The sediments of Lake Lögurinn – A unique proxy record of Holocene glacial meltwater variability in eastern Iceland

The full Holocene development of the large (8100 km2) Vatnajökull ice cap in Iceland with its many outlet glaciers is poorly known. The idea of an early deglaciation, leading to a glacier-free period in mid-Holocene, followed by the Neoglaciation is still the main concept for the glacial history in the North Atlantic region, including Iceland. We have examined a continuous sediment record from the glacier-fed Lake Lögurinn in eastern Iceland to infer Holocene meltwater variability of Eyjabakkajökull, which is a surge-type outlet glacier of the Vatnajökull ice cap. We focus on the early and mid-Holocene, and our data show that Eyjabakkajökull receded rapidly during the final phase of the last deglaciation, and did not deliver glacial meltwater to Lake Lögurinn by 9000 years BP, suggesting that Eyjabakkajökull was significantly smaller than today at that time. The return of glacial meltwater transport to Lake Lögurinn, and thus a return of Eyjabakkajökull is dated to ca 4400 years BP, suggesting an almost 5000 years long glacier-free period during early and mid-Holocene. During this time period, we infer that the 8.2 ka cold event did not cause a significant expansion of Eyjabakkajökull, however, we note a marked decrease in the aquatic productivity in Lake Lögurinn, which is suggested to be the result of shorter ice-free seasons of Lake Lögurinn. The Holocene Thermal Maximum is inferred by a period of maximum Holocene aquatic productivity, and dated to ca 7900–7000 years BP. Following the re-formation of Eyjabakkajökull ca 4400 years BP, we suggest that the glacier reached stable conditions ca 1700 years BP, and remained fairly stable until the later part of the Little Ice Age, when Eyjabakkajökull reached its maximum Holocene extent.

► Holocene glacial meltwater variability of Eyjabakkajökull is examined. ► No, or limited amounts of meltwater was generated in early and mid-Holocene. ► 4400 years BP marks the onset of Neoglaciation in eastern Iceland.