Geological Survey of Denmark and Greenland Bulletin 35, 2016, 67-70 67© 2016 GEUS. Geological Survey of Denmark and Greenland Bulletin 35, 67–70. Open access: www.geus.dk/publications/bull The marine record of the Independence–Danmark fjord system extending out to the Wandel Hav in eastern North Greenland (Fig. 1A) is little known due to the almost per- ennial sea-ice cover, which makes the region inaccessible for research vessels (Nørgaard-Pedersen et al. 2008), and only a few depth measurements have been conducted in the area. In 2015, the Villum Research Station, a new logis- tic base for scientific investigations, was opened at Station Nord. In contrast to the early exploration of the region, it is now possible to observe and track the seasonal character and changes of ice in the fjord system and the Arctic Ocean through remote sensing by satellite radar systems. Satellite data going back to the early 1980s show that the outer part of the Independence–Danmark fjord system is character- ised by perennial sea ice whereas both the southern part of the fjord system and an area 20–30 km west of Station Nord are partly ice free during late summer (Fig. 1B). Hence, marine-orientated field work can be conducted from the sea ice using snow mobiles, and by drilling through the ice to reach the underlying water and sea bottom. Earlier studies have shown that the last deglaciation of the region occurred in the early Holocene (Funder 1989; Nørgaard-Pedersen et al. 2008) and the sea subsequently inundated the fjord system. Based on onshore evidence from eastern North Greenland, beach ridges and frequent deposition of drift wood during the Holocene Thermal Maximum at about 8000–5000 years BP indicate a pe- riod of open water and a mean summer temperature higher than today (Funder et al. 2011). During the first field season in 2015 at the new station, a number of field-based research projects were carried out coordinated by the Arctic Science Partnership (ASP, http:// www.asp-net.org/) and the Arctic Research Centre (ARC) at Aarhus University, Denmark. The Geological Survey of Denmark and Greenland (GEUS) and ARC carried out the fjord sediment coring project described here. The main objective of the marine geoscience field work was to col- lect sediment cores, which can be used to reconstruct past sea-ice variability through recent centuries and millennia. A major aspect was also the impact of sea ice on primary production, mainly diatoms and dinoflagellates and on bio- geochemical cycles and the Arctic ecosystem. This paper presents preliminary results of the sediment coring work and also new information on the bathymetry in the fjord area up to 50 km from Station Nord. A time-series of satellite radar images of sea-ice types in the fjord system provided by the Danish Meteorological Institute (DMI) for the last decade is discussed to better understand the recent sea-ice dynamics in the area. An introduction to the ongoing laboratory work and data processing is also included. Niels Nørgaard-Pedersen, Sofia Ribeiro, Naja Mikkelsen, Audrey Limoges and Marit-Solveig Seidenkrantz Investigations of past climate and sea-ice variability in the fjord area by Station Nord, eastern North Greenland Fig. 1. A: Study area (framed area) near Station Nord and Villum Re- search Station (red star), eastern North Greenland. The average posi- tion of the fast-ice edge toward the Arctic Ocean pack-ice drift is indi- cated. Map source: IBCAO vers. 3.0 (Jakobsson et al. 2012). B: Satellite image (DMI AQUA) of the area from 15 August 2015. PDØ: Prinsesse Dagmar Ø. PTØ: Prinsesse Thyra Ø. PMØ: Prinsesse Margrethe Ø. Arctic Ocean Flade Isblink 50 km Station Nord N PMØ PTØ PDØ Independence Fjord Hagen Fjord Danm ark Fjo rd Arctic Ocean Wandel Hav Flade Isblink 50 km Station Nord PDØ PMØPTØ N Fast ice margin A B G re en la n d 6868 Ice conditions Satellite data show that the northern hemisphere has ex- perienced a significant decrease in sea ice during the past c. 35 years, with a late summer sea-ice net loss in excess of 10% per decade, in addition to decreases seen in ice ex- tent, thickness and age (Perovich & Richter-Menge 2015). Older (>4 years) and thicker sea ice is now only dominant in northern Arctic Canada and off northern Greenland. The large Independence–Danmark fjord system in east- ern North Greenland is characterised by a semi-permanent fast-ice cover (Wadhams 1986) in the outer part and in the inner more southern part by a seasonal ice cover, which breaks up and partly melts during August–September (Fig. 1A). A coastal open water lead (polynya) is often observed between the northern margin of the fast ice and the drift- ing Arctic pack ice. The fast ice in the outer fjord system is protected by three large islands (the ‘Prinsesse islands’; Figs 1, 2), which make it stable for a number of years before parts of it break up (Wadhams 1986 and available satellite data). Very thick and old ice of the ‘sikkussak’ type has, therefore, been observed earlier at the mouth of the fjord system (Wadhams 1986). During exceptionally warm sum- mers the outer fast-ice cover has broken up, for example as observed in mid-August 2003 (Rasmussen 2004). The 2003 event coincided with break-up of the thick fast ice off the large NE Greenland ice stream in 2002 and 2003. While planning our field work we used synthetic ap- erture radar (SAR) and visible band images (AQUA, TERRA) captured over the last decade from DMI (http:// ocean.dmi.dk/arctic/nord.uk.php) in order to characterise the multi-year ice dynamics of the fjord system and to se- lect the sampling sites. Sea-ice radar reflectivity is sensitive to the roughness of the ice and the presence of saltwater droplets within newer ice. Thus, older and more deformed multi-year ice appears white or light grey (more reflection), whereas younger, first-year ice appears dark grey or black (less reflection). Hence, it is possible to identify areas char- acterised by first-year ice and distinguish these from multi- year ice covered areas (Fig. 2). Moreover, by examining the ice-cover character on SAR images from DMI from 2009 onwards, it is possible to date different patches of fast-ice cover. Ice tongues of glacier ice and icebergs debouching out to the sea from the ice cap of Flade Isblink can be iden- tified north-east and south-west of Station Nord (Fig. 2). The SAR and visible band image record for the past dec- ade reveals that the oldest fast ice in the study area is found K22, 23 K33, 34 K1, 2, 3 K11, 12 K29, 30 K4, 5 K27, 28 K7, 8 K26 K31, 32 R1, 2 K9, 10 K17, 18, 19 K24, 25 K15, 16 K13, 14 K20, 21 Depth (m) 0–20 20–40 40–60 60–80 80–100 100–120 120–140 140–160 160–180 180–200 10 km 81°50´N 81°30´N 81°30´N 16°W17°W Prinsesse Dagmar Ø Flade Isblink Station Nord A B Prinsesse Thyra Ø Prinsesse Dagmar Ø Multi-year ice First-year ice First-year ice Glacier front Glacier front Station Nord Flade Isblink 10 km 81°50´N 81°50´N 16°W17°W K33, 34 K1, 2, 3 K11, 12 K29, 30 K4, 5 K27, 28 K7, 8 K26 K31, 32 R1, 2 K9, 10 K17, 18, 19 K24, 25 K15, 16 K13, 14 K20, 21 K22, 23 18°W 18°W 81°40´N 81°40´N Fig. 2. A: Radar satellite image of the study area (SAR Sentinel-1 from 29.01.15), showing areas of seasonal (dark grey) and multi-year ice (light grey). There is no open water. High resolution SAR image (courtesy of Leif Toudal, Danish Meteorological Institute). Red dots: core sites. K: Kajak core. R: Rumohr core. Stippled lines: marine-terminating margins of Flade Isblink. B: Bathymetry data points with colour code for 20 m depth intervals overlain on SAR satellite image. Depth data sources are from the 2015 ASP field season (echo soundings and CTD based data) supplemented by data collected in 2006 by Naja Mikkelsen (GEUS), Yngve Kristoffersen (University of Bergen, Norway), and René Forsberg (DTU Space, Denmark). 69 in the Wandel Hav. This ice appears to be at least 6 years old and may date back to 2004 following the total break- up in 2003. A similar area of older ice patches is situated between the Prinsesse Thyra Ø and Prinsesse Margrethe Ø (Fig. 2). In mid-August 2012, the fast-ice cover at the mouth of the Independence Fjord and Danmark Fjord broke up, creating a wide-open connection to the Arctic Ocean in the area north-west of Prinsesse Thyra Ø. Freeze- up later in 2012 created the constellation of multi-year ice coverage persisting until today. Only the outer rim of the old fast-ice cover may occasionally be eroded by loss of ice fragments, which drift away with the Arctic pack-ice drift. The Flade Isblink ice cap is mainly drained by two out- lets along its western margin. A comparison of earlier maps (Higgins 1991) and 2015 satellite-derived data indicates that the outlet immediately north of Station Nord has re- treated about 13 km southwards between 1991 and 2015. Higgins (1991) estimated the average flow speed of the outlet glacier to be of a few hundred metres per year. Satel- lite radar data from the last decade confirm this estimate, but also indicate that the outlet glaciers have been surging (Joughin et al. 2010). Field work We collected sediment cores from 11 April to 2 May 2015 in the ice-covered fjord area (Figs 2, 3). Sampling took place up to about 30 km from the station along several tran- sects determined according to ice conditions and existing knowledge of bathymetry. We used two snow mobiles with sledges (3–4-person team) for transport. We selected sam- pling sites based on a geo-referenced high-resolution radar satellite image (Sentinel-1 SAR from 31.01.2015) revealing areas of first and multi-year ice as well as glacier-front posi- tions and larger icebergs (Fig. 2). Whenever possible, we targeted sites with thin first-year ice (about 1.0–1.2 m) and avoided sites covered by thick (>3 m) multi-year ice, which was very arduous to drill through. At each core site, we first removed the snow cover, which was usually at least 1 m thick, and used a 9 inch ice-auger to drill two or more overlapping holes in the ice, sufficient- ly large for the coring devices (Fig. 3). At most locations, we measured water depths with an echo sounder, but at oceanographic stations we used CTD data (conductivity, temperature and depth). We sampled sediment with a Ka- jak Sediment Corer (25–75 cm long tube, 45 mm inner diameter), a Rumohr Lot Corer (50–100 cm long tube, 75 mm inner diameter), and at a few stations, with a Van Veen Grab Sampler (top 10 cm surface sediment). We used a tri- pod with a top-mounted hydraulic winch (Pot Hauler) con- nected to a petrol-driven power pack to retrieve the c. 60 kg Rumohr Corer, whereas Kajak cores were retrieved with a hand winch (Fig. 3). Drilling large holes through 1–3 m of sea ice was time-consuming, and we found that Kajak cor- ing was the most efficient approach. We collected duplicate or triplicate Kajak cores at most coring sites and one Kajak core from each site was subsampled at 1 cm intervals at the Villum Research Station. Sea-ice cores were collected using a Kovacs Ice Corer System for biochemical and taxonomic studies of the sea-ice algal communities. Bathymetrical data Apart from a single study of short sediment cores and water-depth measurements south-west and north-west of Prinsesse Dagmar Ø close to Station Nord (Nørgaard- Pedersen et al. 2008) very little is known about the ba- thymetry and sedimentation record of this remote area. Bathymetrical datasets from the limited earlier field pro- jects in the area have, for this study, been updated by new data from the 2015 ASP field season. Earlier data consist of echo soundings carried out in 2006 and reconnaissance data. The 2015 field season dataset consists of echo sound- ing data and CTD-derived bathymetry data. As the CTD data are corrected for water-column velocity differences (due to water masses with different salinities and tempera- tures), these may be considered the most accurate. Water depths increase from c. 20 m near Station Nord to >150 m 20–30 km northwards (Fig. 2B). In front of the gla- cier outlet margin 10–15 km north-east of Station Nord, a trough is found with depths up to 100–150 m right up to the glacier margin at 81°40´N. There is a shallow area between Prinsesse Dagmar Ø and Prinsesse Thyra Ø with water depths between 20 and 30 m, but the depth increases Fig. 3. Recovering a Kajak core with seabed sediments. Photograph: Jesper Hoffmann. 7070 to >100 m towards the north. South of Prinsesse Dagmar Ø, a trough possibly connected to the mouth of the Dan- mark Fjord shows depths in the range of 130–150 m. The trough axis rises to about 115 m c. 10 km from the glacier outlet margin and reaches depths of maximum 50 m at the glacier margin. Preliminary results and outlook A total of 37 sediment cores were retrieved from 17 sites along transects up to c. 30 km from Station Nord (Fig. 2A). Many of the Kajak cores are only a few decimetres long. However, we recovered cores exceeding 0.5 m from more water-rich mud close to glacier margins and at the few Rumohr core sites. A spatial study of sea-ice and productivity proxies includ- ing dinoflagellate cysts, diatoms, foraminifera, biomarker IP25 (a proxy for sea ice) and biogenic silica is currently being conducted for the 17 sampling sites, to establish a baseline of recent conditions that will serve as modern ana- logues for reconstructions of sea-ice variability and changes in oceanographic conditions during earlier time periods. Selected sediment cores are being analysed for 210Pb and 137Cs content to estimate sedimentation rates at the study sites and establish a chronology for the topmost part of the cores. The first dating results show sedimentation rates in the order of 0.04–0.06 cm/y. Preliminary investigations of the microfossil content of the sediments revealed calcareous benthic foraminifera and a few ostracods, particularly at the deeper sites, which allows for the possibility to use 14C dating to establish a robust chronology for the sediment re- cords. Furthermore, studies of the sites located north of Sta- tion Nord show a stronger marine influence, whereas the sites towards the north-west and south have a clear signal of freshwater or glacial influence. Complementary to the climate proxy work, a characterisation of the protist com- munities is being undertaken by germination, growth tests, and molecular analyses (DNA) targeting the two main groups of primary producers: diatoms and dinoflagellates. Investigations of the sampled sea-ice cores showed that dur- ing the early part of the season’s field work the sea ice was barren of algae. This is attributed to light attenuation by the snow (average snow thickness of 1 m). In situ light measure- ments, and fluorescence measurements on 25 sea-ice core samples (bottom 5 cm) using a phytoplankton analyser showed no detectable photosynthetic activity (information from the Phytobiology Team, Aarhus University). The field work provided us with some first insights into an ice-covered, very remote and large fjord system of eastern North Greenland. The preliminary data confirm presence of biogenic remains and sedimentary signatures which can be used as proxies for palaeo-environmental re- constructions and deciphering of the younger part of the Holocene climate history in this region. Acknowledgements We thank Kunuk Lennert, Jesper Hoffman, Egon Frandsen and the late John Lau for logistic support. We thank Leif Toudal (DMI) for making geo-referenced satellite SAR images of the study area available. ASP 2015 oceanographers Igor Dmitrenko and Sergei Kirilov are also acknowledged for sharing CTD depth data. We thank the Station Nord military personnel for their great hospitality and help. The field work was partly financed by the Villum Foundation (grant no. VKR023454 to Sofia Ribeiro) and by the Arctic Research Centre, Aarhus University. References Funder, S. (ed.) 1989: Quaternary geology of the ice-free areas and ad- jacent shelves of Greenland. In: Fulton, R.J. (ed.): Quaternary geol- ogy of Canada and Greenland. The Geology of North America K-1, 741–792. Boulder, Colorado: Geological Society of America. Funder, S., Kjeldsen, K.K., Kjær, K.H. & Ó Cofaigh, C. 2011: The Greenland Ice Sheet during the past 300,000 years: a review. In: Ehlers, J., Gibbard, P.L. & Hughes, P.D. (eds): Quaternary glacia- tions – extent and chronology – a closer look. Developments in Qua- ternary Sciences 15, 699–714. Amsterdam: Elsevier. Higgins, A.K. 1991: North Greenland glacier velocities and calf ice pro- duction. Polarforschung 60, 1–23. 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Authors’ addresses N.N.-P., S.R., N.M. & A.L., Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. E-mail: nnp@geus.dk M.-S. S., Department of Geoscience, Aarhus University, Høegh-Guldbergs Gade 2, DK-8000 Aarhus C, Denmark.