I developed a 1D coupled sea ice-ocean-biological (including ice algae) model to study
the controlling effect of sea ice on primary and biogenic particle export production in the
western Arctic and the impacts of climate change (reduction in sea ice cover duration and
thickness, and in surface freshwater fluxes) on these productions. The model was
developed in two steps to maximize validation of model results with as much data as
possible. I first developed a coupled snow-ice-ice algae model for bottom landfast ice in
Resolute (Canadian Archipelago). Next, I developed and coupled a pelagic component
(NPZD type) to the ice algal model. The coupled model was implemented on the
Mackenzie shelf in the Canadian Beaufort Sea. And finally, I used simulations of future
climate change from the Canadian Global Climate Model (CGCM2) to force the 1D
model and obtain projections of future primary production on the Beaufort Sea shelf for
two 18-year periods (2042-2059, and 2082-2099).
The model results show that ice algae are light limited at the beginning of the bloom, then
fluctuate between light and nutrient limitation, to finally remain nutrient limited toward
the end of the bloom. The bottom ice melt rate regulates the maximum biomass attained
in Resolute, while biomass accumulation remains low in the Beaufort Sea due to nutrient
iv
limitation. The termination of the bloom is triggered by melting of the snow cover and
results from (i) increased ice algal losses due to high bottom ice melt rate and (ii)
decreased ice algal growth due to nutrient limitation caused by the formation of a
meltwater lens below the ice. The snow and sea ice cover melt and/or break-up also
controls the timing of the phytoplankton bloom. However, primary producers on the
Beaufort Sea outer shelf are essentially nutrient limited and total annual primary
production is controlled in part by nutrient “pre-conditioning” in the previous fall and
winter and by the depth of winter convective mixing, that are controlled in part by the
supply of fresh water from runoff and ice melt. The spring bloom sometimes represents
an important fraction of the total annual primary production, which occurs in great part at
the base of the mixed layer. Future projections show an increase in average annual
primary production of 6% between the periods 1975-1992 and 2042-2059, and of 9%
between 1975-1992 and 2082-2099. The relative contribution of the ice algal and spring
phytoplankton blooms to annual primary production is reduced in the future runs due to a
reduction in the length of the ice algal growth season (resulting from earlier snow and ice
melt) and to a reduction in the replenishment of nutrient to the mixed layer in winter. The
duration of the summer subsurface phytoplankton bloom increases, which favours the
development of the main copepod species and leads to an increase in export production
(16% between 1975-1992 and 2082-2099) that is greater than the increase in primary
production. This leads to an increase in averaged simulated e-ratio of 10% between the
first and last period.
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/1795 |
| Date | 26 October 2009 |
| Creators | Lavoie, Diane |
| Contributors | Denman, Kenneth Leslie, Weaver, Andrew J. |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | Available to the World Wide Web |
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