| 1. |
- Erhardt, Tobias, et al.
(författare)
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High-resolution aerosol concentration data from the Greenland NorthGRIP and NEEM deep ice cores
- 2022
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Ingår i: Earth System Science Data. - : Copernicus GmbH. - 1866-3508 .- 1866-3516. ; 14:3, s. 1215-1231
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Tidskriftsartikel (refereegranskat)abstract
- Records of chemical impurities from ice cores enable us to reconstruct the past deposition of aerosols onto polar ice sheets and alpine glaciers. Through this they allow us to gain insight into changes of the source, transport and deposition processes that ultimately determine the deposition flux at the coring location. However, the low concentrations of the aerosol species in the ice and the resulting high risk of contamination pose a formidable analytical challenge, especially if long, continuous and highly resolved records are needed. Continuous flow analysis, CFA, the continuous melting, decontamination and analysis of ice-core samples has mostly overcome this issue and has quickly become the de facto standard to obtain high-resolution aerosol records from ice cores after its inception at the University of Bern in the mid-1990s.Here, we present continuous records of calcium (Ca2+), sodium (Na+), ammonium (NH+4), nitrate (NO-3) and electrolytic conductivity at 1 mm depth resolution from the NGRIP (North Greenland Ice Core Project) and NEEM (North Greenland Eemian Ice Drilling) ice cores produced by the Bern Continuous Flow Analysis group in the years 2000 to 2011 (Erhardt et al., 2021). Both of the records were previously used in a number of studies but were never published in full 1 mm resolution. Alongside the 1 mm datasets we provide decadal averages, a detailed description of the methods, relevant references, an assessment of the quality of the data and its usable resolution. Along the way we will also give some historical context on the development of the Bern CFA system.
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| 2. |
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| 3. |
- Fischer, Hubertus, et al.
(författare)
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Reconstruction of millennial changes in dust emission, transport and regional sea ice coverage using the deep EPICA ice cores from the Atlantic and Indian Ocean sector of Antarctica
- 2007
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Ingår i: Earth and Planetary Science Letters. - : Elsevier BV. - 0012-821X. ; 260, s. 340-354
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Tidskriftsartikel (refereegranskat)abstract
- Continuous sea salt and mineral dust aerosol records have been studied on the two EPICA (European Project for Ice Coring inAntarctica) deep ice cores. The joint use of these records from opposite sides of the East Antarctic plateau allows for an estimate ofchanges in dust transport and emission intensity as well as for the identification of regional differences in the sea salt aerosolsource. The mineral dust flux records at both sites show a strong coherency over the last 150 kyr related to dust emission changes inthe glacial Patagonian dust source with three times higher dust fluxes in the Atlantic compared to the Indian Ocean sector of theSouthern Ocean (SO). Using a simple conceptual transport model this indicates that transport can explain only 40% of theatmospheric dust concentration changes in Antarctica, while factor 5–10 changes occurred. Accordingly, the main cause for the strong glacial dust flux changes in Antarctica must lie in environmental changes in Patagonia. Dust emissions, hence environmentalconditions in Patagonia, were very similar during the last two glacials and interglacials, respectively, despite 2–4 °C warmertemperatures recorded in Antarctica during the penultimate interglacial than today. 2–3 times higher sea salt fluxes found in bothice cores in the glacial compared to the Holocene are difficult to reconcile with a largely unchanged transport intensity and thedistant open ocean source. The substantial glacial enhancements in sea salt aerosol fluxes can be readily explained assuming sea iceformation as the main sea salt aerosol source with a significantly larger expansion of (summer) sea ice in the Weddell Sea than inthe Indian Ocean sector. During the penultimate interglacial, our sea salt records point to a 50% reduction of winter sea icecoverage compared to the Holocene both in the Indian and Atlantic Ocean sector of the SO. However, from 20 to 80 ka beforepresent sea salt fluxes show only very subdued millennial changes despite pronounced temperature fluctuations, likely due to thelarge distance of the sea ice salt source to our drill sites.
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| 4. |
- Ruth, Urs, et al.
(författare)
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Ice core evidence for a very tight link between North Atlantic and east Asian glacial climate
- 2007
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Ingår i: GEOPHYSICAL RESEARCH LETTERS. ; 34:L03706
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Tidskriftsartikel (refereegranskat)abstract
- Corresponding millennial-scale climate changes havebeen reported from the North Atlantic region and from eastAsia for the last glacial period on independent timescalesonly. To assess their degree of synchrony we suggestinterpreting Greenland ice core dust parameters as proxiesfor the east Asian monsoon systems. This allows comparingNorth Atlantic and east Asian climate on the same timescalein high resolution ice core data without relative datinguncertainties. We find that during Dansgaard-Oeschgerevents North Atlantic region temperature and east Asianstorminess were tightly coupled and changed synchronouslywithin 5–10 years with no systematic lead or lag, thusproviding instantaneous climatic feedback. The tight linkbetween North Atlantic and east Asian glacial climate couldhave amplified changes in the northern polar cell to largerscales. We further find evidence for an early onset of aYounger Dryas-like event in continental Asia, which givesevidence for heterogeneous climate change within east Asiaduring the last deglaciation.
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| 5. |
- Steffensen, Jörgen Peder, et al.
(författare)
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High-Resolution Greenland Ice Core Data Show Abrupt Climate Change Happens in Few Years
- 2008
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 321, s. 680-684
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Tidskriftsartikel (refereegranskat)abstract
- The last two abrupt warmings at the onset of our present warm interglacial period, interrupted bythe Younger Dryas cooling event, were investigated at high temporal resolution from the NorthGreenland Ice Core Project ice core. The deuterium excess, a proxy of Greenland precipitationmoisture source, switched mode within 1 to 3 years over these transitions and initiated a moregradual change (over 50 years) of the Greenland air temperature, as recorded by stable waterisotopes. The onsets of both abrupt Greenland warmings were slightly preceded by decreasingGreenland dust deposition, reflecting the wetting of Asian deserts. A northern shift of theIntertropical Convergence Zone could be the trigger of these abrupt shifts of Northern Hemisphereatmospheric circulation, resulting in changes of 2 to 4 kelvin in Greenland moisture sourcetemperature from one year to the next.
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