| |
Records |
Links |
|
Author |
|
|
| |
Title |
Enhancement factors for grounded ice and ice shelves inferred from an anisotropic ice-flow model
|
Type |
Journal Article |
| |
Year |
2010 |
Publication |
Journal Of Glaciology |
Abbreviated Journal |
|
|
| |
Volume |
56 |
Issue |
199 |
Pages |
805 -812 |
|
| |
Keywords |
glaciology, |
|
| |
Abstract |
Polar ice is known to be one of the most anisotropic natural materials. For a given fabric the polycrystal viscous response is strongly dependent on the actual state of stress and strain rate. Within an ice sheet, grounded-ice parts and ice shelves have completely different stress regimes, so one should expect completely different impacts of ice anisotropy on the flow. The aim of this work is to quantify, through the concept of enhancement factors, the influence of ice anisotropy on the flow of grounded ice and ice shelves. For this purpose, a full-Stokes anisotropic marine ice-sheet flowline model is used to compare isotropic and anisotropic diagnostic velocity fields on a fixed geometry. From these full-Stokes results, we propose a definition of enhancement factors for grounded ice and ice shelves, coherent with the asymptotic models used for these regions. We then estimate realistic values for the enhancement factors induced by ice anisotropy for grounded ice and ice shelves.
|
|
| |
Programme  |
458 |
|
| |
Campaign |
|
|
| |
Address |
|
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
International Glaciological Society |
Place of Publication |
|
Editor |
|
|
| |
Language |
|
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
0022-1430 |
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
|
|
| |
Notes |
|
Approved |
yes |
|
| |
Call Number |
|
Serial |
2460 |
|
| Permanent link to this record |
| |
|
| |
|
Author |
Steen-Larsen H C, Masson-Delmotte V, Sjolte J, Johnsen S J, Vinther B M, Bron F-M, Clausen H B, Dahl-Jensen D, Falourd S, Fettweis X, Galle H, Jouzel J, Kageyama M, Lerche H, Minster B, Picard G, Punge H J, Risi C, Salas D, Schwander J, Steffen K, Sveinbjrnsdttir A E, Svensson A, White J, |
|
| |
Title |
Understanding the climatic signal in the water stable isotope records from the NEEM shallow firn/ice cores in northwest Greenland
|
Type |
Journal Article |
| |
Year |
2011 |
Publication |
J. Geophys. Res. |
Abbreviated Journal |
J. Geol. |
|
| |
Volume |
116 |
Issue |
D6 |
Pages |
D06108 - |
|
| |
Keywords |
NEEM, ice cores, Greenland, 3305 Atmospheric Processes: Climate change and variability, 0724 Cryosphere: Ice cores, 3307 Atmospheric Processes: Boundary layer processes, 1863 Hydrology: Snow and ice, 3344 Atmospheric Processes: Paleoclimatology, |
|
| |
Abstract |
Samples of precipitation and atmospheric water vapor were collected together with shallow firn/ice cores as part of the new deep drilling project in northwest Greenland: the NEEM project. These samples were analyzed for their isotope composition to understand the processes affecting the climatic signal archived in the water stable isotope records from the NEEM deep ice core. The dominant moisture source for the snow deposited at the NEEM-site may be originating as far south as 35N from the western part of the Atlantic Ocean. The surface atmospheric water vapor appears in isotopic equilibrium with the snow surface indicating a large water exchange between the atmosphere and snowpack. The interannual variability of NEEM shallow firn/ice cores stable isotope data covering the last ~40 years shows an unexpectedly weak NAO signal. Regional to global atmospheric models simulate a dominant summer precipitation in the NEEM area, suggesting that the intermittency of modern winter precipitation is responsible for the lack of a strong NAO imprint. The interannual variability of NEEM isotope data however shows a strong correlation with interannual variations of Baffin Bay sea ice cover, a relationship consistent with air mass trajectories. NEEM deep ice core isotopic records may therefore provide detailed information on past Baffin Bay sea ice extent. NEEM stable water isotope content increasing trend points to a local warming trend of ~3.0C over the last 40 years.
|
|
| |
Programme |
458 |
|
| |
Campaign |
|
|
| |
Address |
|
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
AGU |
Place of Publication |
|
Editor |
|
|
| |
Language |
|
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
0148-0227 |
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
|
|
| |
Notes |
|
Approved |
yes |
|
| |
Call Number |
|
Serial |
2496 |
|
| Permanent link to this record |
| |
|
| |
|
Author |
Capron E, Landais A, Chappellaz J, Schilt A, Buiron D, Dahl-Jensen D, Johnsen S J, Jouzel J, Lemieux-Dudon B, Loulergue L, Leuenberger M, Masson-Delmotte V, Meyer H, Oerter H, Stenni B, |
|
| |
Title |
Millennial and sub-millennial scale climatic variations recorded in polar ice cores over the last glacial period
|
Type |
Journal Article |
| |
Year |
2010 |
Publication |
Clim. Past |
Abbreviated Journal |
|
|
| |
Volume |
6 |
Issue |
3 |
Pages |
345 -365 |
|
| |
Keywords |
|
|
| |
Abstract |
Since its discovery in Greenland ice cores, the millennial scale climatic variability of the last glacial period has been increasingly documented at all latitudes with studies focusing mainly on Marine Isotopic Stage 3 (MIS 3; 28-60 thousand of years before present, hereafter ka) and characterized by short Dansgaard-Oeschger (DO) events. Recent and new results obtained on the EPICA and NorthGRIP ice cores now precisely describe the rapid variations of Antarctic and Greenland temperature during MIS 5 (73.5-123 ka), a time period corresponding to relatively high sea level. The results display a succession of abrupt events associated with long Greenland InterStadial phases (GIS) enabling us to highlight a sub-millennial scale climatic variability depicted by (i) short-lived and abrupt warming events preceding some GIS (precursor-type events) and (ii) abrupt warming events at the end of some GIS (rebound-type events). The occurrence of these sub-millennial scale events is suggested to be driven by the insolation at high northern latitudes together with the internal forcing of ice sheets. Thanks to a recent NorthGRIP-EPICA Dronning Maud Land (EDML) common timescale over MIS 5, the bipolar sequence of climatic events can be established at millennial to sub-millennial timescale. This shows that for extraordinary long stadial durations the accompanying Antarctic warming amplitude cannot be described by a simple linear relationship between the two as expected from the bipolar seesaw concept. We also show that when ice sheets are extensive, Antarctica does not necessarily warm during the whole GS as the thermal bipolar seesaw model would predict, questioning the Greenland ice core temperature records as a proxy for AMOC changes throughout the glacial period. |
|
| |
Programme |
458 |
|
| |
Campaign |
|
|
| |
Address |
|
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
Copernicus Publications |
Place of Publication |
|
Editor |
|
|
| |
Language |
|
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
1814-9332 |
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
|
|
| |
Notes |
|
Approved |
yes |
|
| |
Call Number |
|
Serial |
2702 |
|
| Permanent link to this record |
| |
|
| |
|
Author |
Dreyfus Gabrielle B, Jouzel Jean, Bender Michael L, Landais Amalle, Masson-Delmotte Valrie, Leuenberger Markus, |
|
| |
Title |
Firn processes and δ15N: potential for a gas-phase climate proxy
|
Type |
Journal Article |
| |
Year |
2010 |
Publication |
Quaternary Science Reviews |
Abbreviated Journal |
Quat Sci Rev |
|
| |
Volume |
29 |
Issue |
1-2 |
Pages |
28 -42 |
|
| |
Keywords |
|
|
| |
Abstract |
|
|
| |
Programme |
458 |
|
| |
Campaign |
|
|
| |
Address |
|
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
|
Place of Publication |
|
Editor |
|
|
| |
Language |
|
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
0277-3791 |
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
|
|
| |
Notes |
|
Approved |
yes |
|
| |
Call Number |
|
Serial |
2703 |
|
| Permanent link to this record |
| |
|
| |
|
Author |
|
|
| |
Title |
Accelerating growth of HFC-227ea (1,1,1,2,3,3,3-heptafluoropropane) in the atmosphere
|
Type |
Journal Article |
| |
Year |
2010 |
Publication |
Atmos. Chem. Phys. |
Abbreviated Journal |
|
|
| |
Volume |
10 |
Issue |
13 |
Pages |
5903 -5910 |
|
| |
Keywords |
|
|
| |
Abstract |
We report the first measurements of 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), a substitute for ozone depleting compounds, in air samples originating from remote regions of the atmosphere and present evidence for its accelerating growth. Observed mixing ratios ranged from below 0.01 ppt in deep firn air to 0.59 ppt in the current northern mid-latitudinal upper troposphere. Firn air samples collected in Greenland were used to reconstruct a history of atmospheric abundance. Year-on-year increases were deduced, with acceleration in the growth rate from 0.029 ppt per year in 2000 to 0.056 ppt per year in 2007. Upper tropospheric air samples provide evidence for a continuing growth until late 2009. Furthermore we calculated a stratospheric lifetime of 370 years from measurements of air samples collected on board high altitude aircraft and balloons. Emission estimates were determined from the reconstructed atmospheric trend and suggest that current “bottom-up” estimates of global emissions for 2005 are too high by a factor of three.
|
|
| |
Programme |
458 |
|
| |
Campaign |
|
|
| |
Address |
|
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
Copernicus Publications |
Place of Publication |
|
Editor |
|
|
| |
Language |
|
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
1680-7324 |
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
|
|
| |
Notes |
|
Approved |
yes |
|
| |
Call Number |
|
Serial |
2709 |
|
| Permanent link to this record |
| |
|
| |
|
Author |
|
|
| |
Title |
What caused Earth's temperature variations during the last 800,000 years? Data-based evidence on radiative forcing and constraints on climate sensitivity
|
Type |
Journal Article |
| |
Year |
2010 |
Publication |
Quaternary Science Reviews |
Abbreviated Journal |
Quat Sci Rev |
|
| |
Volume |
29 |
Issue |
1-2 |
Pages |
129 -145 |
|
| |
Keywords |
|
|
| |
Abstract |
The temperature on Earth varied largely in the Pleistocene from cold glacials to interglacials of different warmths. To contribute to an understanding of the underlying causes of these changes we compile various environmental records (and model-based interpretations of some of them) in order to calculate the direct effect of various processes on Earth's radiative budget and, thus, on global annual mean surface temperature over the last 800,000 years. The importance of orbital variations, of the greenhouse gases CO 2 , CH 4 and N 2 O, of the albedo of land ice sheets, annual mean snow cover, sea ice area and vegetation, and of the radiative perturbation of mineral dust in the atmosphere are investigated. Altogether we can explain with these processes a global cooling of 3.90.8K in the equilibrium temperature for the Last Glacial Maximum (LGM) directly from the radiative budget using only the Planck feedback that parameterises the direct effect on the radiative balance, but neglecting other feedbacks such as water vapour, cloud cover, and lapse rate. The unaccounted feedbacks and related uncertainties would, if taken at present day feedback strengths, decrease the global temperature at the LGM by 8.01.6K. Increased Antarctic temperatures during the Marine Isotope Stages 5.5, 7.5, 9.3 and 11.3 are in our conceptual approach difficult to explain. If compared with other studies, such as PMIP2, this gives supporting evidence that the feedbacks themselves are not constant, but depend in their strength on the mean climate state. The best estimate and uncertainty for our reconstructed radiative forcing and LGM cooling support a present day equilibrium climate sensitivity (excluding the ice sheet and vegetation components) between 1.4 and 5.2K, with a most likely value near 2.4K, somewhat smaller than other methods but consistent with the consensus range of 24.5K derived from other lines of evidence. Climate sensitivities above 6K are difficult to reconcile with Last Glacial Maximum reconstructions.
|
|
| |
Programme |
458 |
|
| |
Campaign |
|
|
| |
Address |
|
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
Elsevier |
Place of Publication |
|
Editor |
|
|
| |
Language |
|
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
0277-3791 |
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
|
|
| |
Notes |
|
Approved |
yes |
|
| |
Call Number |
|
Serial |
2712 |
|
| Permanent link to this record |
| |
|
| |
|
Author |
Landais A, Dreyfus G, Capron E, Masson-Delmotte V, Sanchez-Goi MF, Desprat S, Hoffmann G, Jouzel J, Leuenberger M, Johnsen S, |
|
| |
Title |
What drives the millennial and orbital variations of δ18Oatm?
|
Type |
Journal Article |
| |
Year |
2010 |
Publication |
Quaternary Science Reviews |
Abbreviated Journal |
Quat Sci Rev |
|
| |
Volume |
29 |
Issue |
1-2 |
Pages |
235 -246 |
|
| |
Keywords |
|
|
| |
Abstract |
The isotopic composition of atmospheric oxygen (δ18Oatm) is a complex marker that integrates changes in global sea-level, water cycle, and biosphere productivity. A strong signature of orbital precession has been identified leading to the use of low-resolution measurements of δ18Oatm to date ice core records. However, the drivers of these δ18Oatm variations are still poorly known. Here, we combine records of millennial and orbital scale variations on the NorthGRIP, Vostok, and EPICA Dome C (EDC) ice cores to explore the origin of δ18Oatm variations. We show that, superimposed on the dominant precession signal, millennial δ18Oatm variations record systematic decreases during warm phases of the Dansgaard-Oeschger events and systematic increases during the cold phases.
|
|
| |
Programme |
458 |
|
| |
Campaign |
|
|
| |
Address |
|
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
|
Place of Publication |
|
Editor |
|
|
| |
Language |
|
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
0277-3791 |
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
|
|
| |
Notes |
|
Approved |
yes |
|
| |
Call Number |
|
Serial |
2713 |
|
| Permanent link to this record |
| |
|
| |
|
Author |
Lourantou A, Chappellaz J, Barnola J-M, Masson-Delmotte V, Raynaud D, |
|
| |
Title |
Changes in atmospheric CO2 and its carbon isotopic ratio during the penultimate deglaciation
|
Type |
Journal Article |
| |
Year |
2010 |
Publication |
Quaternary Science Reviews |
Abbreviated Journal |
Quat Sci Rev |
|
| |
Volume |
29 |
Issue |
17-18 |
Pages |
1983 -1992 |
|
| |
Keywords |
|
|
| |
Abstract |
|
|
| |
Programme |
458 |
|
| |
Campaign |
|
|
| |
Address |
|
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
|
Place of Publication |
|
Editor |
|
|
| |
Language |
|
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
0277-3791 |
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
|
|
| |
Notes |
|
Approved |
yes |
|
| |
Call Number |
|
Serial |
2715 |
|
| Permanent link to this record |
| |
|
| |
|
Author |
|
|
| |
Title |
Abrupt change of Antarctic moisture origin at the end of Termination II
|
Type |
Journal Article |
| |
Year |
2010 |
Publication |
Proceedings of the National Academy of Sciences |
Abbreviated Journal |
Proc. Natl. Acad. Sci. U.S.A. |
|
| |
Volume |
107 |
Issue |
27 |
Pages |
12091 -12094 |
|
| |
Keywords |
|
|
| |
Abstract |
|
|
| |
Programme |
458 |
|
| |
Campaign |
|
|
| |
Address |
|
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
|
Place of Publication |
|
Editor |
|
|
| |
Language |
|
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
0027-8424 |
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
|
|
| |
Notes |
|
Approved |
yes |
|
| |
Call Number |
|
Serial |
2716 |
|
| Permanent link to this record |
| |
|
| |
|
Author |
Pol K, Masson-Delmotte V, Johnsen S, Bigler M, Cattani O, Durand G, Falourd S, Jouzel J, Minster B, Parrenin F, Ritz C, Steen-Larsen HC, Stenni B, |
|
| |
Title |
New MIS 19 EPICA Dome C high resolution deuterium data: Hints for a problematic preservation of climate variability at sub-millennial scale in the “oldest ice”
|
Type |
Journal Article |
| |
Year |
2010 |
Publication |
Earth and Planetary Science Letters |
Abbreviated Journal |
Earth Planet. Sci. Lett. |
|
| |
Volume |
298 |
Issue |
1-2 |
Pages |
95 -103 |
|
| |
Keywords |
water stable isotopes, ice cores, Antarctica, isotopic diffusion, |
|
| |
Abstract |
|
|
| |
Programme |
458 |
|
| |
Campaign |
|
|
| |
Address |
|
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
|
Place of Publication |
|
Editor |
|
|
| |
Language |
|
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
0012-821X |
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
|
|
| |
Notes |
|
Approved |
yes |
|
| |
Call Number |
|
Serial |
2717 |
|
| Permanent link to this record |
