Melting Of Ice Sheets Research Articles

Spatial and temporal patterns of land surface temperature in Greenland from 2000-2019

Temperature dynamics on the island of Greenland are an important factor in shaping ecological events. Investigating the land surface temperature (LST) patterns is critical for understanding ecological dynamics across different regions. Further melting of the Greenland ice sheet could deva state marine and terrestrial ecosystems. This study used data from Moderate Resolution Imaging Spectroradiometer satellites to understand the seasonal patterns and patterns of LST over the entire island. Focusing on the period between 2000 and 2019, this study used a natural cubic spline model to identify seasonal patterns for all sub-regions. The data were seasonally adjusted and filtered with a second-order autocorrelation component. The spline was fitted again to identify the LST pattern, and a multivariate regression model was then used to adjust for spatial correlation. We illustrate that most of the land surface of Greenland hasstable temperature trends. These observed patterns in LST in Greenland during the study period suggest that the observed ice-sheet melting in Greenland within the last two decades could be due to other factors, not necessarily LST patterns.

Ocean response to a century of observation-based freshwater forcing around Greenland in EC-Earth3

The acceleration of Greenland ice sheet melting over the past decades is raising concern regarding the impacts on ocean circulation in the North Atlantic and Arctic regions. Global climate models struggle to assess these impacts as they do not include a realistic amount of meltwater from the Greenland ice sheet. Using an extended observation-based dataset of runoff and solid ice discharge for the recent historical period (1920–2019), we force the EC-Earth3 climate model following the ensemble approach and protocol of a previous study using a different model. We observe a slight increase of the ensemble mean AMOC with a large spread in the response: 0.20±0.81\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$0.20\\pm 0.81$$\\end{document} Sv for the maximum AMOC at 45∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{\\circ }$$\\end{document}N. We notice that members with a strong initial AMOC state (18 Sv) show a strengthening of the AMOC, while members with intermediate AMOC strength between 16 and 18 Sv are not affected by the freshwater forcing. Weaker initial AMOC members respond with a mean weakening of -0.21±0.58\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${-}\\,0.21\\pm 0.58$$\\end{document} Sv of the AMOC. The AMOC ensemble spread is reduced by half in the freshwater forced ensemble at the end of the experiment and the negative trend is stronger compared to historical simulations without the forcing. This suggests the possible ability of the freshwater to constrain AMOC variability on multi-decadal time-scales. Comparison of the two ten member ensembles with ORAS5 reanalysis shows a reduction of the surface temperature and salinity biases in the freshwater forced ensemble in key regions such as the North Atlantic subpolar gyre and the Beaufort Gyre relative to the historical simulations. Recent trends are also more aligned with reanalysis in those regions. Arctic Ocean Atlantic Water subsurface core temperature is also closer to reanalysis but still strongly biassed. Members with a high AMOC initial state display an unrealistic Atlantic water layer core depth.

A New Eulerian Iceberg Module for Climate Studies

AbstractIcebergs modulate the effective location of freshwater input from ice sheets into the ocean and therefore play an important role for the climate, especially during times of increased ice discharge (e.g., Heinrich events). None of the models participating in the Paleo Modeling Intercomparison Project simulations of the Last Glacial Maximum or the last deglaciation included icebergs. Here, we present a newly developed dynamic/thermodynamic iceberg module that was specifically designed to be incorporated in climate models used for long‐term climate simulations with interactive ice sheets. In contrast to the widely used Lagrangian iceberg models, it is formulated in an Eulerian framework. This simplifies coupling to ocean models and enhances computational efficiency for glacial climates. In a set of sensitivity experiments, where the module was implemented into an Earth System Model, we validate the model for present‐day climate conditions and test its sensitivity to key parameters. Further, we investigate the effect of iceberg hosing on the Atlantic meridional overturning circulation (AMOC) as compared to traditional freshwater hosing. Varying the hosing rate slowly in time yields a good approximation of the hysteresis curve of the AMOC. We find that the sensitivity of the AMOC to iceberg hosing is stronger than to freshwater hosing in the same ocean point, but weaker as compared to a latitude belt forcing in the North Atlantic. This emphasizes the 2e necessity to include interactive icebergs in long‐term coupled climate simulations to realistically represent melt patterns and the response of the AMOC to freshwater input from melting ice sheets.

Holocene relative sea-level changes along the Caribbean and Pacific coasts of northwestern South America

Abstract Predicting coastal change depends upon our knowledge of postglacial relative sea-level variability, partly controlled by glacio-isostatic responses to ice-sheet melting. Here, we reconstruct the postglacial relative sea-level changes along the Caribbean and Pacific coasts of northwestern South America by numerically solving the sea-level equation with two scenarios of mantle viscosity: global standard average and high viscosity. Our results with the standard model (applicable to the Pacific coast) agree with earlier studies by indicating a mid-Northgrippian high stand of ~2 m. The high-viscosity simulation (relevant to the Caribbean coast) shows that the transition from far- to intermediate-field influence of the Laurentide Ice Sheet occurs between Manzanillo del Mar and the Gulf of Morrosquillo. South of this location, the Colombian Caribbean coast has exhibited a still stand with a nearly constant Holocene relative sea level. By analyzing our simulations considering sea-level indicators, we argue that tectonics is more prominent than previously assumed, especially along the Caribbean coast. This influence prevents a simplified view of regional relative sea-level changes on the northwestern South American coast.

Sediment discharge from Greenland’s marine-terminating glaciers is linked with surface melt

Sediment discharged from the Greenland Ice Sheet delivers nutrients to marine ecosystems around Greenland and shapes seafloor habitats. Current estimates of the total sediment flux are constrained by observations from land-terminating glaciers only. Addressing this gap, our study presents a budget derived from observations at 30 marine-margin locations. Analyzing sediment cores from nine glaciated fjords, we assess spatial deposition since 1950. A significant correlation is established between mass accumulation rates, normalized by surface runoff, and distance down-fjord. This enables calculating annual sediment flux at any fjord point based on nearby marine-terminating outlet glacier melt data. Findings reveal a total annual sediment flux of 1.324 + /− 0.79 Gt yr-1 over the period 2010-2020 from all marine-terminating glaciers to the fjords. These estimates are valuable for studies aiming to understand the basal ice sheet conditions and for studies predicting ecosystem changes in Greenland’s fjords and offshore areas as the ice sheet melts and sediment discharge increase.

Radiolarian assemblages related to the ocean–ice interaction around the East Antarctic coast

Abstract. The Southern Ocean plays a central role in Earth's climate, ecology, and biogeochemical cycles. Therefore, understanding long-term changes in Southern Ocean water masses in the geologic past is essential for assessing the role of the Southern Ocean in the climate system. Radiolarian fossils are a useful tool to reconstruct the water masses of the Southern Ocean. However, the radiolarian assemblages in the high latitudes of the Southern Ocean (south of the polar front (PF)) are still poorly understood. In this paper, we report the radiolarian assemblages in surface marine sediment and plankton tow samples collected from the high latitudes south of the PF. In the surface sediments, four factors (named F1–F4) of the radiolarian assemblages were identified using Q-mode factor analysis, which are related to different water masses and hydrological conditions. F1 is related to the surface waters south of the southern boundary (SB) of the Antarctic Circumpolar Current (ACC), which are cooled by melting sea ice and ice sheets. F2 is associated with water masses north of the SB. A comparison with the vertical distribution of the radiolarian assemblages in plankton tow samples indicates that characteristic species are associated with the Circumpolar Deep Water (CDW) and surface waters north of the SB. F3 is associated with modified Circumpolar Deep Water (mCDW). The radiolarian assemblage of F4 does not seem specifically related to any of the water mass here analyzed. However, the species in this assemblage are typically dwells within ice shelf and/or sea ice edge environments. Radiolarian assemblages here identified and associated with water masses, and ice edge environments are useful to reconstruct the environment south of the PF in the geologic past.

Tracing Englacial Layers in Radargram via Semi-supervised Method: A Preliminary Result

The melting of ice sheets significantly contributes to sea level rise, highlighting the crucial need to comprehend the structure of ice for climate benefits. The stratigraphy of ice sheets revealed through ice layer radargrams gives us a window into historical depth-age correlations and accumulation rates. Harnessing this knowledge is not only crucial for interpreting both past and present ice dynamics, especially concerning the Greenland ice sheet, but also for making informed decisions to mitigate the impacts of climate change. Ice layer tracing is prevalently conducted using manual or semi-automatic approaches, requiring significant time and expertise. This study aims to address the need for efficient and precise tracing methods in a two-step process. This is achieved by utilizing an unsupervised annotation method (i.e., ARESELP) to train deep learning models, thereby reducing the need for extensive and time-consuming manual annotations. Four prominent deep learning-based segmentation techniques, namely U-Net, U-Net+VGG19, U-Net+Inception, and Attention U-Net, are benchmarked. Additionally, various thresholding methods such as binary, Otsu, and CLAHE have been explored to achieve optimal enhancement for the true label annotation images. Our preliminary experiments indicate that the combination of attention U-Net with specific processing techniques yields the best performance in terms of the binary IoU metric.

Polar climate change: a multidisciplinary assessment

The rapid environmental changes in polar regions have been attracting considerable political, public, and scientific attention in recent years. The polar amplification is recognized as a robust feature of the climate system in response to carbon dioxide (CO2) forcing, resulting in sea ice loss, ice sheet melting, and methane release from permafrost thawing. From a physical perspective, this paper examines the polar amplification and sea ice changes for past and future scenarios using satellite, reanalysis, and climate model datasets. From an interdisciplinary perspective, we discuss the potential environmental, socioeconomic, and political effects associated with these changes. The observational data showed enhanced warming and rapid changes in sea ice cover in polar regions. Under the largest future CO2 forcing, climate simulations indicate an unprecedented rise in air temperature and fast sea ice loss, even in low emission scenarios. This results in a number of physical, environmental, and social-economic effects that need to be carefully considered. Polar climate change, however, offers new opportunities, including the local increase in fisheries and the opening of new navigation routes, which substantially impact the world economy. At the same time, it also implies critical environmental consequences associated with many socioeconomic and ecological risks, such as migration or extinction of populations and species; sea level rise; an increase in frequency and intensity of extreme weather in mid-latitudes; and infrastructure damage from permafrost thawing. Even with the advances and improvements in climate modeling in recent decades, the exact nature of these nonlinear interactions is still in debate.

The importance of terrestrial carbon sequestration during Termination 1

ABSTRACTDuring the transition from the Last Glacial Maximum (LGM) to the Holocene, terrestrial carbon sequestration occurred primarily in boreal forests and forest soils largely on landscapes that had been covered by ice sheets. Major processes operating during this period included radiative warming from rising concentrations of atmospheric CO2 (degassing oceans and oxidation of permafrost); increased seasonal warming associated with axial precession; melting of alpine glaciers and ice sheets; exposure of new land surfaces; and sequestration of carbon in expanding terrestrial vegetation and soils. We examine mechanisms of warming that melted glacial ice; temporal and spatial availability of newly exposed landscapes; rates at which plant colonization and soil development occurred; estimates of terrestrial carbon sequestration; and how those processes interacted with one another. Data from the West Antarctic Ice Sheet Divide ice core show that from 18 to 11 cal ka bp the concentration of atmospheric CO2 rose by ≈80 ppmv (≈170 Gt C); published estimates of net terrestrial carbon sequestration (following photosynthesis) are considerably higher (450–1250 Gt C). Thus, accumulation of carbon in terrestrial vegetation and soils played an important role in modulating atmospheric CO2 and, indirectly, Earth's climate during Termination 1, and possibly during earlier Quaternary ice ages.

One decade of temperature change at the North Pole and South Pole using ANN backpropagation algorithm

Global warming is an event in which the average temperature of the atmosphere, ocean and land rises. Changes in atmospheric temperature cause changes in the physical conditions of the atmosphere to become unstable, causing anomalies in weather parameters that cause climate change. In the last decade there have been temperature changes in the North Pole (Greenland) and the South Pole (Antarctica). The impacts caused by temperature changes are melting ice sheets, rising sea levels, extinction of species in large numbers, people living on the coast are threatened by tidal floods, while small islands can sink. To anticipate temperature changes, a model is needed that can forecast air or temperature conditions using Artificial Neural Network with Backpropagation method using Matlab software media. Data obtained from Data Access Viewer of NASA. After training and testing the data, the average value of the prediction results for the south polar region (Antarctica) is -47.910C with a Mean Square Error (MSE) value of 0.0015. Meanwhile, for the North Pole region (Greenland), the average value of the prediction results is -22.410C with an MSE value of 0.0069. By looking at the average value of the prediction results, it can be concluded that the temperature change for the South Pole region (Antarctica) is higher than the temperature change for the North Pole region (Greenland).

Satellite-Derived Lagrangian Transport Pathways in the Labrador Sea

The offshore transport of Greenland coastal waters influenced by freshwater input from ice sheet melting during summer plays an important role in ocean circulation and biological processes in the Labrador Sea. Many previous studies over the last decade have investigated shelfbreak transport processes in the region, primarily using ocean model simulations. Here, we use 27 years of surface geostrophic velocity observations from satellite altimetry, modified to include Ekman dynamics based on atmospheric reanalysis, and virtual particle releases to investigate seasonal and interannual variability in transport of coastal water in the Labrador Sea. Two sets of tracking experiments were pursued, one using geostrophic velocities only, and another using total velocities including the wind effect. Our analysis revealed substantial seasonal variability, even when only geostrophic velocities were considered. Water from coastal southwest Greenland is generally transported northward into Baffin Bay, although westward transport off the west Greenland shelf increases in fall and winter due to winds. Westward offshore transport is increased for water from southeast Greenland so that, in some years, water originating near the east Greenland coast during summer can be transported into the central Labrador Sea and the convection region. When wind forcing is considered, long-term trends suggest decreasing transport of Greenland coastal water during the melting season toward Baffin Bay, and increasing transport into the interior of the Labrador Sea for water originating from southeast Greenland during summer, where it could potentially influence water column stability. Future studies using higher-resolution velocity observations are needed to capture the role of submesoscale variability in transport pathways in the Labrador Sea.

Global terrestrial monsoon area variations since Last Glacial Maximum based on TraCE21ka and PMIP4-CMIP6 simulations

Global monsoon over land (GM_L) have significant variations in their dominated area (GMA_L). The quantitative assessment of changes in GMA_L is essential for understanding spatial environment impacts and the underlying driving mechanism of GM_L evolution. Simulation results of a suite of transient climate evolution simulation over the last 21,000 years (TraCE21ka) and five-model ensemble outputs of the Paleoclimate Modelling Intercomparison Project in their latest phase (fourth, PMIP4-CMIP6) are analyzed to study the changes in global, hemispheric and six sub-monsoon areas over the past 21 ka over land. Both datasets can reproduce large-scale characteristics of GMA_L variability, although there are differences in the magnitudes of their changes. Compared to 0 ka, TraCE21ka simulations reveal that GMA_L reduced by about 4.89 × 106 km2 (decreased by 10.89%) during the Last Glacial Maximum (LGM, 21–18 ka), and reached a maximum of 46.61 × 106 km2 (increased by 3.83%) during the middle Holocene (MH, 9–6 ka). In comparison, the results of PMIP4-CMIP6 yield a smaller change of GMA_L during the LGM (decreased by 3.72%) and a larger magnitude of GMA_L during the MH (increased by 4.73%). The analysis of GMA_L over the past 21 ka reveals the varying influences of external forcing, with insolation playing a dominant role. Rising atmospheric greenhouse gas concentrations (GHG) and ice sheet melting have induced a stepwise expansion in GMA_L during the last deglaciation, superimposed with several abrupt millennial-scale weakened monsoon events under meltwater fluxes (MWF) forcing. After that, insolation caused a gradually declining trend in GMA_L during the Holocene. The position of the Intertropical Convergence Zone (ITCZ) under orbital forcing, leading to an anti-phase reaction between Northern Hemisphere monsoon areas (NHMA_L) and Southern Hemisphere monsoon areas (SHMA_L), particularly after 9 ka. Among the six sub-monsoons, they show diverse variations and regional characteristics under different forcings. Although regional monsoons like Indonesia-Australia monsoon (IAM) exhibit nonlinear behavior due to internal variabilities, the overall response of global monsoons to external forcing is predominantly linear. In addition, changes in the hydrological processes can indicate the formation and expansion of monsoon domains. Moisture budget shows that thermodynamic effect has always dominated monsoon hydrological cycles over the past 21 ka. The differences in regional monsoon hydrological processes arise from the dynamic effect. Moreover, δ18O records have been used to test these numerical simulation results. Which, together with diverse thermodynamic and dynamic component configurations of terrestrial paleo-monsoon variations, would help to better understand the underlying mechanism of global monsoon and its influences in the future.

Role of Snowfall Versus Air Temperatures for Greenland Ice Sheet Melt‐Albedo Feedbacks

AbstractThe Greenland Ice Sheet is a leading contributor to global sea‐level rise because climate warming has enhanced surface meltwater runoff. Melt rates are particularly sensitive to air temperatures due to feedbacks with albedo. The primary melt‐albedo feedback, fluctuation of seasonal snowlines, however, is determined not only by melt but also by antecedent snowfall which could delay the onset of dark glacier ice exposure. Here we investigate the role of snowfall versus air temperatures on ice sheet melt‐albedo feedbacks using satellite remote sensing and atmospheric reanalysis data. We find several lines of evidence that snowline fluctuations are driven primarily by air temperatures and that snowfall is a secondary control. First, standardized linear regressions indicate that the timing of glacier ice exposure is nearly twice as sensitive to air temperatures than antecedent snowfall. Second, in 74% of the ablation zone by area, winter snowfall rates are not significantly correlated with winter air temperatures. This relationship implies that ice sheet melt due to climate warming is unlikely to be compensated by higher snowfall rates in the ablation zone. Third, we find no significant change in snowfall rates in the ablation zone during our 1981–2021 study period. Our findings demonstrate that snowfall is unlikely to reduce future ice sheet melt and that ice sheet meltwater runoff should be accurately predicted by air temperatures. Although given the importance of melt‐albedo feedbacks, ice sheet models that parameterize albedo or are coupled with regional climate models are likely to provide the most accurate projections of mass loss.

West Antarctica’s contribution to sea level rise as Earth’s climate warms

West Antarctica’s contribution to sea level rise as Earth’s climate warms Dr Dan Lubin, Researcher at the Scripps Institution of Oceanography, explores the contribution of West Antarctica to sea level rise as Earth’s climate warms. Sea level rise (SLR) is one of the most pressing concerns with greenhouse gas-induced climate warming. Over one-third of the human population, including nearly two-thirds of the global urban population, lives within 100 km of the sea. SLR increases flooding from storm surges and high tides, deterioration of infrastructure, shoreline erosion, contamination of agriculture, and numerous other hardships. Climate warming causes SLR in two primary ways: the melting of polar ice sheets and glaciers and the thermal expansion of the ocean as it warms. The two largest contributors to SLR from the steadily warming polar regions are the Greenland Ice Sheet (GIS) and the West Antarctic Ice Sheet (WAIS), at approximately 280 and 160 gigatons of ice per year, respectively. The GIS and WAIS have contrasts in the details of their ice mass loss.

Impact of Heavy Metals on the Climate Change

One of the most significant issues facing decision-makers who are committed to achieving the Sustainable Development Goals as outlined in the 2030 Agenda for Sustainable Development is climate change. The effects of climate change are already being seen, including rising temperatures, altered precipitation patterns, changes in ocean currents, melting of ice sheets, rising sea levels, and an increase in the frequency and severity of sea level events. Other effects include melting permafrost, retreating glaciers and ice sheets, an increase in fire-friendly weather, and an increase in the frequency and severity of extreme weather events. This has caused the climate change, including an increase in atmospheric carbon dioxide, along with other climate gasses. Increased frequency and severity of extreme weather events, such as hurricanes, cyclones, and heavy rain, which may affect water quantity and quality, are among them. The primary releases of hazardous chemicals like heavy elements have increased, and this has had an impact on the climate. Keywords: Heavy metals; climate change, Air pollution, water pollution, soil pollution, sediment pollution, measure control pollution.

Impacts of glacial and sea-ice meltwater, primary production, and ocean CO2 uptake on ocean acidification state of waters by the 79 North Glacier and northeast Greenland shelf

The waters adjacent to the Nioghalvfjerdsbræ (79 North Glacier, 79NG) are influenced by Greenland Ice Sheet (GrIS) melt, sea-ice meltwater, and waters on the adjacent northeast Greenland shelf (NEGS). We investigated ocean acidification (OA) variables and the role of freshening, primary production, and air-sea CO2 exchange in Dijmphna Sound (DS) and on the NEGS in the summers of 2012 and 2016. The upper 150 m consisted of Polar Water with Arctic origin that was divided into a fresh surface layer (SL<50 m) and a cold halocline layer (CHL, 50 to 150 m). The layer below 150 m was of Atlantic origin. The SL freshwater was larger in 2012 than in 2016, mainly originated from local 79NG (and GrIS) runoff in DS, whereas on the NEGS in both years, it was mainly from sea-ice melt. The lowest aragonite saturation state (ΩAr) of 1.13 was found in the SL in 2012. Biological CO2 drawdown at primary production caused increased ΩAr in SL, which compensated for most of the ΩAr decrease due to the freshwater dilution of carbonate ions reducing total alkalinity, hence preventing corrosive conditions. This was most pronounced near the 79NG front in 2012, where surface stratification was most pronounced coinciding with large glacial meltwater fractions. Freshening decreased ΩAr by 0.4 at the 79NG front was compensated by biological CO2 drawdown by ~0.5. In 2016, a well-mixed water column in DS and NEGS, with dilution by sea-ice meltwater, caused less compensation on ΩAr by biological CO2 drawdown than in 2012. In future with changing climate and changing ocean chemistry, the increased meltwater effects may overcome the alleviating effects of biological CO2 drawdown on OA with unfavorable conditions for calcifying organisms. However, our study also suggests that primary production may be stimulated by stratification from surface meltwater. In addition, Atlantification and subglacial discharge may result in upwelling of inorganic nutrients that could promote primary production.

An Arctic natural oil seep investigated from space to the seafloor

Due to climate change, decreasing ice cover and increasing industrial activities, Arctic marine ecosystems are expected to face higher levels of anthropogenic stress. To sustain healthy and productive ocean ecosystems, it is imperative to build baseline data to assess future climatic and environmental changes. Herein, a natural oil seep site offshore western Svalbard (Prins Karls Forland, PKF, 80–100 m water depth), discovered using satellite radar images, was investigated using an extensive multiscale and multisource geospatial dataset collected by satellite, aerial, floating, and underwater platforms. The investigated PKF seep area covers roughly a seafloor area of 30,000 m2 and discharges oil from Tertiary or younger source rocks. Biomarker analyses confirm that the oil in the slicks on the sea surface and from the seep on the seafloor have the same origin. Uranium/Thorium dating of authigenic carbonate crusts indicated that the seep had emanated since the Late Pleistocene when ice sheet melting unlocked the hydrocarbons trapped beneath the ice. The faunal communities at the PKF seep are a mix of typical high latitude fauna and taxa adapted to reducing environments. Remarkably, the inhospitable oil-impregnated sediments were also colonized by abundant infaunal organisms. Altogether, in situ observations obtained at the site provide essential insights into the characteristics of high–latitude oil seeps and can be used as a natural laboratory for understanding the potential impacts of human oil discharge into the ocean.

Environmental distribution of per- and polyfluoroalkyl substances (PFAS) on Svalbard: Local sources and long-range transport to the Arctic

The environmental distribution of per- and polyfluoroalkyl substances (PFAS) in water, snow, sediment and soil samples taken along the west coast of Spitsbergen in the Svalbard archipelago, Norwegian Arctic, was determined. The contribution of potential local primary sources (wastewater, firefighting training site at Svalbard airport, landfill) to PFAS concentrations and long-range transport (atmosphere, ocean currents) were then compared, based on measured PFAS levels and composition profiles. In remote coastal and inland areas of Spitsbergen, meltwater had the highest mean ΣPFAS concentration (6.5 ± 1.3 ng L−1), followed by surface snow (2.5 ± 1.7 ng L−1), freshwater (2.3 ± 1.1 ng L−1), seawater (1.05 ± 0.64 ng L−1), lake sediments (0.084 ± 0.038 ng g−1 dry weight (dw)) and marine sediments (<method detection limit (MDL)–0.46 ng g−1 dw, median 0.015 ng g−1 dw). Perfluoroalkyl sulfonates (PFSA) and 6:2 fluorotelomer sulfonate (FTSA) were predominant in water and soil samples influenced by local sources, while perfluoroalkyl carboxylates (PFCA) were predominant in water and sediment from remote coastal and inland areas of Svalbard. The PFAS composition profiles observed in remote areas indicated that atmospheric transport and oxidation of volatile precursors is an important source of PFCA on Svalbard. Shorter-chain PFAS such as perfluorobutanoate (PFBA) were the predominant PFAS in freshwater, reflecting replacement of C8-chained PFAS with shorter-chained compounds. The comparatively high PFAS (especially PFBA) concentration in meltwater indicated that melting of snow and ice during the Arctic spring is an important diffuse local PFAS source. This source may become even more important with climate warming-induced melting of Arctic glaciers and ice sheets. Further studies of mobilisation and transport of PFAS in the Arctic region are needed to confirm this trend.

Climate and atmospheric circulation during the Early and Mid‐Holocene inferred from lake‐carbonate oxygen‐isotope records from western Ireland

ABSTRACTThe Early to Mid‐Holocene experienced marked climate change over the northern hemisphere mid‐latitudes in response to changing insolation and declining ice volume. Oxygen isotopes from lake sediments provide a valuable climate proxy, encoding information regarding temperature, hydroclimate and moisture source. We present oxygen‐isotope records from two lakes in western Ireland that are strongly influenced by the North Atlantic. Excellent replication between the records suggests they reflect regional, not local, influences. Carbonate oxygen‐isotope values peaked at the start of the Holocene, between 11.2 and 11.1 cal ka bp, and then decreased markedly until 6 cal ka bp at both sites. Palaeoecological evidence supports only modest change in temperature or hydroclimate during this interval and we therefore explain the decrease primarily by a reduction in the oxygen‐isotope composition of precipitation (δ18Oppt). We show a similar decrease in δ18O values in a forward model of carbonate isotopes between 12–11 and 6–5 cal ka bp. However, the inferred reduction in δ18Oppt between the Early and Mid‐Holocene in the model is mainly linked to a decrease in the δ18O of the ocean source water from ice sheet melting whereas the lake carbonate isotope records are more consistent with changes in the transport pathway of moisture associated with atmospheric circulation change as the dominant cause.

Exploring the ocean with sound: Telltale acoustic signatures of a changing ocean

Our ocean plays a major role in climate regulation, hosts vast biodiversity, sustains economies, ensures food security, and supports international shipping, tourism, recreation, and human health and security. Yet, the ocean is experiencing unprecedented changes: sea level rise, coral bleaching, ocean acidification, anoxia, accelerated melting of the major ice sheets, shifts in ocean circulation, pollution, overfishing, and increased industrialization. Sound plays a vital role in exploring, understanding, and monitoring these changes over a range of spatial and temporal scales. In this talk, I will focus on the multitude of approaches taken to using sound to understand our changing ocean, the advances in platforms used to enable these studies, the expansion of global ocean observing systems that include measurements of sound as an essential ocean variable, and the enormous complexities in interpreting acoustic signals in a dynamic and evolving ocean landscape. I will end by discussing the opportunities and obstacles associated with globalizing approaches for using sound to improve ocean stewardship.