ice
140576367
Oxygen isotope and palaeotemperature records from six Greenland ice core stations: Camp Century
Oxygen isotope variations spanning the last glacial cycle and the Holocene derived from ice core records for six sites in Greenland (Camp Century, Dye 3, GRIP, GISP2, Renland and NorthGRIP) show strong similarities. This suggests that the dominant influence on oxygen isotope variations reflected in the ice sheet records was regional climatic change. Differences in detail between the records probably reflect the effects of basal deformation in the ice as well as geographical gradients in atmospheric isotope ratios. Palaeotemperature estimates have been obtained from the records using three approaches: (i) inferences based on the measured relationship between mean annual d18O of snow and of mean annual surface temperature over Greenland; (ii) modelled inversion of the borehole temperature profile constrained either by the dated isotopic profile, or (iii) by using Monte Carlo simulation techniques. The third of these approaches was adopted to reconstruct Holocene temperature variations for the Dye 3 and GRIP temperature profiles, which yields remarkably compatible results. A new record of Holocene isotope variations obtained from the NorthGRIP ice core matches the GRIP short term isotope record, and also shows similar long term trends to the Dye 3 and GRIP inverted temperature data. The NorthGRIP isotope record reflects: (i) a generally stronger isotopic signal than is found in the GRIP record; (ii) several short lived temperature fluctuations during the first 1500 yr of the Holocene; (iii) a marked cold event at ca. 8.2 ka (the '8.2 ka event' (iv) optimum temperatures for the Holocene between ca. 8.6 and 4.3 ka, a signal that is 0.6%0 stronger than for the GRIP profile; (v) a clear signal for the Little Ice Age; and (vi) a clear signal of climate warming during the last century. These data suggest that the NorthGRIP stable isotope record responded in a sensitive manner to temperature fluctuations during the Holocene. Copyright (c) 2001 John Wiley Sons, Ltd.
Sigfus J Johnsen Dorthe Dahl-Jensen Neils Gundestrup P Steffesen Henrik Brink Clausen Heinz Miller Valerie Masson-Delmotte Sveinbj Ornsdottir James W C White
12509870
Suppression of ICE and apoptosis in mammary epithelial cells by extracellular matrix
Apoptosis (programmed cell death) plays a major role in development and tissue regeneration. Basement membrane extracellular matrix (ECM) but not fibronectin or collagen, was shown to suppress apoptosis of mammary epithelial cells in tissue culture and in vivo. Apoptosis was induced by antibodies to beta 1 integrins or by overexpression of stromelysin 1, which degrades ECM. Expression of interleukin 1 beta converting enzyme (ICE) correlated with the loss of ECM, and inhibitors of ICE activity prevented apoptosis. These results suggest that ECM regulates apoptosis in mammary epithelial cells through an integrin dependent negative regulation of ICE expression.
Science
Nancy J Boudreau C J Sympson Zena Werb MJ Bissell
14989933
September sea ice cover in the Arctic Ocean projected to vanish by 2100
Arctic sea ice cover is changing rapidly. An analysis of 18 state of the art climate models and observed trends in Arctic sea ice cover over the past three decades indicates that under a scenario of medium future greenhouse gas emissions, the Arctic Ocean will probably be ice free in September before the end of the twenty first century. The Arctic climate is changing rapidly1. From 1979 to 2006, September sea ice extent decreased by almost 25% or about 100,000 km2 per year (ref. 2) In September 2007, Arctic sea ice extent reached its lowest level since satellite observations began3 and in September 2008, sea ice cover was still low. This development has raised concerns that the Arctic Ocean could be ice free in late summer in only a few decades, with important economic and geopolitical implications. Unfortunately, most current climate models underestimate significantly the observed trend in Arctic sea ice decline4, leading to doubts regarding their projections for the timing of ice free conditions. Here we analyse the simulated trends in past sea ice cover in 18 state of art climate models and find a direct relationship between the simulated evolution of September sea ice cover over the twenty first century and the magnitude of past trends in sea ice cover. Using this relationship together with observed trends, we project the evolution of September sea ice cover over the twenty first century. We find that under a scenario with medium future greenhouse gas emissions, the Arctic Ocean will probably be ice free in September before the end of the twenty first century.
Julien Boe Alex Hall Xin Qu
37999241
Historical trends in lake and river ice cover in the northern hemisphere
Freeze and breakup dates of ice on lakes and rivers provide consistent evidence of later freezing and earlier breakup around the Northern Hemisphere from 1846 to 1995. Over these 150 years, changes in freeze dates averaged 5.8 days per 100 years later, and changes in breakup dates averaged 6.5 days per 100 years earlier; these translate to increasing air temperatures of about 1.2 degrees C per 100 years. Interannual variability in both freeze and breakup dates has increased since 1950. A few longer time series reveal reduced ice cover (a warming trend) beginning as early as the 16th century, with increasing rates of change after about 1850.
Science
16601857
Is the Dipole Anomaly a major driver to record lows in Arctic summer sea ice extent
Recent record lows of Arctic summer sea ice extentare found to be triggered by the Arctic atmospheric DipoleAnomaly (DA) pattern. This local, second leading mode ofsea level pressure (SLP) anomaly in the Arctic produced astrong meridional wind anomaly that drove more sea ice outof the Arctic Ocean from the western to the eastern Arcticinto the northern Atlantic during the summers of 1995,1999, 2002, 2005, and 2007. In the 2007 summer, the DAalso enhanced anomalous oceanic heat flux into the ArcticOceanviaBeringStrait,whichacceleratedbottomandlateralmelting of sea ice and amplified the ice albedo feedback. Acoupled ice ocean model was used to confirm the historicalrecord lows of summer sea ice extent.
Jia Wang Jinlun Zhang Eiji Watanabe Motoyoshi Ikeda Kohei Mizobata John E Walsh Xuezhi Bai Bingyi Wu
24567805
How wetting hysteresis influences ice adhesion strength on superhydrophobic surfaces.
In this work, we measured the adhesion strength of artificially created glaze ice (similar to accreted in nature) on rough fluoropolymer based hydrophobic surfaces with different contact angle (CA) and wetting hysteresis. The previously reported direct correlation between ice repellency and CA on superhydrophobic surfaces is shown to be only valid for surfaces with low wetting hysteresis. Another correlation was found between wetting hysteresis and ice adhesion strength on rough surfaces with similar chemistry.
Langmuir the ACS journal of surfaces and colloids
Sergei A Kulinich Masoud Farzaneh
135623231
Ice adhesion on super hydrophobic surfaces
Abstract In this study, ice adhesion strength on flat hydrophobic and rough super hydrophobic coatings with similar surface chemistry (based on same fluoropolymer) is compared. Glaze ice, similar to naturally accreted, was prepared on the surfaces by spraying super cooled water microdroplets at subzero temperature. Ice adhesion was evaluated by spinning the samples at constantly increasing speed until ice delamination occurred. Super hydrophobic surfaces with different contact angle hysteresis were tested, clearly showing that the latter, along with the contact angle, also influences the ice solid adhesion strength.
Sergei A Kulinich Masoud Farzaneh
128578344
Sea ice algae: Major contributors to primary production and algal biomass in the Chukchi and Beaufort Seas during May/June 2002
Abstract Sea ice and water samples were collected at 14 stations on the shelves and slope regions of the Chukchi and Beaufort Seas during the spring 2002 expedition as part of the Shelf Basin Interaction Studies. Algal pigment content, particulate organic carbon and nitrogen, and primary productivity were estimated for both habitats based on ice cores, brine collection and water samples from 5 m depth. The pigment content (0.2 304.3 mg pigments m 2 and primary productivity (0.1 23.0 mg C m 3 h 1 of the sea ice algae significantly exceeded water column parameters (0.2 and 1.0 mg pigments m 3 3 h 1 making sea ice the habitat with the highest food availability for herbivores in early spring in the Chukchi and Beaufort Seas. Stable isotope signatures for ice and water samples did not differ significantly for d 15 N, but for d 13 C (ice: 25.1%0 to 14.2%0; water: 26.1%0 to 22.4%0) The analysis of nutrient concentrations and the pulse amplitude modulated fluorescence signal of ice algae and phytoplankton indicate that nutrients were the prime limiting factor for sea ice algal productivity. The estimated spring primary production of about 1 2 g C m 2 of sea ice algae on the shelves requires the use of substantial nutrient reservoirs from the water column.
Rolf Gradinger
9499453
Little Ice Age
The term Little Ice Age was originally coined by F Matthesin 1939 to describe the most recent 4000 year climaticinterval (the Late Holocene) associated with a particularlydramatic series of mountain glacier advances and retreats,analogous to, though considerably more moderate than, thePleistocene glacial fluctuations. This relatively prolongedperiod has now become known as the Neoglacial period.The term Little Ice Age is, instead, reserved for the mostextensive recent period of mountain glacier expansion and isconventionally defined as the 16th mid 19th century periodduring which European climate was most strongly impacted.This period begins with a trend towards enhanced glacialconditions in Europe following the warmer conditions ofthe so called medieval warm period or medieval climaticoptimum of Europe
Michael Everett Mann
128992565
Formation of mega scale glacial lineations observed beneath a West Antarctic ice stream
Most discharge from large ice sheets takes place through fast flowing ice streams and their speed is strongly modulated by interactions between the ice and the underlying sediments. Seismic surveys and investigations through boreholes have revealed a spatial association between fast ice flow and saturated deformable sediments. Nevertheless, our knowledge of the morphology of the interface between ice and sediments is still limited, resulting in only rudimentary understanding of the basal boundary conditions beneath ice streams and the generation of subglacial bedforms. Here we present radar data from the bed of a West Antarctic ice stream that reveal the presence of mega scale glacial lineations. We combine these data with previously published seismic data and show that these lineations develop in areas of dilatant deforming till and are part of a dynamic sedimentary system that undergoes significant change by erosion and deposition on decadal timescales. We find that the mega scale glacial lineations are indistinguishable from those found on beds of palaeo ice streams, providing conclusive evidence for the hypothesis that highly elongate bedforms are a characteristic of fast flow regions in ice sheets.
Edward Charles King Richard C A Hindmarsh Chris R Stokes