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Abstract The Arctic hydrological cycle is predicted to intensify as the Arctic warms, due to increased poleward moisture transport during summer and increased evaporation from seas once ice‐covered during winter. Records of past Arctic precipitation seasonality are important because they provide a context for these ongoing changes. In some Arctic lakes, stable isotopes of oxygen and hydrogen (δ¹⁸O and δ²H, respectively) vary seasonally, due to seasonal changes in precipitation δ¹⁸O and δ²H. We reconstruct precipitation seasonality from Lake N3, a well‐dated lake sediment archive in Disko Bugt, western Greenland, by generating Holocene records of two proxies that are produced at different times of the year, and therefore record different lake water seasonal isotopic compositions. Aquatic plants synthesize waxes throughout the summer, and their δ²H reflects winter‐biased precipitation δ²H at Lake N3, whereas chironomids synthesize their head capsules between late summer and winter, and their δ¹⁸O reflects summer‐biased precipitation δ¹⁸O at Lake N3. During the middle Holocene at Lake N3, aquatic plant leaf wax was strongly²H‐depleted, while chironomid chitin was¹⁸O‐enriched. We guide interpretations of these records using sensitivity tests of a lake water and energy balance model, where we change precipitation amount and isotope seasonality inputs. The sensitivity tests suggest that the contrasting trends between proxies were likely caused by an increase in precipitation amount during all seasons and an increase in precipitation isotope seasonality, in addition to proxy‐specific mechanisms, highlighting the importance of understanding lake‐ and proxy‐specific systematics when interpreting records from sediment archives. 

Abstract Climate models predict Africa will warm by up to 5°C in the coming century, stressing African societies. To provide independent constraints on model predictions, this study compares two notable reconstructions of East African temperatures to those predicted by Paleoclimate Model Intercomparison Project (PMIP3) and transient TraCE (Transient Climate Evolution) simulations, focusing on the Mid‐Holocene (MH, 5–8 kyr B.P.). Reconstructions of tropical African temperature derived from lake sedimentary archives indicate 1–2.5°C of warming during the MH relative to the 20th century, but most climate models do not replicate the warming observed in these paleoclimate data. We investigate this discrepancy using a new lake proxy system model, with attention to the (potentially non‐stationary) relationship between lake temperature and air temperature. We find amplified lake surface temperature changes compared to air temperature during the MH due to heightened seasonality and precessional forcing. Lacustrine processes account for some of the warming, and highlight how the lake heat budget leads to a rectification of the seasonal cycle; however, the simulated lake heating bias is insufficient to reconcile the full discrepancy between the models and the proxy‐derived MH warming. We find further evidence of changes in mixing depth over time, potentially driven by changes in cloud cover and shortwave radiative fluxes penetrating the lake surface. This may confound interpretation for glycerol dialkyl glycerol tetraethers (GDGT) compounds which exist in the mixed layer, and suggests a need for independent constraints on mixed layer depth. This work provides a new interpretive framework for invaluable paleoclimate records of temperature changes over the African continent.