10:00-12:00 PM EST and 7:00-9:00 PM EST

Stacy Porter

Convening a session

INV06-INV07: Subdecadal Ocean-Atmosphere Variability: Insights from Proxies, Models, and Uncertainty Examinations

https://agu.confex.com/agu/fm20/meetingapp.cgi/Session/112327

07:00 PM EST

Apoorva Shastry

Town Hall

TH033 - Navigating a Nonacademic Research Career: Gain Tips and Insights on How to Stand Out from the Crowd

https://agu.confex.com/agu/fm20/meetingapp.cgi/Session/102409

7:00 - 23:59

Cole Poster

A041: Dust in a Changing Climate: From Small-Scale Insights to Large-Scale Understanding Shape, Size, and Elemental Composition of Individual Aeolian Nano- and Micro-particles Within the Horizontal Ice Core from Taylor Glacier, East Antarctica, During the Last Climatic Cycle

ABSTRACT

Throughout Earth’s most recent climate cycle, aeolian dust concentrations, size distributions, and chemical composition have changed significantly due to differences in sources of emission and atmospheric circulation. In the atmosphere, dust particles serve as direct and indirect climate forcings due to their optical scattering and absorption properties, and because they serve as cloud/ice nuclei, respectively. These forcings influence Earth’s albedo and depend on a particle’s physicochemical properties such as shape, size, and chemical composition. Glacial ice serves as a time-capsule of Earth’s past atmosphere and stratigraphically captures deposited atmospheric dust through time.

Using Scanning Transmission Electron Microscopy (STEM) and Energy Dispersive X-ray Spectrometry (EDXS) we have measured individual nano- and micro-particles that were entrapped in ice sections from the horizontal ice core of Taylor Glacier, East Antarctica. These sections cover Earth’s most recent glacial period, the last glacial-interglacial transition, and the current interglacial period, the Holocene (~45 ky – 8.5 ky BP). In particular, we report measurements of particles smaller than 200 nanometers in glacial ice. Particle dimension, aspect ratio (AR), circularity (CIRC), and chemical-elemental composition have been assessed to understand how these physicochemical properties have changed throughout Earth’s most recent climate cycle and the role they played in changing climate conditions.

19:12 EST

Roxana Sierra

Talk

GC031: Environmental and Climate Change in Global Mountain Regions II

Tracing Past and Present Air Pollution Sources Using Ice Core Records from High-Mountain Glaciers

ABSTRACT

Air pollution is of great concern because it can affect human health, climate, and the environment. Air pollutants originate from anthropogenic and natural sources and can be directly released into the atmosphere as gaseous compounds, particulate matter, black carbon, and organic carbon. They can be transported long distances depending on their physical and chemical characteristics and the prevailing meteorological conditions. Atmospheric monitoring programs and emission inventories have been conducted but are only available for recent decades with varying spatial and temporal resolutions. Thus, natural archives such as ice cores are necessary to trace the spatial and temporal sources of air pollution and to contextualize long-term trends.

In China and South Asia, fossil fuel consumption and deforestation have increased dramatically since the 1970s worsening local and regional air quality. This presentation will highlight histories of trace elements, which can be used as tracers of forest fires (e.g., Mn, Zn) and coal combustion (e.g., Cd, Pb, Sb, Zn), from ice cores retrieved from Tibet and the Himalayas. In particular, records of Cd, Pb, and Zn from the Guliya ice cap in northwestern Tibet, covering the 1971-2015 period, reveal that emission changes in Asia have impacted remote high-altitude glaciers in northwestern Tibet.

In North America, fossil fuel consumption has increased since the Industrial Revolution, but contrary to China and South Asia, the air quality improved after the introduction of the Clean Air Act of 1970. However, forest fires in boreal North America have increased since the 1980s and although they are a natural occurrence of forest ecosystems, human activities have influenced their regime. Using a continuous, high-resolution ice core-derived record of black carbon (~1930-2001 CE) from Bona-Churchill in southeastern Alaska, the possible sources of black carbon will be explored to reconstruct a fire history and determine the factors influencing the 20th century fire regime in southeastern Alaska.

7:00 AM - 11:59 PM

Allison Chartrand

Poster

C022: Understanding Ice Shelf Processes III

Constraining Ice Shelf Basal Channel Melt Rates and Evolution

https://agu.confex.com/agu/fm20/meetingapp.cgi/Paper/674806

ABSTRACT

Meltwater channels that incise into the base of ice shelves remain among the most poorly understood features in the ice shelf/ocean system. Ice shelves are vulnerable to basal melting and it is largely unknown how melt rates within basal channels compare with ice shelf melt rates as a whole, or how the evolution of basal channels impacts ice shelf stability. Using a suite of remotely-sensed, high-resolution surface elevation, ice thickness, and velocity data from the early 2000s to the present, we observe changes in several Greenland and Antarctic basal channels through time and estimate basal melt rates assuming hydrostatic equilibrium. Analyses are performed in both Lagrangian (coordinate system moves with flow) and Eulerian (fixed coordinate system) frameworks in order to capture as much information as possible about channel behavior, which is dependent not only on ice flow, but also on the independent behavior of the underlying meltwater plume which cannot be studied with the data available. We find a variety of evolutionary behaviors of basal channels; some channels remain steady in time and space, with elevated melt rates only at the head, or landward end, some channels, particularly sinuous channels and those near shear margins, experience migration and elevated melt rates at more than one point along their length, and some channels are out of hydrostatic equilibrium where active melt is occurring. We attempt to categorize channels based not only on possible formation mechanism, but also on their evolutionary behavior, with the aim of identifying specific channels and specific behaviors that may negatively impact ice shelf stability. Our basal melt rate estimates and characterization of basal channel behavior are important for the accurate representation of ice shelves in ice sheet models predicting future sea level rise.

13:50 PM EST

Michalea King

Talk

C040. Controls on Marine-Terminating Glacier, Ice Stream, and Ice Shelf Dynamics in Observations and Models I

C040-06 - Modes and drivers of nonuniform outlet glacier response to seasonal meltwater forcing in Greenland

https://agu.confex.com/agu/fm20/meetingapp.cgi/Paper/761624

ABSTRACT

The Greenland Ice Sheet is losing mass due, in part, to widespread acceleration of large outlet glaciers that drain ice directly into the ocean. These glaciers can be dynamically impacted by an influx of surface meltwater to the bed, which reduces ice-bed contact area, increases basal water pressures, and results in temporary acceleration. Our understanding of the interactions between meltwater runoff and outlet glacier flow remains limited, however, due to a paucity of direct in-situ observations of meltwater drainage systems beneath fast moving glaciers. Alternatively, satellite data can be used to monitor dynamic changes and infer evolving subglacial conditions. Here we use remotely sensed observations of ice velocity and surface elevation at all large Greenland outlet glaciers and derive their main mode of seasonal velocity change. We identify three distinct patterns of seasonal change that are indicative of meltwater sensitivity and categorize our subset of glaciers accordingly. We find that mean late-summer glacier velocities across the ice sheet are significantly related to the distribution of meltwater runoff supply, but that this relationship is most robust at glaciers with limited water storage capacity. We then analyze how categorical differences in climatic and geometric variables, including hydropotential gradient, height above flotation, and catchment-scale runoff volume, influence sensitivity to runoff. Lastly, we show how changing geometric conditions, such as retreat or prolonged thinning, can impact a glacier’s typical response to seasonal meltwater injection, and discuss how the effect of summer melt on net ice sheet discharge may evolve in the future.

7:08 AM EST

Jim Stagge

Talk H132: New Approaches to Characterize, Model, and Detect Precipitation Variability: Scientific and Practical Applications I

Incorporating non-stationarity in normalized meteorological drought indices with Bayesian splines

https://agu.confex.com/agu/fm20/meetingapp.cgi/Paper/768727

ABSTRACT

Under non-stationary climate conditions, normalized meteorological drought indices like the Standardized Precipitation Index (SPI) can be sensitive to the normalization reference period. Existing solutions either adopt a quasi-stationary reference period, typically fitting a 30 year subset, or ignore non-stationarity to fit the entire available record. This study proposes an alternative Bayesian approach for the SPI using penalized tensor product splines to simultaneously account for seasonality and multi-decadal non-stationarity for gamma-distributed precipitation. Using this approach, information from the entire instrumental record is retained, while allowing a post-hoc reference period to be chosen, mimicking a typical 30-year climate normal. To test model effectiveness, existing frequentist approaches are contrasted with the proposed spline model using pre-defined synthetic precipitation time series and 6 instrumental precipitation records across a range of hydroclimates. The proposed model more closely matches known probability distributions, decreases parameter uncertainty for the instrumental data, and better captures uncertainty around periods with zero precipitation.

01:09 PM EST

Apoorva Shastry

e-Lightning

EP051 - Machine Learning Applications in Earth Surface Processes Research I

EP051-04 Convolutional Neural Networks to Improve Soil-Cover Maps by Identifying Rock Outcrops in California

https://agu2020fallmeeting-agu.ipostersessions.com/default.aspx?s=B0-65-CC-79-30-44-95-5D-03-0E-B4-EA-D7-4B-D4-15

ABSTRACT

Researchers and land managers use land-cover maps to model how land-cover change impacts water and other elemental fluxes. For instance, whether land surfaces are soil or bare rock impacts hydrological models, carbon storage estimates, and susceptibility models for soil erosion and landslides. In the United States, the available Natural Resources Conservation Service (NRCS) soil maps and National Land Cover Database (NLCD) tend to over- or underestimate extents of rock soil when compared to more detailed maps. In our area of interest in the Sierra Nevada Mountains in California (USA), NRCS soil maps overestimated rock outcrops by 41% and NLCD underestimated the same by 88%. The increasing availability of high-resolution remote sensing imagery can be used along with machine learning techniques to improve regional maps of land-cover, including the distinction between soil and exposed rock surfaces. We built a convolutional neural network (CNN) to differentiate exposed bare rock from soil cover across the Sierra Nevada Mountains using National Aerial Inventory Program (NAIP) 1-m othroimagery. Exposed rock was mapped at eight sites in the Sierra Nevada Mountains, and a CNN was trained to classify these rock outcroppings. In the Sierra Nevada Mountains, the model classifies bare rock with an F1 score of 0.95, which is significantly higher than classical methods and existing databases. This tested CNN model was then used to predict rock outcrops across the Sierra Nevada Mountains (~49,000 km2) and will be applied to the entire state of California. The results are validated with additional training sites. When applied to the entire state of California, we expect the CNN model to similarly improve classification accuracy of rock outcrops. Improved representation of rock outcrops in land cover maps will be important to improve estimates of soil erosion, infiltration for hydrological models, among other applications.

9:05 AM AM EST

Kira Harris, Kasey Krok, Jason Cervenec

e-Lightning

U017-11 Virtual Reality Exploration of Earth's Cryosphere (Invited)

https://agu.confex.com/agu/fm20/meetingapp.cgi/Paper/675569

ABSTRACT

In previous field seasons, scientists from the Byrd Polar and Climate Research Center (Byrd Center) would take rugged, low-cost 360-degree cameras with them on expeditions to remote alpine and polar locations around the world. The video footage collected would document research activities along with breathtaking, and oftentimes dangerous, landscapes. The Center’s Education and Outreach (E&O) staff would utilize this footage to create virtual field experiences, accessible by anyone with an internet connection via a desktop, mobile device, or virtual reality (VR) headset. A Byrd Center team deployed to the Dry Valleys of Antarctica during the 2019-2020 field season was the first to visit their field site with a deliberate plan to create a virtual field experience. This fostered a collaboration between E&O staff and the researchers that resulted in an experience that captures the surrounding landscape, scientific research, and researchers as people. Using an iterative design process, the team co-created an experience with deliberate narrative elements to inspire and educate the public.

Our field experiences have been used to support both synchronous and asynchronous virtual outreach events in 2020, and inspired creation of live virtual tours of various research centers at The Ohio State University to maintain and expand public engagement during the pandemic. To meet increasing requests for information from both educators and researchers, a new how-to website was developed to explain the virtual field experience creation process and describe successful practices implemented by E&O staff. Visit the links provided to stand on the Kennicott Glacier in Alaska, see the summit of the Quelccaya Ice Cap in Peru, sit stream-side with researchers in the Dry Valleys of Antarctica, or even take a tour of the Byrd Center.

04:00 - 20:59 PST

Akbar Adjie Pratama

Poster

B111: Geovirology: Viruses in Earth’s Biomes and Their Impacts on Microbial Ecology and Biogeochemistry II Posters

PST B111-0002 - Towards Standards in Viromics: in silico Evaluation of Viral Identification, Taxonomy, and Auxiliary Metabolic Genes (AMGs) Curation

https://agu.confex.com/agu/fm20/meetingapp.cgi/Paper/760195

ABSTRACT

Viruses influence microbial diversity and global nutrient cycles, and metagenomic approaches have been critical for revealing viral roles across diverse ecosystems. However, the emergent field of viral ecogenomics has many processes that would benefit from comparative benchmarking to better standardize and enable comparison across datasets. Here we evaluate (i) viral identification, (ii) viral classification, and (iii) viral auxiliary genes (AMGs) curation using in silico-generated datasets that mimicked features of viromes and bulk metagenomes to provide guidelines and highlight potential pitfalls of viral metagenomic analyses.

Diverse viral identification tools are now available, e.g. VirSorter, MARVEL, MetaPhinder, deepVirFinder and VIBRANT. The results of our benchmarking show that tools based on gene content including VirSorter, MARVEL and VIBRANT, consistently outperformed other tools except for small (<3kb) viral contigs. Though tools such as, MetaPhinder, and DeepVirFinder outperformed these for small contigs, they did so at the cost of a higher false positive rate, particularly when eukaryotic or mobile element sequences were included in test datasets. For viral classification, variously sized genome fragments were assessed using gene-sharing network analytics (vConTACT2) for concordance against known taxonomy. Taxonomic classification of viral contigs was found to be acceptable (37.5% correct assignation) for contigs >3kb and, quickly improved as fragment length increases (~50% correct assignation for contigs >10kb). Finally, we outline suggestions and best practices for researchers to manually inspect and validate candidate auxiliary metabolic genes (AMGs) in metagenome-assembled viral genomes.

Together these benchmarking experiments provide guidance for researchers seeking to best detect and characterize the myriad viruses ‘hidden’ in diverse sequence datasets.

8:34 - 8:38 PM EST

Olivier Zablocki

Talk

B124: Geovirology: Viruses in Earth’s Biomes and Their Impacts on Microbial Ecology and Biogeochemistry I

Low input, long-read viromics reveals previously hidden abundant viruses and their genomic islands in soil and sea samples

ABSTRACT

Metagenomic long-read sequencing through the Nanopore platform holds the promise of extracting deeper and more complete biological signals compared to short-read data. However, maximizing the benefits of long-reads from low-input samples such as natural viral communities remains challenging. Here we introduce VirION 2, which builds on our previous long-read metagenomic wet-lab and informatics pipeline (VirION) by reducing DNA input 100-fold (now 1 nanogram), generating longer reads (now ~6kb median lengths), and improving accuracy (now 99.97% with short-read correction) – all as benchmarked against short-read data from a seawater sample. In seawater samples, 29% of the most abundant viruses were uniquely found by adding long-read sequencing. As proof of concept, VirION 2 was applied to soil viromes, previously inaccessible to long-read sequencing. These data revealed ~3-fold increase in community-level microdiversity patterns in soil phage communities, as well as ~100-fold increased detection of viral genomic islands, thus highlighting heavy selection pressures at play in soil viruses. Some of these genes were auxiliary metabolic genes, thought to enhance viral reproduction, some of which specific to the soil environment, like sporulation genes. Overall, the application of long-read sequencing to low-input viromes should make more samples accessible, produce more ‘complete’ virus catalogs, while revealing previously missed genomic- and biological-signals.