UBC Theses and Dissertations
Changes to the near surface waters of the Canada Basin, Arctic Ocean from 1993-2009 : an examination of the consequences of warming and freshening to the water mass structure and optical environment Jackson, Jennifer Martine
The near-surface water mass structure in the Canada Basin of the Arctic Ocean was examined from 1993 through 2009. This was a period of rapid change due to warming air and ocean temperatures and subsequent sea ice melt. During this time, the Southern Canada Basin transitioned from a perennially ice-covered to an almost seasonally ice-free ocean. It was found that the freshwater from sea ice melt increased the near-surface stratification. Solar radiation was stored below the surface mixed layer as a near-surface temperature maximum (NSTM). From 1993-2009, the NSTM warmed by up to 1.5◦C, freshened by up to 4 salinity units, expanded northwards, and formed at successively shallower depths. Below the NSTM is a temperature minimum identified as the remnant of the previous winter’s surface mixed layer (rML). Similar to the NSTM, the rML warmed by up to 0.5◦C and freshened by up to 2 salinity units from 1993-2009. Using a 1-D model of heat diffusion, it was found that heat from both the NSTM and Pacific Summer Water (PSW) is diffused to the rML. In warmer years, more heat was diffused to the rML from the NSTM. The freshening of both the NSTM and rML was greatest at stations that were located inside the anticyclonic Beaufort Gyre and this is likely because downwelling caused freshwater from sea ice melt to accumulate inside the gyre. An examination of light attenuation to estimate suspended particle concentrations identified six common attenuation features. These features were at the surface, within the summer halocline, within water that has high fluorescence, within cold water that had the salinity range 32.9 - 33.1, within Atlantic water, and at the bottom. It was found that there was no evidence of increased particle concentrations in the basin from 2003-2008. However, the chlorophyll maximum inside the basin deepened from an average of 45 m in 2003 to 61 m in 2008 and it is likely that this is because the nutricline also descended. The deepening of the chlorophyll maximum is one example of how changes to the near-surface water mass structure from climate change can impact the Arctic Ocean ecosystem.
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