Science Journal:
A Greener Greenland:
Natural Variability of Greenland Climate, Vegetation, and Ice Volume During the Past Million Years
Anne de Vernal* and Claude Hillaire-Marcel
The response of the Greenland ice sheet to global warming is a source of concern notably because of its potential contribution to changes in the sea level. We demonstrated the natural vulnerability of the ice sheet by using pollen records from marine sediment off southwest Greenland that indicate important changes of the vegetation in Greenland over the past million years. The vegetation that developed over southern Greenland during the last interglacial period is consistent with model experiments, suggesting a reduced volume of the Greenland ice sheet. Abundant spruce pollen indicates that boreal coniferous forest developed some 400,000 years ago during the “warm” interval of marine isotope stage 11, providing a time frame for the development and decline of boreal ecosystems over a nearly ice-free Greenland.
Eric J. Steig and Alexander P. Wolfe
Pollen data suggest that the Greenland ice sheet was much smaller during previous warm periods.
Changes in Altitude
Elevation Changes in Antarctica Mainly Determined by Accumulation Variability
Michiel M. Helsen et al
Antarctic Ice Sheet elevation changes, which are used to estimate changes in the mass of the interior regions, are caused by variations in the depth of the firn layer. We quantified the effects of temperature and accumulation variability on firn layer thickness by simulating the 1980–2004 Antarctic firn depth variability. For most of Antarctica, the magnitudes of firn depth changes were comparable to those of observed ice sheet elevation changes. The current satellite observational period (15 years) is too short to neglect these fluctuations in firn depth when computing recent ice sheet mass changes. The amount of surface lowering in the Amundsen Sea Embayment revealed by satellite radar altimetry (1995–2003) was increased by including firn depth fluctuations, while a large area of the East Antarctic Ice Sheet slowly grew as a result of increased accumulation.
Kurt M. Cuffey
Estimating ice sheet mass changes from elevation surveys requires adjustments for snow density variations at the ice sheet surface.
Nature journal:
Improved estimates of upper-ocean warming and multi-decadal sea-level rise
Catia M. Domingues et al
Changes in the climate system’s energy budget are predominantly revealed in ocean temperatures and the associated thermal expansion contribution to sea-level rise. Climate models, however, do not reproduce the large decadal variability in globally averaged ocean heat content inferred from the sparse observational database even when volcanic and other variable climate forcings are included. The sum of the observed contributions has also not adequately explained the overall multi-decadal rise. Here we report improved estimates of near-global ocean heat content and thermal expansion for the upper 300 m and 700 m of the ocean for 1950–2003, using statistical techniques that allow for sparse data coverage and applying recent corrections to reduce systematic biases in the most common ocean temperature observations. Our ocean warming and thermal expansion trends for 1961–2003 are about 50 per cent larger than earlier estimates but about 40 per cent smaller for 1993–2003, which is consistent with the recognition that previously estimated rates for the 1990s had a positive bias as a result of instrumental errors. On average, the decadal variability of the climate models with volcanic forcing now agrees approximately with the observations, but the modelled multi-decadal trends are smaller than observed. We add our observational estimate of upper-ocean thermal expansion to other contributions to sea-level rise and find that the sum of contributions from 1961 to 2003 is about 1.5 (+/-0.4) mm yr-1, in good agreement with our updated estimate of near-global mean sea-level rise (using techniques established in earlier studies) of 1.6 (+/-0.2) mm yr-1.
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
Paul: Catia M. Domingues et al seem to be on the pace now
If they are saying that the last 50 years has seen a sea level rise of 3 inches and we have been told that we have had an 8 inch rise since 1880, then if anything, the rate of rise is slightly lower but generally the same.
Still coming out of the LIA and waiting for greenhouse?
But at least they are increasing the older and reducing the later data, unlike the great adjuster.
One of the interesting aspects of sea level rises lies in our extraction of groundwater.
If land masses are above sea level due to the presence of water being out gassed underneath from magma, then extracting that water would drop the landsurface, as has been observed and documented by Endersbee.
This extracted primal water is then added to the oceans since it cannot be recycled back to its origin.
So rising sea levels, as observed and modelled, assume falsities, that the earth’s topography is fixed and that the only variables are the water cycle.
If there are rising sea levels, the it is more likely a result of human extraction of primary water, than from temperature rises misattributed to oxidation of hyrocarbons, (unless one suscribes to the thermodynmaically inane idea that radiant solar energy is capable of melting the earth’s core.
The paper
Willis J. K., D. P. Chambers, R. S. Nerem (2008), Assessing the globally averaged sea level budget on seasonal to interannual timescales, J. Geophys. Res., 113, C06015, doi:10.1029/2007JC004517.
has been published [thanks to Richard Hanson for alerting us].
The absract reads
“Analysis of ocean temperature and salinity data from profiling floats along with satellite measurements of sea surface height and the time variable gravity field are used to investigate the causes of global mean sea level rise between mid-2003 and mid-2007. The observed interannual and seasonal fluctuations in sea level can be explained as the sum of a mass component and a steric (or density related) component to within the error bounds of each observing system. During most of 2005, seasonally adjusted sea level was approximately 5 mm higher than in 2004 owing primarily to a sudden increase in ocean mass in late 2004 and early 2005, with a negligible contribution from steric variability. Despite excellent agreement of seasonal and interannual sea level variability, the 4-year trends do not agree, suggesting that systematic long-period errors remain in one or more of these observing systems.”
Climate Science has already weblogged on this important paper: see
Important New Paper In Press by Willis And Colleagues On Sea Level Rise And Ocean Heat Content Changes
A major finding from the Willis et al 2008 paper is
“Despite the short period of the present analysis, these results have important implications for climate. First, from 2004 to the present, steric contributions to sea level rise appear to have been negligible. This is consistent with observations of ocean surface temperature, which show relatively little change in the global average between 2003 and 2006 [Smith and Reynolds, 2005, see NCDC global surface temperature anomalies]. It is in sharp contrast, however, to historical analyses of thermal expansion over the past decade [Willis et al., 2004] and the past half-century [Antonov et al., 2005; Lombard et al., 2005; Ishii et al., 2006]. Although the historical record suggests that multiyear periods of little warming (or even cooling) are not unusual, the present analysis confirms this result with unprecedented accuracy.”
Now that this paper has appeared, the global modellng community is challenged to accurately simulate and explain the absence of significant upper ocean heat changes during this time period. The new (June 19 2008) Nature paper by Domingues et al “Improved estimates of upper-ocean warming and multi-decadal sea-level rise“, unfortunately, chose to end its analysis period five years ago (2003). The Editors should have required that they update their study. The Willis et al paper supercedes their time period of analysis.
http://climatesci.org/2008/06/20/diagnosis-of-global-sea-level-and-upper-ocean-heat-content-on-seasonal-to-interannual-timescales-paper-willis-et-al-2008-published/
Paul, Roger’s right. I indicated in an earlier thread that it was curious that Domingues et al’s analysis ended in 2003, and its even more curious now finding that Willis et al (who I mistakenly referred to as a co-author in the other thread) has also written a paper on sea level rise and heat content changes for the period 2003-7. I’m astonished that a paper whose analysis ends in 2003, eventhough there is data available for analysis to be undertaken to the present as is indicated by Willis et al, was approved for publication in Nature.
Lets hope there is some follow-up on this in the next few months.
spangled drongo; I’ve just looked up your name, and did you know you are related to the Trumpet Manucode, Metallic Starling and the Common Koel; you gotta love this country.
The Domingues paper is a farrago; I’ve never seen a more contradictory abstract; what are these statistical technigues which allow for sparse data coverage? It can’t be a Hurst rescaling? I’m not going to spend a buck to find out; and what “overall multi-decadal rise” are they talking about, since there hasn’t been a multi-decadal rise in temp and sea-level is problematic. So we have a paper substantiating a physical situation which doesn’t exist using estimating technigues that “allow for sparse data coverage”.
Cohenite, no I didn’t but I just spent the day with the relos and it wouldn’t surprise me.
Specially the common koel. We’re all slightly cuckoo.
Looks like Hansen’s gone troppo Guardian Newspaper