ALBERT

Description: 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 136 m (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 d18O reach their lowest level in the entire record around 1790. Thereafter the d18O 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.

Description: 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.

Description: Extensive observations on Nivlisen, an ice shelf on Antarctica’s Atlantic coast, are analyzed and combined to obtain a new description of its complex glaciological regime. We generate models of ice thickness (primarily from ground-penetrating radar), ellipsoidal ice surface height (primarily from ERS-1 satellite altimetry), freeboard height (by utilizing precise sea surface information) and ice-flow velocity (from ERS-1/-2 SAR interferometry and GPS measurements). Accuracy assessments are included. Exploiting the hydrostatic equilibrium relation, we infer the ‘apparent air layer thickness’ as a useful measure for a glacier’s density deviation from a pure ice body. This parameter exhibits a distinct spatial variation (ranging from ≈2 to ≈16m) which we attribute to the transition from an ablation area to an accumulation area. We compute mass-flux and mass-balance parameters on a local and areally integrated scale. The combined effect of bottom mass balance and temporal change averaged over an essential part of Nivlisen is –654 ± 170 kg m–2 a–1, which suggests bottom melting processes dominate. We discuss our results in view of temporal ice-mass changes (including remarks on historical observations), basal processes, near-surface processes and ice-flow dynamical features. The question of temporal changes remains open from the data at hand, and we recommend further observations and analyses for its solution.

Description: 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.

Description: 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.

Description: Stabile Wasserisotope eines Eiskerns von Akademii Nauk (Sewernaja Semlja) als Proxies für Paläotemperatur und überregionale atmosphärische Zirkulation Diedrich Fritzsche1), Hanno Meyer1), Rainer Schütt1), Thomas Opel1), 2)1) Alfred-Wegener-Institut für Polar- und Meeresforschung in der Helmholtz-Gemeinschaft, Forschungsstelle Potsdam, Telegrafenberg A 43, 14473 Potsdam. E-mail: Diedrich.Fritzsche@awi.de2) Geographisches Institut, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099 BerlinIm Zentrum der Eiskappe Akademii Nauk auf Sewernaja Semlja wurde 1999-2001 ein 724 m langer Eiskern gebohrt, um paläoklimatische Informationen in Jahresauflösung aus diesem Teil der russischen Arktis zu erhalten. Inzwischen liegen Analysen der Verhältnisse der Isotope Sauerstoff (d18O) und Wasserstoff (dD) in 2,5 cm Auflösung für ein Drittel des etwa die letzten 2650 Jahre umfassenden Klimaarchivs vor. Diese Verhältnisse sind hauptsächlich von der Kondensationstemperatur abhängig, bei der einst der Niederschlag gebildet wurde. Änderungen im d18O- und dD-Signal gelten als bewährte Indikatoren (proxies) für Paläotemperaturen. Die Isotopendaten des vorgestellten Eiskerns gestatten eine hoch aufgelöste Temperaturrekonstruktion für die zentrale russische Arktis, die anhand der seit 1840 vorliegenden meteorologischen Daten der norwegischen Station Vardø kalibriert werden konnte (T (Vardø) [°C] = 0,37* d18O (AN) +8,8; r=0,93 im zehnjährigen gleitenden Mittel). Dansgaard (1964) definiert den Deuterium Excess, eine aus d18O- und dD abgeleitete Größe. Dieser Deuterium Excess enthält zusätzliche paläoklimatische Informationen, die üblicherweise als Indikatoren für relative Luftfeuchte und Meeres-Oberflächen-Temperatur im Quellgebiet angesehen werden (z.B. Merlivat & Jouzel, 1979). Erstmals werden hier Deuterium-Excess-Daten des Eiskerns von Akademii Nauk vorgestellt und mit Literaturwerten verglichen. Für Sewernaja Semlja ergibt sich dabei ein weit kompliziertes Bild als für Grönland, Schottland oder Island. Der Deuterium Excess scheint hier stärker durch sekundäre Verdunstung beeinflusst zu sein und daher eher sich ändernde Zirkulationsmuster widerzuspiegeln, als auf Veränderungen im Quellgebiet hinzuweisen. Literatur:Dansgaard, W. (1964): Stable isotopes in precipitation. Tellus XVI, 436-468.Merlivat, L. & J. Jouzel (1979): Global climate interpretation of the Deuterium-Oxygen 18 relationship for precipitation. Journal of Geophysical Research 84 (C8), 5029-5033.

Description: Ice cores provide a lot of climate and environmental information. A new 724 m deep ice core was drilled on Akademii Nauk ice cap (Severnaya Zemlya) between 1999 and 2001 to gain high resolution proxy data from the Central Russian Arctic. The Akademii Nauk ice core contains significant proxy data for the reconstruction of climate and environmental changes, although the ice cap is affected by summerly melting and infiltration processes, resulting in alteration of the original isotopic and chemical signals.Here we present overview data (mean values over 0.3-1.0 m) of stable water isotopes (δ18O, deuterium excess) and major ions of the uppermost 530 m as well as high resolution data for some special sections. Dating of this ice core is based on reference layers (nuclear weapon tests, volcanoes) and on counting of annual cycles of stable isotopes and electrical conductivity. The age model yielded an age of about 1,500 years for the core section viewed here.δ18O data reflect Eurasian Arctic surface air temperature (SAT) changes and show a generally decreasing trend, culminating in the absolute SAT minimum around 1800. Thereafter the values increased strongly to the absolute maximum around 1930. Whereas this SAT pattern can be interpreted as the termination of the Little Ice Age, no pronounced onset of this cool period or a distinct long-lasting warmer period like the Medieval Warm Period are detectable.The decreasing SAT trend is at least partly caused by the growth of Akademii Nauk ice cap. This is also reflected in the annual layer thickness data and a decreasing overall trend of sea salt ions, which reached their lowest values also around 1800. In contrast, there is no clear trend in ammonium and nitrate observable.After 1800 almost all ions show increasing concentrations until the mid-20th century, followed by a repeated decline in the last decades. The 20th century record is superimposed by the anthropogenic pollution of the Arctic, mainly visible in strong increasing levels of sulphate and nitrate after World War II with highest concentration from the 1960ies to the 1980ies and again decreasing values thereafter. Some of the sharp sulphate peaks could be attributed to certain volcanic eruptions, e.g. Laki/Iceland (1783) and Bezymianny/Kamchatka (1956).