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Abstract
During recent decades, historically unprecedented changes have been observed in the Arctic as climate warming has increased precipitation, river discharge, and glacial as well as sea-ice melting. Additionally, shifts in the Arctic's atmospheric pressure field have altered surface winds, ocean circulation, and freshwater storage in the Beaufort Gyre. These processes have resulted in variable patterns of freshwater export from the Arctic Ocean, including the emergence of great salinity anomalies propagating throughout the North Atlantic. Here, we link these variable patterns of freshwater export from the Arctic Ocean to the regime shifts observed in Northwest Atlantic shelf ecosystems. Specifically, we hypothesize that the corresponding salinity anomalies, both negative and positive, alter the timing and extent of water-column stratification, thereby impacting the production and seasonal cycles of phytoplankton, zooplankton, and higher-trophic-level consumers. Should this hypothesis hold up to critical evaluation, it has the potential to fundamentally alter our current understanding of the processes forcing the dynamics of Northwest Atlantic shelf ecosystems.
Highlights
Shifts in the Arctic’s atmospheric pressure field have altered surface winds, ocean circulation, and freshwater storage in the Beaufort Gyre. These processes have resulted in variable patterns of freshwater export from the Arctic Ocean, including the emergence of great salinity anomalies propagating throughout the North Atlantic
We link these variable patterns of freshwater export from the Arctic Ocean to the regime shifts observed in Northwest Atlantic shelf ecosystems
Arc tic Climate Forcing of Northwest Atl antic Ecosystems during the 1990s In 1989, sea level pressure dropped precipitously in the central Arctic, leading to the most positive Arctic Oscillation (AO) Index of the twentieth century and the emergence of a strongly cyclonic atmospheric circulation anomaly (Figure 1a, Technical Note 1*; Dickson, 1999). This anomaly persisted as a strong cyclonic circulation regime until 1996 and coincided with a reorganization of upper-ocean circulation patterns in the Arctic Ocean (Figure 2a), including a spinning down of the Beaufort Gyre, as quantified by the Arctic Ocean Oscillation (AOO) Index (Figure 1b, Technical Note 1; Proshutinsky and Johnson, 1997; Dukhovskoy et al, 2006; McLaughlin et al, 2011), and an increase in the Arctic Ocean’s freshwater export into the North Atlantic (Steele et al, 2004)
Summary
These processes have resulted in variable patterns of freshwater export from the Arctic Ocean, including the emergence of great salinity anomalies propagating throughout the North Atlantic. We link these variable patterns of freshwater export from the Arctic Ocean to the regime shifts observed in Northwest Atlantic shelf ecosystems.
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