133 research outputs found
A Study of the Organic Dye Nitrazine as an Indicator for Acid-Base Titration
Get PDFThis 13 page thesis examines the organic compound nitrazine as an indicator in acid - base nitrations
Evaluation of Machine Learning Techniques for Estimating Biogeochemical Properties on Seaglider Tracks in the Southern Ocean
No full textThe Southern Ocean is the largest oceanic carbon and heat sink on the planet with
complex dynamics at a variety of scales. Reliable, accurate, and high resolution estimates of
nitrate and carbonate system parameters (hereafter biogeochemical estimates) in the Southern
Ocean would enable the analysis of mesoscale and submesoscale biogeochemical processes
throughout the water column. This work explores the use of multiple methods, including several
from the machine learning literature, for biogeochemical parameter estimation in the Southern
Ocean. Training data for this work includes temperature, salinity, oxygen, and nitrate
measurements from the 2019 R/V Thomas G. Thompson reoccupation of the I06S line and from
Southern Ocean Carbon and Climate Observations and Modeling project (SOCCOM) floats
deployed during this cruise. Four models for the estimation of nitrate were trained and validated
for accuracy; these models included a random forest regression, a generalized additive model, a
multiple linear regression, and a gradient boosted regression tree model. The random forest
regression performed the best out of the four machine and statistical models on our nitrate test
data with a median value for the absolute error of 0.09 μmol kg-1 and an interquartile range of
0.13 μmol kg-1 in the absolute error. Using this random forest model, we predicted the nitrate
concentrations along the high resolution tracks of two Seagliders deployed on this cruise. We
plan to later repeat this estimation process for pH along the Seaglider tracks as well. The nitrate
and pH estimates from the random forest model can be used to improve our understanding of
mesoscale and submesoscale processes related to carbon flux in this region of the Southern
Ocean.
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