Wandel Sea Research Articles

Triassic in the northernmost Atlantic—Linking North Greenland and the southwestern Barents Sea

AbstractThe Wandel Sea Basin in North Greenland was part of the epicontinental Boreal Sea in Triassic time. The basin formed the western margin of the northernmost Atlantic elongated sea connecting southwards with basins along the conjugate Greenland—Norwegian margins. A multidisciplinary dataset including sedimentology, biostratigraphy, organic geochemistry and sedimentary provenance, allow to document its basin evolution. The Wandel Sea Basin was transgressed in the Dienerian with marine deposition prevailing until the Norian. Sediments were mainly sourced from the Greenlandic Caledonian basement and deposited on a 100 km wide shallow marine shelf during the Early Triassic. In Middle Triassic, oil‐prone mudstones formed in oxygen‐depleted deep shelf settings, including eastern Wandel Sea Basin. Detrital zircon U–Pb ages show that by Carnian times, the >1000 km wide, Uralian‐sourced, deltaic shelf had prograded westward across the Barents Sea reaching the eastern north Greenland and de facto nearly closed the northernmost Atlantic Sea.

Meteoric water contribution to sea ice formation and its control of the surface water carbonate cycle on the Wandel Sea shelf, northeastern Greenland

An influx of glacial meltwater has the ability to alter the properties of marine surface waters and their ability to exchange CO2 through changes to water column stratification and the inorganic carbon system. Here, we report how inputs of meteoric water affect the physical and biogeochemical properties of both the water column and the sea ice cover on the Wandel Sea shelf, northeastern Greenland, during spring 2015. The observed depleted δ18O–H2O in the water column, with surface water values as low as –16.3 ‰, suggests a strong input of meteoric water (i.e., water derived from atmospheric precipitation). Depleted δ18O–H2O observed within sea ice (from –21.5 to –8.0 ‰) reflects its formation from surface water that was already depleted isotopically. In addition, a thick snow cover, as present during the study, promotes the formation of snow ice as well as insulates the ice cover. Within sea ice, the resulting relatively warm temperature and low salinity impedes ikaite formation. However, measurements of total dissolved inorganic carbon and total alkalinity indicate that, in both sea ice and the water column, the dissolution of calcium carbonate was the main process affecting the carbonate system. This finding suggests that inputs of glacial meltwater deliver glacier-derived carbonate minerals to the ocean which become incorporated within the ice structure, increasing calcium carbonate dissolution in the water column in the absence of ikaite precipitation within the sea ice. If widespread in glacial-fed waters, bedrock carbonate minerals could increase CO2 sequestration in glacial catchments despite the weakening of the sea ice carbon pump.

NE Greenland Composite Tectono-Sedimentary Element, northern Greenland Sea and Fram Strait

Abstract The NE Greenland margin measures more than 300 km from coast to the continent–ocean transition at its widest part and is in an early state of exploration. It is expected to hold significant petroleum reserves due to a high concentration of large structures and prolific source-rock intervals anticipated in the subsurface. The margin is composed of five tectonic units: (1) the Koldewey Platform; (2) the Danmarkshavn Basin; (3) the Danmarkshavn Ridge; (4) the Thetis Basin; and (5) the Wandel Sea Basin. These units form the NE Greenland Rifted Margin Composite Tectono-Sedimentary Element. Rifting commenced at some time during the Devonian or Carboniferous and recurred during latest Jurassic–Cretaceous time. Major tilted fault blocks and other rift-related structures formed during latest Jurassic–Cretaceous rifting. The structures are typically cored by Triassic–Middle Jurassic sand-prone sequences. Oil-prone Upper Jurassic–lowermost Cretaceous marine source rock caps the structures or is located immediately downdip. A large concentration of structures exists in the eastern Danmarkshavn Basin, the western Thetis Basin and along the edges of the Danmarkshavn Ridge. Other major structures exist in the least data-covered parts of the margin furthest north.

Accelerated sea ice loss in the Wandel Sea points to a change in the Arctic\u2019s Last Ice Area

The Arctic Ocean’s Wandel Sea is the easternmost sector of the Last Ice Area, where thick, old sea ice is expected to endure longer than elsewhere. Nevertheless, in August 2020 the area experienced record-low sea ice concentration. Here we use satellite data and sea ice model experiments to determine what caused this record sea ice minimum. In our simulations there was a multi-year sea-ice thinning trend due to climate change. Natural climate variability expressed as wind-forced ice advection and subsequent melt added to this trend. In spring 2020, the Wandel Sea had a mixture of both thin and—unusual for recent years—thick ice, but this thick ice was not sufficiently widespread to prevent the summer sea ice concentration minimum. With continued thinning, more frequent low summer sea ice events are expected. We suggest that the Last Ice Area, an important refuge for ice-dependent species, is less resilient to warming than previously thought.

Thermo-tectonic development of the Wandel Sea Basin, North Greenland

The Carboniferous–Palaeogene Wandel Sea Basin of eastern North Greenland (north of 80°N, east of 40°W) is an important piece in the puzzle of Arctic geology. It is particularly important for understanding how the Paleocene–Eocene convergence between Greenland, the Canadian Arctic and Svalbard relates to the compressional tectonics in the High Arctic, collectively known as the Eurekan Orogeny. In this study, we present apatite fission-track analysis (AFTA) data and review published vitrinite reflectance data combined with observations from the stratigraphic record to place firmer constraints on the timing of key tectonic events. This research study reveals a long history of episodic burial and exhumation since the collapse of the Palaeozoic fold belts in Greenland. Our results define pre-Cenozoic exhumation episodes in early Permian, Late Triassic, Late Jurassic and mid-Cretaceous times, each involving the removal of kilometre-scale sedimentary covers. Mid-Paleocene exhumation defines the timing of compression along the major fault zones during the first stage of the Eurekan Orogeny, after the onset of sea-floor spreading west of Greenland. Regional exhumation that began at the end of the Eocene led to the removal of most of a kilometre-thick cover that had accumulated during Eocene subsidence and involved a major reverse movement along the Harder Fjord Fault Zone, northern Peary Land. These events took place after the end of sea-floor spreading west of Greenland, and thus, represent post-Eurekan tectonics. Mid–late Miocene exhumation is most likely a consequence of uplift and incision across most of the Wandel Sea Basin study area. The preserved sedimentary sequences of the Wandel Sea Basin represent remnants of thicker strata that likely extended substantially beyond the present-day outline of the basin. We find that the present-day outline of the basin with scattered sedimentary outliers is primarily the result of fault inversion during Eurekan compression followed by deposition and removal of a kilometre-thick overburden.

Middle Jurassic sandstone deposition in the Wandel Sea Basin: evidence from cardioceratid and kosmoceratid ammonites in the Mågensfjeld Formation in Kilen, North Greenland

Age assessments from both palynostratigraphy and macrofossil biostratigraphy of the sandstone-dominated Mågensfjeld Formation, Wandel Sea Basin, North Greenland were hitherto hampered by post-burial thermal degradation of dinoflagellate cysts and a lack of well-preserved macrofossils. The formation was previously assigned to the Upper Cretaceous based on erroneous fossil identifications. Finds of cardioceratid and kosmoceratid ammonites during recent field work now provide the first age control of the unit, demonstrating it to be of late Bajocian – late Bathonian and perhaps Callovian (Middle Jurassic) age. This makes it among the oldest Jurassic units, perhaps even Mesozoic units, recorded in Kilen, North Greenland and eastern North Greenland. Previously, the complex structural and tectonic evolution of the area was poorly understood, and the structural relation of the Mågensfjeld Formation to the surrounding Mesozoic units was a puzzle. The new age assessment simplifies the structural situation in the area significantly. Further, the inference of a large reverse fault previously required to explain the proximity of the Mågensfjeld Formation to neighbouring Jurassic units is now unnecessary. The data show that the Wandel Sea Basin was influenced by the Middle Jurassic transgression and had sufficient accommodation space for marine deposition earlier than previously thought. The unit serves as a key datapoint and analogue for possible Middle Jurassic units in adjacent offshore basins.

Seabird and Marine Mammal at-sea Distribution in the Norwegian, Greenland and Wandel Seas, 2018

Quantitative seabird and marine mammal at-sea distribution was determined in the Norwegian, Greenland and Wandel seas in August 2018 on board the icebreaking RV Polarstern. A total of 7,380 seabirds belonging to 25 species were tallied during 380 transect counts lasting 30 minute each, i.e. a mean value of 19 per count. Cetaceans were represented by seven species (mean of 0.1 per count) and pinnipeds by four species (0.1 per count). Numbers of seabird species and of individuals were low in the Norwegian Sea and the Greenland Sea (12 and 14 species, 4 and 8 individuals per count). They were especially low in the Wandel Sea off North Greenland: seven seabird species (2 individuals per count), mainly ivory gull Pagophila eburnea and fulmar Fulmarus glacialis. Cetaceans were absent and pinnipeds represented by three species only (0.3 per count). These concentrations are extremely low even when compared to other areas of the high Arctic Ocean.

Episodic Atlantic Water Inflow Into the Independence Fjord System (Eastern North Greenland) During the Holocene and Last Glacial Period

Four marine sediment cores from two sites in the Independence Fjord system near the Wandel Sea in eastern North Greenland were analyzed for their dinoflagellate cyst (dinocyst) and foraminiferal fossil content to gain insight into the water mass properties and evolution of the outer fjord system over the Holocene and Last Glacial Period. While regarded as a climate-sensitive region, the climatic history of the area remains largely unknown and has been documented through the study of two composite marine sediment cores only once before. The results presented here reveal that Atlantic waters entered the Independence Fjord episodically during the studied interval. High concentrations of dinocysts and foraminifers in the upper few centimeters of the cores are in line with oceanographic measurements clearly illustrating that Atlantic-sourced waters make up the lower part of the water column in the area in modern times. Radiocarbon dating of foraminiferal tests and increasing microfossil concentrations and diversity towards the top of the cores suggest that this inflow has been occurring for at least 2000 years and intensified towards recent times. The core sections below the upper few centimeters are devoid of (Quaternary) dinocysts and calcareous foraminifera with the exception of the lowermost segments of the longer cores. While low foraminiferal test quantities in these lowermost core sections prevent precise age determination, their radiocarbon ages reveal that they were deposited prior to 30 000 years ago, indicating the existence of a pathway for the occasional intrusion of Atlantic-sourced waters into, and thus relatively small local ice caps around, the fjord system prior to the Last Glacial Maximum. The previously documented early Holocene inflow of Atlantic-sourced waters was not detected in our records, likely suggesting a strong topographical and deglacial control on the routing of these water masses during the early Holocene.

Low Abundance and Biodiversity of Top Predators -Seabirds and Marine Mammalsin High Arctic Seas

This article concerns the comparison of data collected in different high Arctic seas by the same team, mainly same platform (from the bridge of icebreaking RV Poarstern), and thus the same methodology. Drastic differences were noted, from high numbers in the Bering Strait and Chukchi Sea on the one hand, and Fram Strait and Barents Sea on the other. In contrast, abundance, mainly of seabirds, was very low in the Arctic Basin. Most numerous bird species varied in different areas, mainly fulmar, kittiwake, Brünnich’s guillemot and locally ivory gull. Biodiversity was low, as reflected by low numbers of species, a few of them representing the vast majority in numbers of individuals: between 85% and 95% of the total. Cetaceans were close to absent from the High Arctic Ocean, the Wandel Sea off North Greenland and the shallow seas along the North-East Passage; pinnipeds and polar bear were tallied on the Outer Marginal Zone OMIZ, basically absent in the Closed Pack Ice Zone CPI.

Triassic lithostratigraphy of the Wandel Sea Basin, North Greenland

The Wandel Sea Basin in eastern North Greenland forms the northern continuation of the offshore Danmarkshavn Basin and the conjugate margin to the western Barents Shelf south of Spitsbergen. The Triassic succession of eastern North Greenland, up to 700 m thick, spans the Induan (Dienerian) – Norian. The Triassic sediments rest unconformably on Upper Carboniferous and Upper Permian sediments, and are unconformably overlain by Upper Jurassic – Lower Cretaceous deposits. Based on recent fieldwork in the Wandel Sea Basin, five new and revised Triassic formations are described and included in the Trolle Land Group (revised). The Lower Triassic (Induan) Parish Bjerg Formation (revised) consists of marine sandstones, fluvial conglomerates and sandstones, and muddy flood-plain deposits. It is conformably overlain by Lower Triassic (Dienerian – lower Spathian) offshore mudstones with minor sand-dominated intervals of the Ugleungernes Dal Formation (new). The upper Spathian to Ladinian Dunken Formation (revised) is represented mainly by marine sandstones. A marked erosional unconformity characterises the base of the overlying Upper Triassic (Carnian – Norian) Storekløft Formation (new) composed of marginal marine to marine, massive sandstones and conglomerates as well as cross-bedded and biomottled marine sandstones and minor mudstone units. The Isrand Formation (mainly Middle Triassic) consists of laminated mudstones with minor thin sandstone units that were deposited in slope and basin floor settings in the eastern deeper part of the Wandel Sea Basin in Kronprins Christian Land. The Triassic succession of the Wandel Sea Basin represents a well-constrained shallow shelf to deep shelf / basin floor transect and thus forms an excellent outcrop analogue to the time-equivalent intervals in the western Barents Sea basins and the Danmarkshavn Basin offshore North-East Greenland.

Strong Winds Leave Arctic Regions on Thin Ice

A warming event in Siberia caused winds to strip sea ice from the Arctic’s Wandel Sea.

Variability of the Pacific‐Derived Arctic Water Over the Southeastern Wandel Sea Shelf (Northeast Greenland) in 2015–2016

AbstractA portion of the freshwater transport through Fram Strait consists of low‐salinity Pacific‐derived Arctic water flowing southward along the east coast of Greenland. The pathways of this water are currently unclear. An Ice Tethered Profiler deployed over the southeastern Wandel Sea shelf (northeast Greenland) in May 2015 collected a profile every 3 hr for a year recording conductivity‐temperature‐depth (CTD) and Colored Dissolved Organic Matter (CDOM) fluorescence. This was accompanied by velocity observations. The CTD data revealed that the subsurface water (~15–85 m depth) characterized by high CDOM resembles the “cold Halostad” in the Canada Basin formed by the injection of Pacific water. A coastal branch of the Pacific water outflow from the Arctic Ocean supplies the Wandel Sea halostad, which shows a clear seasonal pattern. From July to October–November, the halostad is shallow, more saline, warmer, and with less CDOM. Conversely, from November to April, the halostad deepens, cools, freshens and CDOM increases, likely indicating a higher fraction of Pacific winter water. The CTD surveys, wind and current data, and numerical simulations show that the seasonal variation of wind over the continental slope likely controls seasonal changes of this intermediate water layer. Over northeast Greenland, winter winds have a northerly component from November to April, favoring Ekman transport of the Pacific‐derived water to the Wandel Sea shelf. In contrast, the prevailing southerly summer winds result in retreat of the Pacific‐derived water off the shelf. The landfast ice off‐slope extension modifies wind‐forcing disrupting seasonal patterns.

Descriptive text to the Geological map of Greenland, 1:100 000, Kilen 81 Ø.1 Syd

The geological map sheet of Kilen in 1:100 000 scale covers the south-eastern part of the Carboniferous–Palaeogene Wandel Sea Basin in eastern North Greenland. The map area is dominated by the Flade Isblink ice cap, which separates several minor isolated landmasses. On the semi-nunatak of Kilen, the map is mainly based on oblique photogrammetry and stratigraphical field work while in Erik S. Henius Land, Nordostrundingen and northern Amdrup Land the map is based on field data collected during previous, 1:500 000 scale regional mapping. Twenty-one Palaeozoic–Mesozoic mappable units were identified on Kilen, while the surrounding areas comprise the Late Cretaceous Nakkehoved Formation to the north-east and the Late Carboniferous Foldedal Formation to the south-west. On Kilen, the description of Jurassic–Cretaceous units follows a recently published lithostratigraphy. The Upper Palaeozoic–lowermost Cretaceous strata comprise seven formations and an informal mélange unit. The overlying Lower–Upper Cretaceous succession comprises the Galadriel Fjeld and Sølverbæk Formations, which are subdivided into six and five units, respectively. In addition, the Quaternary Ymer Formation was mapped on south-east Kilen. The Upper Palaeozoic to Mesozoic strata of Kilen are faulted and folded. Several post-Coniacian NNW–SSE-trending normal faults are identified and found to be passively folded by a later N–S compressional event. A prominent subhorizontal fault, the Central Detachment, separates two thrust sheets, the Kilen Thrust Sheet in the footwall and the Hondal Elv Thrust Sheet in the hanging wall. The style of deformation and the structures found on Kilen are caused by compressional tectonics resulting in post-extensional, presumably Early Eocene, folding and thrusting and basin inversion. The structural history of the surrounding areas and their relation to Kilen await further studies.

Descriptive text to the Geological map of Greenland, 1:100 000, Kilen 81 Ø.1 Syd

The geological map sheet of Kilen in 1:100 000 scale covers the south-eastern part of the Carboniferous– Palaeogene Wandel Sea Basin in eastern North Greenland. The map area is dominated by the Flade Isblink ice cap, which separates several minor isolated landmasses. On the semi-nunatak of Kilen, the map is mainly based on oblique photogrammetry and stratigraphical field work while in Erik S. Henius Land, Nordostrundingen and northern Amdrup Land the map is based on field data collected during previous, 1:500 000 scale regional mapping. Twenty-one Palaeozoic–Mesozoic mappable units were identified on Kilen, while the surrounding areas comprise the Late Cretaceous Nakkehoved Formation to the north-east and the Late Carboniferous Foldedal Formation to the south-west. On Kilen, the description of Jurassic–Cretaceous units follows a recently published lithostratigraphy. The Upper Palaeozoic–lowermost Cretaceous strata comprise seven formations and an informal mélange unit. The overlying Lower–Upper Cretaceous succession comprises the Galadriel Fjeld and Sølverbæk Formations, which are subdivided into six and five units, respectively. In addition, the Quaternary Ymer Formation was mapped on south-east Kilen. The Upper Palaeozoic to Mesozoic strata of Kilen are faulted and folded. Several post-Coniacian NNW–SSE-trending normal faults are identified and found to be passively folded by a later N–S compressional event. A prominent subhorizontal fault, the Central Detachment, separates two thrust sheets, the Kilen Thrust Sheet in the footwall and the Hondal Elv Thrust Sheet in the hanging wall. The style of deformation and the structures found on Kilen are caused by compressional tectonics resulting in post-extensional, presumably Early Eocene, folding and thrusting and basin inversion. The structural history of the surrounding areas and their relation to Kilen await further studies.

Update of the seamless 1:500 000 scale geological map of Greenland based on recent field work in the Wandel Sea Basin, eastern North Greenland

Geological maps are core products of national geological surveys and represent the sum of geological knowledge of any given area. However, dedicated and extensive mapping projects in the Arctic are mostly a thing of the past due to difficulty in financing such costly basic research efforts. Today, an overview of the geology of Greenland is portrayed by a seamless digital 1:500 000 scale geological map (Kokfelt et al. 2013; Pedersen et al. 2013), based on printed maps on this scale produced since 1982 by the Geological Survey of Denmark and Greenland (GEUS; see Holst et al. 2013). The digital map now makes it possible to update smaller areas with new, published or otherwise quality-controlled geological data (e.g. Kolb et al. 2016). This ensures that the map reflects the current state of geological knowledge without undertaking extensive new mapping to update individual map sheets, as has previously been the modus operandi. An online version of the map is available from www.greenmin.dk/map. However, procedures are required to ensure that updates are carried out routinely and that the quality and coherence of the updated map is of the Survey’s standards. Results of recent field work in the Wandel Sea Basin (Fig. 1) and in particular the publication of a new geological map sheet Kilen on a scale of 1:100 000 (Svennevig in press) have implications for the geology shown on the above mentioned 1:500 000 scale seamless geological map of Greenland. The post-Devonian part of this map in eastern North Greenland has been updated according to the results of studies published since the publication of the original printed maps (Bengaard & Henriksen 1986; Jepsen 2000). The changes do not call for an update of the 1:2 500 000 scale geological map of Greenland (Henriksen et al. 2009).

The Inferred Formation of a Subice Platelet Layer Below the Multiyear Landfast Sea Ice in the Wandel Sea (NE Greenland) Induced by Meltwater Drainage

AbstractOceanographic and ice‐mass‐balance records are presented from two moorings deployed on landfast multiyear ice in the Wandel Sea (North Greenland) during June–August 2015. Here we show that the melting and drainage of >1 m of snow from June 14 to July 14 created a double‐diffusive vertical stratification which resulted in supercooling of water and enabled the formation of platelet crystals below the sea ice. Although the effect of supercooling, with temperatures up to 0.5°C below the freezing point, might be overestimated considerably in our records, this process led to the formation of ∼1.1–1.2 m‐thick subice platelet layer. While warm water temperatures lead to the complete loss of this layer at one mooring site, the layer persisted through summer and became incorporated into the congelation ice at the second site. The warm water that melted out the platelet layer can be ascribed to two different sources: (1) in situ heating from solar radiation resulting in a temperature increase up to 0.8°C in late July and (2) advection of warm surface water (with temperatures up to 3–4°C) from the ice‐free coastal regions in mid‐August. The combination of processes causing the seasonal growth of a platelet layer and either its subsequent ablation or incorporation into congelation ice is discussed with respect to the ice‐mass balance and stability of the landfast ice cover in the Wandel Sea. Furthermore, this study provides evidence for the formation of a platelet layer in the Arctic, a phenomenon that historically has only been observed in the Antarctic.

Burial history of a folded Cretaceous succession – A case study from the southern part of Kilen, eastern North Greenland

Kilen is a semi-nunatak in the Flade Isblink icecap in eastern North Greenland with exposures of Mesozoic sedimentary rocks, which are part of the Wandel Sea Basin. Cretaceous marine mudstones and interbedded sandstones of the Galadriel Fjeld and Sølverbæk formations are thrusted and folded in large open folds at Gåseslette in the southeastern part of Kilen. Steeply dipping strata, reflecting parasitic folds and small-scale thrusts, are exposed in low cliffs along a c. 9 km NNW–SSE stretch of the Sølverbæk river. The present study is a case study of the thermal history of these outcrops, called the Sølverbæk section. The burial temperatures are calculated from vitrinite reflectance (Ro) values. Tmax-measurements from Rock-Eval type pyrolysis correlate with the Ro-values. The latter reflects the large-scale folds with higher temperatures in anticlines and lower in synclines. The sedimentary successions are dated on basis of dinoflagellate cysts, inoceramid bivalves and ammonites. The dataset demonstrate a correlation between the Tmax -measurements, maximum burial temperatures, and the preservation of dinoflagellate cysts. The burial temperature at the boundary between the Kangoq Ryg Member and the Sølverbæk Formation varies laterally through a restored section and suggest that the northern part of the section was c. 30° hotter than the southern part prior to folding. Five events are distinguished in the thermal history of the Sølverbæk section: (1) Deposition, (2) rotation of the succession, (3) thermal imprinting, (4) uplift, folding and thrusting, (5) final uplift and erosion up to present day. Following a recent structural model for Kilen events 1–3 are interpreted to be caused by Late Cretaceous rifting where (3) represents maximum burial during rifting. Event 4 is explained by basin inversion of presumed Paleocene–Eocene age.

Linking the Modern Distribution of Biogenic Proxies in High Arctic Greenland Shelf Sediments to Sea Ice, Primary Production, and Arctic‐Atlantic Inflow

AbstractThe eastern north coast of Greenland is considered to be highly sensitive to the ongoing Arctic warming, but there is a general lack of data on modern conditions and in particular on the modern distribution of climate and environmental proxies to provide a baseline and context for studies on past variability. Here we present a detailed investigation of 11 biogenic proxies preserved in surface sediments from the remote High Arctic Wandel Sea shelf, the entrance to the Independence, Hagen, and Danmark fjords. The composition of organic matter (organic carbon, C:N ratios, δ13C, δ15N, biogenic silica, and IP25) and microfossil assemblages revealed an overall low primary production dominated by benthic diatoms, especially at the shallow sites. While the benthic and planktic foraminiferal assemblages underline the intrusion of chilled Atlantic waters into the deeper parts of the study area, the distribution of organic‐walled dinoflagellate cysts is controlled by the local bathymetry and sea ice conditions. The distribution of the dinoflagellate cyst Polarella glacialis matches that of seasonal sea ice and the specific biomarker IP25, highlighting the potential of this species for paleo sea ice studies. The information inferred from our multiproxy study has important implications for the interpretation of the biogenic‐proxy signal preserved in sediments from circum‐Arctic fjords and shelf regions and can serve as a baseline for future studies. This is the first study of its kind in this area.

Arctic Ocean outflow and glacier–ocean interactions modify water over the Wandel Sea shelf (northeastern Greenland)

Abstract. The first-ever conductivity–temperature–depth (CTD) observations on the Wandel Sea shelf in northeastern Greenland were collected in April–May 2015. They were complemented by CTDs taken along the continental slope during the Norwegian FRAM 2014–2015 drift. The CTD profiles are used to reveal the origin of water masses and interactions with ambient water from the continental slope and the tidewater glacier outlet. The subsurface water is associated with the Pacific water outflow from the Arctic Ocean. The underlying halocline separates the Pacific water from a deeper layer of polar water that has interacted with the warm Atlantic water outflow through the Fram Strait, recorded below 140 m. Over the outer shelf, the halocline shows numerous cold density-compensated intrusions indicating lateral interaction with an ambient polar water mass across the continental slope. At the front of the tidewater glacier outlet, colder and turbid water intrusions were observed at the base of the halocline. On the temperature–salinity plots these stations indicate a mixing line that is different from the ambient water and seems to be conditioned by the ocean–glacier interaction. Our observations of Pacific water are set within the context of upstream observations in the Beaufort Sea and downstream observations from the Northeast Water Polynya, and clearly show the modification of Pacific water during its advection across the Arctic Ocean. Moreover, ambient water over the Wandel Sea slope shows different thermohaline structures indicating the different origin and pathways of the on-shore and off-shore branches of the Arctic Ocean outflow through the western Fram Strait.

Storm-induced water dynamics and thermohaline structure at the tidewater Flade Isblink Glacier outlet to the Wandel Sea (NE Greenland)

Abstract. In April 2015, an ice-tethered conductivity–temperature–depth (CTD) profiler and a down-looking acoustic Doppler current profiler (ADCP) were deployed from the landfast ice near the tidewater glacier terminus of the Flade Isblink Glacier in the Wandel Sea, NE Greenland. The 3-week time series showed that water dynamics and the thermohaline structure were modified considerably during a storm event on 22–24 April, when northerly winds exceeded 15 m s−1. The storm initiated downwelling-like water dynamics characterized by on-shore water transport in the surface (0–40 m) layer and compensating offshore flow at intermediate depths. After the storm, currents reversed in both layers, and the relaxation phase of downwelling lasted ∼ 4 days. Although current velocities did not exceed 5 cm s−1, the enhanced circulation during the storm caused cold turbid intrusions at 75–95 m depth, which are likely attributable to subglacial water from the Flade Isblink Ice Cap. It was also found that the semidiurnal periodicities in the temperature and salinity time series were associated with the lunar semidiurnal tidal flow. The vertical structure of tidal currents corresponded to the first baroclinic mode of the internal tide with a velocity minimum at ∼ 40 m. The tidal ellipses rotate in opposite directions above and below this depth and cause a divergence of tidal flow, which was observed to induce semidiurnal internal waves of about 3 m height at the front of the glacier terminus. Our findings provide evidence that shelf–basin interaction and tidal forcing can potentially modify coastal Wandel Sea waters even though they are isolated from the atmosphere by landfast sea ice almost year-round. The northerly storms over the continental slope cause an enhanced circulation facilitating a release of cold and turbid subglacial water to the shelf. The tidal flow may contribute to the removal of such water from the glacial terminus.