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Abstract. The northern sector of the Greenland Ice Sheet is considered to beparticularly susceptible to ice mass loss arising from increased glacierdischarge in the coming decades. However, the past extent and dynamics ofoutlet glaciers in this region, and hence their vulnerability to climatechange, are poorly documented. In the summer of 2019, the Swedish icebreakerOden entered the previously unchartered waters of Sherard Osborn Fjord, whereRyder Glacier drains approximately 2 % of Greenland's ice sheet into theLincoln Sea. Here we reconstruct the Holocene dynamics of Ryder Glacier andits ice tongue by combining radiocarbon dating with sedimentary faciesanalyses along a 45 km transect of marine sediment cores collected betweenthe modern ice tongue margin and the mouth of the fjord. The resultsillustrate that Ryder Glacier retreated from a grounded position at thefjord mouth during the Early Holocene (> 10.7±0.4 ka cal BP) and receded more than 120 km to the end of Sherard Osborn Fjord by theMiddle Holocene (6.3±0.3 ka cal BP), likely becoming completelyland-based. A re-advance of Ryder Glacier occurred in the Late Holocene,becoming marine-based around 3.9±0.4 ka cal BP. An ice tongue,similar in extent to its current position was established in the LateHolocene (between 3.6±0.4 and 2.9±0.4 ka cal BP) andextended to its maximum historical position near the fjord mouth around 0.9±0.3 ka cal BP. Laminated, clast-poor sediments were deposited duringthe entire retreat and regrowth phases, suggesting the persistence of an icetongue that only collapsed when the glacier retreated behind a prominenttopographic high at the landward end of the fjord. Sherard Osborn Fjordnarrows inland, is constrained by steep-sided cliffs, contains a number ofbathymetric pinning points that also shield the modern ice tongue andgrounding zone from warm Atlantic waters, and has a shallowing inlandsub-ice topography. These features are conducive to glacier stability andcan explain the persistence of Ryder's ice tongue while the glacier remainedmarine-based. However, the physiography of the fjord did not halt thedramatic retreat of Ryder Glacier under the relatively mild changes inclimate forcing during the Holocene. Presently, Ryder Glacier is groundedmore than 40 km seaward of its inferred position during the Middle Holocene,highlighting the potential for substantial retreat in response to ongoingclimate change. 

In order to document changes in Holocene glacier extent and activity inNEGreenland (~73° N) we study marine sediment records that extend from the fjords (PS2631 andPS2640), across the shelf (PS2623 andPS2641), to the Greenland Sea (JM07‐174GC). The primary bedrock geology of the source areas is the Caledonian sediment outcrop, including Devonian red beds, plus early Neoproterozoic gneisses and early Tertiary volcanics. We examine the variations in colour (CIE*), grain size, and bulk mineralogy (from X‐ray diffraction of the <2 mm sediment fraction). Fjord corePS2640 in Sofia Sund, with a marked red hue, is distinct in grain size, colour and mineralogy from the other fjord and shelf cores. Five distinct grain‐size modes are distinguished of which only one is associated with a coarse ice‐rafting signal – this mode is rare in the mid‐ and late Holocene. A sediment unmixing program (SedUnMixMC) is used to characterize down‐core changes in sediment composition based on the upper late Holocene sediments from coresPS2640 (Sofia Sund),PS2631 (Kaiser Franz Joseph Fjord) andPS2623 (south of Shannon Is), and surface samples from the Kara Sea (as an indicator of transport from the Russian Arctic shelves). Major changes in mineral composition are noted in all cores with possible coeval shifts centredc. 2.5, 4.5 and 7.5 cal. kaBP(±0.5 ka) but are rarely linked with changes in the grain‐size spectra. CoarseIRD(>2 mm) andIRD‐grain‐size spectra are rare in the last 9–10 cal. kaBPand, in contrast with areas farther south (~68° N), there is no distinctIRDsignal at the onset of neoglaciation. Our paper demonstrates the importance of the quantitative analysis of sediment properties in clarifying source to sink changes in glacial marine environments.