They Came From the Pacific: How Changing Arctic Currents Could Contribute to an Ecological Regime Shift in the Atlantic Ocean

Abstract

The Arctic Ocean is rapidly changing. With warming waters, receding sea ice, and changing circulation patterns, it has been hypothesized that previously closed ecological pathways between the Pacific and Atlantic Oceans will be opened as we move toward a seasonally ice-free Arctic. The discovery of the Pacific diatom Neodenticula seminae in the Atlantic suggests that a tipping point may have already been reached and this “opening up” of the Arctic could already be underway. Here, we investigate how circulation connectivity between the Pacific and Atlantic Oceans has changed in recent decades, using a state-of-the-art high-resolution ocean model and a Lagrangian particle-tracking method. We identify four main trans-Arctic pathways and a fifth route that is sporadically available with a shorter connectivity timescale. We discuss potential explanations for the existence of this “shortcut” advective pathway, linking it to a shift in atmospheric and oceanic circulation regimes. Advective timescales associated with each route are quantified, and seasonal and interannual trends in the main four pathways are discussed, including an increase in Fram Strait outflow relative to the Canadian Archipelago. In conclusion, we note that while tipping points for ecological connectivity are species dependent, even the most direct routes require multiannual connectivity timescales.