| 1. |
- Pilla, Rachel M., et al.
(författare)
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Deeper waters are changing less consistently than surface waters in a global analysis of 102 lakes
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Globally, lake surface water temperatures have warmed rapidly relative to air temperatures, but changes in deepwater temperatures and vertical thermal structure are still largely unknown. We have compiled the most comprehensive data set to date of long-term (1970–2009) summertime vertical temperature profiles in lakes across the world to examine trends and drivers of whole-lake vertical thermal structure. We found significant increases in surface water temperatures across lakes at an average rate of + 0.37 °C decade−1, comparable to changes reported previously for other lakes, and similarly consistent trends of increasing water column stability (+ 0.08 kg m−3 decade−1). In contrast, however, deepwater temperature trends showed little change on average (+ 0.06 °C decade−1), but had high variability across lakes, with trends in individual lakes ranging from − 0.68 °C decade−1 to + 0.65 °C decade−1. The variability in deepwater temperature trends was not explained by trends in either surface water temperatures or thermal stability within lakes, and only 8.4% was explained by lake thermal region or local lake characteristics in a random forest analysis. These findings suggest that external drivers beyond our tested lake characteristics are important in explaining long-term trends in thermal structure, such as local to regional climate patterns or additional external anthropogenic influences.
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| 2. |
- Bentley, Michael J., et al.
(författare)
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A community-based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum
- 2014
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 100, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- A robust understanding of Antarctic Ice Sheet deglacial history since the Last Glacial Maximum is important in order to constrain ice sheet and glacial-isostatic adjustment models, and to explore the forcing mechanisms responsible for ice sheet retreat. Such understanding can be derived from a broad range of geological and glaciological datasets and recent decades have seen an upsurge in such data gathering around the continent and Sub-Antarctic islands. Here, we report a new synthesis of those datasets, based on an accompanying series of reviews of the geological data, organised by sector. We present a series of timeslice maps for 20 ka, 15 ka, 10 ka and 5 ka, including grounding line position and ice sheet thickness changes, along with a clear assessment of levels of confidence. The reconstruction shows that the Antarctic Ice sheet did not everywhere reach the continental shelf edge at its maximum, that initial retreat was asynchronous, and that the spatial pattern of deglaciation was highly variable, particularly on the inner shelf. The deglacial reconstruction is consistent with a moderate overall excess ice volume and with a relatively small Antarctic contribution to meltwater pulse la. We discuss key areas of uncertainty both around the continent and by time interval, and we highlight potential priorities for future work. The synthesis is intended to be a resource for the modelling and glacial geological community.
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| 3. |
- Höbig, Nicole, et al.
(författare)
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Lake Banyoles (northeastern Spain) : A Last Glacial to Holocene multi-proxy study with regard to environmental variability and human occupation
- 2012
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Ingår i: Quaternary International. - Oxford : Elsevier. - 1040-6182 .- 1873-4553. ; 274, s. 205-218
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Tidskriftsartikel (refereegranskat)abstract
- Analyses of a 67-m long sediment core from Lake Banyoles (northeastern Spain) have revealed evidence for the palaeoclimate history of the northern Iberian Peninsula. Investigations have included high-resolution and non-destructive sediment-physical, geochemical, and optical methods to generate proxies indicative of sedimentologic variability and climate change. Primary stratigraphic control is based on C-14 and U-series dates of organic and inorganic material, as well as tephra from the Late Pleistocene Olot volcanic episode. While preliminary ages obtained for the core base date back to approximately 60 ka, the Last Glacial Maximum (23-19 ka) interval ends at 15 m. The top 8 m of deposits accumulated in the Holocene. Several slump events were observed in the core section, as were microtectonic structures, which constrain the movement. Evidence for palaeoclimate variations in element ratios is interpreted to represent effects of Heinrich Events H0-H5. Associated changes in environmental conditions (e.g., humidity) may have affected human occupation during the Palaeolithic-Neolithic period. Implications on human occupation in northeastern Iberia due to climate changes are discussed from archeological findings and cave sediments in neighboring areas and are analyzed with respect to the palaeolimnologic of lake Banyoles. (C) 2012 Elsevier Ltd and INQUA. All rights reserved.
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| 4. |
- Pilla, Rachel M., et al.
(författare)
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Global data set of long-term summertime vertical temperature profiles in 153 lakes
- 2021
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Ingår i: Scientific Data. - : Springer Nature. - 2052-4463. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Climate change and other anthropogenic stressors have led to long-term changes in the thermal structure, including surface temperatures, deepwater temperatures, and vertical thermal gradients, in many lakes around the world. Though many studies highlight warming of surface water temperatures in lakes worldwide, less is known about long-term trends in full vertical thermal structure and deepwater temperatures, which have been changing less consistently in both direction and magnitude. Here, we present a globally-expansive data set of summertime in-situ vertical temperature profiles from 153 lakes, with one time series beginning as early as 1894. We also compiled lake geographic, morphometric, and water quality variables that can influence vertical thermal structure through a variety of potential mechanisms in these lakes. These long-term time series of vertical temperature profiles and corresponding lake characteristics serve as valuable data to help understand changes and drivers of lake thermal structure in a time of rapid global and ecological change.
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| 5. |
- Svendsen, John Inge, et al.
(författare)
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Maximum extent of the Eurasian ice sheets in the Barents and Kara Sea region during the Weichselian
- 1999
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Ingår i: Boreas. - : Wiley. - 1502-3885 .- 0300-9483. ; 28:1, s. 92-114
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Tidskriftsartikel (refereegranskat)abstract
- Based on field investigations in northern Russia and interpretation of offshore seismic data, we have made a preliminary reconstruction of the maximum ice-sheet extent in the Barents and Kara Sea region during the Early/Middle Weichselian and the Late Weichselian. Our investigations indicate that the Barents and Kara ice sheets attained their maximum Weichselian positions in northern Russia prior to 50 000 yr BP, whereas the northeastern flank of the Scandinavian Ice Sheet advanced to a maximum position shortly after 17000 calendar years ago. During the Late Weichselian (25 000–10000 yr BP), much of the Russian Arctic remained ice-free. According to our reconstruction, the extent of the ice sheets in the Barents and Kara Sea region during the Late Weichselian glacial maximum was less than half that of the maximum model which, up to now, has been widely used as a boundary condition for testing and refining General Circulation Models (GCMs). Preliminary numerical-modelling experiments predict Late Weichselian ice sheets which are larger than the ice extent implied for the Kara Sea region from dated geological evidence, suggesting very low precipitation.
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| 6. |
- Brigham-Grette, Julie, et al.
(författare)
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Pliocene warmth, polar amplification, and stepped pleistocene cooling recorded in NE arctic russia
- 2013
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Ingår i: Science. - : American Association for the Advancement of Science. - 0036-8075 .- 1095-9203. ; 340:6139, s. 1421-1427
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the evolution of Arctic polar climate from the protracted warmth of the middle Pliocene into the earliest glacial cycles in the Northern Hemisphere has been hindered by the lack of continuous, highly resolved Arctic time series. Evidence from Lake El'gygytgyn, in northeast (NE) Arctic Russia, shows that 3.6 to 3.4 million years ago, summer temperatures were similar to 8 degrees C warmer than today, when the partial pressure of CO2 was similar to 400 parts per million. Multiproxy evidence suggests extreme warmth and polar amplification during the middle Pliocene, sudden stepped cooling events during the Pliocene-Pleistocene transition, and warmer than present Arctic summers until similar to 2.2 million years ago, after the onset of Northern Hemispheric glaciation. Our data are consistent with sea-level records and other proxies indicating that Arctic cooling was insufficient to support large-scale ice sheets until the early Pleistocene.
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| 7. |
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| 8. |
- Frank, U., et al.
(författare)
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A 350 ka record of climate change from Lake El'gygytgyn, Far East Russian Arctic : refining the pattern of climate modes by means of cluster analysis
- 2013
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 9:4, s. 1559-1569
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Tidskriftsartikel (refereegranskat)abstract
- Rock magnetic, biochemical and inorganic records of the sediment cores PG1351 and Lz1024 from Lake El'gygytgyn, Chukotka peninsula, Far East Russian Arctic, were subject to a hierarchical agglomerative cluster analysis in order to refine and extend the pattern of climate modes as defined by Melles et al. (2007). Cluster analysis of the data obtained from both cores yielded similar results, differentiating clearly between the four climate modes warm, peak warm, cold and dry, and cold and moist. In addition, two transitional phases were identified, representing the early stages of a cold phase and slightly colder conditions during a warm phase. The statistical approach can thus be used to resolve gradual changes in the sedimentary units as an indicator of available oxygen in the hypolimnion in greater detail. Based upon cluster analyses on core Lz1024, the published succession of climate modes in core PG1351, covering the last 250 ka, was modified and extended back to 350 ka. Comparison to the marine oxygen isotope (delta O-18) stack LR04 (Lisiecki and Raymo, 2005) and the summer insolation at 67.5 degrees N, with the extended Lake El'gygytgyn parameter records of magnetic susceptibility (kappa(LF)), total organic carbon content (TOC) and the chemical index of alteration (CIA; Minyuk et al., 2007), revealed that all stages back to marine isotope stage (MIS) 10 and most of the substages are clearly reflected in the pattern derived from the cluster analysis.
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| 9. |
- Juschus, Olaf, et al.
(författare)
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Late Quaternary Lake-Level Changes of Lake El´gygytgyn, NE Siberia
- 2011
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Ingår i: Quaternary Research. - 0033-5894 .- 1096-0287. ; 76, s. 411-451
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Tidskriftsartikel (refereegranskat)abstract
- Lake El'gygytgyn is situated in a 3.6 Ma old impact crater in northeastern Siberia. Presented here is areconstruction of the Quaternary lake-level history as derived from sediment cores from the southern lakeshelf. There, a cliff-like bench 10 m below the modern water level has been investigated. Deep-watersediments on the shelf indicate high lake levels during a warm Mid-Pleistocene period. One period with lowlake level prior to Marine Oxygen Isotope Stage (MIS) 3 has been identified, followed by a period of high lakelevel (10 m above present). In the course of MIS 2 the lake level dropped to −10 m. At the end of MIS 2 thebench was formed and coarse beach sedimentation occurred. Subsequently, the lake level rose rapidly to theHolocene level. Changes in water level are likely linked to climate variability. During relatively temperateperiods the lake becomes free of ice in summer. Strong wave actions transport sediment parallel to the coastand towards the outlet, where the material tends to accumulate, resulting in lake level rise. During coldperiods the perennial lake ice cover hampers any wave activity and pebble-transport, keeping the outlet openand causing the lake level to drop.
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| 10. |
- Melles, Martin, et al.
(författare)
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2.8 million years of arctic climate change from Lake El'gygytgyn, NE Russia
- 2012
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 337:6092, s. 315-320
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Tidskriftsartikel (refereegranskat)abstract
- The reliability of Arctic climate predictions is currently hampered by insufficient knowledge of natural climate variability in the past. A sediment core from Lake El'gygytgyn in northeastern (NE) Russia provides a continuous, high-resolution record from the Arctic, spanning the past 2.8 million years. This core reveals numerous "super interglacials" during the Quaternary; for marine benthic isotope stages (MIS) 11c and 31, maximum summer temperatures and annual precipitation values are similar to 4 degrees to 5 degrees C and similar to 300 millimeters higher than those of MIS 1 and 5e. Climate simulations show that these extreme warm conditions are difficult to explain with greenhouse gas and astronomical forcing alone, implying the importance of amplifying feedbacks and far field influences. The timing of Arctic warming relative to West Antarctic Ice Sheet retreats implies strong interhemispheric climate connectivity.
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