Surface velocity and ice thickness of the Müller ice cap, Axel Heiberg Island

Muller ice cap is situated on Axel Heiberg Island in Arctic Canada. It is characterised by a mountanious region separating the ice cap in the east from the outlet glaciers in the west. Research has taken place on the outlet glaciers of the ice cap since 1959, but only limited research has been conducted on the main ice cap, and no full depth ice cores have ever been drilled. The interesting location of the ice cap facing the Arctic Ocean, the chance of finding ice dating back to the Innuitian Ice Sheet, and the fact that no full depth ice cores have been drilled, makes it an obvious place to do so. In order to achieve a long and undisturbed chronology of the ice core, one needs to find a location for the drilling site, where there is a great ice thickness, low surface velocity and little melt. In this project the aim is to make surface velocity maps of the ice cap and estimate the ice thickness to be able to come up with suggestions of possible drill site areas.Surface velocities are calculated using feature tracking of optical satellite images from the Landsat satellites in the period of 2004-2019. A median velocity map of all Landsat 8 velocity maps is used as validation in modelling the ice thickness and in the investigation of possible drill site areas.To estimate the ice thickness various methods are used and are being compared to the ice thickness measured by Operation IceBridge. The first method is an iterative inverse method where the ice sheet model PISM works as a forward model. The model is found to work rather well on the ice cap, with a root mean squared error (RMS) of 138.9 m, but overestimates the ice thickness on the outlet glaciers. The second model uses a simple inversion of the shallow ice approximation. It overestimates the ice thickness in areas with low surface slope, but has a RMS of 131.4 m on the ice cap. The third and and fourth models uses Monte Carlo sampling methods of the shallow ice approximation without and with sliding, respectively. The latter uses an initial ice thickness guess, and the modelled ice thickness was proofed not to differ from that initial guess at all. The RMSs on the icecap of the two models were found to be 132.1 m and 129.9 m, respectively. Finally, the fifth model uses the PISM setup but with an initial geometry defined by the SIA inversion. The RMS on the ice cap is found to be 135.4 m.Based on the median Landsat 8 surface velocity map, the modelled ice thicknesses and the surface elevation from the Arctic Digital Elevation Model, a map of suggested drill site areas is made. The site which fulfilled the criteria the most is located at 526629 m easting and 8866463 m northing in UTM zone 15N. In this site the surface velocity is 1.2 m yr−1, the surface elevation is 1804 m and the modelled ice thicknesses varies from 535-579 m. The melt in this area is estimated to be less than 20 melt days per year based on the backscatter from Sentinel-1.

Contrasting styles of magmatism and rifting in the High Arctic LIP, Sverdrup Basin, Canadian Arctic

<p>Located along the Canadian polar continental margin, the Sverdrup Basin is an elongated, intracontinental sedimentary basin that originated during Carboniferous-Early Permian rifting. Starting in the Early Cretaceous, volcanic complexes (VC) were emplaced throughout the basin, which are associated with the High Arctic Large Igneous Province (HALIP). Geochronological and geochemical data on HALIP rocks exposed on Axel Heiberg Island and northern Ellesmere Island suggest several discrete stages of emplacement; (1) voluminous mafic intrusive activity of tholeiitic character accompanied by minor extrusive volcanism at <em>ca</em>. 125-110 Ma (VC1a<strong>); </strong>the eruption of tholeiitic flood basalts on Axel Heiberg Island at <em>ca</em>. 100-90 Ma (VC1b); the emplacement of mildly alkaline lava flows, sills and dykes on Ellesmere Island at <em>ca</em>. 100-90 Ma (VC2);<strong> </strong>and the eruption of a suite of alkaline lava flows from central volcanoes at <em>ca</em>. 85-75 Ma (VC3). Each magmatic episode is characterized by a distinctive eruptive style and coherent geochemical signature regardless of the mode of emplacement. In this context, onshore manifestations of the HALIP can be viewed as time-markers in the evolution of the adjacent polar continental margin.</p><p>We use digital plate tectonic models, constructed via the <em>GPlates</em> software, to explore the parallel development of the Sverdrup Basin and proto-Arctic Ocean (Amerasia Basin) during the Early Cretaceous, and the transition from a sedimentary to volcanic Sverdrup Basin. Plate reconstructions of the Amerasia Basin at <em>ca</em>. 125 Ma suggest two zones of extension; one within the Canada Basin, which may include seafloor spreading, (Zone 1, more distal to the Sverdrup Basin) and the second further northwards in the Alpha-Mendeleev Ridge and Makarov Basin domains offshore northern Ellesmere Island (Zone 2, proximal to the northeastern portion of the Sverdrup Basin). The potential for enhanced melting caused by mantle flow (possibly related to the arrival of a mantle plume) towards the Sverdrup Basin depocentre could explain widespread magmatism of tholeiitic character from <em>ca</em>. 125-90 Ma (VC1). The transition to mildly alkaline (VC2) and alkaline magmatism (VC3) at <em>ca</em>. 100 Ma may have signaled the end of extension in Zone 1. The persistence of localized extension in Zone 2 could explain the shift in magmatic style and compositional diversity of igneous rocks emplaced at intrusive complexes (VC2) vs constructional volcanic edifices (VC3). In addition, greater depth to Moho along the northeastern Sverdrup Basin may have contributed to restricted mantle flow in Zone 2. We propose that the spatio-temporal evolution of HALIP magmatism in the Sverdrup Basin during the Cretaceous relates to (1) different styles of tectonic extension (distal vs proximal, protracted vs discrete, widespread vs narrow, seafloor spreading vs hyper-extensional rifting), and (2) the presence of hot, thin lithosphere close to the basin depocentre vs cold and thick lithosphere in the northeastern part of the basin.</p>

Supplemental Material: Carbon isotope and sequence stratigraphy of the upper Isachsen Formation on Axel Heiberg Island (Nunavut, Canada): High Arctic expression of oceanic anoxic event 1a in a deltaic environment

<div>Geochemical data and the age models presented in this study.<br></div><div><br></div><div><br></div><div><br></div><div><br></div>

Supplemental Material: Carbon isotope and sequence stratigraphy of the upper Isachsen Formation on Axel Heiberg Island (Nunavut, Canada): High Arctic expression of oceanic anoxic event 1a in a deltaic environment

<div>Geochemical data and the age models presented in this study.<br></div><div><br></div><div><br></div><div><br></div><div><br></div>

Apparent Collapse of the Peary Caribou (Rangifer tarandus pearyi) Population on Axel Heiberg Island, Nunavut, Canada

In spring 2019, we conducted a comprehensive abundance and distribution survey for Peary caribou (Rangifer tarandus pearyi) and muskox (Ovibos moschatus) on Axel Heiberg Island, Nunavut, Canada. Although much of Axel Heiberg Island is rugged and extensively glaciated, areas east of the Princess Margaret mountain range have high productivity given the latitude and have supported relatively large numbers of Peary caribou and muskoxen. This region of the island has been previously identified as a potential High Arctic refugium. The last island-wide survey, in 2007, estimated 4237 muskoxen (95% confidence interval [CI] [3371:5325]) and 2291 Peary caribou (95% CI [1636:3208]); based on our 2019 results, it appears that muskox numbers have been stable on Axel Heiberg Island since then. Using distance sampling and density surface models, we estimated 3772 muskoxen (95% CI [3001:4742]) on Axel Heiberg Island during our 2019 survey. In contrast, Peary caribou, which is listed as an endangered species under the Canadian Species at Risk Act, appear to have declined dramatically from the 2007 estimate. During the 2019 survey, we observed only six Peary caribou and could not generate an island-wide estimate. Abrupt declines in numbers are characteristic of the species and are usually related to poor winter conditions such as dense snowpack or extreme weather events that result in widespread ground-fast icing. However, the limited monitoring information available at the northern extent of Peary caribou range presents major challenges to our understanding of the mechanisms leading to this near total absence of approximately 20% of range-wide Peary caribou numbers.

Metagenome-Assembled Genome of USCα AHI, a Potential High-Affinity Methanotroph from Axel Heiberg Island, Canadian High Arctic

Metagenomic sequencing of active-layer cryosols from the Canadian High Arctic has yielded a nearly complete genome for an atmospheric CH4-oxidizing bacterium belonging to upland soil cluster α (USCα). This genome contains genes involved in CH4 metabolism, H2 metabolism, and multiple carbon assimilation pathways.

High latitude meteoric δ18O compositions from the Cenomanian Bastion Ridge Formation, Axel Heiberg Island, Canadian Arctic Archipelago: a palaeoclimate proxy from the Sverdrup Basin

Stable isotope analyses of a siderite-cemented siltstone from the Cenomanian Bastion Ridge Formation, Axel Heiberg Island, Canada, produce a range of δ18O values from −21.9 to −18.4‰ Vienna Pee Dee Belemnite (VPDB), and δ13C values ranging from 2.0 to 4.4‰ VPDB. A meteoric siderite line of −18.95 ± 0.33‰ VPDB is calculated from siderite cements of the authigenic component. At estimated palaeolatitude of 68–72° N and palaeotemperature range from 12.6 to 13.7°C, the calculated δ18O range of palaeoprecipitation is −23.3 to −23.0‰ Vienna Standard Mean Ocean Water (VSMOW). This result is compatible with other published meteoric water δ18O datasets from Cretaceous Arctic studies, but is near the lower end of the range of estimated δ18O values. The modern δ18O empirical relationship of Dansgaard and Earth System models simulating meteoric δ18O values does not yield results for palaeopolar regions that match proxy δ18O datasets. Orographic effects of contemporaneous mountain belts and seasonal biases in groundwater recharge have been proposed to explain this paradox regarding depleted meteoric water δ18O values from proxy data in greenhouse worlds. Evidence for local to regional orographic effects and alpine snowmelt biasing groundwater recharge is lacking for the Sverdrup Basin deposits, further indicating that the Dansgaard relationship does not apply to ancient greenhouse worlds.

Enigmatic massive sulphide mineralization in the High Arctic Large Igneous Province, Nunavut, Canada

Modern mineral exploration strategies should take into account nontraditional metallogenic models for a given geological environment. Here we document the first detailed study of a massive sulphide showing associated with the High Arctic Large Igneous Province (HALIP) and Sverdrup Basin and in fact, only the second example of mineralization described from Axel Heiberg Island, Queen Elizabeth Islands, Canadian Arctic Archipelago. The Between Lake showing (western Axel Heiberg Island) is a small massive sulphide occurrence within scree/talus below a large ridge of gabbro. It was originally described by explorationists as an orthomagmatic sulphide occurrence hosted within a dioritic dyke. New petrographic and mineralogical analyses indicate that the showing consists predominantly of pyrrhotite with lesser pyrite, trace chalcopyrite, and rare sphalerite. No Ni- or Pb-bearing sulphide minerals were detected. Geochemically, the showing contains some Co and Cu, rare Zn, and generally very low Ni contents (<9 ppm). Sulphur isotope ratios of sulphide minerals range from +3.6 to + 6.6‰, somewhat heavier than expected for magmatic-derived S but isotopically lighter than S associated with local evaporite diapirs (+5.8‰ to +12.2‰). Orthomagmatic sulphides hosted in the diorite typically exhibit even lighter isotopic ratios of –3.9‰ to –1.00‰. The data are consistent with potential mafic–siliciclastic volcanogenic massive sulphide mineralization, or the like, the first documented in the HALIP. High heat flow associated with extensive HALIP magmatism was likely the driving force for such mineralization. Mineral prospectivity in Canada’s High Arctic had been predicated upon the potential presence of magmatic Ni – Cu – platinum group element sulphide mineralization. Rather than negating this potential, our findings provide evidence for additional metallogenic potential for this region of Nunavut.

A revised stratigraphic framework for Cretaceous sedimentary and igneous rocks at Mokka Fiord, Axel Heiberg Island, Nunavut, with implications for the Cretaceous Normal Superchron

New data and interpretations on geological relationships of igneous rocks at Mokka Fiord, Axel Heiberg Island, Nunavut, provide insight into the timing and nature of magmatism associated with the Sverdrup Basin and High Arctic Large Igneous Province (HALIP). Field relationships indicate that the igneous rocks, previously interpreted to be volcanic flows, are most likely an intrusive unit discordant to regional bedding. An intrusive origin helps resolve chronostratigraphic inconsistencies in previous work. The host rocks are palynologically constrained to be late Barremian to late Aptian in age and are interpreted to be Paterson Island or Walker Island member of the Isachsen Formation. If the igneous body is intrusive, it’s previously reported Ar–Ar age (102.5 ± 2.6 Ma) is no longer in conflict with accepted stratigraphic interpretations and probably reflects the emplacement age of the intrusion. Lingering uncertainties in interpreting the normal and reverse magnetic polarities determined in the previous work remain, and both are considered viable. Although this uncertainty precludes definitive conclusions on the significance of paleomagnetic data at Mokka Fiord, examination of the stratigraphic, paleomagnetic, and geochronologic relationships there highlight potential for the study of excursions, or reversed magnetic polarity subchrons, in the Cretaceous Normal Superchron elsewhere in the HALIP.