Midsommersø records the Holocene glacial history of Wandel Dal, Inutoqqat Nunaat (Peary Land) northern Greenland

Reconstructing past ice extent and climate at the margins of the Greenland Ice Sheet (GrIS) offers important insights into the sensitivity of the ice sheet and its peripheral regions to climate forcing. Wandel Dal is a valley in northern Greenland that drains the northern margin of the GrIS as well as several ice caps. The valley was also an important landscape corridor for Inuit cultures beginning in the mid-Holocene. Here we examine the Holocene deglaciation and climate history of Wandel Dal based on analysis of sediment cores from Lake Midsommer (Midsommersø). We analyzed physical sediment properties, carbon and nitrogen content, grain size, diatom assemblages, and scanning X-ray fluorescence profiles to reconstruct physical and biological changes in the lake that were influenced by variations in glacier meltwater input, snowpack melt, precipitation, and lake primary productivity over the last c. 8.2 kyr. We find evidence that meltwater input to the lake was highest from at least c. 8.2 to c. 6.5 cal ka BP, delivering highly minerogenic sediments characterized by dense clay with frequent coarse layers. At c. 6.5 cal ka BP, there was an abrupt transition to sediment that is less dense, more organic rich, and where diatoms first appear. We interpret these changes to represent a significant reduction of meltwater input due to reduced ice extent within the catchment. These conditions lasted until c. 3.9 cal ka BP when we infer a shift to colder and drier conditions based on diatom and grain size data, which suggest longer periods of ice cover and reduced runoff to the lake. These conditions persisted until c. 50 years ago when diatom diversity dramatically increased due to recent climate warming. Our results add new constraints to the climate and deglaciation history of Inutoqqat Nunaat (Peary Land) and provide context for the Paleo-Inuit settlement history of Wandel Dal. • Holocene climate history of Wandel is reconstructed using lake sediment from Lake Midsommer. • Meltwater input to the lake was greatest from at least c. 8.2 to 6.5 cal ka BP. • Reduced ice extent in the catchment and more mild conditions inferred from c. 6.5 to 3.9 cal ka BP. • Abrupt shift to cold and dry conditions at c. 3.9 cal ka BP - lasted until c. 50 years ago. • Migration of Independence I people into Wandel Dal at end of the local Holocene thermal maximum.