the role of ocean thermal expansion in last interglacial sea level rise 1 a compilation of paleoceanographic data and a coupled atmosphere ocean climate model were used to examine global ocean surface temperatures of the last interglacial lig period and to produce the first quantitative estimate of the role that ocean thermal expansion likely played in driving sea level rise above present day during the lig our analysis of the paleoclimatic data suggests a peak lig global sea surface temperature sst warming of 0 7 0 6 c compared to the late holocene our lig climate model simulation suggests a slight cooling of global average sst relative to preindustrial conditions sst 0 4 c with a reduction in atmospheric water vapor in the southern hemisphere driven by a northward shift of the intertropical convergence zone and substantially reduced seasonality in the southern hemisphere taken together the model and paleoceanographic data imply a minimal contribution of ocean thermal expansion to lig sea level rise above present day uncertainty remains but it seems unlikely that thermosteric sea level rise exceeded 0 4 0 3 m during the lig this constraint along with estimates of the sea level contributions from the greenland ice sheet glaciers and ice caps implies that 4 1 to 5 8 m of sea level rise during the last interglacial period was derived from the antarctic ice sheet these results reemphasize the concern that both the antarctic and greenland ice sheets may be more sensitive to temperature than widely thought

larsen ice shelf has progressively thinned the retreat and collapse of antarctic peninsula ice shelves in tandem with a regional atmospheric warming has fueled speculation as to how these events may be related satellite radar altimeter measurements show that between 1992 and 2001 the larsen ice shelf lowered by up to 0 27 0 11 meters per year the lowering is explained by increased summer meltwater and the loss of basal ice through melting enhanced ocean driven melting may provide a simple link between regional climate warming and the successive disintegration of sections of the larsen ice shelf

a warning model based on temporal changes of coda q for volcanic activity at nevado del ruiz volcano colombia the coda q has been calculated for nevado del ruiz volcano colombia nrv from 1985 to 1999 by using a single scattering model during this period the inverse of q q 1 proportional to attenuation exhibited a long term decrease with time as well as shorter term variations related to the volcanic activity q 1 increased prior to volcanic crises and decreased afterward based on these observations a seismic warning criterion has been developed the parameters frequency band size of moving average window and threshold levels necessary to evidence clear and significant short term changes in q 1 have been investigated and appropriated values are proposed we suggest a phenomenological model with three stages for the short term temporal changes in q 1 at nrv firstly q 1 increases before a volcanic crises because of accumulation of gas and or liquid which decreases the aspect ratio of fluid pockets and increases the fractional volume of fluid in the rocks and the pore aspect ratio secondly q 1 starts to decrease during the crises by the discharging of fluids such as gas water etc from the volcano finally q 1 becomes more stable after the crisis at a lower value because of the degassing and or increasing of rigidity of the medium because of the long term crystallization and cooling processes q 1 seems to be a promising monitoring tool at nrv it is possible that the observed temporal changes of q 1 combined with other parameters may help to predict with greater accuracy a volcanic crisis at nrv

ice sheets and sea level in the tandem papers on the stability of the antarctic and greenland ice sheets by j t overpeck b l otto bliesner and co workers paleoclimatic evidence for future ice sheet instability and rapid sea level rise j t overpeck et al reports 24 mar p 1747 simulating arctic

eruption forecasting at kilauea volcano hawaii data from a network of seismometers a tiltmeter and the pattern of summit inflation between eruptions have made qualitative eruption forecasting possible on kilauea volcano for over 20 years this paper formulates quantitative forecasting by calculating the probability of an eruption based on current levels of tilt tilt rate seismicity and fortnightly tide plots of eruption probability as a function of various parameters are derived using a set of 29 eruptions during 1959 1979 the method tests the precursory significance of various parameters over different time scales and determines probabilities by comparing data before eruptions with data values generally tilt level is an eruption precursor significant to better than 99 9 when averaged over any interval from 1 to 20 days tilt rate is a precursor significant to better than 99 999 but noise in the data requires that it be averaged over 30 days or more earthquakes are a short term precursor significant to better than 99 when averaged over 1 10 days for larger earthquakes near the summit caldera and over 5 20 days for very small earthquakes within the caldera the fortnightly modulation of tides influences eruption probability and has a precursory significance of 97 probabilities are independent of the time elapsed since the last eruption the eruption probability when tested against the eruption record from which it was derived is significant to the 99 98 level when compared with random guessing ongoing 1 day 7 day and 30 day forecasts are calculated by computer at the hawaiian volcano observatory and supplement the qualitative interpretation of geophysical data

gravity and tilt earth tides measured on an active volcano mt etna sicily abstract three kinemetrics tiltmeters and an askania tidal gravimeter were installed on mt etna sicily in order to test if previously reported anomalous tides are a permanent feature of the volcano s deformation two of the tiltmeters were installed near the summit of the volcano and the third on its flank the gravimeter recorded tides both on the volcano and 30 km away at catania comparison of the measured m2 tidal amplitudes and phases with values predicted theoretically shows that the gravity tides both on the volcano and at catania are within 4 of the theoretical values m2 tidal tilts are all less than 2 5 times those predicted theoretically these results imply that the anomalous tidal behaviour on mt etna reported previously is possibly a transient phenomenon associated with eruptions rather than a permanent modification of the solid earth tide by the volcanic structure

sea level rise due to polar ice sheet mass loss during past warm periods background although thermal expansion of seawater and melting of mountain glaciers have dominated global mean sea level gmsl rise over the last century mass loss from the greenland and antarctic ice sheets is expected to exceed other contributions to gmsl rise under future warming to better constrain polarice sheetresponse to warmer temperatures we draw on evidence from in terglacial periods in the geologic record that ex perienced warmer polar temperatures and higher gmsls than present coastal records of sea level from these previous warm periods dem onstrate geographic variability because of the influence of several geophysical processes that operate across a range of magnitudes and time scales inferring gmsl and ice volume changes from these reconstructions is nontrivial and generally requires the use of geophysical models advances interdisciplinary studies of geo logic archives have ushered in a new era of deciphering magnitudes rates and sources of sea level rise advances in our understanding of polar ice sheet response to warmer climates have been made through an increase in the number and geographic distribution of sea level reconstructions better ice sheet constraints and the recognition that several geophysical processes cause spatially complex patterns in sea level in particular accounting for glacial isostatic processes helps to decipher spatial variability in coastal sea level records and has reconciled a number of site specific sea level reconstructions for warm periods that have oc curred within the past several hundred thou sand years this enables us to infer that during recent interglacial periods small increases in

response of the east antarctica ice sheet to sea level rise a nonsteady ice flow model that explicitly includes longitudinal stresses is used to study the effects of marginal changes on the interior portions of an ice sheet sea level rise is found to cause a wave of thinning to propagate upglacier and this wave is slowed diffused and damped at the ice divide at dome c in central east antarctica post wisconsinan sea level rise is modeled as having caused 110 m thinning with response now 70 complete if accumulation rates increased by 10 at the same time then calculated net thinning has been only 75 m ice sheet response to changes in sea level and accumulation rate is relatively rapid response to temperature changes is an order of magnitude slower response times are shorter if the marginal position of an ice sheet is controlled

progressive increase in ice loss from greenland 1 laser altimeter measurements over greenland show increasing thickening rates above 2000 m reflecting increasing snowfall in a warming climate but near coastal thinning rates have increased substantially since the mid 1990s and net mass loss more than doubled from an average of 4 50 gt yr 1 between 1993 4 and 1998 9 to 57 105 gt yr 1 between 1998 9 and 2004 this increasing trend is very similar to findings from independent mass budget studies but differs widely from ers radar altimeter results this may result from limitations associated with the large ers footprint over sloping and undulating surfaces that typify fast narrow glaciers where thinning is most pronounced

glacier acceleration and thinning after ice shelf collapse in the larsen b embayment antarctica 1 ice velocities derived from five landsat 7 images acquired between january 2000 and february 2003 show a two to six fold increase in centerline speed of four glaciers flowing into the now collapsed section of the larsen b ice shelf satellite laser altimetry from icesat indicates the surface of hektoria glacier lowered by up to 38 6 m in a six month period beginning one year after the break up in march 2002 smaller elevation losses are observed for crane and jorum glaciers over a later 5 month period two glaciers south of the collapse area flask and leppard show little change in speed or elevation seasonal variations in speed preceding the large post collapse velocity increases suggest that both summer melt percolation and changes in the stress field due to shelf removal play a major role in glacier dynamics

measurements of time variable gravity show mass loss in antarctica using measurements of time variable gravity from the gravity recovery and climate experiment satellites we determined mass variations of the antarctic ice sheet during 2002 2005 we found that the mass of the ice sheet decreased significantly at a rate of 152 80 cubic kilometers of ice per year which is equivalent to 0 4 0 2 millimeters of global sea level rise per year most of this mass loss came from the west antarctic ice sheet

tilt observations using borehole tiltmeters 1 analysis of tidal and secular tilt we have designed a borehole tilt meter using two horizontal pendulums which have periods of 1 s we have installed the instru ments at seven sites in colorado and wyoming to evaluate the secular tilt the tides and the coherence between nearby instruments using 28 days of data from boulder colorado the standard deviations of the tidal estimates are 5 for the semidiurnal component m2 and 9 for the diurnal component 01 that include the body tide the ocean load and the topographic correction to better than the estimated uncertainty tidal measurements at erie colorado have larger possibly nonrandom variability that may be caused by a coupling between the tides and long period tilts the coherence between nearby instruments is 20 5 for frequencies ranging from 0 5 to 2 cycles per day but drops to a much smaller value outside of this range the secular tilt rate is quite variable and ranges from 0 1 to 1 prad yr measurements at erie colorado and in yellowstone national park wyoming exhibit an annual or biannual periodicity with an amplitude of about 1 prad which is consistent with a l f2 extrapolation of the diurnal noise power to longer periods the estimates agree with models

tropical tales of polar ice evidence of last interglacial polar ice sheet retreat recorded by fossil reefs of the granitic seychelles islands abstract in the search for a record of eustatic sea level change on glacial interglacial timescales the seychelles ranks as one of the best places on the planet to study owing to its location with respect to the former margins of northern hemisphere ice sheets that wax and wane on orbital cycles the local or relative sea level history is predicted to lie within a few meters of the globally averaged eustatic signal during the last interglacial period we have surveyed and dated last interglacial fossil corals to ascertain peak sea level and hence infer maximum retreat of polar ice sheets during this time interval we observe a pattern of gradually rising sea level in the seychelles between 129 and 125 thousand years ago ka with peak eustatic sea level attained after 125 ka at 7 6 1 7 m higher than present after accounting for thermal expansion and loss of mountain glaciers this sea level budget would require 5 8 m of polar ice sheet contribution relative to today s volume of which only 2 m came from the greenland ice sheet this result clearly identifies the antarctic ice sheet as a significant source of melt water most likely derived from one of the unstable marine based sectors in the west and or east antarctic ice sheet furthermore the establishment of a 5 9 1 7 m eustatic sea level position by 128 6 0 8 ka would require that partial ais collapse was coincident with the onset of the sea level highstand

the 1985 nevado del ruiz volcano catastrophe anatomy and retrospection abstract this paper seeks to analyze in an objective way the circumstances and events that contributed to the 1985 nevado del ruiz catastrophe in order to provide useful guidelines for future emergencies the paper is organized into two principal parts in the first part an anatomy of the catastrophe is developed as a step by step chronicle of events and actions taken by individuals and organizations during the period november 1984 through november 1985 this chronicle provides the essential background for the crucial events of november 13 this year long period is broken down further to emphasize important chapters the gradual awareness of the awakening of the volcano a long period of institutional skepticism reflecting an absence of credibility the closure of the credibility gap with the september 11 phreatic eruption followed by an intensive effort to gird for the worst and a detailed account of the day of reckoning the second part of the paper retrospection examines the numerous complicated factors that influenced the catastrophic outcome and attempts to cull a few lessons from armero in order to avoid similar occurrences in the future in a nutshell the government on the whole acted responsibly but was not willing to bear the economic or political costs of early evacuation or a false alarm science accurately foresaw the hazards but was insufficiently precise to render reliable warning of the crucial event at the last possible minute catastrophe was therefore a calculated risk and this combination the limitations of prediction detection the refusal to bear a false alarm and the lack of will to act on the uncertain information available provided its immediate and most obvious causes but because the crucial event occurred just two days before the armero emergency management plan was to be critically examined and improved the numerous circumstances which delayed progress of emergency management over the previous year also may be said to have contributed to the outcome thus the catastrophe was not caused by technological ineffectiveness or defectiveness nor by an overwhelming eruption or by an improbable run of bad luck but rather by cumulative human error by misjudgment indecision and bureaucratic shortsightedness armero could have produced no victims and therein dwells its immense tragedy

the future of ice sheets and sea ice between reversible retreat and unstoppable loss we discuss the existence of cryospheric tipping points in the earth s climate system such critical thresholds have been suggested to exist for the disappearance of arctic sea ice and the retreat of ice sheets once these ice masses have shrunk below an anticipated critical extent the ice albedo feedback might lead to the irreversible and unstoppable loss of the remaining ice we here give an overview of our current understanding of such threshold behavior by using conceptual arguments we review the recent findings that such a tipping point probably does not exist for the loss of arctic summer sea ice hence in a cooler climate sea ice could recover rapidly from the loss it has experienced in recent years in addition we discuss why this recent rapid retreat of arctic summer sea ice might largely be a consequence of a slow shift in ice thickness distribution which will lead to strongly increased year to year variability of the arctic summer sea ice extent this variability will render seasonal forecasts of the arctic summer sea ice extent increasingly difficult we also discuss why in contrast to arctic summer sea ice a tipping point is more likely to exist for the loss of the greenland ice sheet and the west antarctic ice sheet

deformation monitoring at nevado del ruiz colombia october 1985 march 1988 abstract deformation studies began at nevado del ruiz 23 days before the devastating 13 november 1985 eruption at least 12 months after precursory seismicity and fumarolic activity began the late start in geodetic monitoring limited number of stations in the pre eruption network and inconsistent patterns in the observed deformation limit conclusions about intrusive activity in the months and weeks prior to the eruption however the data require that the magma source of the devastating eruption was either deeper than 7 km or if shallow recovered the same volume and position within one week of the eruption geodetic monitoring resumed 1 week after the eruption and by april 1986 included 11 tilt leveling stations 38 edm lines and 7 short leveling lines a network capable of detecting emplacement or movement of magma volumes as small as 3 mcm 3 106 m3 to a depth of 2 3 km using a point source model 10 mcm to 7 km 50 mcm to 10 km and 200 mcm to 15 km beneath ruiz in addition 4 telemetered tiltmeters provided the capability of detecting in real time the fairly rapid ascent of much smaller magma bodies stations established to detect instability of the summit ice cap after the eruption were discontinued in early 1986 the data collected from the geodetic networks have higher than normal variance but demonstrate that little or no cumulative deformation of ruiz occurred from october 1985 through march 1988 thus little if any magma intruded above 5 km beneath the summit during or after the 13 november 1985 eruption this lack of significant intrusive activity agrees with the surprisingly low seismic energy release under ruiz and makes direct degassing of a large batholith an improbable explanation of the large sulfur flux to date at ruiz part of the variance in the geodetic data results from real but noncumulative deformation that may in part be pressure buffered by a fairly large geothermal water gas mixture for which abundant physical evidence exists part of the noncumulative deformation some of the fairly dispersed and low level seismicity under ruiz and some phreatic events appear to correlate with seasonal precipitation patterns hence rain snow loading and groundwater interaction may cause deformation events and possibly help trigger some phreatic explosions and seismic events at ruiz and as search of the literature reveals at other volcanoes in metastable states

tracer transport in the greenland ice sheet constraints on ice cores and glacial history the climate history and dynamics of the greenland ice sheet are studied using a coupled model of the depositional provenance and transport of glacier ice allowing simultaneous prediction of the detailed isotopic stratigraphy of ice cores at all the major greenland sites adopting a novel method for reconstructing the age depth relationship we greatly improve the accuracy of semi lagrangian tracer tracking schemes and can readily incorporate an age dependent ice rheology the larger aim of our study is to impose new constraints on the glacial history of the greenland ice sheet leading sources of uncertainty in the climate and dynamic history are encapsulated in a small number of parameters the temperature and elevation isotopic sensitivities the glacial interglacial precipitation contrast and the effective viscosity of ice in the flow law comparing predicted and observed ice layering at ice core sites we establish plausible ranges for the key model parameters identify climate and dynamic histories that are mutually consistent and recover the past depositional elevation of ice cores to ease interpretation of their climatic records with the coupled three dimensional model of ice dynamics and provenance transport we propose a method to place all the ice core records on a common time scale and use discrepancies to adjust the reconstructed climate history analysis of simulated grip ice layering and borehole temperature profiles confirms that the grip record is sensitive to the dynamic as well as to the climatic history but not enough to strongly limit speculation on the state of the greenland ice sheet during the eemian in contrast our study indicates that the dye 3 and camp century ice cores are extremely sensitive to ice dynamics and greatly constrain eemian ice sheet reconstructions we suggest that the maximum eemian sea level contribution of the ice sheet was in the range of 3 5 4 5 m

velocity structure and a seismic model for nevado del ruiz volcano colombia abstract a seismic tomographic study was performed for nevado del ruiz volcano nrv using more than 1500 high quality local and regional three low p wave velocity low v p and low s wave velocity low v s zones were found one low v s zone at depths 2 4 km located beneath the volcano a second low v p and low v s zone at depths 5 10 km located beneath the crater elongated and dipping to the e se and a third low v p and low v s zone at 10 to 12 km farther to the east these three low v p and low v s zones are believed to be the location of heat sources a high velocity zone for both p and s waves was found at shallow depths 0 5 km around the active crater the upper part 0 2 km depth of the high v p and high v s zone was characterized by low v p v s ratios v p v s ratios 1 80 the low v p v s zone is correlated with a steam dominated geothermal system the high v p v s is interpreted as an intrusive body of magmatic origin which includes partial melting zones associated with low v s anomalies a small low v p zone in which long period lp earthquakes were clustered was found to the southwest of the volcano based on the data obtained with the tomography in combination with seismicity geochemistry geology and gravimetry we suggest a model for the seismic activity of nrv volcano tectonic vt earthquakes that occur very often in swarm like patterns located in several clusters around the volcano seem to be due to changes in stress produced by the passing of fluids and or gas through many small cracks a fault and a caldera like structure separate the vt swarms located to the west of the volcano from the source of lp earthquakes

on the strong ground motion attenuation in spain in the last two decades all earthquake hazard studies in spain have been done using the attenuation deduced from the isoseismal maps of the most important earthquakes however it is well known that the preferred parameter to measure the size of any shock is magnitude and consequently the knowledge of acceleration as a function of magnitude and distance is basic to any new hazard determination the installation of a strong motion network in spain with more than a hundred digital instruments set up in the last 15 years made possible the recording of more than 447 shocks in the moment magnitude range of 1 3 m 6 3 however only 149 shocks were processed corresponding to magnitudes greater than 3 and a distance of less than 100 km values of the maximum horizontal acceleration recorded on firm soil permitted us to make a regression analysis which has been compared with similar previously published relationships additionally the southwestern part of spain is also affected by a marine source area of different very low attenuation but there are not enough recordings to attempt a regression analysis in this case the only strong motion data gathered for the area was checked against the two intensity attenuation relationships available after conversion of maximum intensity to moment magnitude and intensity to acceleration showing a reasonable behavior of the newest intensity attenuation law gathered for the area

eruption of the nevado del ruiz volcano colombia on 13 november 1985 tephra fall and lahars a small plinian eruption of the nevado del ruiz volcano in colombia ejected 3 5 x 1010 kilograms of mixed dacite and andesite tephra on 13 november 1985 with a maximum column height of 31 kilometers above sea level small pyroclastic flows and surges generated during the initial stage of the eruption caused surface melting of approximately 10 of the volcano9s ice cap leading to meltwater floods the erosive floods incorporated soils and loose sediments from the volcano9s flanks and developed into lahars which claimed at least 25 000 lives