Melting Of Land Ice Research Articles

Isle of Man, Galapagos and sunspot data show net cooling hid double exponential ocean warming danger: +3°C in 2014, +4°C likely by 2016.

Anthropogenic global warming (AGW) heat is trapped by the greenhouse gas (GHG) blanket, and the ocean surface layer. It is 93% in the ocean and drives atmospheric warming. The 111-year mean daily surface temperatures are 10.5±0.5°C at Port Erin (PE) Isle of Man compared with 9.6±4.8°C in Central England (CET) air. The Port Erin 5½-year max-min heat cycle synchronizes to the 11-year solar heat pump sunspot cycle. Tropical heat arrives 2 years after a solar maximum on wind-driven currents in the stratified sea surface. Runoff from bottom-up melted Arctic icesheets arrives 3½ year later at solar minimum. These warm and cold waters are the biodiversity source. PE is unique with seasonal meltwaters of Pacific and Atlantic origin. The North Pacific warms twice as fast as other oceans. All ocean near-surface gyre currents harmonize with sunspot cycles. Net cooling by polar icemelt masks catastrophic exponential ocean warming and icemelt. Eleven counter-rotating surface gyres carry heat and nutrients globally in verified ocean surface circulation system.Exponential growth is unsustainable in a finite system. It trends to infinity. Double-exponential gets there twice as quickly. The GHG blanket, grown double-exponentially for 250 years, is now in control. Ocean heat absorption takes 150-250 years. Arctic icemelt increases double-exponentially. The Arctic long-term annual freeze-melt volume cycle is 16.8±1.3 thousand cubic km per year. Polar land icemelt adds ~500 km3 per year. Freeze-brine of salinity >40‰ and temperature –1°C, sinks to the bottom. Equatorial evaporative-brine of salinity >36.4‰ and >28°C floats subsurface under fresh warm layers thickening westwards in tropical meridional cells to ~75m depth. This is consistent with observed extreme weather.Heat imbalance forced Pacific Ocean temperatures above proposed limits of +2°C in 1993, to +3°C in 2014, and is on track for +4°C for 2016. Century-long daily records confirm processes ongoing for 300 years. Coast locations are where impacts are felt and real-time data collected. Corporate governance degraded physics teaching in only 60 years. Individual discovery and data collection was lost. Big science is unnecessary. Satellites cannot do plankton tows. Computer models are governed by the rule of ‘garbage-in garbage-out’. They must be verified by in situ data that cannot be collected retrospectively. Continuous timeseries surface profile data from fixed ocean station locations on a global variable-boundary network are essential. Scientists, if well-trained in ocean experimental physics, can do the hard work.Time-poor scientists, stripped of their intellectual property rights, under rewarded, poorly educated, and ruthlessly exploited by growth-obsessed commercial interests, missed catastrophic global warming and multiple extreme consequences. Climate scientists abandoned classical physics and Newton-Hooke field verification in favor of unverified beliefs, models, and apps. Climate studies confuse heat with temperature, do not include basal icemelt, density temperature-salinity function, Clausius-Clapeyron evaporation exponential skin temperature function, asymmetric brine-heat sequestration, solar and tidal pumping, infra-red GHG heat trap, vertical tropical cells, freshwater warm pools; or wind-driven surface currents at 3 percent of windspeed. Climate model mistaken assumptions lead to the absurd conclusion that evaporation in the Labrador Sea at midnight in midwinter is greater than at the midday Equator.The Isle of Man provides an ideal location for continued monitoring and mitigation research, teaching and public service in a dedicated non-commercial independent multidisciplinary university-type setting. Quality teaching is the major priority. Commercial monopoly rights need replacement with free, fully open discussions and publications. Quality not quantity should be paramount. Internationally competitive academics should control subservient lower paid support staff.Every day without ocean surface data means vital scientific truth lost of interest and concern to all populations. Predictions are groundless without accurate continuous ocean surface data. Skeptics, politicians, statisticians, those with stakes in the status quo, and established research censors obstructing scientific progress squabble in ignorance while the globe burns.

Polar facts in the age of polarization

Many drivers of polar-region change originate in mid-latitude industrial societies, so public perceptions there matter. Building on earlier surveys of US public knowledge and concern, a series of New Hampshire state surveys over 2011–2015 tracked public knowledge of some basic polar facts. Analysis indicates that these facts subjectively fall into two categories: those that are or are not directly connected to beliefs about climate change. Responses to climate-linked factual questions, such as whether Arctic sea ice area has declined compared with 30 years ago, are politicized as if we were asking for climate-change opinions. Political divisions are less apparent with factual questions that do not suggest climate change, such as whether the North Pole is on land or sea ice. Only 38% of respondents could answer that question correctly, and even fewer (30%) knew or guessed correctly that melting of Greenland and Antarctic land ice, rather than Arctic sea ice, could potentially do the most to raise sea levels. At odds with the low levels of factual knowledge, most respondents say they have a moderate amount or a great deal of understanding about climate change. A combination of low knowledge with high self-assessed understanding characterizes almost half our sample and correlates with political views. The low knowledge/high understanding combination is most prevalent among Tea Party supporters, where it reaches 61%. It also occurs often (60%) among people who do not believe climate is changing. These results emphasize that diverse approaches are needed to communicate about science with people having different configurations of certainty and knowledge.

The land-ice contribution to 21st-century dynamic sea level rise

Abstract. Climate change has the potential to influence global mean sea level through a number of processes including (but not limited to) thermal expansion of the oceans and enhanced land ice melt. In addition to their contribution to global mean sea level change, these two processes (among others) lead to local departures from the global mean sea level change, through a number of mechanisms including the effect on spatial variations in the change of water density and transport, usually termed dynamic sea level changes. In this study, we focus on the component of dynamic sea level change that might be given by additional freshwater inflow to the ocean under scenarios of 21st-century land-based ice melt. We present regional patterns of dynamic sea level change given by a global-coupled atmosphere–ocean climate model forced by spatially and temporally varying projected ice-melt fluxes from three sources: the Antarctic ice sheet, the Greenland Ice Sheet and small glaciers and ice caps. The largest ice melt flux we consider is equivalent to almost 0.7 m of global mean sea level rise over the 21st century. The temporal evolution of the dynamic sea level changes, in the presence of considerable variations in the ice melt flux, is also analysed. We find that the dynamic sea level change associated with the ice melt is small, with the largest changes occurring in the North Atlantic amounting to 3 cm above the global mean rise. Furthermore, the dynamic sea level change associated with the ice melt is similar regardless of whether the simulated ice fluxes are applied to a simulation with fixed CO2 or under a business-as-usual greenhouse gas warming scenario of increasing CO2.

Sea level rise and its coastal impacts

AbstractGlobal warming in response to accumulation of human‐induced greenhouse gases inside the atmosphere has already caused several visible consequences, among them increase of the Earth's mean temperature and ocean heat content, melting of glaciers, and loss of ice from the Greenland and Antarctica ice sheets. Ocean warming and land ice melt in turn are causing sea level to rise. Sea level rise and its impacts on coastal zones have become a question of growing interest in the scientific community, as well as in the media and public. In this review paper, we summarize the most up‐to‐date knowledge about sea level rise and its causes, highlighting the regional variability that superimposes the global mean rise. We also present sea level projections for the 21st century under different warming scenarios. We next address the issue of the sea level rise impacts. We question whether there is already observational evidence of coastal impacts of sea level rise and highlight the fact that results differ from one location to another. This suggests that the response of coastal systems to sea level rise is highly dependent on local natural and human settings. We finally show that in spite of remaining uncertainties about future sea levels and related impacts, it becomes possible to provide preliminary assessment of regional impacts of sea level rise.

Global sea level trend during 1993–2012

Projection of future sea level change relies on the understanding of present sea-level trend and how it has varied in the past. Here we investigate the global-mean sea level (GMSL) change during 1993–2012 using Empirical Mode Decomposition, in an attempt to distinguish the trend over this period from the interannual variability. It is found that the GMSL rises with the rate of 3.2±0.4mm/yr during 1993–2003 and started decelerating since 2004 to a rate of 1.8±0.9mm/yr in 2012. This deceleration is mainly due to the slowdown of ocean thermal expansion in the Pacific during the last decade, as a part of the Pacific decadal-scale variability, while the land-ice melting is accelerating the rise of the global ocean mass-equivalent sea level. Recent rapid recovery of the rising GMSL from its dramatic drop during the 2011 La Niña introduced a large uncertainty in the estimation of the sea level trend, but the decelerated rise of the GMSL appears to be intact.

Widespread freshening in the Seasonal Ice Zone near 140°E off the Adélie Land Coast, Antarctica, from 1994 to 2012

Long-term water mass changes during 1994-2012 are examined from nine repeat hydrographic sections in the Seasonal Ice Zone along 140°E, off Antarctica. Significant freshening trends are detected within most of the water masses from the bottom to surface. Bottom Water freshened by 0.008-0.009 decade -1 below isopycnal surfaces and its layer thickness decreased by 120-160 dbar decade-1 throughout the study period. In addition to general thinning, the layer thickness was anomalously thin in 2012, suggesting a possible link with the sudden calving of the Mertz Glacier Tongue and subsequent reduction in sea-ice production. Winter Water freshened by 0.03 decade-1 throughout the study period, with significant interannual variability. In the offshore region, a long-term increase in precipitation can explain a substantial portion of the freshening trend. The Lower Circumpolar Deep Water on the continental slope underwent freshening at the same rate as the Bottom Water during the last two decades. Modified Shelf Water also shows robust freshening at a rate of 0.03 decade-1. Combined with the freshening of near-surface and Bottom Water masses in this region, these data indicate freshening of the entire water column over the continental slope. This widespread freshening is broadly consistent with the enhancement of the global hydrological cycle, together with a possible acceleration of land ice melting. Key Points Antarctic Bottom Water freshened off Adelie Coast, Antarctica, during 1994-2012 Precipitation increase can cause a significant part of Winter Water freshening The freshening is consistent with the enhancement of global hydrological cycle ©2013. American Geophysical Union. All Rights Reserved.

Data–model comparison of Holocene sea-level change in the circum-Caribbean region

Relative sea-level (RSL) reconstructions from the circum-Caribbean region were interpreted using a glacial isostatic adjustment (GIA) model with the aims to quantify the contribution of this process to both the temporal and spatial forms of the RSL observations and remove the GIA signal to estimate land ice volume change (eustasy) during the mid-to-late Holocene. To infer an optimal GIA parameter set, the RSL data were used to determine best-fitting Earth viscosity model parameters for two different global ice histories. The RSL data indicate a clear preference (95% confidence) for relatively high viscosity values: >0.8×1021Pas in the upper mantle and >3×1022Pas in the lower mantle. The data were not able to discriminate (at 95% confidence) between lithospheric thickness values ranging between 71 and 120km, although the thickest value considered produced the best fits. RSL predictions based on the best-fitting model parameters indicate a spatial variability across the region of up to ~7m during the early to mid-Holocene which is large enough to introduce significant error when using the entire dataset to produce a single regional RSL curve without correcting for GIA. When corrected for GIA, the most precise data from the region indicate about 3–4m of land ice melt (eustasy) from ~7calkyrB.P. to ~3–2calkyrB.P., although we note that there is considerable scatter in these corrected data. This likely reflects GIA model limitations, such as the assumption of lateral homogeneity in a region that contains several plate boundaries, the influence of tectonic processes (which were not modelled), as well as errors and an underestimate of the uncertainty in the RSL reconstructions.

A scaling approach to project regional sea level rise and its uncertainties

Abstract. Climate change causes global mean sea level to rise due to thermal expansion of seawater and loss of land ice from mountain glaciers, ice caps and ice sheets. Locally, sea level can strongly deviate from the global mean rise due to changes in wind and ocean currents. In addition, gravitational adjustments redistribute seawater away from shrinking ice masses. However, the land ice contribution to sea level rise (SLR) remains very challenging to model, and comprehensive regional sea level projections, which include appropriate gravitational adjustments, are still a nascent field (Katsman et al., 2011; Slangen et al., 2011). Here, we present an alternative approach to derive regional sea level changes for a range of emission and land ice melt scenarios, combining probabilistic forecasts of a simple climate model (MAGICC6) with the new CMIP5 general circulation models. The contribution from ice sheets varies considerably depending on the assumptions for the ice sheet projections, and thus represents sizeable uncertainties for future sea level rise. However, several consistent and robust patterns emerge from our analysis: at low latitudes, especially in the Indian Ocean and Western Pacific, sea level will likely rise more than the global mean (mostly by 10–20%). Around the northeastern Atlantic and the northeastern Pacific coasts, sea level will rise less than the global average or, in some rare cases, even fall. In the northwestern Atlantic, along the American coast, a strong dynamic sea level rise is counteracted by gravitational depression due to Greenland ice melt; whether sea level will be above- or below-average will depend on the relative contribution of these two factors. Our regional sea level projections and the diagnosed uncertainties provide an improved basis for coastal impact analysis and infrastructure planning for adaptation to climate change.

Tide gauge‐based sea level variations since 1950 along the Norwegian and Russian coasts of the Arctic Ocean: Contribution of the steric and mass components

We investigate sea level change and variability in some areas of the Arctic region over the 1950–2009 period. Analysis of 62 long tide gauge records available during the studied period along the Norwegian and Russian coastlines shows that coastal mean sea level (corrected for Glacial Isostatic Adjustment and inverted barometer effects) in these two areas was almost stable until about 1980 but since then displayed a clear increasing trend. Until the mid‐1990s, the mean coastal sea level closely follows the fluctuations of the Arctic Oscillation (AO) index, but after the mid‐to‐late 1990s the co‐fluctuation with the AO disappears. Since 1995, the coastal mean sea level (average of the Norwegian and Russian tide gauge data) presents an increasing trend of ∼4 mm/yr. Using in situ ocean temperature and salinity data down to 700 m from three different databases, we estimated the thermosteric, halosteric and steric (sum of thermosteric and halosteric) sea level since 1970 in the North Atlantic and Nordic Seas region (incomplete data coverage prevented us from analyzing steric data along the Russian coast). We note a strong anti‐correlation between the thermosteric and halosteric components both in terms of spatial trends and regionally averaged time series. The latter show a strong change as of ∼1995 that indicates simultaneous increase in temperature and salinity, a result confirmed by the Empirical Orthogonal Function decomposition over the studied region. Regionally distributed steric data are compared to altimetry‐based sea level over 1993–2009. Spatial trend patterns of observed (altimetry‐based) sea level over 1993–2009 are largely explained by steric patterns, but residual spatial trends suggest that other factors contribute, in particular regional ocean mass changes. Focusing again on Norwegian tide gauges, we then compare observed coastal mean sea level with the steric sea level and the ocean mass component estimated with GRACE space gravimetry data and conclude that the mass component has been increasing since 2003, possibly because of the recent acceleration in land ice melt.

Tracking Earth’s Energy: From El Niño to Global Warming

The state of knowledge and outstanding issues with respect to the global mean energy budget of planet Earth are described, along with the ability to track changes over time. Best estimates of the main energy components involved in radiative transfer and energy flows through the climate system do not satisfy physical constraints for conser- vation of energy without adjustments. The main issues relate to the downwelling longwave (LW) radiation and the hydrological cycle, and thus the surface evaporative cooling. It is argued that the discrepancy is 18% of the surface latent energy flux, but only 4% of the downwelling LW flux and, for various reasons, it is most likely that the latter is astray in some calculations, including many models, although there is also scope for precipitation estimates to be revised. Beginning in 2000, the top-of-atmosphere radiation measurements provide stable estimates of the net global radiative imbalance changes over a decade, but after 2004 there is ''missing energy'' as the observing system of the changes in ocean heat content, melting of land ice, and so on is unable to account for where it has gone. Based upon a number of climate model experiments for the twenty-first century where there are stases in global surface temperature and upper ocean heat content in spite of an identifiable global energy imbalance, we infer that the main sink of the missing energy is likely the deep ocean below 275 m depth.

Rising sea level may cause decline of fringing coral reefs

Coral reefs are major marine ecosystems and critical resources for marine diversity and fisheries. These ecosystems are widely recognized to be at risk from a number of stressors, and added to those in the past several decades is climate change due to anthropogenically driven increases in atmospheric concentrations of greenhouse gases. Most threatening to most coral reefs are elevated sea surface temperatures and increased ocean acidity [e.g., Kleypas et al., 1999; Hoegh‐Guldberg et al., 2007], but sea level rise, another consequence of climate change, is also likely to increase sedimentary processes that potentially interfere with photosynthesis, feeding, recruitment, and other key physiological processes (Figure 1). Anderson et al. [2010] argue compellingly that potential hazardous impacts to coastlines from 21st‐century sea level rise are greatly underestimated, particularly because of the rapid rate of rise. The Intergovernmental Panel on Climate Change estimates that sea level will rise in the coming century (1990–2090) by 2.2–4.4 millimeters per year, when projected with little contribution from melting ice [Meehl et al., 2007]. New studies indicate that rapid melting of land ice could substantially increase the rate of sea level rise [Grinsted et al., 2009; Milne et al., 2009].

Contemporary Sea Level Rise

Measuring sea level change and understanding its causes has considerably improved in the recent years, essentially because new in situ and remote sensing observations have become available. Here we report on most recent results on contemporary sea level rise. We first present sea level observations from tide gauges over the twentieth century and from satellite altimetry since the early 1990s. We next discuss the most recent progress made in quantifying the processes causing sea level change on timescales ranging from years to decades, i.e., thermal expansion of the oceans, land ice mass loss, and land water-storage change. We show that for the 1993-2007 time span, the sum of climate-related contributions (2.85 +/- 0.35 mm year(-1)) is only slightly less than altimetry-based sea level rise (3.3 +/- 0.4 mm year(-1)): approximately 30% of the observed rate of rise is due to ocean thermal expansion and approximately 55% results from land ice melt. Recent acceleration in glacier melting and ice mass loss from the ice sheets increases the latter contribution up to 80% for the past five years. We also review the main causes of regional variability in sea level trends: The dominant contribution results from nonuniform changes in ocean thermal expansion.

On the origins of Earth rotation anomalies: New insights on the basis of both “paleogeodetic” data and Gravity Recovery and Climate Experiment (GRACE) data

The theory previously developed to predict the impact on Earth's rotational state of the late Pleistocene glaciation cycle is extended. In particular, we examine the extent to which a departure of the infinite time asymptote of the viscoelastic tidal Love number of degree 2, “k2T,” from the observed “fluid” Love number, “kf,” impacts the theory. A number of tests of the influence of the difference in these Love numbers on theoretical predictions of the model of the glacial isostatic adjustment (GIA) process are explored. Relative sea level history predictions are shown not to be sensitive to the difference even though they are highly sensitive to the influence of the changing rotational state itself. We also explore in detail the accuracy with which the Gravity Recovery and Climate Experiment (GRACE) satellite system is able to observe the global GIA process including the time‐dependent amplitude of the degree 2 and order 1 spherical harmonic components of the gravitational field, the only components that are significantly influenced by rotational effects. It is explicitly shown that the GRACE observation of these properties of the time‐varying gravitational field is sufficiently accurate to rule out the values predicted by the ICE‐5G (VM2) model of Peltier (2004). However, we also note that this model is constrained only by data from an epoch during which modern greenhouse gas induced melting of both the great polar ice‐sheets and small ice sheets and glaciers was not occurring. Such modern loss of grounded continental ice strongly influences the evolving rotational state of the planet and thus the values of the degree 2 and order 1 Stokes coefficients as they are currently being measured by the GRACE satellite system. A series of sensitivity tests are employed to demonstrate this fact. We suggest that the accuracy of scenarios for modern land ice melting may be tested by ensuring that such scenarios conform to the GRACE observations of these crucial time‐dependent Stokes coefficients.

Use of GRACE determined secular gravity rates for glacial isostatic adjustment studies in North-America

Monthly geopotential spherical harmonic coefficients from the GRACE satellite mission are used to determine their usefulness and limitations for studying glacial isostatic adjustment (GIA) in North-America. Secular gravity rates are estimated by unweighted least-squares estimation using release 4 coefficients from August 2002 to August 2007 provided by the Center for Space Research (CSR), University of Texas. Smoothing is required to suppress short wavelength noise, in addition to filtering to diminish geographically correlated errors, as shown in previous studies. Optimal cut-off degrees and orders are determined for the destriping filter to maximize the signal to noise ratio. The halfwidth of the Gaussian filter is shown to significantly affect the sensitivity of the GRACE data (with respect to upper mantle viscosity and ice loading history). Therefore, the halfwidth should be selected based on the desired sensitivity. It is shown that increase in water storage in an area south west of Hudson Bay, from the summer of 2003 to the summer of 2006, contributes up to half of the maximum estimated gravity rate. Hydrology models differ in the predictions of the secular change in water storage, therefore even 4-year trend estimates are influenced by the uncertainty in water storage changes. Land ice melting in Greenland and Alaska has a non-negligible contribution, up to one-fourth of the maximum gravity rate. The estimated secular gravity rate shows two distinct peaks that can possibly be due to two domes in the former Pleistocene ice cover: west and south east of Hudson Bay. With a limited number of models, a better fit is obtained with models that use the ICE-3G model compared to the ICE-5G model. However, the uncertainty in interannual variations in hydrology models is too large to constrain the ice loading history with the current data span. For future work in which GRACE will be used to constrain ice loading history and the Earth's radial viscosity profile, it is important to include realistic uncertainty estimates for hydrology models and land ice melting in addition to the effects of lateral heterogeneity.

Quantifying the AMOC feedbacks during a 2×CO2 stabilization experiment with land-ice melting

The response of the Atlantic Meridional Overturning Circulation (AMOC) to an increase in atmo- spheric CO2 concentration is analyzed using the IPSL-CM4 coupled ocean-atmosphere model. Two simulations are integrated for 70 years with 1%/year increase in CO2 concentration until 2·CO2, and are then stabilized for further 430 years. The first simulation takes land-ice melting into account, via a simple parameterization, which results in a strong freshwater input of about 0.13 Sv at high latitudes in a warmer climate. During this scenario, the AMOC shuts down. A second simulation does not include this land-ice melting and herein, the AMOC recovers after 200 years. This behavior shows that this model is close to an AMOC shutdown threshold under global warming conditions, due to continuous input of land-ice melting. The analysis of the origin of density changes in the Northern Hemisphere convection sites allows an identifi- cation as to the origin of the changes in the AMOC. The processes that decrease the AMOC are the reduction of surface cooling due to the reduction in the air-sea tem- perature gradient as the atmosphere warms and the local freshening of convection sites that results from the increase in local freshwater forcing. Two processes also control the recovery of the AMOC: the northward advection of posi- tive salinity anomalies from the tropics and the decrease in sea-ice transport through the Fram Strait toward the con- vection sites. The quantification of the AMOC related feedbacks shows that the salinity related processes con- tribute to a strong positive feedback, while feedback re- lated to temperature processes is negative but remains small as there is a compensation between heat transport and surface heat flux in ocean-atmosphere coupled model. We conclude that in our model, AMOC feedbacks amplify land-ice melting perturbation by 2.5.

Are basal Ediacaran (635 Ma) post-glacial “cap dolostones” diachronous?

A layer of shallow-water dolostone (“cap dolostone”) with idiosyncratic sedimentary structures was deposited across continental margins world-wide in the aftermath of the terminal Cryogenian snowball Earth. The dolostone has a global average thickness of 18.5 m and is interpreted stratigraphically in different ways in the current literature: as diachronous (top and bottom) and tracking glacioeustatic flooding, as semi-diachronous (bottom diachronous, top isochronous) and outlasting the flood, or as isochronous (top and bottom) and recording ocean-wide changes over time subsequent to deglaciation. Each interpretation carries a different implication for the timescale of cap dolostones and their isotopic signatures, and therefore for their origin. In northern Namibia, we studied the Keilberg cap dolostone (635 Ma) across the Otavi carbonate bank and down a contiguous submarine paleoslope to estimated depths of ∼ 0.5 km. We find giant wave ripples and other wave-generated structures in all areas, including the lower slope, pointing to a base-level change of large amplitude. No other formation in the carbonate succession contains wave-generated bedforms on the lower slope. Carbon isotope records from the bank are similar in shape and absolute value, irrespective of thickness. Slope records are also similar to one another, but different in shape and value from those on the bank. If the cap is isochronous, lower-slope waters were enriched in 13C by 2–3‰ compared with the bank, which seems improbable. If diachronous, the lower slope, upper slope and bank records collectively describe a sigmoidal δ 13C curve over time with a net decline of 4.4‰. In addition, a lateral gradient of 1.0‰/100 km existed from the inner to outer bank. If the flooding was rapid (< 10 kyr), as suggested by ice-melting models, the δ 13C change may reflect strong surface warming, methane release, and kinetic isotope effects associated with rapid carbonate production. If the transgression was prolonged (> 100 kyr), as implied by actualistic interpretation of paleomagnetic reversals in this and other cap dolostones, the δ 13C change could record Rayleigh distillation associated with the drawdown of a large atmospheric CO 2 reservoir, built up during the preceding snowball glaciation. Either way, the sedimentology and isotopes support the diachronous interpretation, and are inconsistent with the semi-diachronous and isochronous models. The base-level rise of ∼ 0.5 km implies a glacioeustatic origin, meaning that cap dolostone sedimentation was synchronous with land ice melting. This leaves the actualistic interpretation of reversal frequency and speed in cap dolostones in conflict with ice-melting models.

Present-day sea-level change: A review

Understanding of sea-level change has improved considerably over the last decade. Present-day knowledge of sea-level change is derived from tide gauge observations and satellite altimetry measurements. The average rate of sea-level change obtained from tide gauges over the last 50 years is + 1.8 ± 0.3 mm yr −1 . In comparison, altimeter measurements from TOPEX/Poseidon and Jason-1 have shown an average rise of + 3.1 ± 0.4 mm yr −1 since 1993. It is not clear yet whether the larger rate of rise of the last decade reflects acceleration or decadal fluctuation. The causes of the present-day rate are a combination of increases in ocean temperatures and land ice melt from mountain glaciers, Greenland, and Antarctica. Regional variability in sea-level change, as evidenced by the quasi global coverage of altimeter satellites, appears dominated by non uniform change of thermal expansion. New satellite technologies, such as InSAR, ICESat, and GRACE make significant contributions to understanding sea-level change. To cite this article: R.S. Nerem et al., C. R. Geoscience 338 (2006).

Perspectives on present-day sea level change: a tribute to Christian le Provost

In this paper, we first discuss the controversial result of the work by Cabanes et al. (Science 294:840–842, 2001), who suggested that the rate of past century sea level rise may have been overestimated, considering the limited and heterogeneous location of historical tide gauges and the high regional variability of thermal expansion which was supposed to dominate the observed sea level. If correct, this conclusion would have solved the problem raised by the IPCC third assessment report [Church et al, Cambridge University Press, Cambridge, pp 881, 2001], namely, the factor two difference between the 20th century observed sea level rise and the computed climatic contributions. However, recent investigations based on new ocean temperature data sets indicate that thermal expansion only explains part (about 0.4 mm/year) of the 1.8 mm/year observed sea level rise of the past few decades. In fact, the Cabanes et al.’s conclusion was incorrect due to a contamination of abnormally high ocean temperature data in the Gulf Stream area that led to an overestimate of thermal expansion in this region. In this paper, we also estimate thermal expansion over the last decade (1993–2003), using a new ocean temperature and salinity database. We compare our result with three other estimates, two being based on global gridded data sets, and one based on an approach similar to that developed here. It is found that the mean rate of thermosteric sea level rise over the past decade is 1.5±0.3 mm/year, i.e. 50% of the observed 3 mm/year by satellite altimetry. For both time spans, past few decades and last decade, a contribution of 1.4 mm/year is not explained by thermal expansion, thus needs to be of water mass origin. Direct estimates of land ice melt for the recent years account for about 1 mm/year sea level rise. Thus, at least for the last decade, we have moved closer to explaining the observed rate of sea level rise than the IPCC third assessment report.

Sea Level Changes under Increasing Atmospheric CO2in a Transient Coupled Ocean-Atmosphere GCM Experiment

Abstract Climate change resulting from the enhanced greenhouse effect of increasing atmospheric CO2 concentrations is expected to bring about global and local changes in sea level. A global rise in sea level would result from thermal expansion of seawater and from melting of land ice, while changes in ocean dynamics and atmospheric pressure patterns could alter relative sea surface topography. Global and local sea level changes have been diagnosed from a 75-yr experiment with a version of the U.K. Meteorological Office coupled ocean-atmosphere general circulation model in which the CO2 concentration increases at 1% per year. Over the final decade, the component of mean global average sea level rise caused by thermal expansion is 90 mm; on this time scale, a significant contribution is expected from melting of mountain glaciers, but the model does not represent these. Sea level rises over practically the entire ocean area, but there is considerable variation in the magnitude, showing that the global figure...

The Effects of a Rising Sea Level on Maritime Limits and Boundaries

The sea level is rising. One of the causes of this phenomenon is the so-called ‘greenhouse effect’. This concept refers to the rising of the temperature of the atmosphere as a result of the increase of the concentration of carbon dioxide and several other gases in the atmosphere. One of the consequences of this rise in temperature is the melting of land ice, in particular glaciers and the ice-caps of Greenland and perhaps Antarctica. This melting water enters the ocean, which results, in combination with the expansion of sea water as a consequence of its higher temperature, in a rising of the sea level.