Difference between revisions of "GLEON Metabolism 1"

Revision as of 02:30, 26 March 2015

GLEON WORKING GROUP

These tasks are associated with one subgroup under the GLEON Metabolism 1 Working Group, better known as the Catchment-Lake Age-of-Carbon THEORY Subgroup .

Participants: Tom Harmon, Paul Hanson, Gopal Bhatt, Stuart Jones, Sam Oliver, Hilary Dugan, Roxanna Ayllon, Yang Cui

===Workflow=== (outcome of G16 breakout sessions)

1. Develop Conceptual Model [Tom, Paul, Gopal]
   
2. Paul and Gopal reach out for AoW code
   
3. Translation to r-coding: AoW to rAoW (ruh’ ow!) [Stuart, Sam, Hilary, Gopal]
   
4. Lit. review targeting carbon transformation rates [Roxanna, Yang]
   
5. Define model space [Sam]
   
6. Lit. review of prospective study gradients [Roxanna, Kevin]
   
7. Gradient Sensitivity Analysis (TBD at later date)
   

Skype Mtg #1 (12/30/14)

Attendees: Tom H, Kevin R, Stuart J, Hilary D

Summary - At G16, we decided to attempt to develop and use an Age of Carbon approach based on Duffy (2010), and use it to explore lake metabolism-catchment connections. In this Skype meeting, we revisited the method and Tom noted some good papers to read for people who want to come up to speed on the approach. Then, we discussed our approach to exploring the solution space of the "age" models we plan to develop.

The method is based on moment analysis, and results in relatively simple expressions (mathematically) for quantifying the age of water in idealized watersheds. Although Duffy (2010) opens the door to reactive transport, he stuck mainly with the age of water or conservative tracers. We decided to try to (1) reproduce the first two cases in Duffy (2010) and (2) extend the analysis to include 1st order decay of organic carbon constituents. The two cases involve a simplistic watershed characterized by a volume V and flow Q, and a similar but slightly more complex ideal watershed characterized by a mobile (Vm) and immobile (Vim) volumes--we decided that his might be one level of complexity that would be interesting to explore. Stuart and Tom are starting to work on the equations and Stuart (post-meeting) had some luck getting started with developing the solutions in Mathematica). Eventually, we may wish to develop R-scripts.

In terms of the solutions space, we discussed a broad approach associated with exploring key lake-catchment parameters. Kevin suggested the Wisconsin LTER lakes as a good set of lakes because they have long-term data on both the lakes and the catchments, and there is a reasonably good variety between Northern and Southern Wisconsin in terms of land use, vegetation, soils and geology. We decided to go with this suggestion and Kevin is getting some data organized. --Tom Harmon (talk) 12:23, 7 January 2015 (PST)

NOTE: Chris and his group have a good page on this site chronicling the approach in the paper and extending it: http://www.organicdatascience.org/ageofwater/index.php/Develop_mathematical_model_of_age_of_water_and_carbon#Concept

Post-Skype Mtg #1 Development

Paul requested the Mathematica scripts from Chris Duffy, and Chris is happy to help. Chris requested that Tom and Gopal sit in on their (Paul, Chris and Yolanda Gil) Organic Data Science project meeting. This will be an opportunity to learn a little more about Chris's analysis and we can fill him in on our proposed approach (and get some good feedback!). --Tom Harmon (talk) 12:23, 7 January 2015 (PST)

Skype Mtg #2 (02/18/2015)

Attendees: Tom, Paul, Stuart, Sam, Hilary

Summary: Stuart described version 1.0 of the the r-Age of Carbon (r-AoC) script and made the script available to the working group. Version 1.0 (based on Duffy 2010) currently includes:

(1) A conservative tracer model that doesn’t consider age; to remind myself and anyone else how these work; (2) The conservative tracer model that includes Chris’s age moment; (3) An adaptation of #2 with a first-order decay added; and (4) A model that allows for dynamic control volume, first order decay, and events in inlet discharge or concentration. This last model (4) is a general model that can recreate the special cases #2 and #3 above. With the decay parameter (d) set to zero, model (4) can recreate figures 2, 3, and 4 from Duffy 2010.

Stuart also mentioned that it may be a relatively straightforward extension of the script to enable us to add more 'compartments' to the model (e.g., epilimnion and hypolimnion, fast groundwater and slow groundwater, etc.).

Most of the group remarked that they were still digesting the "age" approach in Duffy (2010), and we charged everyone with practicing with r-AoC and, using the Wisconsin LTER lake-catchment data compiled by Kevin, try to come up with some potential applications of the AoC approach.

Paul suggested, and we all agreed, that once we become more familiar with the approach and r-AoC, we could try to gather for a concentrated effort/workshop aimed at crafting some research objectives, sorting out tasks, and making a leap in progress. We also agreed that it would be great to involve Chris Duffy soon to help with ideas and directions.

Skype Mtg #3 (03/25/2015)

Attendees: Tom, Sam, Hilary, Roxanna, Kevin, Paul

Summary: Picking up from the previous meeting, a couple of us presented what we had been able to get done with r-AoC.

Sam noted that there were some errors in the LTER data summary spreadsheet; Kevin will revisit that and resend the spreadsheet.

Sam ran r-AoC for several of the LTER lakes, and we talked through the results, mainly trying to get everyone a feel for the model output (focusing mostly on concentration and age time series outputs). Sam posted the plots from these simulations as .pdf files (see Task tree at top of the page: Decay examples).

Tom attempted ran r-AoC for the catchment side of the problem. He first developed a simple expression for catchment turnover rate (inverse of residence time) based on Darcy's Law. The approach assumes the groundwater (GW) gradient is the same as the ground surface gradient, and that the soil permeability is applicable for groundwater (homogeneous sediments). These two parameters provide the 1D GW flux and that flux divided by a horizontal travel distance provides a rough estimate of the catchment residence time. For the horizontal travel distance, he proposed using the sqrt(CLArea_ratio), where CLArea_ratio is the catchment-to-lake area ratio. There are probably a lot of ways to try to parameterize the GW turnover rate, but this is a start. The estimated residence times for the LTER lake catchments ranged from 6.5 days (Big Muskellunge) to 172 days (Mendota) [note: these need to be rechecked]. Tom did not post his methods and results yet but will do so well before the next meeting.

The group feels like there is some interesting science to be done using the AoC approach and will continue to develop ideas and test simulations. We recognized that we are deficient in terms of key parameters like the carbon decay constants (d). Roxanna is going to start a literature review in this area, looking for other estimates or approaches to making these estimates for temperate lakes and catchments. Hilary will try to point us to some isotope papers that might help us come up to speed on the subject of carbon age in a catchment-lake system, and to constrain/check our model parameters. Paul added the point that we may end up turning this challenge around by using the model to inform hypotheses about carbon ages.

We need a repository for papers, so Tom agreed to share a Drop Box folder with everyone. Coming soon.

Lastly, we pushed the next meeting back 1 week to April 22 due to some travel conflicts (sorry about that! --Tom)