| 1. |
- Dahl-Jensen, D., et al.
(författare)
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Eemian interglacial reconstructed from a Greenland folded ice core
- 2013
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 493:7433, s. 489-494
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Tidskriftsartikel (refereegranskat)abstract
- Efforts to extract a Greenland ice core with a complete record of the Eemian interglacial (130,000 to 115,000 years ago) have until now been unsuccessful. The response of the Greenland ice sheet to the warmer-than-present climate of the Eemian has thus remained unclear. Here we present the new North Greenland Eemian Ice Drilling ('NEEM') ice core and show only a modest ice-sheet response to the strong warming in the early Eemian. We reconstructed the Eemian record from folded ice using globally homogeneous parameters known from dated Greenland and Antarctic ice-core records. On the basis of water stable isotopes, NEEM surface temperatures after the onset of the Eemian (126,000 years ago) peaked at 8 +/- 4 degrees Celsius above the mean of the past millennium, followed by a gradual cooling that was probably driven by the decreasing summer insolation. Between 128,000 and 122,000 years ago, the thickness of the northwest Greenland ice sheet decreased by 400 +/- 250 metres, reaching surface elevations 122,000 years ago of 130 +/- 300 metres lower than the present. Extensive surface melt occurred at the NEEM site during the Eemian, a phenomenon witnessed when melt layers formed again at NEEM during the exceptional heat of July 2012. With additional warming, surface melt might become more common in the future.
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| 2. |
- Jevrejeva, S., et al.
(författare)
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Trends and acceleration in global and regional sea levels since 1807
- 2014
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 113, s. 11-22
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Tidskriftsartikel (refereegranskat)abstract
- We use 1277 tide gauge records since 1807 to provide an improved global sea level reconstruction and analyse the evolution of sea level trend and acceleration. In particular we use new data from the polar regions and remote islands to improve data coverage and extend the reconstruction to 2009. There is a good agreement between the rate of sea level rise (3.2 +/- 0.4 mm.yr(-1)) calculated from satellite altimetry and the rate of 3.1 +/- 0.6 mm.yr(-1) from tide gauge based reconstruction for the overlapping time period (1993-2009). The new reconstruction suggests a linear trend of 1.9 +/- 0.3 mm.yr(-1) during the 20th century, with 1.8 +/- 0.5 mm.yr(-1) since 1970. Regional linear trends for 14 ocean basins since 1970 show the fastest sea level rise for the Antarctica (4.1 +/- 0.8 mm.yr(-1)) and Arctic (3.6 +/- 0.3 mm.yr(-1)). Choice of CIA correction is critical in the trends for the local and regional sea levels, introducing up to 8 mm.yr(-1) uncertainties for individual tide gauge records, up to 2 mm.yr(-1) for regional curves and up to 03-0.6 mm.yr(-1) in global sea level reconstruction. We calculate an acceleration of 0.02 +/- 0.01 mm.yr(-2) in global sea level (1807-2009). In comparison the steric component of sea level shows an acceleration of 0.006 mm.yr(-2) and mass loss of glaciers accelerates at 0.003 mm.yr(-2) over 200 year long time series.
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| 3. |
- Jevrejeva, S, et al.
(författare)
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Potential for bias in 21st century semiempirical sea level projections
- 2012
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 117, s. D20116-
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Tidskriftsartikel (refereegranskat)abstract
- We examine the limitations of a semiempirical model characterized by a sea level projection of 73 cm with RCP4.5 scenario by 2100. Calibrating the model with data to 1990 and then simulating the period 1993–2009 produces sea level in close agreement with acceleration in sea level rise observed by satellite altimetry. Nonradiative forcing contributors, such as long-term adjustment of Greenland and Antarctica ice sheets since Last Glacial Maximum, abyssal ocean warming, and terrestrial water storage, may bias model calibration which, if corrected for, tend to reduce median sea level projections at 2100 by 2–10 cm, though this is within the confidence interval. We apply the semiempirical approach to simulate individual contributions from thermal expansion and small glacier melting. Steric sea level projections agree within 3 cm of output from process-based climate models. In contrast, semiempirical simulation of melting from glaciers is 26 cm, which is twice large as estimates from some process-based models; however, all process models lack simulation of calving, which likely accounts for 50% of small glacier mass loss worldwide. Furthermore, we suggest that changes in surface mass balance and dynamics of Greenland ice sheet made contributions to the sea level rise in the early 20th century and therefore are included within the semiempirical model calibration period and hence are included in semiempirical sea level projections by 2100. Antarctic response is probably absent from semiempirical models, which will lead to a underestimate in sea level rise if, as is probable, Antarctica loses mass by 2100.
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| 4. |
- Jevrejeva, S., et al.
(författare)
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Sea level projections to AD2500 with a new generation of climate change scenarios
- 2012
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 80-81, s. 14-20
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Tidskriftsartikel (refereegranskat)abstract
- Sea level rise over the coming centuries is perhaps the most damaging side of rising temperature (Anthoff et al., 2009). The economic costs and social consequences of coastal flooding and forced migration will probably be one of the dominant impacts of global warming (Sugiyama et al., 2008). To date, however, few studies (Nicholls et al., 2008; Anthoff et al., 2009) on infrastructure and socio-economic planning include provision for multi-century and multi-metre rises in mean sea level. Here we use a physically plausible sea level model constrained by observations, and forced with four new Representative Concentration Pathways (RCP) radiative forcing scenarios (Moss et al., 2010) to project median sea level rises of 0.57 for the lowest forcing and 1.10 m for the highest forcing by 2100 which rise to 1.84 and 5.49 m respectively by 2500. Sea level will continue to rise for several centuries even after stabilisation of radiative forcing with most of the rise after 2100 due to the long response time of sea level. The rate of sea level rise would be positive for centuries, requiring 200-400 years to drop to the 1.8 mm/yr 20th century average, except for the RCP3PD which would rely on geoengineering.
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| 5. |
- Moore, John C, et al.
(författare)
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The historical global sea level budget
- 2011
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Ingår i: Annals of Glaciology. - 0260-3055 .- 1727-5644. ; 52:59, s. 8-14
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the global sea-level budget since 1850. Good estimates of sea-level contributions from glaciers and small ice caps, the Greenland ice sheet and thermosteric sea level are available over this period, though considerable scope for controversy remains in all. Attempting to close the sea-level budget by adding the components results in a residual displaying a likely significant trend of 0.37 mm a-1 from 1955 to 2005, which can, however, be reasonably closed using estimated melting from unsurveyed high-latitude small glaciers and ice caps. The sea-level budget from 1850 is estimated using modeled thermosteric sea level and inferences from a small number of mountain glaciers. This longer-term budget has a residual component that displays a rising trend likely associated with the end of the Little Ice Age, with much decadal-scale variability that is probably associated with variability in the global water cycle, ENSO and long-term volcanic impacts.
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