Ice Volume Changes Research Articles

An upper-bound estimate for the accuracy of glacier volume–area scaling

Abstract. Volume–area scaling is the most popular method for estimating the ice volume of large glacier samples. Here, a series of resampling experiments based on different sets of synthetic data is presented in order to derive an upper-bound estimate (i.e. a level achieved only within ideal conditions) for its accuracy. For real-world applications, a lower accuracy has to be expected. We also quantify the maximum accuracy expected when scaling is used for determining the glacier volume change, and area change of a given glacier population. A comprehensive set of measured glacier areas, volumes, area and volume changes is evaluated to investigate the impact of real-world data quality on the so-assessed accuracies. For populations larger than a few thousand glaciers, the total ice volume can be recovered within 30% if all data currently available worldwide are used for estimating the scaling parameters. Assuming no systematic bias in ice volume measurements, their uncertainty is of secondary importance. Knowing the individual areas of a glacier sample for two points in time allows recovering the corresponding ice volume change within 40% for populations larger than a few hundred glaciers, both for steady-state and transient geometries. If ice volume changes can be estimated without bias, glacier area changes derived from volume–area scaling show similar uncertainties to those of the volume changes. This paper does not aim at making a final judgement on the suitability of volume–area scaling as such, but provides the means for assessing the accuracy expected from its application.

Increased sensitivity of the Plio-Pleistocene northwest Pacific to obliquity forcing

Insolation-driven changes in poleward heat transport and changes in greenhouse gas concentrations can explain aspects of the rise of obliquity-paced climate variability during the Pliocene–Pleistocene transition. Based on an alkenone-based sea surface temperature (SST) reconstruction of the Kuroshio Current Extension (KCE), we propose here that emergence of this region as the primary locus of ocean–atmosphere heat transfer in the Pacific Ocean promoted Northern Hemisphere Glaciation (NHG). Our record shows that with intensification of NHG at 2.7 Ma, the KCE cooled 2–4 °C during glacial intervals, likely in NH winter/spring. These high-amplitude 41-kyr SST cycles slightly lead δO18 variations, ruling out global ice-volume changes as the primary cause. The lead of SST over δO18 cycles matches the phasing between these two proxies observed in the tropics, supporting changes in CO2 concentrations as a unifying mechanism of ocean surface temperature change. However, the amplitude of the KCE SST cycle is twice that of the tropical records, pointing to an additional, regional process. We infer that cooling of the North Pacific sea surface by the East Asian winter monsoon and associated westerlies intensified during glacial intervals. This transfer of heat and moisture from the ocean to the atmosphere potentially furthered glacial formation by accelerating snow fall in North America. Therefore, these results might also support a role for tropical–extratropical heat balance in enhancing glacial growth via the obliquity pacing.

Asynchronous Little Ice Age glacier fluctuations in Iceland and European Alps linked to shifts in subpolar North Atlantic circulation

Records of past glacier fluctuations are an important source of paleoclimate data and provide context for future changes in global ice volume. In the North Atlantic region, glacier chronologies can be used to track the response of terrestrial environments to variations in marine conditions including circulation patterns and sea ice cover. However, the majority of glacier records are discontinuous and temporally restricted, owing in part to the extensive advance of Northern Hemisphere glaciers during the Little Ice Age (LIA), the most recent and severe climate anomaly of the Neoglacial period. Here, we combine an absolutely dated and continuous record of Langjökull ice marginal fluctuations with new reconstructions of sediment flux through the past 1.2 ka using varved sediments from Hvítárvatn, a proglacial lake in Icelandʼs central highlands. Large spatial and temporal variations in sediment flux related to changing ice cap dimensions are reconstructed from six sediment cores and seismic reflection profiles. Sediment data reveal two discrete phases of ice expansion occurring ca. 1400 to 1550 AD and ca. 1680 to 1890 AD. These advances are separated by a persistent interval of ice retreat, suggesting that a substantial period of warming interrupted LIA cold. The pattern of Icelandic glacier activity contrasts with that of European glaciers but shows strong similarities to reconstructed changes in North Atlantic oceanographic conditions, indicating differing regional responses to coupled ocean–atmosphere–sea ice variations. Our data suggest that subpolar North Atlantic circulation dynamics may have led to coherent asynchronous glacier fluctuations during the mid LIA and highlight the importance of circulation variability in triggering and transmitting multidecadal scale climate changes to nearby terrestrial environments.

Interhemispheric anti-phasing of orbitally driven monsoon intensity: Implications for ice-volume forcing in the high latitudes

The influence of precession on the redistribution of insolation on the top of the atmosphere predicts that climate change in the low latitudes is out of phase between the hemispheres. We test this prediction by the most direct approach, the analysis of terrestrial climate records, as they provide direct information on regional changes in the atmosphere. A review of evidence from absolutely-dated climate records shows that precession drives an interhemispheric anti-phasing of monsoon intensity. Maxima of boreal monsoon intensity are opposed by minima of austral monsoon intensity and vice versa.The interhemispheric anti-phasing of monsoon intensity implies that low-to-high latitude climate gradients are asymmetric between the hemispheres; periods with maximum boreal monsoon intensity steepen the gradient in the NH but flatten it in the SH and vice versa. These precession driven changes are superimposed on obliquityʼs influence on meridional climate gradients; high obliquity causes flat gradients and low obliquity steep gradients.We propose the hypothesis that orbitally driven changes of low-to-high latitude climate gradients drive ice-volume changes in the high latitudes. To test the hypothesis we quantify a proxy for the climate gradients and predict ice-volume forcing in the NH and SH during the last 120 ka. Then we use the contributions of both hemispheres to predict global ice-volume forcing. The comparison with records related to global ice volume verifies our ice-volume hypothesis. Therefore, ice-volume changes can be predicted for the NH and SH separately.

Orbital-scale climate change and glacioeustasy during the early Late Ordovician (pre-Hirnantian) determined from δ18O values in marine apatite

Research Article| July 01, 2013 Orbital-scale climate change and glacioeustasy during the early Late Ordovician (pre-Hirnantian) determined from δ18O values in marine apatite M. Elrick; M. Elrick 1Earth & Planetary Sciences Department, University of New Mexico, Albuquerque, New Mexico 87131, USA Search for other works by this author on: GSW Google Scholar D. Reardon; D. Reardon 1Earth & Planetary Sciences Department, University of New Mexico, Albuquerque, New Mexico 87131, USA Search for other works by this author on: GSW Google Scholar W. Labor; W. Labor 1Earth & Planetary Sciences Department, University of New Mexico, Albuquerque, New Mexico 87131, USA Search for other works by this author on: GSW Google Scholar J. Martin; J. Martin 1Earth & Planetary Sciences Department, University of New Mexico, Albuquerque, New Mexico 87131, USA Search for other works by this author on: GSW Google Scholar A. Desrochers; A. Desrochers 2Department of Earth Sciences, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada Search for other works by this author on: GSW Google Scholar M. Pope M. Pope 3Geology and Geophysics Department, Texas A&M, College Station, Texas 77483, USA Search for other works by this author on: GSW Google Scholar Geology (2013) 41 (7): 775–778. https://doi.org/10.1130/G34363.1 Article history received: 03 Jan 2013 rev-recd: 13 Feb 2013 accepted: 19 Feb 2013 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation M. Elrick, D. Reardon, W. Labor, J. Martin, A. Desrochers, M. Pope; Orbital-scale climate change and glacioeustasy during the early Late Ordovician (pre-Hirnantian) determined from δ18O values in marine apatite. Geology 2013;; 41 (7): 775–778. doi: https://doi.org/10.1130/G34363.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract This study focuses on the ∼10 m.y. before the latest Ordovician (Hirnantian) glaciation; we test whether orbital-scale climatic fluctuations controlled the growth and melting of continental glaciers, resulting in glacioeustatic sea-level changes and the development of widespread marine sedimentary cycles. δ18O values of conodont apatite from 14 Late Ordovician (Katian) cycles range from ∼17‰ to 21‰. Isotopic values decrease and are lowest in the deepest water facies and increase and are highest in shallow-water facies, supporting the hypothesis that glacioeustasy was the dominant control on water-depth changes. Measured intracycle δ18O changes of 0.7‰–2.5‰ were controlled by changes in ice volume (<60 m sea-level changes), sea-surface temperatures (<5 °C), and potentially local increases in seawater evaporation during drier and/or windier glacial stages. These interpreted orbital-scale climate changes and resultant large glacial ice-volume changes support recent interpretations of a dynamic and prolonged Ordovician greenhouse to icehouse transition. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Obliquity and long eccentricity pacing of the Middle Miocene climate transition

AbstractThe Middle Miocene East Antarctic ice sheet expansion (EAIE), which is indicated by an abrupt ~1‰ increase in global benthic foraminiferal δ18O at ~13.8 Ma, marks the Middle Miocene climate transition (MMCT) and has been related to astronomically modulated changes in the global carbon cycle. Here, we present high resolution (3–4 kyr) benthic foraminiferal δ18O and δ13C records from IODP Site U1337 in the central equatorial Pacific, which spans the period 12.2–15.8 Ma. The isotopic records clearly demonstrate significant imprints from periodic variations in the Earth's orbital parameters, particularly the obliquity (40 kyr) and the long eccentricity (400 kyr) cycles. While the benthic δ18O and δ13C exhibit nearly identical amplitudes for glacial‐interglacial cycles from 15.8 to 12.2 Ma, the long‐term trends in the benthic δ18O and δ13C had started to reverse after the beginning of the EAIE. Within the 400‐kyr band, the benthic −δ18O and δ13C displays a constant phase relationship between 15.8 and 12.2 Ma. At the 41‐kyr band, however, a phase reversal reaching &gt;180° between −δ18O and δ13C occurs from 13.8 Ma to 14.0 Ma during the period of the EAIE. A similar phase relationship of benthic foraminiferal −δ18O and δ13C at the 400‐kyr band and the 41‐kyr band is also observed at ODP Site 1146 from the northern South China Sea. This phase jump occurs when the long‐term trends in δ18O and δ13C split, suggesting a decoupling of the global ice volume and ocean carbon reservoir changes during the Middle Miocene.

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.

Contribution of Icelandic ice caps to sea level rise: Trends and variability since the Little Ice Age

In total, Icelandic ice caps contain ∼3600 km3 of ice, which if melted would raise sea level by ∼1 cm. Here, we present an overview of mass changes of Icelandic ice masses since the end of the 19th century. They have both gained and lost mass during this period. Changes in ice volume have been estimated both through surface mass balance measurements (performed annually since ∼1990) and differencing of digital elevation models derived from various satellite and airborne observations. While the glaciers showed little mass loss as the 20th century began, losses increased rapidly after 1925, peaked in the 1930s and 1940s, and remained significant until the 1960s. After being near‐zero or even positive during the 1980s and early 1990s, glacier mass budgets declined considerably, and have since the mid‐1990s shown an average annual loss of 9.5±1.5 Gt a−1, contributing ∼0.03 mm a−1 to sea level rise. Since 1995 interannual variability in mass loss is high, ranging from 2.7 to 25.3±1.5 Gt a−1, corresponding to surface mass balances of −0.2 to −2.2 ± 0.15 m we a−1. This variability is driven by climate fluctuations and also by transient reduction of albedo due to volcanic eruptions.

Surface water hydrography of the Kuroshio Extension during the Pliocene–Pleistocene climate transition

Abstract The Pliocene–Pleistocene climate transition offers an opportunity to study the effect of glaciation on the ocean–climate system. We present a Globigerinoides ruber δ18O record from Ocean Drilling Program Site 1208 (Kuroshio Current Extension; KCE). This exclusively (sub)tropical foraminifer, a summer/fall mixed-layer dweller at the KCE, affords the first long (3.0 Ma to 1.8 Ma) orbital-scale (2.5-kyr time step) account of the sea surface in this area. The section's temperature-corrected benthic foraminiferal δ18O record constrains global changes in ice volume, yielding a Δδ18O record that primarily reflects summer/fall KCE hydrography (temperature and salinity). A 0.3‰ decrease in Δδ18O values at 2.7 Ma coincides with the onset of Northern Hemisphere glaciation, indicating as much as 1.5 °C warming during the summer/fall to suggest that the subtropical North Pacific sea surface provided heat and moisture for expanding ice sheets. On the orbital scale, the 41-kyr cycle that dominates high-latitude climate is absent from the Δδ18O record, indicating a stable surface water hydrographic regime on this time scale. Rather, the Δδ18O record varies at and is coherent with the 19-kyr precessional component of the regional insolation curve, supporting a direct response to subtropical insolation and insensitivity to extra-regional forcing factors, such as ice sheets.

SEA SURFACE TEMPERATURE CHANGE IN SOUTH CHINA SEA SINCE PLEISTOCENE AND ITS PALEOCLIMATIC IMPLICATIONS

The thermal history of the southern South China Sea(SCS) exhibited a reducing tendency since Pleistocene.The temperature profile is characterized by a cooling trend during glaciations but remains steady during interglaciations.Meridional thermal gradient between southern and northern SCS reflects the Eastern Asian Winter Monsoon(EAWM) change.Thermal gradient history during the past 2 Ma indicated that EAWM was strengthened before mid-Pleistocene and weakened since then,but restrengthened in the later Quaternary.This long term trend is superimposed by orbital glacial cycles with the EAWM stronger during interglaciations and weaker during glaciations.Tectonic uplifting of the Tibetan Plateau may have important influence on the strengthening of EAWM in the mid-Pleistocene.Global ice volume and ENSO changes may be the main reasons for the overall trend and the orbital cycle of EAWM.

A model reconstruction of the Antarctic sea ice thickness and volume changes over 1980–2008 using data assimilation

Sea ice variability in the Southern Ocean has a complex spatio-temporal structure. In a global warming context, the Antarctic sea ice cover has slightly expanded over the recent decades. This increase in sea ice extent results, however, from the sum of positive and negative regional trends and is influenced by a wide range of modes of climate variability. An additional view on sea ice thickness and volume changes would improve our understanding. Still, no large-scale multi-decadal well-sampled record of Antarctic sea ice thickness exists to date. To address this issue, we assimilate real sea ice concentration data into the ocean–sea ice model NEMO-LIM2 using an ensemble Kalman filter and demonstrate the positive impacts on the global sea ice cover. This paper reports the 1980–2008 evolution (monthly anomalies, trends plus their uncertainty ranges) of sea ice volume and thickness in different sectors of the Southern Ocean. We find that the global Antarctic sea ice volume has risen at a pace of 355±338km3/decade (5.6±5.3%/decade) during this period, with an increase in the Ross and Weddell Seas (150±124 and 209±362km3/decade, respectively) and a decrease in the Amundsen–Bellingshausen Seas (-45±54km3/decade). Sea ice volume anomalies co-vary well with extent anomalies, and exhibit yearly to decadal fluctuations. The results stress the need to analyze sea ice changes at the regional level first and then at the hemispheric level.

Improved ice loss estimate of the northwestern Greenland ice sheet

[1] We estimate ice volume change rates in the northwest Greenland drainage basin during 2003–2009 using Ice, Cloud and land Elevation Satellite (ICESat) laser altimeter data. Elevation changes are often reported to be largest near the frontal portion of outlet glaciers. To improve the volume change estimate, we supplement the ICESat data with altimeter surveys from NASA's Airborne Topographic Mapper from 2002 to 2010 and NASA's Land, Vegetation and Ice Sensor from 2010. The Airborne data are mainly concentrated along the ice margin and thus have a significant impact on the estimate of the volume change. Our results show that adding Airborne Topographic Mapper and Land, Vegetation and Ice Sensor data to the ICESat data increases the catchment-wide estimate of ice volume loss by 11%, mainly due to an improved volume loss estimate along the ice sheet margin. Furthermore, our results show a significant acceleration in mass loss at elevations above 1200 m. Both the improved mass loss estimate along the ice sheet margin and the acceleration at higher elevations have implications for predictions of the elastic adjustment of the lithosphere caused by present-day ice mass changes. Our study shows that the use of ICESat data alone to predict elastic uplift rates biases the predicted rates by several millimeters per year at GPS locations along the northwestern coast.

Ice-volume changes, bias estimation of mass-balance measurements and changes in subglacial lakes derived by lidar mapping of the surface of Icelandic glaciers

AbstractIcelandic glaciers cover ∼11 000 km2 in area and store ∼3600 km3 of ice. Starting in 2008 during the International Polar Year, accurate digital elevation models (DEMs) of the glaciers are being produced with airborne lidar. More than 90% of the glaciers have been surveyed in this effort, including Vatnajökull, Hofsjökull, Myrdalsjökull, Drangajökull, Eyjafjallajökull and several smaller glaciers. The publicly available DEMs are useful for glaciological and geological research, including studies of ice-volume changes, estimation of bias in mass-balance measurements, studies of jökulhlaups and subglacial lakes formed by subglacial geothermal areas, and for mapping of crevasses. The lidar mapping includes a 500-1000 m wide ice-free buffer zone around the ice margins which contains many glacio-geomorphological features, and therefore the new DEMs have proved useful in geological investigations of proglacial areas. Comparison of the lidar DEMs with older maps confirms the rapid ongoing volume changes of the Icelandic ice caps which have been shown by mass-balance measurements since 1995/96. In some cases, ice-volume changes derived by comparing the lidar measurements with older DEMs are in good agreement with accumulated ice-volume changes derived from traditional mass-balance measurements, but in other cases such a comparison indicates substantial biases in the traditional mass-balance records.

Cenozoic landscape and ice drainage evolution in the Lambert Glacier–Amery Ice Shelf system

Abstract Landforms and sediments in the Prince Charles Mountains record the timing and magnitude of Cenozoic palaeotopographic changes in the Lambert Glacier–Amery Ice Shelf system. A review of geomorphic and sedimentological evidence indicates that considerable (&gt;1–2 km) glacial incision into a pre-glacial palaeosurface occurred along the major outlet glaciers during the Cenozoic. This erosion was in turn the likely driver for uplift that averaged c. 50 m/Ma along the flank of the Amery Ice Shelf since at least the mid-Miocene Epoch. The volume of eroded material is an order of magnitude greater than the quantity of sediment presently preserved in Prydz Bay, suggesting considerable export of Cenozoic sediment off the continental shelf. The magnitude of erosion recorded in the Prince Charles Mountains is sufficient to have focussed Cenozoic ice-drainage patterns, but was too slow to have driven Quaternary changes in ice volume.

Ice volume changes (1936–1990–2007) and ground-penetrating radar studies of Ariebreen, Hornsund, Spitsbergen

Ariebreen is a small (0.37 km2)-valley glacier located in southern Spitsbergen. Our ground-penetrating radar surveys of the glacier show that it is less than 30 m thick on average, with a maximum thickness of 82 m, and it appears to be entirely cold. By analysing digital terrain models of the ice surface from different dates, we determine the area and volume changes during two periods, 1936-1990 and 1990-2007. The total ice volume of the glacier has decreased by 73% during the entire period 1936-2007, which is equivalent to a mean mass balance rate of -0.61±0.17 m y-1 w.eq. The glacier thinning rate has increased markedly between the first and second periods, from -0.50±0.22 to -0.95±0.17 m y-1 w.eq.Keywords: Ice-volume changes; ground-penetrating radar; thinning rate; Ariebreen; Spitsbergen; Svalbard(Published: 1 August 2013)To access the supplementary material for this article, please see Supplementary files in the column to the right (under Article Tools)Citation: Polar Research 2013, 32, 11068, http://dx.doi.org/10.3402/polar.v32i0.11068

Pliocene-Pleistocene Climate Change At the NE Tibetan Plateau Deduced From Lithofacies Variation In the Drill Core SG-1, Western Qaidam Basin, China

Abstract The Pliocene–Pleistocene sedimentologic evolution of the western Qaidam Basin at the NE Tibetan Plateau was studied on the nearly thousand-meter-deep drill core SG-1 (spanning ca. 2.8–0.1 Ma), recovered from the Chahansilatu sub-depression with an average recovery rate of 95%. Lithofacies variation records the regional climatic change in relation to Asian drying and Tibetan Plateau uplift. Sedimentary textures and structures demonstrate a continuous slight coarsening and an increase of evaporites upward. We recognized five lithofacies: (1) gray-black laminated mudstone, (2) gray massive mudstone and siltstone, (3) bedded halite, (4) loose muddy halite, and (5) brownish-yellowish saliferous siltstone and mudstone, representing (1) semi-deep fresh to semi-brackish lake, (2) shallow brackish lake, (3) perennial saline lake, (4) playa saline lake, and (5) saline mudflat conditions, respectively. Variation of the lithofacies through the core demonstrates a clear trend of lake shrinkage since the late Pliocene and the final termination of the Chahansilatu paleolake. Accelerations of lake shrinkages are observed at ca. 2.5 Ma, 2.2 Ma, 1.6 Ma, 1.2 Ma, 0.9 Ma, 0.6 Ma, and 0.1 Ma. Our results suggest that the long-term stepwise drying of the Asian inland may have been forced by the change of the global ice volume.

Orbitally paced shifts in the particle size of Antarctic continental shelf sediments in response to ice dynamics during the Miocene climatic optimum

The AND-2A drill hole (ANDRILL [Antarctic Geological Drilling Program] Southern McMurdo Sound Project), ∼10 km from the East Antarctica coastline, records nearly 6 m.y. of sedimentation across the Miocene climatic optimum at a high-latitude site. Sedimentological studies of bedforms and particle size distributions indicate that the paleoenvironment was strongly affected by waves and currents, consistent with deposition in a glacially influenced neritic environment. We document abrupt shifts in mud percent within glacial-interglacial cycles ca. 17.8 Ma and between ca. 16.7 and 15.7 Ma that we attribute to the hydrodynamic effects of wave stirring tied to episodes of ice growth and decay. Although wave climate and geodynamic forcing of the paleobathymetry simultaneously affect wave stirring on a high-latitude shelf, both are ultimately controlled by the size of the ice sheet. The mud percent record displays cyclicity at short-eccentricity time scales (94–99 k.y.) and, unexpectedly, ice retreat phases interpreted from the particle size record coincide with eccentricity minima. We attribute the eccentricity-paced ice retreat phases during the late Early Miocene polythermal glacial conditions and the cool orbital parameters to marine ice sheet instability in response to changes in ocean circulation and heat transport. The particle size record of the AND-2A core provides unique near-field evidence for orbitally paced changes in high-latitude climate and ice volume during the Miocene climatic optimum and important insights into the mechanisms of ice sheet growth and decay in a period of global warmth.

The Antarctic viewpoint of the Central Paratethys: cause, timing, and duration of a deep valley incision in the Middle Miocene Alpine–Carpathian Foredeep of Lower Austria

Global, glacio-eustatic sea-level changes massively influenced the depositional history of the Central Paratethyan region. Here, we correlate Middle Miocene global δ18O-shifts with ice volume changes on Antarctica and sea-level changes with corresponding phases of erosion (valley incision) and deposition in the Lower Austrian part of the Alpine–Carpathian Foredeep. This allows the exact dating of the valley formation. Two periods of positive δ18O-shifts resulted in sea-level drops of about 60 and 40 m, respectively. The first drop in the late Langhian (middle Badenian) at c. 13.9 Ma (Mi3b) was fast and caused severe erosion on the emerged foredeep. In a second, less pronounced step around 13.0 Ma (Mi4) in the middle Serravallian (late Badenian), the base level was further deepened after a period of alternating erosion and deposition. The combined sea-level change (80–120 m) fits well with the maximum thickness of Sarmatian sediments drilled within incised valley (110 m). The global sea-level falls affected not only the geological history of the foredeep. The intensive erosion (valley incision) is combined with delta progradation in the adjacent Vienna Basin. Due to this massive sea-level drop, the interruption of marine connections resulted in vast salt deposits and faunal crises within the Central Paratethys during this time.

Rapid coupling between ice volume and polar temperature over the past 150,000 years

Current global warming necessitates a detailed understanding of the relationships between climate and global ice volume. Highly resolved and continuous sea-level records are essential for quantifying ice-volume changes. However, an unbiased study of the timing of past ice-volume changes, relative to polar climate change, has so far been impossible because available sea-level records either were dated by using orbital tuning or ice-core timescales, or were discontinuous in time. Here we present an independent dating of a continuous, high-resolution sea-level record in millennial-scale detail throughout the past 150,000 years. We find that the timing of ice-volume fluctuations agrees well with that of variations in Antarctic climate and especially Greenland climate. Amplitudes of ice-volume fluctuations more closely match Antarctic (rather than Greenland) climate changes. Polar climate and ice-volume changes, and their rates of change, are found to covary within centennial response times. Finally, rates of sea-level rise reached at least 1.2 m per century during all major episodes of ice-volume reduction.

Investigating the timescales of glacial landscape evolution using numerical modelling

The sequence of feedbacks that characterized 100-kyr glacial cycles of the past million years remains uncertain, hampering an understanding of the interconnections between insolation, ice sheets, greenhouse gas forcing, and climate. Critical to addressing this issue is an accurate interpretation of the marine δ18O record, the main template for the Ice Ages. This study uses a global compilation of 49 paired sea surface temperature-planktonic δ18O records to extract the mean δ18O of surface ocean seawater over the past 800 kyr, which we interpret to dominantly reflect global ice volume. The results indicate that global surface temperature, inferred deep ocean temperature, and atmospheric CO2 decrease early during each glacial cycle in close association with one another, whereas major ice sheet growth occurs later in glacial cycles. These relationships suggest that ice volume may have exhibited a threshold response to global cooling, and that global deglaciations do not occur until after the growth of large ice sheets. This phase sequence also suggests that the ice sheets had relatively little feedback on global cooling. Simple modeling shows that the rate of ice volume change through time is largely determined by the combined influence of insolation, temperature, and ice sheet size, with possible implications for the evolution of glacial cycles over the past three million years.