Summer High‐Wind Events and Phytoplankton Productivity in the Arctic Ocean.

At the base of the marine food web, phytoplankton are an essential component of the Arctic Ocean ecosystem and carbon cycle. Especially after sea ice retreats and light becomes more available to the Arctic Ocean each summer, phytoplankton productivity is limited by nutrient availability, which can be replenished by vertical mixing of the water column. One potential mixing mechanism is gale‐force wind associated with summer storm activity. Past studies show that sustained high winds (>10 m s−1) impart sufficient stress on the ocean surface to induce vertical mixing, and it has been speculated that greater storm activity may increase net primary productivity (NPP) on a year‐to‐year timescale. We test this idea using a combination of satellite products and reanalysis data from 1998 to 2018. After controlling for the amount of open water, sea‐surface temperature, and wind direction, we find evidence that greater frequency of high‐wind events in summer is associated with greater seasonal NPP in the Barents, Laptev, East Siberian, and southern Chukchi Seas. This relationship is only robust for the Barents and southern Chukchi Seas, which are more strongly impacted by inflow of relatively nutrient‐rich water from the Atlantic and Pacific Oceans, respectively. In other words, stormier summers may have higher productivity in several regions of the Arctic Ocean, but especially the two inflow seas. Additionally, a recent rise in high‐wind frequency in the Barents Sea may have contributed to the simultaneous increase in NPP. Plain‐Language Summary: Microscopic phytoplankton are an essential component of the Arctic Ocean ecosystem because they are the base of the marine food web. Sea ice in the Arctic Ocean limits phytoplankton growth by reducing how much sunlight reaches the ocean surface, but sea ice is becoming less common in the Arctic Ocean over time. This increases the importance of another limit on phytoplankton: nutrients. Phytoplankton near the surface use up nutrients rapidly in spring, so summer growth is limited by the rate that nutrients are replenished. Past studies have shown that individual storms with strong winds can stir up enough nutrients from deeper waters to temporarily enhance phytoplankton activity. We find that this is not simply a localized or short‐term impact. Stormier summers tend to have higher productivity in several regions of the Arctic Ocean. We also find that the frequency of high‐wind events has increased in recent years, so although the decline in Arctic sea ice can explain much of the increase in phytoplankton growth over 1998–2018, an increase in storminess is also a likely part of the story. Key Points: Past studies suggest that wind‐induced mixing enhances Arctic Ocean phytoplankton productivity by increasing nutrient availabilityGreater frequency of summer high‐wind events is associated with enhanced NPP in the two inflow seas (Barents Sea and southern Chukchi Sea)Positive trend of NPP for the Barents Sea in recent years is partly explained by increased frequency of high‐wind events [ABSTRACT FROM AUTHOR]