Numerical models are powerful and widely used tools for environmental prediction; however, any model prediction contains errors due to imperfect model parameterizations, insufficient model resolution, numerical errors, imperfect initial and boundary conditions etc. A variety of approaches is applied to quantify, correct and minimize these errors including skill assessments, bias correction and formal data assimilation. All of these require observations and benefit from comprehensive data sets. In this thesis, two aspects related to the quantification and correction of errors in biological ocean models are addressed: (i) A new bias correction method for a biological ocean model is evaluated, and (ii) a novel approach for expanding the set of typically available phytoplankton observations is
assessed.
The bias correction method, referred to as frequency-dependent nudging, was proposed
by Thompson et al. (Ocean Modelling, 2006, 13:109-125) and is used to nudge a model
only in prescribed frequencies. A desirable feature of this method is that it can preserve
high frequency variability that would be dampened with conventional nudging. The method
is first applied to an idealized signal consisting of a seasonal cycle and high frequency
variability. In this example, frequency-dependent nudging corrected for the imposed
seasonal bias without affecting the high-frequency variability. The method is then applied
to a non-linear, 1 dimensional (1D) biogeochemical ocean model. Results showed that
application of frequency-dependent nudging leads to better biogeochemical estimates than
conventional nudging.
In order to expand the set of available phytoplankton observations, light measurements
from sensors attached on grey seals where assessed to determine if they provide a useful
proxy of phytoplankton biomass. A controlled experiment at Bedford Basin showed
that attenuation coefficient estimates from light attenuation measurements from seal tags
were found to correlate significantly with chlorophyll. On the Scotian Shelf, results of
the assessment indicate that seal tags can uncover spatio-temporal patterns related to
phytoplankton biomass; however, more research is needed to derive absolute biomass
estimates in the region.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:NSHD.ca#10222/28453 |
| Date | 28 June 2013 |
| Creators | Lagman, Karl Bryan |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
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