Eurasian Arctic climate over the past millennium as recorded in the Akademii Nauk ice core (Severnaya Zemlya)

ABSTRACTTemporal variations of the radionuclide 10Be are broadly synchronous across the globe and thus provide a powerful tool to synchronize ice core chronologies from different locations. We compared the 10Be record of the Akademii Nauk (AN) ice core (Russian Arctic) for the time period CE 1590–1950 to the 10Be records of two well-dated Greenland ice cores (Dye3 and NGRIP). A high correlation (r = 0.59) was found between the AN and Dye3 records whereas the correlation with NGRIP was distinctly lower (r = 0.45). Sources of deviations may include local fluctuations in the deposition of 10Be due to changes in the precipitation patterns, and artefacts due to the core-sampling strategy. In general, the existing age model was validated, confirming the AN ice core to be a unique and well-dated source of palaeoclimate parameters for the Russian Arctic. We further used numerical simulations to test the influence of the core-sampling strategy on the results and derived an optimized sampling strategy for the deeper parts of the ice core.

Between 1999 and 2001, a 724 m long ice core was drilled on Akademii Nauk, the largest glacier on Severnaya Zemlya, Russian Arctic. The drilling site is located near the summit. The core is characterized by high melt-layer content. The melt layers are caused by melting and even by rain during the summer. We present high-resolution data of density, electrical conductivity (dielectrical profiling), stable water isotopes and melt-layer content for the upper 136m (120 m w.e.) of the ice core. The dating by isotopic cycles and electrical conductivity peak identification suggests that this core section covers approximately the past 275 years. Singularities of volcanogenic and anthropogenic origin provide well-defined additional time markers. Long-term temperatures inferred from 12 year running mean averages of δ18O reach their lowest level in the entire record around 1790. Thereafter the δ18O values indicate a continuously increasing mean temperature on the Akademii Nauk ice cap until 1935, interrupted only by minor cooling episodes. The 20th century is found to be the warmest period in this record.

Abstract. In July of 1931, on the eve of International Polar Year II, an Arctic flight of the Graf Zeppelin rigid airship was organized. This flight was a realization of the idea of F. Nansen, who advocated the use of airships for the scientific exploration of the Arctic territories, which were poorly studied and hardly accessible at that time. The route of the airship flight was Berlin – Leningrad – Arkhangelsk – Franz Josef Land – Severnaya Zemlya – the Taimyr Peninsula – Novaya Zemlya – Arkhangelsk – Berlin. One of scientific goals of the expedition was to measure the H and D geomagnetic field components. Actually, the first aeromagnetic survey was carried out in the Arctic during the flight. After the expedition, only preliminary results of the geomagnetic measurements, in which an anomalous behavior of magnetic declination in the high-latitude part of the route was noted, were published. Our paper is concerned with the first aeromagnetic measurements in the Arctic and their analysis based on archival and modern data on the magnetic field in the Barents and Kara sea regions. It is shown that the magnetic field along the flight route had a complicated structure, which was not reflected in the magnetic charts of those times. The flight was very important for future development of aero- and ground-based magnetic surveys in the Arctic, showing new methods in such surveys.

Snowpack emissions are recognized as an important source of gas‐phase reactive bromine in the Arctic and are necessary to explain ozone depletion events in spring caused by the catalytic destruction of ozone by halogen radicals. Quantifying bromine emissions from snowpack is essential for interpretation of ice‐core bromine. We present ice‐core bromine records since the pre‐industrial (1750 CE) from six Arctic locations and examine potential post‐depositional loss of snowpack bromine using a global chemical transport model. Trend analysis of the ice‐core records shows that only the high‐latitude coastal Akademii Nauk (AN) ice core from the Russian Arctic preserves significant trends since pre‐industrial times that are consistent with trends in sea ice extent and anthropogenic emissions from source regions. Model simulations suggest that recycling of reactive bromine on the snow skin layer (top 1 mm) results in 9–17% loss of deposited bromine across all six ice‐core locations. Reactive bromine production from below the snow skin layer and within the snow photic zone is potentially more important, but the magnitude of this source is uncertain. Model simulations suggest that the AN core is most likely to preserve an atmospheric signal compared to five Greenland ice cores due to its high latitude location combined with a relatively high snow accumulation rate. Understanding the sources and amount of photochemically reactive snow bromide in the snow photic zone throughout the sunlit period in the high Arctic is essential for interpreting ice‐core bromine, and warrants further lab studies and field observations at inland locations.

Is the 20th century warming unprecedented in the Siberian north?

From 1999 to 2001 a 724 m deep ice core was drilled on Akademii Nauk ice cap, Severnaya Zemlya, to gain high-resolution proxy data from the central Russian Arctic. Despite strong summertime meltwater percolation, this ice core provides valuable information on the regional climate and environmental history. We present data of stable water isotopes, melt-layer content and major ions from the uppermost 57 m of this core, covering the period 1883–1998. Dating was achieved by counting seasonal isotopic cycles and using reference horizons. Multi-annual δ18O values reflect Eurasian sub-Arctic and Arctic surface air-temperature variations. We found strong correlations to instrumental temperature data from some stations (e.g. r = 0.62 for Vardø, northern Norway). The δ18O values show pronounced 20th-century temperature changes, with a strong rise about 1920 and the absolute temperature maximum in the 1930s. A recent decrease in the deuterium-excess time series indicates an increasing role of the Kara Sea as a regional moisture source. From the multi-annual ion variations we deduced decreasing sea-salt aerosol trends in the 20th century, as reflected by sodium and chloride, whereas sulphate and nitrate are strongly affected by anthropogenic pollution.

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.

Glaciers and ice caps of the Russian Arctic are currently experiencing accelerating mass loss as a result of strong atmospheric and oceanic warming in the Barents and Kara Sea (BKS) region. Since 2010, this loss has been driven by both increased surface ablation, and dramatic shifts in ice dynamics at individual drainage basins across the entire Eurasian High Arctic. Here, we provide a high‐resolution spatial and temporal overview of ice surface elevation change and mass imbalance across both Novaya Zemlya and Severnaya Zemlya using CryoSat‐2 interferometric swath altimetry from 2010 to 2018. We find a total mass imbalance of −300 kg m−2 a−1, marked by a strong east‐to‐west gradient, with higher rates of loss over Novaya Zemlya (9.7 ± 0.5 Gt a−1 at 431 ± 22 kg m−2 a−1) in the west compared to Severnaya Zemlya (1.7 ± 0.1 Gt a−1 at 97 ± 8 kg m−2 a−1) in the east. Correlation between time series of surface elevation change and climate forcing reveals a quasi‐linear relationship between coupled ocean‐atmospheric forcing and glacier change over Novaya Zemlya, in agreement with similar findings from east Greenland. We further discern the likely role of ocean warming as the key factor driving dynamic ice loss in Severnaya Zemlya, owing to increasingly warm Atlantic Waters circulating along the Eurasian continental margin. We conclude that simple, linear relationships between environmental forcing and glacier change may be sufficiently accurate to parametrize ice loss in regions where synchronous, coupled ocean‐atmosphere forcing prevails.

Temperature reconstruction for Arctic glaciers

Many glaciers are subject to melting due to high summer air temperatures. Here, the presence of meltwater in the subsurface layers of the glacier bulk, and its subsequent percolation and refreezing are implemented in the calibration of a paleothermometer. Accounting for the melt feature index and the measured oxygen-isotope ratio allows for calibration of the paleothermometer and comparison of different climatic proxies. The results of reconstructions agree with previous reconstructions at the depth of attenuation of the seasonal climate signals, which supports the validity of the paleothermometer calibration. The sensitivity of the reconstruction to variations of the model parameters was also studied. It was found that most likely snow–firn sequence and temperature fields were subjected to significant change due to current warming. Temperature changes in the snow–firn thickness of Akademii Nauk (Severnaya Zemlya, Russian High Arctic) and Austfonna (Svalbard) ice caps exceed by ∼6˚C the average Arctic temperature anomalies for the last 150 years. The reconstruction of the past surface temperatures and the parameters of the subsurface heat source due to refreezing of meltwater lead to the conclusion that meltwater spreads inside two to four annual layers for Akademii Nauk and Austfonna ice caps, respectively.

Abstract. The role of sea ice in the Earth climate system is still under debate, although it is known to influence albedo, ocean circulation, and atmosphere–ocean heat and gas exchange. Here we present a reconstruction of 1950 to 1998 AD sea ice in the Laptev Sea based on the Akademii Nauk ice core (Severnaya Zemlya, Russian Arctic). The chemistry of halogens bromine (Br) and iodine (I) is strongly active and influenced by sea ice dynamics, in terms of physical, chemical and biological process. Bromine reacts on the sea ice surface in autocatalyzing "bromine explosion" events, causing an enrichment of the Br / Na ratio and hence a bromine excess (Brexc) in snow compared to that in seawater. Iodine is suggested to be emitted from algal communities growing under sea ice. The results suggest a connection between Brexc and spring sea ice area, as well as a connection between iodine concentration and summer sea ice area. The correlation coefficients obtained between Brexc and spring sea ice (r = 0.44) as well as between iodine and summer sea ice (r = 0.50) for the Laptev Sea suggest that these two halogens could become good candidates for extended reconstructions of past sea ice changes in the Arctic.

Age model and stable oxygen isotope mean values of ice core SZ99 from Akademii Nauk ice cap on Severnaya Zemlya

A deep ice core has been drilled on Akademii Nauk ice cap, Severnaya Zemlya, Eurasian Arctic. High-resolution chemical analysis has been carried out for the upper 53 m of this ice core to study its potential as an atmospheric aerosol archive, despite strong meltwater percolation. These records show that a seasonal atmospheric signal cannot be deduced. However, strong year-to-year variations have allowed the core to be dated, and a mean annual net mass balance of 0.46 m w.e. a-1 was deduced. The chemical signature of an extraordinarily high peak in electrical conductivity at 26 m depth pointed clearly to the eruption of Bezymianny, Kamchatka, in 1956. However, in general, peaks in the electrical conductivity are not necessarily related to deposition of volcanogenic sulphur aerosol. In contrast, maximum sulphate and nitrate concentrations in the ice could be related to maximum SO2 and NOx anthropogenic emissions in the 1970s, probably caused by the nickel- and copper-producing industries in Norilsk and on the Kola peninsula or by industrial combustion processes occurring in the Siberian Arctic. In addition, during recent decades sulphate and nitrate concentrations declined by 80% and 60%, respectively, reflecting a decrease in anthropogenic pollution of the Arctic basin.

The paper presents first results from the upper 54m of a 723.91m ice core drilled on Akademii Nauk ice cap, Severnaya Zemlya, Eurasian Arctic, in 1999– 2001, supplemented by data from shallow ice cores. the glacier’s peculiarity is the infiltration and refreezing of meltwater, which changes the original isotopic and chemical signals. Therefore, stratigraphical observations in these ice cores are more difficult than in those from central Greenland or Antarctica. However, the 1963 maximum of artificial radioactivity from atmospheric nuclear tests is clearly detectable in the deep ice core, and the δ18O profile of a 12.82 m shallow core shows annual variations. Consequently, at least for the upper part of the main core, an almost seasonal time resolution of palaeoclimate record could be expected. the Chernobyl layer is detected by increased 137Cs activity at depths of 11.81–12.51m related to the AD 2000 surface. the resulting mean annual net mass balance is 53±2 g cm–2 a–1. Data from dielectric profiling of the main core show considerable peaks in conductivity; one of them is interpreted as a volcano event. According to the resulting chronology, this part of the core represents approximately the last 100 years.

Glaciers in the Russian High Arctic have undergone accelerated mass loss due to atmospheric and oceanic warming in the Barents–Kara Sea region. Most studies have concentrated on the western Barents–Kara sector, despite evidence of accelerating mass loss as far east as Severnaya Zemlya. However, long-term trends in glacier change on Severnaya Zemlya are largely unknown and this record may be complicated by surge-type glaciers. Here, we present a long-term assessment of glacier change (1965–2021) on Severnaya Zemlya and a new inventory of surge-type glaciers using declassified spy-satellite photography (KH-7/9 Hexagon) and optical satellite imagery (ASTER, Sentinel-2A, Landsat-4/5 TM and 8 OLI). Glacier area reduced from 17 053 km2 in 1965 to 16 275 in 2021 (−5%; mean: −18%, max: −100%), with areal shrinkage most pronounced at land-terminating glaciers on southern Severnaya Zemlya, where there is a recent (post-2010s) increase in summer atmospheric temperatures. We find that surging may be more widespread than previously thought, with three glaciers classified confirmed as surge-type, eight as likely to have surged and nine as possible, comprising 11% of Severnaya Zemlya's 190 glaciers (37% by area). Under continued warming, we anticipate accelerated retreat and increased likelihood of surging as basal thermal regimes shift.