Future Sea Ice-Ocean and Biological Productivity Changes in the North Water Polynya Region under Policy Relevant Warming Levels

Jed Lenetsky , Alexandra Jahn, Partick Ugrinow, Christopher Wyburn-Powell, Rajan Patel, Hannah Zanowski

The North Water Polynya (NOW) is one of the most productive biological regions in the Arctic with high importance to Inuit and Greenlandic communities. To provide insights into the potential changes of this region as global temperatures rise, we investigated the sea ice, and physical and biological oceanic responses of the NOW to low (2 °C) and high (>3.5 °C) levels of warming using the Community Earth System Model version 1. As global temperatures increase, sea ice production decreases, spring open water area increases, and summer open water areas in the NOW region connect with open water in central Baffin Bay earlier in the melt season. These sea ice changes contribute to increased stratification, which in turn, leads to increased concentrations of nutrient-rich West Greenland Irminger Waters at depth while decreasing surface nutrient concentrations. At low warming levels in the eastern NOW region, warmer water temperatures increase phytoplankton growth rates despite the decrease in surface nutrients, leading to an increase in peak primary production relative to the historical period. In contrast, for high warming in both the eastern and western NOW regions, biological primary production decreases, despite the warmer water temperatures, because increased stratification and decreased surface nutrient concentrations limit phytoplankton production. For all assessed warming levels, changing phytoplankton community composition drives a loss of ecosystem productivity at higher trophic levels. Internal variability plays a negligible role in driving these future sea ice and ocean changes, highlighting the importance of limiting further global temperature increases in order to avoid large changes to the NOW ecosystem.