Lagrangian-based estimates of Net Community Production Overall goal: estimation of community production rates by tracking satellite- derived C inventories over time and space Problem: Various satellite productivity estimates presently rely on single images of stocks and state variables to infer rates of change. They do account for actual changes over time. Potential solution: Multiple views/day from GeoCAPE or a swarm of LEO sensors can enable monitoring of biogeochemical inventories within a water parcel as they evolve over time.
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Lagrangian-based estimates of Net Community Production Overall goal: estimation of community production rates by tracking satellite-derived C inventories.
Part 1: The Lagrangian Experiment Approach:1. Tracked a drogue at 12m (7 cruises over 16 days) 2. Kept track of oxygen and particle inventories We assume these are equivalent (within the context of a homogenous water mass)
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Lagrangian-based estimates of Net Community Production
Overall goal: estimation of community production rates by tracking satellite-derived C inventories over time and space
Problem: Various satellite productivity estimates presently rely on single images of stocks and state variables to infer rates of change. They do account for actual changes over time.
Potential solution: Multiple views/day from GeoCAPE or a swarm of LEO sensors can enable monitoring of biogeochemical inventories within a water parcel as they evolve over time.
Lagrangian-based Studies in the coastal Gulf of Maine (supplements to NASA-Carbon NNX08AL80G).
Part 1: A Lagrangian field experiment to determine net community productivity NCP in the Gulf of Maine
Olivia DeMeo (MS Student, UNH), Joe Salisbury (UNH)
Part 2: Tracking particle inventories with a high resolution circulation model to infer NCP
Bror Jonsson (Princeton), Joe Salisbury (UNH), Amala Mahadevan, (Boston University)
Part 1: The Lagrangian Experiment
Approach: 1. Tracked a drogue at 12m (7 cruises over 16 days)2. Kept track of oxygen and particle inventories
We assume these are equivalent (within the context of a homogenous water mass)
• Raw oxygen, bbp and c-660 and f-chl from profiles were corrected with bottle data
• Oxygen inventories corrected for thermodynamic variability, air-sea flux and diffusion, then converted to carbon using the Redfield ratio
• Inventories (down to 1% surface PAR) were differenced over time
• Additional correction for DOCex, POC flux and bubble injection are underway
Data/ data processingData/ data processing
Cruise data examples: Time-depth f-chlorophyll (mg/m3)
Time-depth biological Oxygen Anomaly (μmol/m3)
y = 0.1882x – 0.2243
r2 = 0.45
Results: optically-derived particle inventories versus NCPChlorophyll (C:Chl = 90:1)
r2 = 0.76y = 0.1058x – 0.2125
r2 = 0.85y = 0.1432x + 0.0124
Newly corrected for DOCex, POC flux and bubble injection. The slope is close to 1
• The Good: Significant relationships between optically derived particle inventories and NCP. Corrections for DOCex, POC sinking and bubble injection brought slopes close to one.
• The Bad: oxygen > particles. We either have too much oxygen or too few particles. Very dependant on the above corrections.
Conclusions for part 1Conclusions for part 1
Premise:
Part 2: Estimating NCP by tracking sat particle inventories in a Lagrangian contextJonsson, Salisbury, Mahadevan, Campbell (2009) Jonsson, Salisbury, Mahadevan (2011)
PCt1
PCt2
(PCt2 - PCt1)
(t2 - t1)NCP
PC = satChl * *ze
ze =loge(0.01)=K490
modified from Behrenfeld et al., 2005***Movie examples shown w/ chl
PC inventory helps give an estimate of NCP
chl
mg
C m
-2 d
-1
Net community productivity (gC m2 d-1)
What we’re working on now: Time and space requirements for satellite data to enable particle inventory tracking
300m, hourly model and daily cloud free 250 and 500m MODIS data to:
1.Simulate differences in “net radiance production” between Eularian versus Lagrangian determinations over the course of a day.
2.Run the same simulation using increasingly large pixel resolutions.
The first run using high res circulation and 500m MODIS
How do our results help inform the GEO-CAPE SWG?
1.Results from part 1 suggest that sub daily changes in particle inventories can be use to to track daytime NCP rates2.3-5 determinations per day may be enough for daily NCP estimates provided the advective component is adequately resolved3.For part 2: Preliminary work shows promise towards estimating rates from satellite tracking of particle inventories in a Lagrangian context.4.In work still to be done, we anticipate considerable differences between the Lagrangian and Eularian approach (using high resolution data)