| Summary: | Many high-resolution terrestrial physical and organic matter proxy records from Iceland capture departures from the smoothly decreasing trend in Northern Hemisphere summer insolation that primarily drives climate throughout the Holocene, suggesting that other feedbacks and forcings exhibit control on the climate system. Iceland is located in the north Atlantic, where climate is complicated by major oceanic and atmospheric currents, and is therefore a key location for understanding the complex mechanisms that control the climate system. In the central highlands, a high desert plateau in the center of Iceland, early Holocene climatic conditions and the causes behind subsequent evolution the climate still remains relatively unexplored. In this study, a new Holocene climate record based on physical and organic matter proxies from shallow lake Arnarvatn Stóra (ARN) in the central highlands is compared with a nearby soil section and glacier-dominated lake proxy record from Hvítárvatn (HVT), about 30 km away from ARN on the other side of the Langjökull ice cap. The deglaciation of ARN occurred at ~10.54 ka in response to high Northern Hemisphere summer insolation, which continued into the early Holocene (10.5-7.9 ka) and caused warm conditions evidenced by high algal productivity and low sediment accumulation rate (SAR) indicates rapid soil development around the ARN catchment. This warmth was interrupted by a cooling event between 8.7-7.9 ka, suggested by increased SAR, possibly due to pulses of freshwater released into the North Atlantic from the waning Laurentide Ice Sheet. Mid-Holocene (7.9-5.0 ka) warmth is detected in the ARN record by an increase in aquatic macrophytes, high algal productivity, and maximum catchment stability, though the magnitude of this warmth compared to the early Holocene is unknown. Because this mid-Holocene warmth persists nearly 3 ka after peak insolation, it is likely due to increased advection of warm Atlantic waters to the coast of Iceland, as is suggested by marine core proxy data. ...
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