Spatiotemporal Variability in the Holocene Extent of Pikialasorsuaq (North Water Polynya), Baffin Bay

Abstract The North Water Polynya (NOW, Inuktitut: Sarvarjuaq , Kalaallisut: Pikialasorsuaq ), in northern Baffin Bay, is the largest polynya and one of the most productive regions in the Arctic. As modern climate change continues, the polynya's future is uncertain—if it ceases to exist, there will be negative consequences for regional biodiversity and the sustenance of indigenous communities. Here, we reconstruct the Holocene evolution of the NOW to understand the oceanographic and climatic conditions that led to its inception and subsequent variability. Using four marine sediment records, we analyzed mineralogy, biogenic silica, benthic and planktic foraminifera, and lipid biomarkers to reconstruct seasonal sea ice, primary productivity, and ocean temperature. Our results demonstrate that during the Early Holocene, when Parry Channel was open, but Nares Strait was closed to Arctic Surface Water (ASW) throughflow, higher temperatures led to upper water column stratification, low sea ice, and low primary productivity. Following the opening of Nares Strait (∼8,400 cal yr BP), sea ice remained low, and despite increased nutrient‐rich ASW throughflow through Nares Strait, the polynya did not yet exist. During the Middle Holocene ∼4,400 cal years ago, the NOW developed in northeastern Baffin Bay alongside increased sea ice. However, the polynya did not expand to its modern size, encompassing northwestern Baffin Bay, until the last two millennia, when Holocene climate was the coldest. This implies that as temperature continues to rise and exceed that of the Early to Middle Holocene, the NOW is at risk of collapse in the 21st Century.