Ellesmere Island Research Articles

Varying contributions of greenhouse gases, aerosols and natural forcings to Arctic land surface air temperature changes

The Arctic has warmed rapidly over the past century, with widespread negative impacts on local and surrounding environments. Previous studies have estimated the overall effects of individual groups of anthropogenic forcing agents on Arctic warming. However, the spatial patterns and temporal variabilities of the separate contributions of greenhouse gases (GHGs), natural forcing agents (NATs; solar radiation and volcanic activity combined) and other anthropogenic (OANT) forcing agents (which are dominated by aerosols) on Arctic land surface air temperatures remain underexamined. Here, we use CMIP6 (the Sixth Phase of the Coupled Model Intercomparison Project) models to quantify the separate contributions of GHGs, NATs and OANT forcing agents to Arctic land surface air temperature changes and analyze their spatial and temporal change patterns from 1915 to 2014. The results show that GHGs alone have warmed the Arctic by 2.72 °C/century (90% confidence interval: 1.42 °C–4.03 °C), 61.8% of which has been offset by OANT agents. The GHG-induced warming peaks are found in Ellesmere Island, Severnaya Zemlya and Svalbard (above 4 °C/century), while the largest cooling effects (above −2 °C/century) induced by OANT agents occurred in Krasnoyarsk Krai and Severnaya Zemlya. A further temporal evolution analysis indicates that the effects of GHGs and OANT forcings have been gradually and robustly detected over time; this increases our confidence in projecting future Arctic climate changes via CMIP6 models.

Multi-Polarisation C-Band SAR Imagery to Estimate the Recent Dynamics of the d’Iberville Glacier

To monitor polar regions is of paramount importance for climatological studies. Climate change due to anthropogenic activities is inducing global warming that, for example, has resulted in glacier melting. This has had a significant impact on sea levels and ocean circulation. In this study, the temporal trend of the marine-terminated d’Iberville glacier (Ellesmere Island, Canada) is analysed using C-band synthetic aperture radar satellite imagery collected by the Radarsat-2 and Sentinel-1 missions. The data set consists of a time series of 10 synthetic aperture radar data collected from 2010 to 2022 in dual-polarimetric imaging mode, where a horizontally polarised electromagnetic wave was transmitted. An automatic approach based on a global threshold constant false alarm rate method is applied to the single- and dual-polarisation features, namely the HH-polarised normalised radar cross-section and a combination of the HH- and HV-polarised scattering amplitudes, with the aim of extracting the ice front of the glacier and, therefore, estimating its behaviour over time. Independent collocated satellite optical imagery from the Sentinel-2 multi-spectral instrument is also considered, where available, to support the experimental outcomes. The experimental results show that (1) the HH-polarised normalised radar cross-section achieved better performance with respect to the dual-polarised feature, especially under the most challenging case of a sea-ice infested sea surface; (2) when the HH-polarised normalised radar cross-section was considered, the ice front extraction methodology provided a satisfactory accuracy, i.e., a root mean square error spanning from about 1.1 pixels to 3.4 pixels, depending on the sea-surface conditions; and (3) the d’Iberville glacier exhibited, during the study period, a significant retreat whose average surface velocity was 160 m per year, resulting in a net ice area loss of 2.2 km2 (0.18 km2 per year). These outcomes demonstrate that the d’Iberville glacier is behaving as most of the marine-terminated glaciers in the study area while experiencing a larger ice loss.

Plant reproductive phenology along an elevation gradient in the extreme environment of the Canadian High Arctic

ABSTRACT Background The extreme environment of the Canadian High-Arctic is experiencing unprecedented climate change with temperatures rising at three times the global average. There is a compelling need to understand how the phenology of Arctic plants will respond. However, long-term High-Arctic phenology monitoring is challenging due to the region’s remoteness. Aim To predict phenological responses of Arctic plants to climate change using an elevation gradient with associated temperature gradient as a proxy for climate change. Methods Flowering and seed dispersal times of seven Arctic species were recorded along an elevation gradient on Ellesmere Island, Nunavut, Canada in 2015 and related to air temperature measured at plant height and growing day degree (GDD). Results Flowering and seed dispersal times were earliest at the warmest site. A significant relationship with temperature was observed in flowering times of five species and seed dispersal times of one species. Conspecifics experienced fewer GDD at peak flowering at the coldest site than at warmer sites. Conclusions Temperature gradient observations provide insights into phenology–temperature relationships that complement long-term monitoring and enhance our ability to understand the impacts of climate change in remote regions. However, potential species adaptation along the temperature gradient should be taken into account. This single summer of results should be viewed with caution.

Slow change since the Little Ice Age at a far northern glacier with the potential for system reorganization: Thores Glacier, northern Ellesmere Island, Canada

Relatively little is known about the glaciers of northern Ellesmere Island, Canada. Here we describe the first field and remote sensing observations of Thores Glacier, located 50 km inland from the Arctic Ocean. The glacier is slow-moving, with maximum velocities of 26 m a−1 and a maximum observed thickness of 360 ± 4.3 m. There has been little change in terminus position since at least 1959, with a maximum advance of 170 m at the northwest terminus ending on land and retreat up to 130 m at the southeast terminus ending in Thores Lake. There is little evidence for change since the Little Ice Age as bedrock weathering patterns suggest retreat of no more than 20–30 m around most of the glacier margin. The supraglacial drainage network is generally poorly developed, without moulins and with few crevasses, and therefore no evidence of water reaching the glacier bed. This is supported by one-dimensional modelling, which suggests current basal temperatures of −7.0 °C to −12.0 °C along the centerline. Thores Glacier currently dams Thores Lake, which causes drainage to flow to the southeast. However, if the glacier thins or retreats sufficiently, regional drainage will reverse and flow to the north, and Thores Lake would no longer exist.

An unusual Pliocene arvicoline-like cricetid rodent from Ellesmere Island in the Canadian Arctic

An unusual Pliocene arvicoline-like cricetid rodent from Ellesmere Island in the Canadian Arctic

Phanerozoic Record of Northern Ellesmere Island, Canadian High Arctic, Resolved Through 40Ar/39Ar and (U‐Th)/He Geochronology

AbstractThe northern margin of Ellesmere Island, Canada, has experienced a complex geological history throughout the Phanerozoic, including multiple episodes of orogenesis and first‐order depositional cycles related to Circum‐Arctic evolution. Whereas previous studies have documented the structural and stratigraphic record of these events, supporting geochronological data are sparse. To constrain the age of these tectonic episodes, we apply 40Ar/39Ar geochronology and (U‐Th)/He low‐temperature thermochronology methods to polydeformed fault zones that bisect the Pearya terrane and Franklinian Basin of northern Ellesmere Island. Multiple single crystal 40Ar/39Ar dating of micas resulted in sample‐dependent date dispersion, with some samples exhibiting robust Paleozoic ages corresponding to the assembly and accretion of the Pearya terrane. Other samples yielded intra‐sample date dispersion that spanned the Late Paleozoic and Mesozoic, suggestive of a previously unreported post‐Ellesmerian and pre‐Eurekan history. Zircon and apatite (U‐Th)/He dates are largely Eocene in age, with dominant populations of c. 48 and c. 41 Ma, respectively. Inverse thermal history modeling of (U‐Th)/He data indicates episodic Mesozoic burial and unroofing coinciding with changes in the regional stress regime, and rapid cooling during nascent (>53 Ma) and initial (53–47 Ma) phases of Eurekan deformation. When integrated, our data provide temporal constraints on the timing of deformation, structural reactivation, and the Phanerozoic burial and erosive history of northern Ellesmere Island.

Automated Detection of Retrogressive Thaw Slumps in the High Arctic Using High-Resolution Satellite Imagery

Retrogressive thaw slumps (RTS) are considered one of the most dynamic permafrost disturbance features in the Arctic. Sub-meter resolution multispectral imagery acquired by very high spatial resolution (VHSR) commercial satellite sensors offer unique capacities in capturing the morphological dynamics of RTSs. The central goal of this study is to develop a deep learning convolutional neural net (CNN) model (a UNet-based workflow) to automatically detect and characterize RTSs from VHSR imagery. We aimed to understand: (1) the optimal combination of input image tile size (array size) and the CNN network input size (resizing factor/spatial resolution) and (2) the interoperability of the trained UNet models across heterogeneous study sites based on a limited set of training samples. Hand annotation of RTS samples, CNN model training and testing, and interoperability analyses were based on two study areas from high-Arctic Canada: (1) Banks Island and (2) Axel Heiberg Island and Ellesmere Island. Our experimental results revealed the potential impact of image tile size and the resizing factor on the detection accuracies of the UNet model. The results from the model transferability analysis elucidate the effects on the UNet model due the variability (e.g., shape, color, and texture) associated with the RTS training samples. Overall, study findings highlight several key factors that we should consider when operationalizing CNN-based RTS mapping over large geographical extents.

Preliminary paleopalynology of the Kanguk Formation (Upper Cretaceous), Remus Creek, Canadian Arctic Archipelago: II. Terrestrial Palynomorphs

A total of 78 terrestrial palynomorph taxa were identified from 39 samples collected at about one metre intervals from the Kanguk Formation (Upper Cretaceous) on Remus Creek, Ellesmere Island, Canadian Arctic Archipelago. The terrestrial palynomorphs constitute 49 % of total palynomorphs and are found in a marine facies where dinocysts and acritarchs are abundant. However, in the upper part of the section the terrestrial taxa dominate over marine palynomorphs indicating regressive conditions. Miospores and gymnosperm and angiosperm pollen grains, throughout the section, are small and thin-walled with varying degrees of preservation. Taxodiaceae-Cupressaceae pollen are the most abundant with common ocurrences of smooth trilete miospores and the accessory presence of small tricolpate pollen. The majority of the terrestrial taxa of the Kanguk Formation can be assigned to a Late Cretaceous boreal realm. Their character, distribution and variations in relative percentages through the section imply initial transgressive conditions followed by regressive conditions in the upper half of the section. The Kanguk terrestrial palynomorph assemblage suggests that the nearby continental areas were vegetated. The Taxodiaceae-Cupressaceae complex associated with terrestrial paralic environments was probably the dominant regional vegetation and, despite the high latitud, most likely, an open boreal forest compossed of gymnosperms was present in the area. A small, but significant, fraction of the total of the terrestrial assemblages is considered to be reworked from Albian-Cenomanian sediments probably from the underlying Hassel Formation. Thus, reworked taxa document the existence of an unconformity between these formations.

Preliminary paleopalynology of the Kanguk Formation (Upper Cretaceous), Remus Creek, Canadian Arctic Archipelago: I. Marine Palynomorphs

A 39 m section of the Kanguk Formation (Upper Turonian to Lower Campanian) on Remus Creek, Ellesmere Island, was sampled at about one inetre intervals to provide stratigraphic control on palynomorph taxa present. These samples yield well-preserved marine and terrestrial palynofloras represented by a total of 181 taxa, of which 103 are dinocysts and acritarchs and represent 51 % of the population. Based on the abundance and type of taxa present the section can be divided into a lower, dinocyst dominated interval, and an upper interval, where dinocysts are present in lower numbers and terrestrial palynomorphs dominate. In the lower part dinocysts are abundant, diverse and well-preserved. Chorate cysts are the most abundant in terms of species diversity and numbers of specimens, however, cavate dinocysts are common also. In turn, in the upper part of the section, marine palynomorphs are much less common, poorly preserved and sporadic in occurrence. Acritarchs account for a small but significant proportion of the marine assemblages. Small numbers of taxa of Albian-Cenomanian age are considered to be reworked from the underlying Hassel Formation. This indicates an unconformity between the Hassel and Kanguk formations. 

P–T–t Path of Unusual Garnet–Kyanite–Staurolite– Amphibole Schists, Ellesmere Island, Canada—Quartz Inclusion in Garnet Barometry and Monazite Petrochronology

Abstract Garnet–kyanite–staurolite assemblages with large, late porphyroblasts of amphibole form garbenschists in Ordovician volcaniclastic rocks lying immediately south of the Pearya terrane on northernmost Ellesmere Island, Canada. The schist, which together with carbonate olistoliths makes up the Petersen Bay Assemblage (PBA), displays a series of parallel isograds that mark an increase in metamorphic grade over a distance of 10 km towards the contact with Pearya; however, a steep, brittle Cenozoic strike-slip fault with an unknown amount displacement disturbs the earlier accretionary relationship. The late amphibole growth, probably due to fluid ingress, is clear evidence of disequilibrium conditions in the garbenschist. In order to recover the P–T history of the schists, we construct isochemical phase equilibrium models for a nearby garnet–mica schist that escaped the fluid event and compare the results to quartz inclusion in garnet (QuiG) barometry for a garbenschist and the metapelitic garnet schist. Quartz inclusions are confined to garnet cores and the QuiG results, combined with Ti-in-biotite and garnet–biotite thermometry, delineate a prograde path from 480 to 600°C and 0.7 to 0.9 GPa. This path agrees with growth zoning in garnet deduced from X-ray maps of the spessartine component in garnet. The peak conditions obtained from pseudosection modelling using effective bulk composition and the intersection of garnet rim with matrix biotite and white mica isopleths in the metapelite are 665°C at ≤0.85 GPa. Three generations of monazite (I, II and III) were identified by textural characterization, geochemical composition (REE and Y concentrations) and U–Pb ages measured by ion microprobe. Monazite I occurs in the matrix and as inclusions in garnet rims and grew at peak P–T conditions at 397 ± 2 Ma (2σ) from the breakdown of allanite. Monazite II forms overgrowths on matrix Monazite I grains that are oriented parallel to the main schistosity and yield ages of 385 ± 2 Ma. Monazite III, found only in the garbenschist, is 374 ± 6 Ma, which is interpreted as the time of amphibole growth during fluid infiltration at lower temperature and pressure on a clockwise P–T path that remained in the kyanite stability field. These results point to a relatively short (≈12 Myr) Barrovian metamorphic event that affected the schists of the PBA. An obvious heat source is lacking in the adjacent Pearya terrane, but we speculate it was large Devonian plutons—similar to the 390 ± 10 Ma Cape Woods granite located 40 km across strike from the fault—that have been excised by strike-slip. Arc fragments that are correlative to the PBA are low grade; they never saw the heat and were not directly involved in Pearya accretion.

AUTOMATED RECOGNITION OF PERMAFROST DISTURBANCES USING HIGH-SPATIAL RESOLUTION SATELLITE IMAGERY AND DEEP LEARNING MODELS

Abstract. The accelerated warming conditions of the high Arctic have intensified the extensive thawing of permafrost. Retrogressive thaw slumps (RTSs) are considered as the most active landforms in the Arctic permafrost. An increase in RTSs has been observed in the Arctic in recent decades. Continuous monitoring of RTSs is important to understand climate change-driven disturbances in the region. Manual detection of these landforms is extremely difficult as they occur over exceptionally large areas. Only very few studies have explored the utility of very high spatial resolution (VHSR) commercial satellite imagery in the automated mapping of RTSs. We have developed deep learning (DL) convolution neural net (CNN) based workflow to automatically detect RTSs from VHRS satellite imagery. This study systematically compared the performance of different DLCNN model architectures and varying backbones. Our candidate CNN models include: DeepLabV3+, UNet, UNet++, Multi-scale Attention Net (MA-Net), and Pyramid Attention Network (PAN) with ResNet50, ResNet101 and ResNet152 backbones. The RTS modeling experiment was conducted on Banks Island and Ellesmere Island in Canada. The UNet++ model demonstrated the highest accuracy (F1 score of 87%) with the ResNet50 backbone at the expense of training and inferencing time. PAN, DeepLabV3, MaNet, and UNet, models reported mediocre F1 scores of 72%, 75%, 80%, and 81% respectively. Our findings unravel the performances of different DLCNNs in imagery-enabled RTS mapping and provide useful insights on operationalizing the mapping application across the Arctic.

WOOD JAMS OR BEAVER DAMS? PLIOCENE LIFE, SEDIMENT AND LANDSCAPE INTERACTIONS IN THE CANADIAN HIGH ARCTIC

ABSTRACT During the mid-Pliocene (Zanclean, ca. ∼ 3.9 Ma), parts of the Canadian High Arctic experienced mean annual temperatures that were 14–22°C warmer than today and supported diverse boreal-type forests. The landscapes of this vegetated polar region left behind a fragmented sedimentary record that crops out across several islands in the Canadian Arctic Archipelago as the Beaufort Formation and correlative strata. Paleoecological information from these strata provides a high-fidelity window onto Pliocene environments, and prominent fossil sites yield unparalleled insights into Cenozoic mammal evolution. Significantly, many of the strata reveal evidence for life-sediment interactions in a warm-climate Arctic, most notably in the form of extensive woody debris and phytoclast deposits. This paper presents original field data that refines the sedimentological context of plant debris accumulations from the anactualistic High Arctic forests, most notably at the ‘Fyles Leaf Beds' and ‘Beaver Pond' fossil-bearing sites in the ‘high terrace deposits' of central Ellesmere Island. The former is a remarkably well-preserved, leaf-rich deposit that is part of a complex of facies associations representing lacustrine, fluvio-deltaic and mire deposition above a paleotopographic unconformity. The latter yields tooth-marked woody debris within a peat layer that also contains a rich assemblage of vertebrate and plant fossils including abundant remains from the extinct beaver-group Dipoides. Here we present sedimentological data that provide circumstantial evidence that the woody debris deposit at Beaver Pond could record dam-building in the genus, by comparing the facies motif with new data from known Holocene beaver dam facies in England. Across the Pliocene of the High Arctic region, woody debris accumulations are shown to represent an array of biosedimentary deposits and landforms including mires, driftcretions, woody bedforms, and possible beaver dams, which help to contextualize mammal fossil sites, provide facies models for high-latitude forests, and reveal interactions between life and sedimentation in a vanished world that may be an analogue to that of the near-future.

Newly Documented Behaviour of Free-Ranging Arctic Wolf Pups

Whereas much is known about the behavior and development of captive young wolf (Canis lupus) pups, less detail has been published about some aspects of free-ranging wolf pup behavior. This article synthesizes 42 observations of free-ranging Arctic wolf pups from ages 13 through 52 days made during 10 summers from 1987 through 2006 on Ellesmere Island, Nunavut, Canada. Besides listing key behaviors such as howling and caching, I record unique observations of ages of pup urination without adult stimulation (22, 33, 42, 52 days), knowledge of which is important to studies of wolf domestication, and of a 48-day-old pup that traveled 39 km during a 12 h and 19 min round trip between the den and a prey carcass, including a 26.5 km trek in 5 h. These observations should lead to a deeper and more complete understanding of this critical period of pup growth and development.

Age and significance of the Fire Bay assemblage: an Ordovician arc fragment within the Clements Markham belt, northwestern Ellesmere Island, Canada

The Fire Bay Formation of Trettin (1998), Clements Markham belt, Ellesmere Island, Canada, includes volcanic rocks described as Silurian in age based on Llandovery graptolites in adjacent clastic rocks. New field observations suggest the Llandovery fossils are from packages of the Silurian Danish River and/or Lands Lokk formations that are fault-bounded rather than stratigraphically tied to Ordovician sections that contain a 470.0 ± 0.2 Ma lithic tuff, volcaniclastic units with maximum depositional ages (MDAs) of 466 ± 2 and 462 ± 2 Ma based on detrital zircon, volcanic clasts with ages of 498 ± 6, 478 ± 4, and 477 ± 8 Ma, and Ordovician conodonts and graptolites of Darriwilian and Sandbian age, respectively. Since the Fire Bay Formation of Trettin (1998) lacks a type section and is fault-bounded with ambiguous age relationships, Ordovician volcanic units and fault-bounded clastic rocks correlated with the Hazen Formation are both included in the Fire Bay assemblage following the original interpretations of Trettin and Nowlan (1990). The Fire Bay assemblage records juvenile Ordovician arc magmatism proximal to the Pearya terrane. The adjacent Lands Lokk Formation yields bimodal age peaks at 440–430 and 465 Ma, MDA of 424 ± 3 Ma, and εHf(t) values of −5 to +10. The signature matches Ordovician Pearya units and Silurian circum-Arctic arc sources but there is no evidence for Silurian arc magmatism between the Pearya terrane and Laurentian margin, compatible with Pearya accretion during oblique Ordovician arc collision and Silurian sinistral translation along the northern Laurentian margin.

LOWER CAMBRIANRUSOPHYCUSFROM ELLESMERE ISLAND, ARCTIC CANADA: ICHNOFOSSIL OF A PREDATORY, NON-TRILOBITE ARTHROPOD

ABSTRACTCruziana and Rusophycus are commonly assumed to be trilobite trace fossils, although associated exoskeletons are almost invariably absent from host strata. In the lower Cambrian Dallas Bugt Formation of Ellesmere Island, Arctic Canada, high-energy, cross-laminated sandstones locally with dense populations of large Skolithos are overlain by thin-bedded, bioturbated, argillaceous, medium-grained glauconitic sandstones of lagoonal aspect, yielding Rusophycus along with an assortment of other “worm” burrows. Some specimens of Rusophycus are located over small Skolithos shafts and the bottoms of Arenicolites, suggesting a predator-prey relationship. Many preserve the impression of a strongly vaulted carapace with a broad, triangular dorsal outline between 1 cm and 7 cm across. A blunt anterior “prow” projects slightly forward and arches dorsally, forming a keyhole-shaped notch. The arthropod dug into the sediment up to 5 cm deep with an antero-posterior angle of up to ∼ 45° from the sea floor; in some cases it dug obliquely laterally and rarely sideways. Retroverse scratches—preserved in hyporelief as sharp-crested ridges—suggest about 20 pairs of endopodites tipped by a pair of small claws typically dug in unison, the anterior ones starting with a V-angle of 140° and decreasing posteriorly to 90°, in rare cases more tightly. Limb length increased posteriorly, although none extended beyond the carapace. Leg muscles were strong enough to rake through the muddy sand and pull inwards either straight or in a slightly forward-curving arc, but were also slightly flexible to wiggle around obstacles. Some specimens show subsequent re-burrowing which produced cross-cutting and opposed scratches. No evidence for exopodite brushings is present. Successive carapace imprints and scratches organized in transverse rugae in some specimens suggest repeatedly plunging and digging as the arthropod pulled backward in the sediment. This was likely aided by a stout trunk and a fan-shaped uropod-like structure flanking the telson which increased grip and leverage. A pair of eye stalks may have projected from the anterior notch, and these could have been retracted during digging, but there is no evidence for antennae. The tracemaker was not a trilobite but an unrelated crustacean-like arthropod, although there is no known late early Cambrian body fossil to which it can be ascribed. The specimens are classified as Rusophycus jenningsi (Fenton and Fenton, 1937) and a neotype is selected for this ichnospecies from the Gog Group near where it was first collected. Its range extends from the southern Canadian Rocky Mountains north along depositional strike to Victoria Island and northwest to Ellesmere Island and northern Greenland. Two new ichnofamilies are established: Rusophycidae and Cruzianidae.

Rare stromatoporoids from the Lower Devonian (Emsian) of Nevada, and their biostratigraphic and paleobiogeographic significance

AbstractTwo previously known species of stromatoporoids are reported from Nevada: Stromatoporella perannulata, from the Bartine Member of the McColley Canyon Formation (middle Emsian); and Stictostroma moosense, from the Oxyoke Canyon Sandstone (uppermost Emsian). A new species, Syringodictyon nevadense n. sp., is described from the Coils Creek Member of the McColley Canyon Formation (upper Emsian). Stromatoporella perannulata also occurs in Emsian-age strata on Ellesmere Island, arctic Canada, and in strata of Emsian and/or Eifelian age in Ontario, New York, Ohio, and Kentucky. Outside Nevada, Syringodictyon is confined to the Emsian of Ellesmere Island, and Emsian/Eifelian of Ontario and New York. Stictostroma moosense is known from only the Emsian/Eifelian of Ontario.It is concluded that the three Nevada specimens are Emsian in age. This implies that in other localities where two of the species, S. perannulata and S. moosense, occur in strata where the placement of the Emsian-Eifelian boundary is in question, it might be higher than previously thought. The presence of the two species, plus Syringodictyon, in both the Old World Realm (Nevada, arctic Canada) and the Eastern Americas Realm (Ontario, New York, Ohio, Kentucky), infers a selective marine connection between the two realms that was not available to other taxa. The breach in the inter-realm barrier most likely occurred as a shallow seaway across the Canadian Shield.UUID: http://zoobank.org/e73023c6-88ca-4b4d-9b01-f74a75b99c43

Late Neoarchean terrane and Paleoproterozoic HT–UHT metamorphism on southern Devon Island, Canadian Arctic

The northernmost exposures of the Laurentian shield in Canada outcrop on Devon and Ellesmere islands, near the tectonic domains of the ≥2.6 Ga Rae Province and ca. 2.0–1.9 Ga Thelon–Inglefield orogenic arc. We report (Th)–U–Pb zircon and monazite ages along with phase equilibrium modelling pressure–temperature estimates for southern Devon Island, the only area on Devon or Ellesmere islands with previously known Archean rocks. Our results demonstrate that southern Devon Island is a late Neoarchean (ca. 2.55–2.47 Ga) terrane composed of lower to middle crustal, granulite facies rocks with evidence of anatexis and pervasive solid-state ductile deformation. Protoliths of clinopyroxene–garnet quartzofeldspathic gneiss, orthopyroxene quartzofeldspathic gneiss, two-pyroxene metabasite and biotite granite gneiss were emplaced between ca. 2.55–2.51 Ga, and a clastic sedimentary protolith for rutile–garnet metasedimentary rocks was deposited at ca. ≥2.47 Ga. Earlier, poorly constrained metamorphic events are recorded at ca. 2.54, 2.47 and 2.30 Ga, possibly associated with pulses of the Arrowsmith orogen (ca. 2.5–2.3 Ga). Most recently, this terrane was reworked by high temperature (HT) to ultrahigh temperature (UHT) metamorphism at ca. 1.91 Ga during with the Thelon–Inglefield orogen; obtaining peak P–T conditions of ca. 9 kbar and >850 °C. The discovery of a sapphirine–quartz metapelite assemblage is a first for the Canadian Arctic and is diagnostic evidence of UHT conditions within the Thelon-Inglefield orogenic zone.

Seasonal and Multiyear Flow Variability on the Prince of Wales Icefield, Ellesmere Island: 2009–2019

AbstractOver the last two decades, Trinity, Wykeham, Ekblaw, and Cadogan glaciers have retreated and been identified as the primary sources of iceberg flux from Prince of Wales (POW) Icefield, Ellesmere Island, accounting for ∼83% of total solid ice discharge. In this study, we used a total of 167 Radarsat‐2 Synthetic Aperture Radar scene pairs collected between 2009 and 2019 to derive winter surface velocities of these four major basins of the POW Icefield. Over this period both Cadogan and Ekblaw glaciers underwent multiyear acceleration and deceleration limited to their lower parts, consistent with characteristics of “pulse‐type” glaciers. Trinity and Wykeham glaciers are currently the fastest flowing glaciers in the CAA and are grounded below sea level for ∼40 km up‐glacier from their termini. Both glaciers underwent multiyear repeating periods of velocity acceleration between 2009 and 2019 which coincided with significant thinning at their termini. As of 2017, Trinity and Wykeham were each within ∼10 m of flotation over their lowermost 4 km. We also identified a shift in flow since 2014 on Trinity and Wykeham, after which winter flow rates began to propagate up‐glacier and were nearly identical to flow rates observed throughout the rest of the year, indicating that seasonal variability in flow has become less apparent in recent years. Our findings suggest that Trinity and Wykeham glaciers have transitioned to a flow type dominated by dynamic thinning, which is strongly influenced by subglacial topography and may be susceptible to instability of the glacier front and large‐scale collapse.

Using Stable Water Isotope Composition (δ18O and δ2H) to Track the Interannual Responses of Arctic and Tropical Andean Water Bodies to Rising Air Temperatures

AbstractLakes in the Arctic and tropical Andes are experiencing some of the largest temperature increases on the planet with coeval marked limnological changes, but little data exist on water balance parameters from these regions. Here, we present a unique data set of water stable isotope composition (δ18O and δ2H) from a suite of 49 water bodies in the Canadian Arctic (Resolute Bay, Cornwallis Island, and Cape Herschel, Ellesmere Island) and the tropical Andes (Cajas National Park, Ecuador) spanning various years from 2009 to 2016. We show that an increase in air temperature over the study period resulted in evaporative enrichment of water isotopes in most Arctic sites highlighting the significance of evaporative losses to small Arctic ponds during the prolonged ice‐free summers now experienced in this part of the world. Exceptions include some Arctic waterbodies that received abundant snowmelt and large, ice‐covered lakes less prone to evaporation. Data from the Andean lakes indicated evaporative effects were minimal due to abundant precipitation. These data, in combination with limnological records and paleolimnological research from each region, provide a holistic view on how freshwater ecosystems are responding to recent warming in climatically sensitive Arctic and Andean environments.

Interannual Variability in Methane and Nitrous Oxide Concentrations and Sea‐Air Fluxes Across the North American Arctic Ocean (2015–2019)

AbstractBetween 2015 and 2018, we collected approximately 2,000 water column measurements of methane (CH4) and nitrous oxide (N2O) concentrations in the North American Arctic Ocean during summer and early fall. We also obtained 25 measurements of CH4 and N2O concentrations in rivers along the Northwest Passage and Ellesmere Island in midsummer 2017–2019. Our results show that N2O is generated in the highly productive Bering and Chukchi Seas and transported northeastward, producing a persistent subsurface N2O peak in the Beaufort Sea. The Chukchi and Beaufort Sea sediments are a significant source of CH4 to the water column. These sedimentary sources and associated water column consumption display significant spatial gradients and interannual variability. CH4 isotope data demonstrate the importance of CH4 oxidation across the study region. We find that rivers are not a significant source of CH4 or N2O to the Arctic Ocean at the time of year sampled. The estimated annual sea‐air flux across the study region (2.3 million km2) had a median (first quartile, third quartile) of 0.009 (0.002, 0.023) Tg CH4 y−1 and −0.003 (−0.013, 0.010) Tg N y−1. These results suggest that the North American Arctic Ocean currently plays a negligible role in global CH4 and N2O budgets. Our expansive data set, with observations at many repeat stations, provides a synopsis of present‐day Arctic CH4 and N2O distributions and their range of variability, as well as a benchmark against which future climate‐dependent changes can be evaluated.