Abstract
Abstract. It is expected that coastal erosion, upwelling, and increased river runoff from Arctic warming will increase the concentration of suspended particles in the Arctic Ocean. Here we analyze in situ transmissometer and fluorometer data from the summers of 2003 through 2008 and bottle-derived particulate organic carbon (POC) and total suspended solids (TSS) measurements sampled in the summers of 2006 and 2007 from the Canada Basin and surrounding shelves. We divided our study area into five regions to account for the significant spatial variability and found that the highest attenuation, POC and TSS values were observed along the Beaufort shelf and the lowest values were located along the eastern shelf of the Canada Basin. We then explored the correlation of POC and TSS with beam attenuation coefficients to assess the viability of estimating POC concentrations from archived transmissometer data. POC (but not TSS) and attenuation were well-correlated over the Northwind Ridge, in the Canada Basin interior, and along the eastern shelf of the Canada Basin. Neither TSS nor POC were well-correlated with attenuation along the entire Beaufort shelf. An interannual comparison of the attenuation and fluorescence data was done. We found no evidence of increasing attenuation from the summers of 2003 through 2008 and, although not statistically significant, it even appeared that attenuation decreased over time in the upper 25 m of the Northwind Ridge and in the 25–100 m layer (that includes the chlorophyll maximum) of the eastern Beaufort shelf and within the Canada Basin. In the Canada Basin interior, the subsurface chlorophyll maximum deepened at a rate of 3.2 m per year from an average of 45 m in 2003 to 61 m in 2008, an example of how changes to the Arctic climate are impacting its ecology.
Highlights
Climate change is predicted to increase upwelling, coastal erosion and river runoff and these effects will likely increase suspended particle concentrations in the Arctic Ocean and its surrounding shelves (Carmack et al, 2006)
These are (i) the eastern Beaufort shelf, a shelf-slope region in the southeastern Canada Basin with a bottom depth less than 3500 m that is influenced by outflow from the Mackenzie River; (ii) the western Beaufort shelf, a shelf-slope area with a bottom depth less than 3500 m that includes Barrow Canyon; (iii) the eastern Northwind Ridge slope, a feature with depths from about 950–3500 m between the Northwind Abyssal Plain and the Canada Basin, (iv) the Canada Basin interior, with a bottom depth greater than 3500 m; and (v) the eastern Canada Basin shelf, a shelfslope area with a bottom depth less than 3500 m that lies www.ocean-sci.net/6/799/2010/
Along the eastern shelf of the Canada Basin, we found that the high attenuation, low particulate organic carbon (POC) outlier was found within the nepheloid layer at a depth of 500 m
Summary
Climate change is predicted to increase upwelling, coastal erosion and river runoff and these effects will likely increase suspended particle concentrations in the Arctic Ocean and its surrounding shelves (Carmack et al, 2006). Particles supplied by these processes in the western Arctic Ocean (see map in Fig. 1) are primarily inorganic (Macdonald et al, 1998; O’Brien et al, 2006). The above concentrations were among the lowest ever observed for an open ocean system, and the Canada Basin was described as a biological desert (Kinney et al, 1971; Gordon and Cranford, 1985). In 1994, POC samples were collected in summer during the joint CanadaUS expedition from the Chukchi Sea to the North Pole and values in the upper 100 m were about five times greater than previous estimates, suggesting that the Canada Basin is seasonally productive (Wheeler et al, 1997) and actively cycles carbon (Wheeler et al, 1996)
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