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Look here for a daily summary of AGU16, as seen through the lens of the Pacific Northwest National Laboratory...

Daily Summary

December 16, 2016

Day Five of AGU16

Day Five Image
Bags picture by Rebecca Lauzon, a geomorphology PhD candidate at Duke University.

Say it ain't so.

Yes: December 16, today, is the last day of AGU16, a small city of 24,000 Earth and space scientists that for five days bumped up the population of San Francisco by a brainy three-one hundredths of a percent.

The American Geophysical Union fall meeting drew enough people to cause catastrophic lines at morning coffee emporiums, to supply enough eyes and ears for 20,000 talks and posters, and (is this scientific?) to bring on heavy rain.

The Pacific Northwest National Laboratory (PNNL) will add its own voices to the last day, with talks that include glimpses at the science of South Asian monsoons, how microbes breathe, Amazon basin convection triggers, climate data going back two millennia, and the risks of induced seismicity.

PNNL posters (too many to count without coffee) will include looks at an aquaplanet world, modeling plant root systems, upgrades at a climate observation site in Alaska, soil hydraulics, and analyzing river sediments.

Join us for a day-long look at last-day events.

DTFs, Reconstructing climate, and South Asian Monsoons

For PNNL scientists, a string of final talks at AGU16 began early and wrapped up late. Some morning talks were lightly attended. Had the exodus begun? One snapshot caught nine PNNL staffers at the airport on their way out of San Francisco.

"It's Friday, and people have started to head home," said Ben Bond-Lamberty, a research scientist with the Joint Global Change Research Institute (JGCRI), a partnership of PNNL and the University of Maryland. He estimated that attendance at the huge event might have slipped 20 percent overnight.

Then again, there was a lot of talk terrain that offered Earth and space science amazement. One attendee tweeted in the morning: "Is there a word for too many great #AGU16 talks going on at the same time? A German word maybe?"

One of the great ones was Bond-Lamberty's talk, which led off the morning's list of PNNL oral presentations. It was on a new way to represent heterotrophic respiration at the large scales needed for climate models. And it got some Twitter love even before he took to the stage in Moscone West.

With good reason. Sometimes big deals come in small packages.

The Earth's soil, along with its oceans and lakes, are vast lungs, taking in and breathing out gases that interact with the atmosphere. Part of this breathing cycle is the carbon dioxide produced when organisms in the soil and water respire. This heterotrophic respiration (HR), the work of both animals and microbes, is a major part of the "carbon flux" - the dynamic breathing cycle - between ecosystems and the atmosphere.

Most carbon fluxes can be measured at the large scales useful to global Earth System Models. But HR, despite its great importance to the planet's carbon cycle, cannot be directly measured at scales larger than a relatively small chamber.

This means HR comprises a large and relatively uncertain component of the carbon cycles that affect ecosystems on a global scale.

Bond-Lamberty called on climate-modeling scientists to develop data-driven "decomposition functional types" (DFTs) analogous to plant functional types (PFT), a classification scheme already in wide use. (PFTs provide an organizational structure for representing properties in a vegetation model that is useful for climate and land-use researchers.)

In the future, Bond-Lamberty told his audience, DTFs could be built into global models, providing the ecological and climate change communities with robust, scalable estimates of HR.

Then the morning talks jumped from microbes to millennia in a morning talk by Hansi Alice Singh, a Linus Pauling Distinguished Postdoctoral Fellow at the lab, whose special interest is climate dynamics in polar regions. (Her morning talk began just as Bond-Lamberty's ended, making it nearly true that the last day of AGU16 begins and ends with her two presentations. Her last is slated for a shade before 6 p.m.)

Singh outlined a new perspective from the Last Millennial Reanalysis (LMR), an approach to reconstructing paleoclimate features. It compares data from climate proxies (like ocean sediments and ice cores) to data from models. She and a co-author using LMR to examine Atlantic Multidecadal Variability (AVM) over the last two thousand years. AVM expresses surface temperature fluxes over a scale of decades in the North Atlantic basin.

The Atlantic Ocean and most continents warm; sea ice thins over the Arctic and retreats over the Greenland-Iceland-Norwegian seas; and equatorial precipitation shifts northward.

Then the handoff: Just as Singh ended her talk, PNNL atmospheric scientist L. Ruby Leung started her second of the conference, an invited oral presentation on systematic errors in simulating South Asian monsoon precipitation. She and three co-authors propose using the Model for Prediction across Scales to explore potential improvements in simulating South Asian monsoon precipitation. It's a way of providing regional refinements, at resolutions from a few kilometers to 30.

"Leung is going thru the equations that make up the model she's using for monsoons in India," tweeted PNNL science writer Mary Beckman from the audience. "Cool to see the nuts & bolts explained!"

Leung also credited co-author Samson Hagos, a PNNL atmospheric scientist, as "the mastermind behind the work she is presenting," tweeted Beckman.

CMIP5, Aquaplanets, and 3D Images of a Live Plant

Hagos, it turns out, was busy at that moment - and from 8 a.m. onward - explaining his poster on Indian monsoon precipitation to passers-by. It points to a little-understood bias in CMIP5 (Coupled Model Intercomparison Project Phase 5) models. Hagos and three co-authors offered an explanation of the bias: that it is linked to the way the models treat convection over the equatorial Indian Ocean.

A few steps away, a poster by PNNL's Jian Lu outlined a way of better understanding precipitation extremes. He developed a diagnostics scheme for col umn water vapor, and applied it to a pair of aquaplanet model simulations in order to quantify the "higher moments" of the global hydrological cycle.

A few rows further up in the hall, lead author Tamas Varga stood by a poster on in-soil imaging of a live plant - his first poster at an AGU conference. It won him a prompt tweet. (Plant roots play a critical role in plant-soil-microbe interactions in the rhizosphere. Their activities have important implications for farming, forest management, and climate change.)

Varga is a senior research scientist at the Environmental Molecular Sciences Laboratory (EMSL), a U.S. Department of Energy national science user facility located on the PNNL campus. Its scientists were a big part of AGU16 activity.

He and three co-authors used x-ray computed tomography (CT) to non-invasively image a specimen of an ornamental grass called prairie dropseed. They obtained a 3D image of the root structure, and enacted a pore-scale simulation of root-soil-groundwater interactions. This approach, said Varga earlier, provides realistic simulations of these critical ecosystems, and could be directly linked to up-scaled models.

"It went very well, I think," he wrote afterward of the morning poster session. "A lot of people stopped by. Some were interested in the modeling aspect, more were interested in how x-ray CT imaging could be applied to their research."

Varga offered his poster visitors useful suggestions, he said, "and may have recruited a couple potential EMSL users."

Posters have great import at a conference like AGU16t. "It seemed like many great discussions were initiated by the posters," said Varga. "And some of the sessions, like my Biogeochemical sessions, were pretty crowded."

Take a look at the PNNL video interview with Varga about his tomography work.

Science Poem, Views of the Amazon, and Lagrangian Analysis

You have to love a conference of 24,000 scientists where for a moment (via Twitter) attention is focused on a carbon-dated grasshopper leg found in a deep core sample from Fremont Glacier in Wyoming. That moment was like a poem about the places curiosity sometimes leads.

Getting to PNNL's afternoon talks was a lot easier than reaching down into 152 meters of ice for insect parts. The talk by Zhangshuan “Jason” Hou, for instance, merely required getting to the third floor of the Moscone Center by 2:40 p.m., though it involved going underground too, after a fashion.

In their paper, Hou and four co-authors used a new transport simulator to more systematically than ever quantify the risks and uncertainties associated with induced seismicity. That happens when carbon dioxide, on its way to sequestration, is injected into faulted geologic formations. Long-term injection of carbon dioxide can have a significant effect on the elastic stiffness and permeability of formation rocks.

Hou is in the Hydrology Technical Group in PNNL's Energy and Environment directorate (EED).

Instead of the ground, PNNL post-doc Koichi Sakaguchi, an atmospheric scientist, reached for the skies. His talk explored the convection triggers for wet-season precipitation over the southwestern Amazon. The Amazon basin plays a significant role in large-scale circulations and biogeochemical cycles. But there is what Sakaguchi earlier called a "ubiquitous" bias regarding Amazonian precipitation in models.

He and his three co-authors, among other aims, set out to identify model components responsible for the bias. They used the Community Atmosphere Model, version 5 (CAM5).

Another look at the Amazon came in a talk by Yilin Fang, who is also part of the EED Hydrology Technical Group. Her presented paper, which has five co-authors, was a search for insights from one- and three-dimensional models of the hydrology of a small central Amazonian watershed. Current Earth System Models have limited ability to represent key features of tropical hydrology, including the water available for plant use.

Yep, it was the Amazon region again that played a central role in one of the very last PNNL talks on the very last day and hour of AGU16. Yun Qian and five co-authors assessed the uncertainty and sensitivity of model simulations related to surface fluxes and land-atmosphere coupling over the Amazon region. Their study aimed to quantify the relative importance and uncertainties of different physical processes and parameters that affect simulated surface fluxes and land-atmosphere coupling strength over the Amazon region.

Taking PNNL scientists to the end of the AGU16 road was Hansi Alice Singh (featured earlier) in her second talk of the day. It offered a Lagrangian perspective on aerial hydrologic cycle changes in a warmer world.

Much of the large-scale change in the hydrologic cycle in a warmer world can be explained by the Clausius-Clapeyron scaling of atmospheric moisture with temperature. But Singh and her four co-authors wondered: Does a Lagrangian analysis of change in the hydrologic cycle offer a different view?

They formulated a novel matrix operator framework to consider how the relationships between moisture source (evaporation) and moisture sink (precipitation) evolve in a warmer world. Among their observations: In a warmer world, remote moisture sources constitute a larger fraction of precipitation.

Moist Stability, Hyporheic Exchanges, and River Hot Spots

It was the poster presenters from PNNL (and many other places) who filled in the conference's last moments. Their 6x4-foot science summaries were on display until 6 p.m.

For PNNL post-doc and atmospheric scientist Bryce Harrop that meant representing his two ca-authors (the aforementioned Leung and Lu) in front of a poster that explained how they used a normalized gross moist stability framework to understand the onset of monsoons. Accurately modeling the onset of monsoon remains a challenge in climate science.

PNNL mechanical engineer Jie Bao welcomed visitors to his five-author poster that explained their attempt to quantify hyporheic exchanges in a large-scale reach (section) of a river. It required coupling 3D computational fluid dynamics simulations of both the surface and subsurface.

Hyporheic exchanges between river water and groundwater is an important mechanism for biogeochemical processes. (These include carbon and nitrogen cycling and the biodegradation of organic contaminants.) But quantifying the relative influences of these exchanges is very challenging in a large river. Bao and his collaborators demonstrate a high resolution computational fluid dynamics model to simulate these hard-to-measure hyporheic exchanges.

In a related research pursuit, PNNL atmospheric scientist Xingyuan Chen and six co-authors assembled a poster summarizing their research on the spatial and temporal variability of groundwater and surface water interactions. They were in search of increased understanding of the biogeochemical hot spots and "hot moments" along a representative hyporheic corridor on the Columbia River.

In the poster, Chen and the others presented a multi-year, multi-sensor dataset from a network of monitoring wells located within the study corridor. That span of time includes a large variation in climate conditions, and low-flow to high-flow hydrograph regimes. (The extent of river water intrusion varied by as much as 50 percent between a low-flow and a high-flow year.) As this dataset is further integrated with complementary geophysical and biogeochemical measurements, the authors say, it can guide the development of a predictive model of biogeochemical activity within this dynamic interaction zone.

The End, with Words

Here we are: the end of AGU16. For a few days more the Twittersphere will light up with favorite moments, no doubt. Many out there are already little pearls and poems - on Pluto’s atmosphere, the food lover's guide to volcanos, recording acoustic waves in the stratosphere, and that seismogram of an octopus sitting on a geophone.

Then there are the bits of science twitterature someone should collect. Many were about the challenges of communicating, a theme that threaded through AGU16 talks in the late afternoon. One tweeter asked, "Do space people know how to talk to rock people or air people?"

Another hit the modern nail on the head, with a good takeaway for scientists everywhere trying to convey their Earth and space research. "If we don't explain it simply," the tweet went, "people won't understand how cool it is."

December 2017? See you in New Orleans.