Greenland Glaciers Research Articles

Data supporting 'Atlantic Water intrusion triggers rapid retreat and regime change at previously stable Greenland glacier'

Data supporting 'Atlantic Water intrusion triggers rapid retreat and regime change at previously stable Greenland glacier'

Data supporting 'Atlantic Water intrusion triggers rapid retreat and regime change at previously stable Greenland glacier'

Data supporting 'Atlantic Water intrusion triggers rapid retreat and regime change at previously stable Greenland glacier'

Data supporting 'Atlantic Water intrusion triggers rapid retreat and regime change at previously stable Greenland glacier'

Data supporting 'Atlantic Water intrusion triggers rapid retreat and regime change at previously stable Greenland glacier'

Synchronous Retreat of Southeast Greenland's Peripheral Glaciers

AbstractRecently, scientific attention has focused on estimating Greenland's dynamic mass loss through changes to flow speeds, thickness, and length on its marine outlet glaciers. For the ice sheet outlet glaciers, dynamic mass loss has been found to be highly sensitive to changes in climate and individual glacier geometry. For the ice‐sheet‐independent marine glaciers around Greenland's periphery, dynamic mass loss is presently overlooked. Here, we apply an open‐source, automated method of measuring glacier length changes using satellite imagery, to produce highly detailed records of length changes for 135 peripheral marine glaciers in southeast Greenland. We find evidence for anomalous retreat across 56 glaciers coincident with elevated surface melt in 2016, with melt 22% above the 2013–2019 average. Our detailed observations resolve the widespread, rapid, and synchronous response of these independent marine glaciers to increased meltwater input in 2016, indicating that their dynamics may be more sensitive to atmospheric warming than currently thought.

The multi-year comparisons of chlorophyll and sea ice in Greenland Sea and Barents Sea and their relationships with the North Atlantic Oscillation

The Arctic Ocean (AO) has experienced very significant warming in recent decades with clear impacts on the extent and depth of sea ice cover. Sea ice serves as a primary habitat and plays an important role in the AO marine food web. The surface distributions of chlorophyll_a (CHL), sea ice concentration (ICE), sea surface temperature (SST) and North Atlantic Oscillation (NAO) are analyzed in the study region (20°W-50°E, 70°N-80°N) over the decade (2003–2014). This region spans the Barents Sea (BS), Norwegian (NS) and Greenland Sea (GS). In general, the peak of spatial averaged CHL in the BS was about 60% higher than the GS. Due to elevated SST in the southern BS, CHL was much higher especially in 2010 and 2013. In 2011, there was a strong meridional gradient in CHL decreasing from south to north of the BS, and also a strong zonal gradient from the southern GS to the southern BS. The northern GS had higher CHL than the southern GS due to the increased ice melting and nutrient-enriched runoff from east Greenland glaciers to the northern and western coastal regions of the GS. Seasonal peaks of spatially averaged CHL occurred in April or May and were about two weeks earlier in the BS than the GS. Higher ice melt in the northern BS was the main reason for CHL blooms especially in 2010 and 2011. Earlier and more extensive ice melting and a persistent negative NAO index causing atmospheric circulation patterns that favoured ice loss were the possible drivers of enhanced phytoplankton blooms in 2010. A previous negative winter NAO is thought to be linked to an increase in ICE in the following spring. NAO is mostly negative during spring in the GS. Sea ice melt was positively correlated with CHL in the northern sector of the study region.

Unravelling the long-term, locally heterogenous response of Greenland glaciers observed in archival photography

Abstract. We present an approach for extracting quantifiable information from archival aerial photographs to extend the temporal record of change over a region of the central eastern Greenland Ice Sheet. The photographs we use were gathered in the 1930s as part of a surveying expedition, and so they were not acquired with photogrammetric analysis in mind. Nevertheless, we are able to make opportunistic use of this imagery, as well as additional, novel datasets, to explore changes at ice margins well before the advent of conventional satellite technology. The insights that a longer record of ice margin change bring is crucial for improving our understanding of how glaciers are responding to the changing climate. In addition, our work focuses on a series of relatively small and little studied outlet glaciers from the eastern margin of the ice sheet. We show that whilst air and sea surface temperatures are important controls on the rates at which these ice masses change, there is also significant heterogeneity in their responses, with non-climatic controls (such as the role of bathymetry in front of calving margins) being extremely important. In general, there is often a tendency to focus either on changes of the Greenland Ice Sheet as a whole, or on regional variations. Here, we suggest that even this approach masks important variability, and full understanding of the behaviour and response of the ice sheet requires us to consider changes that are taking place at the scale of individual glaciers.

Risk of Environmental Management in Countries of African Union

A comparative assessment and analysis of risk of environmental management across the African Union has been carried out. It is mainly characterized by two types of natural hazards: lithospheric — earthquakes, volcanism and related processes, and hydrometeorological — droughts, floods, accompanying landslides and soil degradation caused by global climate change and anthropogenic changes in the landscapes. A great hazard for tourist business, which is a basis of economy of island states with high enough level of development, is a sharp rise in the level of World Ocean as a result of melting of glaciers in Antarctica and Greenland. The sector most exposed to natural hazards in the African Union is agriculture, which suffers from soil erosion and degradation, droughts, desertifi cation and landslides. Vast areas of the African continent are at low risk of exploitation because they are uninhabited and undeveloped. Th ese are pristine areas with naturally developed landscapes where extreme natural processes and phenomena certainly occur, but there is simply no one and nothing to affect them. Good disaster resilience is related to the overall high level of economic development of the countries — Seychelles, Mauritius, South Africa, the political will of the governance structures and well-established security systems — Algeria, Tunisia, Egypt, and the growing infl uence of private capital in recent years on national disaster protection policies — Nigeria, Ghana, Cape Verde. Countries with low disaster resilience are the poorest countries in the world, with widespread famine, epidemics, forced migration due to ongoing military conflicts and coups d’état, poverty, etc. Correlation and regression analysis for the countries of the African Union has shown the dependence of the risk of environmental management coeffi cient on nominal GDP per capita per year, although the correlation coefficientis rather low. The highest risk is observed in the poorest countries that are unable to cope with natural disasters on their own, where natural hazards are widespread — Ethiopia, Rwanda, Burundi, Somalia and Eritrea. Low risk is ensured in countries with developed economies and eff ective government — Mauritius, South Africa, Algeria, Tunisia, etc.

Long‐Term Infrasonic Monitoring of Land and Marine‐Terminating Glaciers in Greenland

AbstractA period of 18 years of infrasonic recordings was analyzed from a microbarometer array (I18DK) in northwestern Greenland, near Qaanaaq. A huge number of infrasonic detections, over 700,000, have been made in I18DKs soundscape during the Arctic summers. Simultaneously identified were both calving events from marine‐terminating glaciers and discharge related acoustics from a land‐terminating glacier. This infrasonic activity is correlated to sea‐surface and atmospheric temperature, respectively. Inter‐yearly to daily variations were retrieved showing a strong variability in infrasonic detection rates and hence glacier activity. The highest number of infrasonic detections were found in recent years from the land‐terminating glacier. The latter is supported by actual discharge measurements and partly by a discharge model. It is concluded that monitoring infrasound from glaciers can complement other techniques to remotely and passively get insights into glacier dynamics with high temporal and spatial resolution.

Greenland tidewater glacier advanced rapidly during era of Norse settlement

Abstract Our ability to improve prognostic modeling of the Greenland Ice Sheet relies on understanding the long-term relationships between climate and mass flux (via iceberg calving) from marine-terminating tidewater glaciers (TWGs). Observations of recent TWG behavior are widely available, but long-term records of TWG advance are currently lacking. We present glacial geomorphological, sedimentological, archaeological, and modeling data to reconstruct the ~20 km advance of Kangiata Nunaata Sermia (KNS; the largest tidewater glacier in southwest Greenland) during the first half of the past millennium. The data show that KNS advanced ~15 km during the 12th and 13th centuries CE at a rate of ~115 m a−1, contemporaneous with regional climate cooling toward the Little Ice Age and comparable to rates of TWG retreat witnessed over the past ~200 years. Presence of Norse farmsteads proximal to KNS demonstrates their resilience to climate change, manifest as a rapidly advancing TWG in a cooling climate. The results place limits on the magnitude of ice-margin advance and demonstrate TWG sensitivity to climate cooling as well as warming. These data combined with our grounding-line stability analysis provide a long-term record that validates approaches to numerical modeling aiming to link calving to climate.

Future Climate Scenarios for Northern Baffin Bay and the Pikialasorsuaq (North Water Polynya) Region

ABSTRACT Northern Baffin Bay is distinct due to the presence of the North Water Polynya, a region referred to as “Pikialasorsuaq” by Inuit in Greenland and “Sarvarjuaq” by Inuit in Canada. Surrounding communities rely on the polynya as hunting and shipping grounds for much of the year due to its lower sea ice concentration and high primary productivity; however, Arctic warming threatens the dynamics of the region by altering the sea ice cycle, oceanic heat content and freshwater input. The aim of this study is to examine the future of northern Baffin Bay and Pikialasorsuaq under various climate warming scenarios using the Nucleus for Modelling of the Ocean (NEMO) engine, coupled to the Louvain-la-Neuve (LIM2) sea ice model. Five experiments were run on a resolution Arctic and Northern Hemispheric Atlantic (ANHA4) configuration over the period 1981–2070 forced by a range of global climate models. By 2070 there is a significant decrease in sea ice thickness and concentration, with an overall warming and salinity increase in the upper 500 m of the water column. Increased freshwater input from melting Greenland glaciers results in a more muted salinity increase in the top 50 m, while deeper waters are impacted by increased penetration of warm, saline Atlantic Water into Baffin Bay through Davis Strait. These physical changes impact the formation of the polynya in the future. The polynya is expected to continue to form on the eastern side near Greenland through mixing of warm Atlantic Waters to the surface, while the western side near Ellesmere Island has an increased ice area flux through Nares Strait and increased stratification. Additionally, there is a shallowing of mixed layer depth and increase in density stratification under the greatest warming scenarios. Implications to biogeochemical properties include a 0.5% decrease in total alkalinity, a 3.4% decreased in dissolved oxygen concentration but no net change in annual phytoplankton primary production. However, there are large changes in the phytoplankton bloom dynamics, including a 50% decrease in the autumn bloom and a 20-day advance in the spring bloom. Overall, our study suggests significant oceanographic changes which could lead to a loss of the recurrent polynya in its historical state, and shifts in primary production which could have, as yet uncertain, consequences for the food web and higher trophic levels.

Multi-decadal retreat of marine-terminating outlet glaciers in northwest and central-west Greenland

Abstract. The retreat and acceleration of marine-terminating outlet glaciers in Greenland over the past 2 decades have been widely attributed to climate change. Here we present a comprehensive annual record of glacier terminus positions in northwest and central-west Greenland and compare it against local and regional climatology to assess the regional sensitivity of glacier termini to different climatic factors. This record is derived from optical and radar satellite imagery and spans 87 marine-terminating outlet glaciers from 1972 through 2021. We find that in this region, most glaciers have retreated over the observation period and widespread regional retreat accelerated from around 1996. The acceleration of glacier retreat coincides with the timing of sharp shifts in ocean surface temperatures, the duration of the sea-ice season, ice-sheet surface mass balance, and meltwater and runoff production. Regression analysis indicates that terminus retreat is most sensitive to increases in runoff and ocean temperatures, while the effect of offshore sea ice is weak. Because runoff and ocean temperatures can influence terminus positions through several mechanisms, our findings suggest that a variety of processes – such as ocean-interface melting, mélange presence and rigidity, and hydrofracture-induced calving – may contribute to, but do not conclusively dominate, the observed regional retreat.

Challenging the southern boundary of active rock glaciers in West Greenland

AbstractRock glaciers (RGs) are landscape features impacting the composition and magnitude of runoff and, given their ice content, they are used as indicators for past and present climate conditions. While our knowledge of RG coverage has improved over recent years in many mountainous regions, there is very little information available for RGs in Greenland. Here, we provide evidence for an active RG in West Greenland, about 230 km south of what previously has been identified as the southern limit of active RGs. We present field evidence such as bottom temperature of the snow pack and surface displacements and indicate how these results could be utilized in further studies to better assess RG distribution or their ice content.

Rapid basal melting of the Greenland Ice Sheet from surface meltwater drainage

Subglacial hydrologic systems regulate ice sheet flow, causing acceleration or deceleration, depending on hydraulic efficiency and the rate at which surface meltwater is delivered to the bed. Because these systems are rarely observed, ice sheet basal drainage represents a poorly integrated and uncertain component of models used to predict sea level changes. Here, we report radar-derived basal melt rates and unexpectedly warm subglacial conditions beneath a large Greenlandic outlet glacier. The basal melt rates averaged 14 mm ⋅d-1 over 4 months, peaking at 57 mm ⋅d-1 when basal water temperature reached +0.88 ∘C in a nearby borehole. We attribute both observations to the conversion of potential energy of surface water to heat in the basal drainage system, which peaked during a period of rainfall and intense surface melting. Our findings reveal limitations in the theory of channel formation, and we show that viscous dissipation far surpasses other basal heat sources, even in a distributed, high-pressure system.

Arctic Unicorns and the Secret Sounds of a Glacial Fjord

The successful deployment of a seafloor seismometer near the calving front of a Greenland glacier has opened a new avenue to study hidden glacial processes and the behavior of fjord-dwelling wildlife.

Improved Estimation of Glacial‐Earthquake Size Through New Modeling of the Seismic Source

AbstractThe number of gigaton‐sized iceberg‐calving events occurring annually at Greenland glaciers is increasing, part of a larger trend of accelerating mass loss from the Greenland Ice Sheet. Though visual observation of large calving events is rare, ∼60 glacial earthquakes generated by these calving events are currently recorded each year by regional and global seismic stations. An empirical relationship between iceberg size and MCSF, a summary measure of glacial‐earthquake size, was recently demonstrated by Olsen and Nettles (2019), https://doi.org/10.1029/2019JF005054. However, MCSF is known to be sensitive to choices made in modeling the seismic source. We incorporate constraints on the seismic source from laboratory studies of calving and test multiple source time functions using synthetic and observed glacial‐earthquake waveforms. We find that a simple, fixed time function with a shape informed by laboratory results greatly improves estimates of earthquake size. The average ratio of estimated to true peak force values is 1.03 for experiments using our preferred source model, compared with an average of 0.3 for models used in previous studies. We find that maximum‐force values estimated from waveform modeling depend far less on model choices than does MCSF, and therefore prefer maximum force as a measure of glacial‐earthquake size. Using both synthetic and real data, we confirm a correlation between maximum force and iceberg mass. Our results support the possibility of developing useful scaling relationships between seismic observables and physical parameters controlling glacier calving.

Image classification of marine-terminating outlet glaciers in Greenland using deep learning methods

Abstract. A wealth of research has focused on elucidating the key controls on mass loss from the Greenland and Antarctic ice sheets in response to climate forcing, specifically in relation to the drivers of marine-terminating outlet glacier change. The manual methods traditionally used to monitor change in satellite imagery of marine-terminating outlet glaciers are time-consuming and can be subjective, especially where mélange exists at the terminus. Recent advances in deep learning applied to image processing have created a new frontier in the field of automated delineation of glacier calving fronts. However, there remains a paucity of research on the use of deep learning for pixel-level semantic image classification of outlet glacier environments. Here, we apply and test a two-phase deep learning approach based on a well-established convolutional neural network (CNN) for automated classification of Sentinel-2 satellite imagery. The novel workflow, termed CNN-Supervised Classification (CSC) is adapted to produce multi-class outputs for unseen test imagery of glacial environments containing marine-terminating outlet glaciers in Greenland. Different CNN input parameters and training techniques are tested, with overall F1 scores for resulting classifications reaching up to 94 % for in-sample test data (Helheim Glacier) and 96 % for out-of-sample test data (Jakobshavn Isbrae and Store Glacier), establishing a state of the art in classification of marine-terminating glaciers in Greenland. Predicted calving fronts derived using optimal CSC input parameters have a mean deviation of 56.17 m (5.6 px) and median deviation of 24.7 m (2.5 px) from manually digitised fronts. This demonstrates the transferability and robustness of the deep learning workflow despite complex and seasonally variable imagery. Future research could focus on the integration of deep learning classification workflows with free cloud-based platforms, to efficiently classify imagery and produce datasets for a range of glacial applications without the need for substantial prior experience in coding or deep learning.

Surface Elevation Change of Glaciers Along the Coast of Prudhoe Land, Northwestern Greenland From 1985 to 2018

AbstractOutlet glaciers in Greenland exhibited rapid frontal retreat, thinning, and flow acceleration in the 21st century. In contrast to a number of studies in the last two decades, long‐term glacier changes are not well known, hence limiting the understanding of ongoing glacier retreat. In this study, we present surface elevation changes of 16 glaciers along the coast of Prudhoe Land, northwestern Greenland, using digital elevation models between 1985 and 2018. All the glaciers experienced surface lowering at a mean rate of −0.55 ± 0.24 m a−1 over the period of study. Surface elevation change has shown a clear shift from 0.14 ± 0.17 m a−1 in 1985–2001 to −1.31 ± 0.20 m a−1 in 2001–2018. Thinning after 2001 was more significant at the glaciers terminating in Inglefield Bredning, represented by the most rapid thinning of Tracy and Farquhar Glaciers at −3.91 ± 0.13 and −2.91 ± 0.18 m a−1, respectively. Glaciers terminating in shallower fjords directly connected to Baffin Bay showed a thinning rate 40% slower than those in the Inglefield Bredning region. Warming trends in atmospheric and ocean temperature since the late 1990s are most likely triggers of the glacier regime shift around 2001. The heterogeneity in the glacier change is attributed to the glacier geometry and fjord bathymetry of each individual glacier, since glaciers terminating in deep fjords are subjected to greater acceleration and are more affected by deep ocean warming.

A fully-coupled 3D model of a large Greenlandic outlet glacier with evolving subglacial hydrology, frontal plume melting and calving

AbstractWe present the first fully coupled 3D full-Stokes model of a tidewater glacier, incorporating ice flow, subglacial hydrology, plume-induced frontal melting and calving. We apply the model to Store Glacier (Sermeq Kujalleq) in west Greenland to simulate a year of high melt (2012) and one of low melt (2017). In terms of modelled hydrology, we find perennial channels extending 5 km inland from the terminus and up to 41 and 29 km inland in summer 2012 and 2017, respectively. We also report a hydrodynamic feedback that suppresses channel growth under thicker ice inland and allows water to be stored in the distributed system. At the terminus, we find hydrodynamic feedbacks exert a major control on calving through their impact on velocity. We show that 2012 marked a year in which Store Glacier developed a fully channelised drainage system, unlike 2017, where it remained only partially developed. This contrast in modelled behaviour indicates that tidewater glaciers can experience a strong hydrological, as well as oceanic, control, which is consistent with observations showing glaciers switching between types of behaviour. The fully coupled nature of the model allows us to demonstrate the likely lack of any hydrological or ice-dynamic memory at Store Glacier.

Decoupling of particles and dissolved iron downstream of Greenlandic glacier outflows

Glaciers can be a significant and locally dominant source of iron (Fe), a biologically essential micronutrient, in high latitude coastal seas. The vast majority of this glacial Fe delivery is associated with particles, yet the speciation of the solid-phase Fe and specifically the relationships that govern exchange between particulate and dissolved Fe phases in these environments are poorly described. In this work, we performed measurements of in situ dissolved Fe (dFe) along meltwater and particle plumes in three transects around Disko Bay and Ameralik Fjord (West Greenland). Measurements of dFe were combined with Fe K-edge X-ray absorption spectroscopy analysis of ∼40 suspended sediment samples obtained from the same transects and from select depth profiles down to 300 m. We observed relatively constant dFe levels (4 to 10 nM for nearly all dFe measurements) across fjords with widely varying particulate Fe(II) contents (from 20 to 90% Fe(II)), indicating that dFe concentrations had little dependence on the oxidation state of Fe in the suspended sediment. Particulate Fe data were grouped by underlying bedrock geology, with suspended sediment consisting of 80-90% biotite-like Fe(II) in fjords with Precambrian shield geology and poorly-ordered Fe(III) particles (<20-30% Fe(II)) in one fjord with suspended sediments derived from tertiary basalts. Our characterization data indicated no significant change in the average Fe oxidation state and bonding environment of particles along the fjord transects, implying that Fe(II) in biotite-like coordination is not a readily labile Fe form on this spatial scale. Our results suggest that dFe in these glacially-modified coastal waters is buffered at a relatively constant low nM concentration due to factors other than particle Fe mineralogy and that glacier-derived Fe phases are relatively inert on this spatial scale.

Satellite and ground based estimates for ice surface velocities in the part of central Dronning Maud Land, East Antarctica: Implications for ice flux calculations

The ice sheet and glaciers of Antarctica and Greenland represent the largest sources of freshwater on planet Earth. The understanding and quantification of their dynamic properties such as albedo, precipitation, ice mass movement, and ice elevation changes are critical for the improved climate and mass balance models. The present study utilizes space-borne optical and synthetic aperture radar (SAR) imagery to measure the ice surface velocity at high spatial resolution for a part of the central Dronning Maud Land (cDML), East Antarctica. The datasets from Landsat-8 and Sentinel-1 SAR satellite are used for ice stream velocity estimation using feature-offset tracking and differential interferometric SAR (DInSAR) methods. The derived velocity products are validated with ground based stakes network at annual time scale. The fundamental ice flow laws are used to estimate the ice outflux or discharge for selected ice stream drainage basins of cDML at fluxgate locations. The ice stream basin has been delineated using combination of elevation, slope and continental scale velocity maps. The ice influx for study area is estimated using ECMWF fifth generation reanalysis (ERA5) and Regional Atmospheric Climate Model (RACMO) v2.3 model outputs. The estimated influx and outflux are in the ranges of 0.18–4.167 Gt/y and 0.201 to 1.278 Gt/y respectively, indicating net positive mass balance for the selected area.