Deglaciation of Boknafjorden, south-western Norway

We present 30 ¹⁰Be ages from glacial erratic boulders to constrain the deglaciation of the Scandinavian Ice Sheet in the Boknafjorden region, south-western Norway. The southern part of the island Karmøy, located at the mouth of this fjord system, became free of glacier ice before 16 ka, probably because of the sudden break up of the Norwegian Channel Ice Stream at 20–18 ka. The ice sheet margin then stabilized at the fjord mouth until a second retreat phase commenced at or slightly before 16 ka. A calving bay developed in Boknafjorden after 16 ka, and in the course of the next millennium the ice front retreated to the inner fjord branches. In contrast, a major outlet glacier that filled the Hardangerfjorden farther to the north did not start to retreat from the fjord mouth until after 15 ka, probably in response to the Bølling warming. Thus, not only did Boknafjorden experience major retreat before Bølling warmth, but there was a variable response of south-western fjord glaciers in Norway consistent with prior observations of non-climatic forcing of marine-terminating outlet glaciers.