal and local meteoric water line (LMWL) generated by one year of event-based sampling to those resulting from multi-year monthly sampling at the closest Global Network of Isotopes in Precipitation (GNIP) stations. The question we seek to answer is whether data from different sampling strategies, periods, and locations within the eastern Great Lakes region in North America converge on a regional-scale LMWL and seasonal signal.
From October 2012-present precipitation samples were collected in Kent, Ohio, filtered and analyzed by a Picarro L-2130i at Kent State University. The closest GNIP sites are Coshocton, Ohio, USA and Simcoe, Ontario, Canada; monthly data was downloaded from a database. For each site, we graphed the ?18O versus ?2H and added a linear trendline to represent the LMWL and fit sine waves to the data to assess seasonal isotopic signal.
Based on the event data, Kent has the most isotopically depleted precipitation, but when looking at monthly samples, it falls between Simcoe to the north and Coshocton to the south. This suggests that, in this region, isotopically light precipitation events are more important in terms of their frequency than their amount. LMWLs for each site were similar. Comparing the LMWLs generated from the event samples and monthly data, monthly data had a slightly lower slope and d-excess. For Coshocton, amplitude of the seasonal sine wave for ?18O is 6.2‰, for Simcoe the sine wave is 4.3 ‰. For the Kent dataset, event-based data produced a sine wave with amplitude of 6.1‰, while monthly data resulted in a 4.9‰ amplitude wave. While it is possible that the amplitude of a wave fit to monthly data would increase with data points that represent isotopically extreme months, it is likely that curves fit to monthly data will frequently under-represent the variability in precipitation isotopes as measured at event and sub-event timescales. Both the LMWL and seasonal signal analysis suggest a greater variability in precipitation isotope signatures during the winter relative to the summer in the eastern Great Lakes region.
Congratulations to Darren Reilly who did a wonderful job defending his MS thesis on Tuesday. Darren’s thesis focused on the identification of groundwater pollution and its sources in rural northeastern Pennsylvania residential water wells. Darren will be preparing his thesis for publication in a journal and is looking for a job in the energy or environmental sectors. Check him out on LinkedIn.
Congratulations also to Alison Reynolds who won first place in the Kent State Undergraduate Research Symposium, Geology/Geography category for her poster on “Sensitivity of precipitation isotope meteoric water lines and seasonal signals to sampling frequency and location.” Aly is a junior this year, and will be continuing to be a valuable member of our research group this summer and next year before heading somewhere fabulous for graduate school.
Congrats Darren and Aly. It is a pleasure to work with such passionate and dedicated students.
This work is being conducted by undergraduate lab member, Allison Reynolds. Allison presented her work as part of the CUAHSI/USGS Virtual Workshop on applications of laser specs to hydrology and biogeochemistry. From that workshop, she will have an extended abstract published in a USGS open file report, and her poster will continue to be viewable on-line. She will also be presenting results at the inaugural Kent State Undergraduate Research Symposium in April. And of course, she’s going to keep working on new data and analyses and aiming for publication. Go Aly!
Sensitivity of precipitation isotope meteoric water lines and seasonal signals to sampling frequency and location
Allison R. Reynolds (firstname.lastname@example.org) and Anne J. Jefferson (advisor)
Department of Geology, Kent State University, Kent, OH 44242
Our purpose is to compare seasonal signal and local meteoric water line (LMWL) generated by analyzing hydrogen and oxygen isotopes in precipitation for one year of event-based sampling to those from multi-year monthly sampling at the closest Global Network of Isotopes in Precipitation (GNIP) stations. The question we seek to answer is whether data from different sampling strategies, periods, and locations within the eastern Great Lakes region on a regional-scale LMWL and seasonal signal. We collected precipitation samples after each event in Kent, OH. Samples were analyzed with a Picarro L-2130i. The closest GNIP sites are Coshocton, Ohio and Simcoe, Ontario. LMWLs and seasonal signals derived from monthly samples were broadly similar along a 300 km north-south transect in the US eastern Great Lakes Region. Monthly volume-weighted averages of event precipitation under-represent event scale isotopic variability, based on samples from Kent, Ohio.
Radar is increasingly used to measure precipitation in hydrologic science applications. It’s handy because it can be both frequent and areally distributed.
This NWS newsletter does a great job of going over the basics of how weather radar can be used to derive rainfall rates and totals. This page gives a seamless map of 1-day precipitation totals for the US, derived from radar measurements. Pretty sweet! The videos below give more information on ground-based and space-based radar rainfall applications.
Or in space:
The upcoming launch of the Global Precipitation Measurement (GPM) satellite will greatly expand space-based precipitation measurements. The launch is currently scheduled for the 27th of February, but there is a media event on NASA TV on Monday, January 27th.
Also, follow @NASA_Rain on twitter to learn about the upcoming Global Precipitation Mission launch and the science behind it.
If you live in the eastern 1/3 of the US and you haven’t started paying attention to Hurricane Sandy, today is THE day. This odd late-season storm is going to hit the northeastern and mid-Atlantic coast hard, having already stormed across the Caribbean, killing at least 48 people.
Much like we saw with Isaac earlier this year, the damage in slow-moving and relatively weak hurricanes (Sandy is a Category 1 currently) comes from all of the water in inland flooding and from the storm surge along the coast. When Sandy hits shore someplace between Delaware and New York City on Monday night, the storm surge is expected to be especially fearsome. As Ben Strauss at Climate Central explains:
- Sandy is projected to create tall storm surges, due to an enormous wind field influencing wide areas of ocean.
- The surge may be prolonged, due to the storm’s large size and slow movement. This means many areas will experience surge combined with at least one high tide.
- With a full moon near, tides are running high to begin with.
- Rivers swollen by significant rainfall may compound tides and surge locally.
- Sea level rise over the past century has raised the launch pad for storms and tides to begin with, by more than a foot across most of the Mid-Atlantic. Sinking land has driven part of this rise, but global warming, which melts glaciers and expands ocean water by heating it, appears to be the dominant factor across much of the region.
In Sandy’s path, as with Irene last year, lies the densely populated east coast. Which is why knowledgeable people are now talking about Sandy as likely to be a multi-billion dollar disaster. Jeff Masters of Weather Underground estimates that there could be as much as a billion dollars of wind damages and associated power losses, with flooding costing another billion in losses, and if the New York City transit system floods losses could run into the tens of billions.
And all of that is just the hurricane. Added on top of that is the potential convergence of the hurricane with a very deep upper-level trough over the central U.S. and unusually strong high-latitude blocking. Blocking occurs when a high pressure dome stays in the same place for several days or longer, blocking eastern flow of the polar jet stream, producing “seemingly endless stretches” of the same weather, and pushing storms far off their usual tracks. As explained by Will Komaromi of the Rosenstiel School of Marine and Atmospheric Science at the University of Miami:
“Normally a hurricane weakens as it moves northward, as it encounters an increasingly unfavorable environment. This means greater wind shear, drier air, and lower sea surface temperatures. However, with phasing [convergence] events, the tropical system merges with the mid-latitude system in such a way that baroclinic instability (arising from sharp air temperature/density gradients) and extremely divergent air at the upper-levels more than compensates for a decreasingly favorable environment for tropical systems.”
Komaromi goes on to explain that the Atlantic Gulf Stream is unusually warm for this time of year, allowing Sandy to remain stronger than it might have while out to see. Also, the extra strong blocking over the North Atlantic will mean that the hurricane moves very slowly and the storm will track farther west over the US rather than curving out to the mid-ocean. Komaromi shows that this is extremely similar to the 1991 “Perfect Storm”, subject of the book and movie of the same name.
The fallout of all this meteorological fury is likely to be felt both at the coast and far inland. The quantitative precipitation forecast for NOAA for the next five days shows eight states with areas expected to receive more than 4 inches (101 mm) of precipitation. Far more unusual than lots of rain is the possibility that Sandy will be a “snow-i-cane” dumping up to 12 inches (304 mm) of snow in the mountains of Virginia and West Virginia, and possibly into Tennessee and North Carolina. With leaves still on the trees in southern and coastal regions, the wind, rain, and snow will play havoc with above ground power lines. Widespread power outages are considered likely all the way into western Pennsylvania, New York, and West Virginia. Even in Ohio, my area is considered in the “possible” zone for power failures.
In addition to watching the weather and taking the necessary steps to prepare ourselves for whatever blows our way, a small group of scientists will be collecting precipitation samples for isotopic analyses by Gabe Bowen’s group at the University of Utah. If you live in the area affected by Sandy and want to help collect precipitation, look for more information here. I’ve already gotten 1.2 inches (30 mm) of rain since yesterday afternoon, and we’re not even seeing the storm effects yet. I’m likely to get another 4 inches (100 mm) by Thursday.
A somewhat larger group of geoscientists will be working on their posters and talks while hoping to avoid power outages and travel delays that could scuttle plans to attend the Geological Society of America meeting in Charlotte, North Carolina. Charlotte is not at all in the storm’s path, so if we can get there, everything should be fine.* I’m hopeful that the freeways will be open through West Virginia by Friday night, when I’ll drive south to convene two sessions, lead a field trip, and present a poster. But I worry for colleagues in the full brunt of the storm and hope that they have both adequate time to prepare for and attend the meeting. I’m also crossing my fingers that virtually all infrastructure is functioning again by Tuesday, November 6th, and that everyone affected by the storm will be able to cast their votes in a very important election.
As I contemplate coming events, I find the song “Storm Comin'” by The Wailing Jennys has been playing in my head almost constantly. I love how it captures the tension and anticipation of a storm rolling towards you across the plains or ocean.** Unfortunately, I wouldn’t recommend following this advice for emergency preparedness, instead you should take a make an emergency kit along the lines of this one and pay attention to watches, warnings, and evacuations in your area. Be safe everyone.
*Disclaimer here about being neither a meteorologist nor a disaster recovery expert, so don’t take my word as a guarantee. Also I’m glad I’m not in Italy.
**For me, music is poetry, so consider this my entry from the upcoming Accretionary Wedge carnvial on geo-poetry.
Cross-posted at Highly Allochthonous
Even though we all think of the freezing point of water as 0 °C, very pure water remains a liquid until about -40 °C. Water crystallizes to ice in the presence of tiny nucleation particles in the atmosphere. These particles can be sea spray, soot, dust … and bacteria.
Bacteria are particularly good at ice nucleation (IN), causing it to occur at temperatures as high as -2 °C. As Ed Yong described 3 years ago:
The fact that bacteria like P. syringae nucleate ice crystals has been known for decades. They can be used for gee-whiz science demonstrations, and, at a much larger scale, as one method for creating artificial snow. On the flip side, the presence of P. syringae is also also makes plants more likely to be frost damaged at temperatures just below freezing. Only in the last several years, though, has the role of bacteria in producing precipitation from the atmosphere begun to be appreciated.
Ice-forming bacteria like Pseudomonas syringae rely on a unique protein that studs their surfaces. Appropriately known as ice-nucleating protein, its structure mimics the surface of an ice crystal. This structure acts as a template that forces neighbouring water molecules into a pattern which matches that of an ice lattice. By shepherding the molecules into place, the protein greatly lowers the amount of energy needed for ice crystals to start growing.
First, Brent Christner and colleagues discovered that every freshly fallen snow sample they collected, even in Antarctica, contained these ice nucleating bacteria. In the resulting 2008 Science paper, they noted:
The samples analyzed were collected during seasons and in locations (e.g., Antarctica) devoid of deciduous plants, making it likely that the biological IN we observed were transported from long distances and maintained their ice-nucleating activity in the atmosphere…our results indicate that these particles are widely dispersed in the atmosphere, and, if present in clouds, they may have an important role in the initiation of ice formation, especially when minimum cloud temperatures are relatively warm.
Then researchers in the Amazon rainforest discovered that primary biological aerosol (PBA) particles, including plant fragments, fungal spores…and yes, bacteria, were a dominant contributor to ice nucleation in clouds above the rainforest. (Even the though the Earth surface is hot in the Amazon, high enough in the troposphere, it’s still below freezing.) As Pöschl and colleagues reported in Science in 2010:
Measurements and modeling of IN concentrations during AMAZE-08 suggest that ice formation in Amazon clouds at temperatures warmer than –25°C is dominated by PBA particles… Moreover, the supermicrometer particles can also act as “giant” [cloud condensation nuclei] CCN, generating large droplets and inducing warm rain without ice formation.
The latest contribution to the growing understanding of bacteria’s role in precipitation was recently presented at the American Society of Microbiology meeting. Alexander Michaud studied hailstones that fell on his Montana State University campus, and as reported by the BBC:
He analysed the hailstones’ multi-layer structure, finding that while their outer layers had relatively few bacteria, the cores contained high concentrations. “You have a high concentration of ‘culturable’ bacteria in the centres, on the order of thousands per millilitre of meltwater,” he told the meeting.
What all of this adds up to is that we now know that bacteria and other biological particles are prevalent in the atmosphere around the world and are stimulating multiple forms of precipitation. As a hydrologist, I think I can wrap my head around this. But what’s really wild is the feedback between biological productivity and precipitation and the possibility that the ice nucleating bacteria moving in the atmosphere may be an evolutionary trait.
Precipitation stimulated by ice nucleation above an ecosystem where the bacteria or other biological particles were emitted sustains the ecosystem that created those particles. As Pöschl et al write:
Accordingly, the Amazon Basin can be pictured as a biogeochemical reactor using the feedstock of plant and microbial emissions in combination with high water vapor, solar radiation, and photo-oxidant levels to produce [secondary organic aerosols] SOA and PBA particles (31, 32). The biogenic aerosol particles serve as nuclei for clouds and precipitation, sustaining the hydrological cycle and biological reproduction in the ecosystem.
Or, in discussion of the recent hailstone findings [from the BBC]:
Dr Christner, also present at the meeting, said the result was another in favour of the bio-precipitation idea – that the bacteria’s rise into clouds, stimulation of precipitation, and return to ground level may have evolved as a dispersal mechanism. … “We know that biology influences climate in some way, but directly in such a way as this is not only fascinating but also very important.”
Christner, B., Morris, C., Foreman, C., Cai, R., & Sands, D. (2008). Ubiquity of Biological Ice Nucleators in Snowfall Science, 319 (5867), 1214-1214 DOI: 10.1126/science.1149757
Pöschl U, Martin ST, Sinha B, Chen Q, Gunthe SS, Huffman JA, Borrmann S, Farmer DK, Garland RM, Helas G, Jimenez JL, King SM, Manzi A, Mikhailov E, Pauliquevis T, Petters MD, Prenni AJ, Roldin P, Rose D, Schneider J, Su H, Zorn SR, Artaxo P, & Andreae MO (2010). Rainforest aerosols as biogenic nuclei of clouds and precipitation in the Amazon. Science (New York, N.Y.), 329 (5998), 1513-6 PMID: 20847268