Abstract
Continental slopes – steep regions between the shelf break and abyssal ocean – play key roles in the climatology and ecology of the Arctic Ocean. Here, through review and synthesis, we find that the narrow slope regions contribute to ecosystem functioning disproportionately to the size of the habitat area (∼6% of total Arctic Ocean area). Driven by inflows of sub-Arctic waters and steered by topography, boundary currents transport boreal properties and particle loads from the Atlantic and Pacific Oceans along-slope, thus creating both along and cross-slope connectivity gradients in water mass properties and biomass. Drainage of dense, saline shelf water and material within these, and contributions of river and meltwater also shape the characteristics of the slope domain. These and other properties led us to distinguish upper and lower slope domains; the upper slope (shelf break to ∼800 m) is characterized by stronger currents, warmer sub-surface temperatures, and higher biomass across several trophic levels (especially near inflow areas). In contrast, the lower slope has slower-moving currents, is cooler, and exhibits lower vertical carbon flux and biomass. Distinct zonation of zooplankton, benthic and fish communities result from these differences. Slopes display varying levels of system connectivity: (1) along-slope through property and material transport in boundary currents, (2) cross-slope through upwelling of warm and nutrient rich water and down-welling of dense water and organic rich matter, and (3) vertically through shear and mixing. Slope dynamics also generate separating functions through (1) along-slope and across-slope fronts concentrating biological activity, and (2) vertical gradients in the water column and at the seafloor that maintain distinct physical structure and community turnover. At the upper slope, climatic change is manifested in sea-ice retreat, increased heat and mass transport by sub-Arctic inflows, surface warming, and altered vertical stratification, while the lower slope has yet to display evidence of change. Model projections suggest that ongoing physical changes will enhance primary production at the upper slope, with suspected enhancing effects for consumers. We recommend Pan-Arctic monitoring efforts of slopes given that many signals of climate change appear there first and are then transmitted along the slope domain.
Highlights
MOTIVATION AND DEFINITIONSContinental slopes are a ubiquitous tectonic feature of the global ocean, long recognized for their central climatological and ecological roles at the interface of shelves and basins (Springer et al, 1996; Colloca et al, 2004; Azzellino et al, 2008; Bertram et al, 2017)
Once we have described bio-physical features along the above gradients and zones, we integrate physical and biological information to conceptualize the ecological functions that Arctic continental slopes add to the Arctic Ocean system in section “Functions of the Slope: System Connectivity vs. Separation.”
The band of enhanced polar cod biomass in the Beaufort Sea is located where the relatively warm Pacific Summer Water (PSW) and upper Atlantic Layer encroach the bottom along the continental slope (Parker-Stetter et al, 2011; Crawford et al, 2012; Majewski et al, 2016)
Summary
MOTIVATION AND DEFINITIONSContinental slopes are a ubiquitous tectonic feature of the global ocean, long recognized for their central climatological and ecological roles at the interface of shelves and basins (Springer et al, 1996; Colloca et al, 2004; Azzellino et al, 2008; Bertram et al, 2017). Driven by inflows of sub-Arctic waters and steered by topography, boundary currents transport boreal properties and particle loads from the Atlantic and Pacific Oceans along-slope, creating both along and cross-slope connectivity gradients in water mass properties and biomass.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have