ALBERT

Description: A marine sediment core from Vaigat in Disko Bugt, West Greenland, has been analysed in terms of lithology, dinoflagellate cysts and foraminifera in order to evaluate the influence of oceanographic variability on West Greenland glacier stability. The data show that during the past 5200 years the Atlantic foraminiferal abundance in the subsurface waters of the West Greenland Current (WGC) episodically increased, indicating periods of increases in the inflow of subsurface warm Atlantic water at 2000 - 1500 cal. yr BP and 1300 cal. yr BP as well as periods of less pronounced increased bottom-water temperatures around 4700 - 4000 cal. yr BP, 3100 - 2800, 2600, 1000 - 800, 500 - 400, and at 200 cal. yr. The sedimentological and dinoflagellate cyst data indicate that these episodes with enhanced advection of Irminger Sea-derived waters are accompanied by increased iceberg rafting, which we link to increased iceberg calving in relation to destabilization of the Jakobshavn Isbrae. The long-term trend in the data documents the end of a late-Holocene Thermal Maximum between 5200 and 4300 cal. yr BP and a final onset of the Neoglaciation at 3500 cal. yr BP. Increased responses of the iceberg rafting after 3500 cal. yr BP, reflects a westward/seaward advance of the glacier margin in relation to onset of Neoglaciation and a development of the glacier into a floating tongue after 2000 cal. yr BP. A comparison of our record with a record from the eastern North Atlantic indicates that a NAO-like anomaly pattern between subsurface waters in West Greenland and atmospheric temperature in the Eastern North Atlantic may have been operating during most of the late Holocene. However, during the past 1000 years the NAO signal may have weakened as some other mode of climate variability overprints the anti-phase climate signal in this region.

Description: This dataset includes the SST reconstruction, ice-rafted debris measurements, and age model of core FOX12-02R. In recent years, several large outlet glaciers in Greenland have lost their floating ice tongue, but little is known about their stability over longer time-scales. Here, we compile historical documents to demonstrate a major ice tongue collapse of Kangerlussuaq Glacier between 1932- 1933. This event resulted in nine kilometer retreat, which is more than during any of the glacier's recent major retreat events. Sediment cores from the fjord are used to reconstruct sea surface temperatures (SSTs) and to investigate a potential sedimentological trace of the collapse. Local SSTs increased during the 1920s, consistent with other regional air and ocean temperature records, suggesting a climatic trigger for the collapse. Fjord bathymetry played an important role too, as the (partially-) pinned ice tongue retreated off a submarine moraine during the event. This historical analogue of glacier tongue collapse emphasizes the fragility of remaining ice tongues in North Greenland within a warming climate.

Description: A chronology was developed using ²¹⁰Pb excess (²¹⁰Pbₓₛ; T1/2 =22.3 yr) and ¹³⁷Cs (T1/2=30 years). Sediment samples were freeze dried, powdered and measured for radioisotopes on a low-background, well- type germanium detector. Activities of ²¹⁰Pb, ²²⁶Ra, and ¹³⁷Cs were corrected for self-adsorption and decay since core collection. The constant flux-constant sedimentation (CF-CS) approach was applied.

Description: During the early 2000s the Greenland Ice Sheet experienced the largest ice-mass loss of the instrumental record, largely as a result of the acceleration, thinning and retreat of large outlet glaciers in West and southeast Greenland. The quasi-simultaneous change in the glaciers suggests a common climate forcing. Increasing air and ocean temperatures have been indicated as potential triggers. Here, we present a record of calving activity of Helheim Glacier, East Greenland, that extends back to about AD 1890, based on an analysis of sedimentary deposits from Sermilik Fjord, where Helheim Glacier terminates. Specifically, we use the annual deposition of and grains as a proxy for iceberg discharge. Our record reveals large fluctuations in calving rates, but the present high rate was reproduced only in the 1930s. A comparison with climate indices indicates that high calving activity coincides with a relatively strong influence of Atlantic water and a lower influence of polar water on the shelf off Greenland, as well as with warm summers and the negative phase of the North Atlantic Oscillation. Our analysis provides evidence that Helheim Glacier responds to short-term fluctuations of large-scale oceanic and atmospheric conditions, on timescales of 3-10 years.

Description: This data set includes grain size analyses and SST reconstructions from core AXC1432 in Nørre Skjoldungensund, SE-Greenland. Furthermore it contains water temperatures calculated from mesurements from https://www.ICES.dk and from the HadISST dataset. Heat transport via ocean currents can affect the melting of marine-terminating glaciers in Greenland. Studying past changes of marine-terminating glaciers allows assessing the regional sensitivity of the Greenland Ice Sheet (GrIS) to ocean temperature changes in the context of a warming ocean. Here, we present a high-resolution multi-proxy marine sediment core study from Skjoldungen Fjord, close to the marine-terminating Thrym Glacier. Grain-size data is obtained to reconstruct the calving activity of Thrym Glacier, sortable silt is used as a proxy for fjord water circulation and sea surface temperatures (SSTs) are reconstructed from alkenone paleothermometry (Uk'37). Measurements of 210Pb, 137Cs and 14C indicate that the core covers the past 220 years (1796 CE to 2013 CE). Comparisons with modelled SST data (HadISST) and instrumental temperatures (ICES) suggest that the SST proxy record reflects temperature variability of the surface waters over the shelf and that alkenones are advected into the fjord. Additionally, average temperatures and the amplitude of fluctuations are influenced by alkenones advected from upstream the Irminger Current. We find that the SST record compares well with other alkenone-based reconstructions from SE-Greenland, and thus features regional shelf water variability. The calving activity as well as the terminus position of Thrym Glacier did not seem to respond to the SST variability. Limited ice-ocean interactions owing to the specific setting of the glacier would explain this. Instead, the fjord circulation may have been influenced by enhanced meltwater production as well as to larger scale changes in the AMOC.