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High-resolution ice core records from coastal Antarctica are particularly useful to inform our understanding of environmental changes and their drivers. Here, we present a decadally resolved record of sea-salt sodium (a proxy for open-ocean area) and non-sea salt calcium (a proxy for continental dust) from the well-dated Roosevelt Island Climate Evolution (RICE) core, focusing on the time period between 40–26 ka BP. The RICE dust record exhibits an abrupt shift towards a higher mean dust concentration at 32 ka BP. Investigating existing ice-core records, we find this shift is a prominent feature across Antarctica. We propose that this shift is linked to an equatorward displacement of Southern Hemisphere westerly winds. Subsequent to the wind shift, data suggest a weakening of Southern Ocean upwelling and a decline of atmospheric CO2 to lower glacial values, hence making this shift an important glacial climate event with potentially important insights for future projections. Antarctic ice core records provide insights into past environmental conditions. Here, an abrupt, synchronous increase in dust from ice cores in Antarctica is identified that suggests a sudden equatorward shift of westerly winds and coincides with a reduction in atmospheric CO2. [ABSTRACT FROM AUTHOR]

Climate during the last glacial period was marked by abrupt instability on millennial timescales that included large swings of temperature in and around Greenland (Daansgard–Oeschger events) and smaller, more gradual changes in Antarctica (AIM events). Less is known about the existence and nature of similar variability during older glacial periods, especially during the early Pleistocene when glacial cycles were dominantly occurring at 41 kyr intervals compared to the much longer and deeper glaciations of the more recent period. Here, we report a continuous millennially resolved record of stable isotopes of planktic and benthic foraminifera at IODP Site U1385 (the "Shackleton Site") from the southwestern Iberian margin for the last 1.5 million years, which includes the Middle Pleistocene Transition (MPT). Our results demonstrate that millennial climate variability (MCV) was a persistent feature of glacial climate, both before and after the MPT. Prior to 1.2 Ma in the early Pleistocene, the amplitude of MCV was modulated by the 41 kyr obliquity cycle and increased when axial tilt dropped below 23.5 ∘ and benthic δ18O exceeded ∼3.8 ‰ (corrected to Uvigerina), indicating a threshold response to orbital forcing. Afterwards, MCV became focused mainly on the transitions into and out of glacial states (i.e. inceptions and terminations) and during times of intermediate ice volume. After 1.2 Ma, obliquity continued to play a role in modulating the amplitude of MCV, especially during times of glacial inceptions, which are always associated with declining obliquity. A non-linear role for obliquity is also indicated by the appearance of multiples (82, 123 kyr) and combination tones (28 kyr) of the 41 kyr cycle. Near the end of the MPT (∼0.65 Ma), obliquity modulation of MCV amplitude wanes as quasi-periodic 100 kyr and precession power increase, coinciding with the growth of oversized ice sheets on North America and the appearance of Heinrich layers in North Atlantic sediments. Whereas the planktic δ18O of Site U1385 shows a strong resemblance to Greenland temperature and atmospheric methane (i.e. Northern Hemisphere climate), millennial changes in benthic δ18O closely follow the temperature history of Antarctica for the past 800 kyr. The phasing of millennial planktic and benthic δ18O variation is similar to that observed for MIS 3 throughout much of the record, which has been suggested to mimic the signature of the bipolar seesaw – i.e. an interhemispheric asymmetry between the timing of cooling in Antarctica and warming in Greenland. The Iberian margin isotopic record suggests that bipolar asymmetry was a robust feature of interhemispheric glacial climate variations for at least the past 1.5 Ma despite changing glacial boundary conditions. A strong correlation exists between millennial increases in planktic δ18O (cooling) and decreases in benthic δ13C , indicating that millennial variations in North Atlantic surface temperature are mirrored by changes in deep-water circulation and remineralization of carbon in the abyssal ocean. We find strong evidence that climate variability on millennial and orbital scales is coupled across different timescales and interacts in both directions, which may be important for linking internal climate dynamics and external astronomical forcing. [ABSTRACT FROM AUTHOR]

Large volcanic eruptions occurring in the last glacial period can be detected by their accompanying sulfuric acid deposition in continuous ice cores. Here we employ continuous sulfate and sulfur records from three Greenland and three Antarctic ice cores to estimate the emission strength, the frequency and the climatic forcing of large volcanic eruptions that occurred during the second half of the last glacial period and the early Holocene, 60–9 kyr before 2000 CE (b2k). Over most of the investigated interval the ice cores are synchronized, making it possible to distinguish large eruptions with a global sulfate distribution from eruptions detectable in one hemisphere only. Due to limited data resolution and large variability in the sulfate background signal, particularly in the Greenland glacial climate, we only list Greenland sulfate depositions larger than 20 kgkm-2 and Antarctic sulfate depositions larger than 10 kgkm-2. With those restrictions, we identify 1113 volcanic eruptions in Greenland and 737 eruptions in Antarctica within the 51 kyr period – for which the sulfate deposition of 85 eruptions is found at both poles (bipolar eruptions). Based on the ratio of Greenland and Antarctic sulfate deposition, we estimate the latitudinal band of the bipolar eruptions and assess their approximate climatic forcing based on established methods. A total of 25 of the identified bipolar eruptions are larger than any volcanic eruption occurring in the last 2500 years, and 69 eruptions are estimated to have larger sulfur emission strengths than the Tambora, Indonesia, eruption (1815 CE). Throughout the investigated period, the frequency of volcanic eruptions is rather constant and comparable to that of recent times. During the deglacial period (16–9 kab2k), however, there is a notable increase in the frequency of volcanic events recorded in Greenland and an obvious increase in the fraction of very large eruptions. For Antarctica, the deglacial period cannot be distinguished from other periods. This confirms the suggestion that the isostatic unloading of the Northern Hemisphere (NH) ice sheets may be related to the enhanced NH volcanic activity. Our ice-core-based volcanic sulfate records provide the atmospheric sulfate burden and estimates of climate forcing for further research on climate impact and understanding the mechanism of the Earth system. [ABSTRACT FROM AUTHOR]

In this paper, we present an electric-thermal drill with a novel design of a melting head that was developed within the EnEx-RANGE project. The design combines a short melting head with a large surface area of parabolic shape. It was succesfully tested in the laboratory as well as on Alpine glaciers (Langenferner and Mittelbergferner) and at the Ross Ice Shelf in Antarctica. In all these different environments, a high melting speed per specific power of typically 8.8 cm3 w-1 h-1 is achieved that is close to the ideal maximum bound of ~10.5-11.8 cm³ w-1 h-1 when neglecting all heat losses. It has also been demonstrated that the melting probe can be operated with typical equipment of small-scale field camps including a small power generator. [ABSTRACT FROM AUTHOR]

We analyzed the single‐grain mineralogical composition of aeolian dust transported to central East Antarctica for provenance purposes. Comparison with data from the last glacial period shows for the first time disappearance of carbonates during the Holocene related to sea level rise and suppressed deflation from the Argentinean continental shelf, exposed during Marine Isotope Stage 2. Zeolites, related to alteration of volcanic glass in the subglacial/periglacial environment of Patagonia, show a similar behavior. The remaining minerals, remarkably similar between the two climatic periods, are compatible with a Pampean and Patagonian provenance, but Holocene data show a more pronounced volcanic and metamorphic imprint and presence of minerals related to warm climate weathering environments compatible with an additional contribution from subtropical latitudes of South America. These results do not imply a major large‐scale reorganization of atmospheric circulation after the last climatic transition. Plain Language Summary: Aeolian mineral dust particles transported through the atmosphere from the austral continents to the Antarctic ice sheet represent a tracer of atmospheric circulation and transport, as well as being a source of information about environmental conditions within dust source regions. Many lines of evidence suggest that central East Antarctic dust is sourced from South America during the last glacial period, whereas there is not a general consensus about dust provenance during the Holocene. A major limitation to this problem is represented by the extremely low dust concentration in Antarctic ice during interglacials. In this study, we analyzed the single‐grain mineralogy of more than 2,300 mineral dust particles transported by winds to Dome C during four different time windows within the Holocene, the current interglacial. Comparing results with those obtained from dust deposited during the last glacial period, we observe that some minerals that are typically associated to glacial climate conditions in Patagonia almost disappear during Holocene, while the remaining minerals are compatible with a South American provenance in both climate periods. Data thus suggest that the dominant atmospheric circulation patterns did not experience a significant change with climate. However, data suggest an additional contribution from subtropical South American latitudes during Holocene. Key Points: The mineralogy of more than 2,300 aeolian dust particles windblown to central East Antarctica (Dome C) during the Holocene was identifiedDisappearance of carbonate dust during the Holocene relates to sea level rise and suppressed deflation from the Argentinean shelfAeolian dust suggests Pampean and Patagonian provenance in the Holocene and a lower latitude contribution, without major circulation changes [ABSTRACT FROM AUTHOR]

In the modern climate, the ocean below 2 km is mainly filled by waters sinking into the abyss around Antarctica and in the North Atlantic. Paleoproxies indicate that waters of North Atlantic origin were instead absent below 2 km at the Last Glacial Maximum, resulting in an expansion of the volume occupied by Antarctic origin waters. In this study we show that this rearrangement of deep water masses is dynamically linked to the expansion of summer sea ice around Antarctica. A simple theory further suggests that these deep waters only came to the surface under sea ice, which insulated them from atmospheric forcing, and were weakly mixed with overlying waters, thus being able to store carbon for long times. This unappreciated link between the expansion of sea ice and the appearance of a voluminous and insulated water mass may help quantify the ocean's role in regulating atmospheric carbon dioxide on glacial-interglacial timescales. Previous studies pointed to many independent changes in ocean physics to account for the observed swings in atmospheric carbon dioxide. Here it is shown that many of these changes are dynamically linked and therefore must co-occur. [ABSTRACT FROM AUTHOR]

The article presents a study which investigates on the use of radar diagnosis to determine the subglacial condition in Dronning Maud Land in East Antarctica. The study was performed to three ground-based and pulse-modulated radar sounders, wherein two radar sounders have a centre frequency of 179MHz. The study shows that returned power decreases in the area as ice becomes thicker.

Central East Antarctic ice cores preserve stratigraphic records of mineral dust originating from remote sources in the Southern Hemisphere, and represent useful indicators of climatic variations on glacial-interglacial time scales. The peripheries of the East Antarctic Ice Sheet, where ice-free areas with the potential to emit dust exist, have been less explored from this point of view. Here, we present a new profile of dust deposition flux and grain size distributions from an ice core drilled at Talos Dome (TALDICE, Northern Victoria Land, East Antarctica), where there is a significant input of dust from proximal Antarctic ice-free areas. We analyze dust and stable water isotopes variations from the Last Glacial Maximum to the Late Holocene, and compare them to the EPICA Dome C profiles from central East Antarctica. The smaller glacial-interglacial variations at Talos Dome compared to Dome C and a distinctive decreasing trend during the Holocene characterize the TALDICE dust profile. By deciphering the composite dust signal from both remote and local sources, we show the potential of this combined proxy of source activity and atmospheric transport to give information on both regional and larger spatial scales. In particular, we show how a regional signal, which we relate to the deglaciation history of the Ross Sea embayment, can be superimposed to the broader scale glacial-interglacial variability that characterizes other Antarctic sites. [ABSTRACT FROM AUTHOR]

During glacial periods, atmospheric CO2 concentration increases and decreases by around 15 ppm. At the same time, the climate changes gradually in Antarctica. Such climate changes can be simulated in models when the AMOC (Atlantic Meridional Oceanic Circulation) is weakened by adding fresh water to the North Atlantic. The impact on the carbon cycle is less straightforward, and previous studies give opposite results. Because the models and the fresh water fluxes were different in these studies, it prevents any direct comparison and hinders finding whether the discrepancies arise from using different models or different fresh water fluxes. In this study we use the CLIMBER-2 coupled climate carbon model to explore the impact of different fresh water fluxes. In both preindustrial and glacial states, the addition of fresh water and the resulting slow-down of the AMOC lead to an uptake of carbon by the ocean and a release by the terrestrial biosphere. The duration, shape and amplitude of the fresh water flux all have an impact on the change of atmospheric CO2 because they modulate the change of the AMOC. The maximum CO2 change linearly depends on the time integral of the AMOC change. The different duration, amplitude, and shape of the fresh water flux cannot explain the opposite evolution of ocean and vegetation carbon inventory in different models. The different CO2 evolution thus depends on the AMOC response to the addition of fresh water and the resulting climatic change, which are both model dependent. In CLIMBER-2, the rise of CO2 recorded in ice cores during abrupt events can be simulated under glacial conditions, especially when the sinking of brines in the Southern Ocean is taken into account. The addition of fresh water in the Southern Hemisphere leads to a decline of CO2, contrary to the addition of fresh water in the Northern Hemisphere. [ABSTRACT FROM AUTHOR]

The article focuses on the deep ice core drilling in Lake Vostok, Antarctica. It states that the drilling started in the 1970s using thermal drill system hanged on a cable. It cites that the Vostok ice core provided a detailed paleoclimate record during the past four glacial-interglacial cycles that occurs every 100,000 years. It also mentions that studies of sub-glacial water properties are important parts for the drilling project in Lake Vostok.

During the last glacial/interglacial transition the Earth's climate underwent abrupt changes around 14.6 kyr ago. Temperature proxies from ice cores revealed the onset of the Bølling/Allerød (B/A) warm period in the north and the start of the Antarctic Cold Reversal in the south. Furthermore, the B/A was accompanied by a rapid sea level rise of about 20m during meltwater pulse (MWP) 1A, whose exact timing is a matter of current debate. In-situ measured CO2 in the EPICA Dome C (EDC) ice core also revealed a remarkable jump of 10±1 ppmv in 230 yr at the same time. Allowing for the modelled age distribution of CO2 in firn, we show that atmospheric CO2 could have jumped by 20-35 ppmv in less than 200 yr, which is a factor of 2-3.5 greater than the CO2 signal recorded in-situ in EDC. This rate of change in atmospheric CO2 corresponds to 29-50% of the anthropogenic signal during the last 50 yr and is connected with a radiative forcing of 0.59-0.75 W m-2. Using a model-based airborne fraction of 0.17 of atmospheric CO2, we infer that 125 Pg of carbon need to be released into the atmosphere to produce such a peak. If the abrupt rise in CO2 at the onset of the B/A is unique with respect to other Dansgaard/Oeschger (D/O) events of the last 60 kyr (which seems plausible if not unequivocal based on current observations), then the mechanism responsible for it may also have been unique. Available δ13CO2 data are neutral, whether the source of the carbon is of marine or terrestrial origin. We therefore hypothesise that most of the carbon might have been activated as a consequence of continental shelf flooding during MWP-1A. This potential impact of rapid sea level rise on atmospheric CO2 might define the point of no return during the last deglaciation. [ABSTRACT FROM AUTHOR]

Antarctica has a complex and multifaceted geologic and oceanographic history that has influenced and shaped patterns of marine invertebrate diversity. This evolutionary history consists of major events on a wide range of time scales such as the formation of the Antarctic Polar Front (25–41 million years ago) to repeated glacial cycles during the past million years. These factors variably influenced genetic connectivity of fauna to produce a highly unique, but incredibly diverse marine community. Use of molecular phylogeographic methods is creating the need to revise our understanding of Antarctic patterns of biodiversity. In particular, almost every phylogeographic study carried out to date, suggests that the biodiversity of Antarctic marine shelf fauna is considerably underestimated. In discovering this diversity, some lineages (i.e., cryptic lineages) show no diagnostic morphological differences whereas others (i.e., unrecognized species) show differences that were unknown to science. The sea star genus Odontaster is among the best-studied of Antarctic invertebrate groups. Nonetheless, two unrecognized lineages were recently discovered along the Antarctic Peninsula, which is one of the best-studied regions in Antarctica. Herein, we elucidate the molecular and morphological uniqueness of these species and name them O. roseus and O. pearsei. The latter is in honor of John Pearse, an Antarctic biologist, as well as past President and long-time member of the Society of Integrative and Comparative Biology. [ABSTRACT FROM AUTHOR]

Rapid warming and consequent ice-shelf collapse have focused attention on the glacial record of the Antarctic Peninsula. Here, we present the fi rst record of terrestrial organic material exposed by recently retreating ice that bears on past glacier extent and climate in this sensitive region. Radiocarbon dates show that ice on Anvers Island was at or behind its present position at 700-970 cal. yr B.P., coincident with ice reduction elsewhere in the Southern Hemisphere. Moreover, the data indicate that present reduced ice extent on the western Antarctic Peninsula is not unprecedented and is similar to that experienced during at least three periods in the last 5600 yr. [ABSTRACT FROM AUTHOR]

The retreat history of the West Antarctic Ice Sheet (WAIS) since the Last Glacial Maximum is important for understanding the process of rapid deglaciation, constraining models that seek to predict the future trajectory of the ice sheet, and for estimating rates of sea-level change. Here we report new glacial geologic data from the southwestern Weddell Sea embayment that demonstrate that this part of the WAIS was thinner than previously suggested, and that there was progressive thinning of the ice sheet by 230-480 m since ca. 15 ka. We use geomorphological data and a numerical ice sheet model to reconstruct the ice sheet in the Weddell Sea at the Last Glacial Maximum. The volume of this ice would have added between 1.4 and 2.0 m to postglacial sea-level rise and would not have been suffi cient to contribute signifi cantly to meltwater pulse 1A, a rapid rise in sea level ∼14,200 yr ago. [ABSTRACT FROM AUTHOR]

Stable isotope ratios of oxygen and hydrogen in the Antarctic ice core record have revolutionized our understanding of Pleistocene climate variations and have allowed reconstructions of Antarctic temperature over the past 800,000 years (800 kyr; refs 1, 2). The relationship between the D/H ratio of mean annual precipitation and mean annual surface air temperature is said to be uniform ±10% over East Antarctica and constant with time ±20% (refs 3–5). In the absence of strong independent temperature proxy evidence allowing us to calibrate individual ice cores, prior general circulation model (GCM) studies have supported the assumption of constant uniform conversion for climates cooler than that of the present day. Here we analyse the three available 340 kyr East Antarctic ice core records alongside input from GCM modelling. We show that for warmer interglacial periods the relationship between temperature and the isotopic signature varies among ice core sites, and that therefore the conversions must be nonlinear for at least some sites. Model results indicate that the isotopic composition of East Antarctic ice is less sensitive to temperature changes during warmer climates. We conclude that previous temperature estimates from interglacial climates are likely to be too low. The available evidence is consistent with a peak Antarctic interglacial temperature that was at least 6 K higher than that of the present day —approximately double the widely quoted 3 ± 1.5 K (refs 5, 6). [ABSTRACT FROM AUTHOR]

A semi-empirical model has been developed to reproduce glacial–interglacial changes of continental dust and marine sodium concentrations (factor of ∼50 and ∼5, respectively) observed in inland Antarctic ice cores. The model uses conceptual pathways of aerosols within the high troposphere; assumes the dry deposition of impurities on the Antarctic surface; uses estimates of aerosol transit times taken independent of climate; assumes a temperature-dependent removal process during aerosol pathways from the mid-latitudes. The model is fitted to the data over the last four climate cycles from Vostok and EPICA Dome C Antarctic sites. As temperature is cooling, the aerosol response suggests different modes of climate couplings between latitudes, which can be continuous or below temperature thresholds for sodium and dust, respectively. The model estimates a southern South America dust source activity two to three times higher for glacial periods than for the Holocene and a glacial temperature over the Southern Ocean 3–5 °C cooler. Both estimates appear consistent with independent observations. After removal of temperature effects, dust and sodium residuals for both sites show orbital frequencies in opposite phase at the precession timescale. Such long-term insolation-related modulation of terrestrial and marine aerosol input, could provide a chemical pacemaker useful for refining ice core chronologies. [ABSTRACT FROM AUTHOR]

Recent data revealed that metazoans such as mites and springtails have persisted in Antarctica throughout several glacial–interglacial cycles, which contradicts the existing paradigm that terrestrial life was wiped out by successive glacial events and that the current inhabitants are recent colonizers. We used molecular phylogenetic techniques to study Antarctic microchlorophyte strains isolated from lacustrine habitats from maritime and continental Antarctica. The 14 distinct chlorophycean and trebouxiophycean lineages observed point to a wide phylogenetic diversity of apparently endemic Antarctic lineages at different taxonomic levels. This supports the hypothesis that long-term survival took place in glacial refugia, resulting in a specific Antarctic flora. The majority of the lineages have estimated ages between 17 and 84 Ma and probably diverged from their closest relatives around the time of the opening of Drake Passage (30–45 Ma), while some lineages with longer branch lengths have estimated ages that precede the break-up of Gondwana. The variation in branch length and estimated age points to several independent but rare colonization events. [ABSTRACT FROM AUTHOR]

Ice cores extracted from the Antarctic ice sheet suggest that glacial conditions, and the relationship between isotopically derived temperatures and atmospheric have been constant over the last 800,000 years of the Late Pleistocene epoch. But independent lines of evidence, such as the extent of Northern Hemisphere ice sheets, sea level and other temperature records, point towards a fluctuating severity of glacial periods, particularly during the more extreme glacial stadials centred around 340,000 and 420,000 years ago (marine isotope stages 10 and 12). Previously unidentified mechanisms therefore appear to have mediated the relationship between insolation, CO2 and climate. Here we test whether northward migration of the subtropical front (STF) off the southeastern coast of South Africa acts as a gatekeeper for the Agulhas current, which controls the transport of heat and salt from the Indo-Pacific Ocean to the Atlantic Ocean. Using a new 800,000-year record of sea surface temperature and ocean productivity from ocean sediment core MD962077, we demonstrate that during cold stadials (particularly marine isotope stages 10 and 12), productivity peaked and sea surface temperature was up to 6 °C cooler than modern temperatures. This suggests that during these cooler stadials, the STF moved northward by up to 7° latitude, nearly shutting off the Agulhas current. Our results, combined with faunal assemblages from the south Atlantic show that variable northwards migration of the Southern Hemisphere STF can modulate the severity of each glacial period by altering the strength of the Agulhas current carrying heat and salt to the Atlantic meridional overturning circulation. We show hence that the degree of northwards migration of the STF can partially decouple global climate from atmospheric partial pressure of carbon dioxide, , and help to resolve the long-standing puzzle of differing glacial amplitudes within a consistent range of atmospheric . [ABSTRACT FROM AUTHOR]

Ice-sheet development in Antarctica was a result of significant and rapid global climate change about 34 million years ago. Ice-sheet and climate modelling suggest reductions in atmospheric carbon dioxide (less than three times the pre-industrial level of 280 parts per million by volume) that, in conjunction with the development of the Antarctic Circumpolar Current, led to cooling and glaciation paced by changes in Earth’s orbit. Based on the present subglacial topography, numerical models point to ice-sheet genesis on mountain massifs of Antarctica, including the Gamburtsev mountains at Dome A, the centre of the present ice sheet. Our lack of knowledge of the present-day topography of the Gamburtsev mountains means, however, that the nature of early glaciation and subsequent development of a continental-sized ice sheet are uncertain. Here we present radar information about the base of the ice at Dome A, revealing classic Alpine topography with pre-existing river valleys overdeepened by valley glaciers formed when the mean summer surface temperature was around 3 °C. This landscape is likely to have developed during the initial phases of Antarctic glaciation. According to Antarctic climate history (estimated from offshore sediment records) the Gamburtsev mountains are probably older than 34 million years and were the main centre for ice-sheet growth. Moreover, the landscape has most probably been preserved beneath the present ice sheet for around 14 million years. [ABSTRACT FROM AUTHOR]

We correlate the China loess and Antarctica ice records to address the inter-hemispheric climate link over the past 800ka. The results show a broad coupling between Asian and Antarctic climates at the glacial-interglacial scale. However, a number of decoupled aspects are revealed, among which marine isotope stage (MIS) 13 exhibits a strong anomaly compared with the other interglacials. It is characterized by unusually positive benthic oxygen (8180) and carbon isotope (δ13C) values in the world oceans, cooler Antarctic temperature, lower summer sea surface temperature in the South Atlantic, lower CO2 and CH4 concentrations, but by extremely strong Asian, Indian and African summer monsoons, weakest Asian winter monsoon, and lowest Asian dust and iron fluxes. Pervasive warm conditions were also evidenced by the records from northern high-latitude regions. These consistently indicate a warmer Northern Hemi- sphere and a cooler Southern Hemisphere, and hence a strong asymmetry of hemispheric climates during MIS-13. Similar anomalies of lesser extents also occurred during MIS-11 and MIS-5e. Thus, MIS-13 provides a case that the Northern Hemisphere experienced a substantial warming under relatively low concentrations of greenhouse gases. It suggests that the global climate system possesses a natural variability that is not predictable from the simple response of northern summer insolation and atmospheric CO2 changes. During MIS-13, both hemispheres responded in different ways leading to anomalous continental, marine and atmospheric conditions at the global scale. The correlations also suggest that the marine δ18O record is not always a reliable indicator of the northern ice-volume changes, and that the asymmetry of hemispheric climates is one of the prominent factors controlling the strength of Asian, Indian and African monsoon circulations, most likely through modulating the position of the inter-tropical convergence zone (ITCZ) and land-sea thermal contrasts. [ABSTRACT FROM AUTHOR]

Changes in past atmospheric carbon dioxide concentrations can be determined by measuring the composition of air trapped in ice cores from Antarctica. So far, the Antarctic Vostok and EPICA Dome C ice cores have provided a composite record of atmospheric carbon dioxide levels over the past 650,000 years. Here we present results of the lowest 200 m of the Dome C ice core, extending the record of atmospheric carbon dioxide concentration by two complete glacial cycles to 800,000 yr before present. From previously published data and the present work, we find that atmospheric carbon dioxide is strongly correlated with Antarctic temperature throughout eight glacial cycles but with significantly lower concentrations between 650,000 and 750,000 yr before present. Carbon dioxide levels are below 180 parts per million by volume (p.p.m.v.) for a period of 3,000 yr during Marine Isotope Stage 16, possibly reflecting more pronounced oceanic carbon storage. We report the lowest carbon dioxide concentration measured in an ice core, which extends the pre-industrial range of carbon dioxide concentrations during the late Quaternary by about 10 p.p.m.v. to 172–300 p.p.m.v. [ABSTRACT FROM AUTHOR]

Today, Antarctica exhibits some of the harshest environmental conditions for life on Earth. During the last glacial period, Antarctic terrestrial and marine life was challenged by even more extreme environmental conditions. During the present interglacial period, polar life in the Southern Ocean is sustained mainly by large-scale primary production. We argue that during the last glacial period, faunal populations in the Antarctic were limited to very few areas of local marine productivity (polynyas), because complete, multiannual service and ice shelf coverage shut down most of the Southern Ocean productivity within today's seasonal sea-ice zone. Both marine sediments containing significant numbers of planktonic and benthic foraminifera and fossil bird stomach oil deposits in the adjacent Antarctic hinterland provide indirect evidence for the existence of polynyas during the last glacial period. We advocate that the existence of productive oases in the form of polynyas during glacial periods was essential for the survival of marine and most higher-trophic terrestrial fauna. Reduced to such refuges, much of today's life in the high Antarctic realm might have hung by a thread during the last glacial period, because limited resources available to the food web restricted the abundance and productivity of both Antarctic terrestrial and marine life. [ABSTRACT FROM AUTHOR]

The Milankovitch theory of climate change proposes that glacial–interglacial cycles are driven by changes in summer insolation at high northern latitudes. The timing of climate change in the Southern Hemisphere at glacial–interglacial transitions (which are known as terminations) relative to variations in summer insolation in the Northern Hemisphere is an important test of this hypothesis. So far, it has only been possible to apply this test to the most recent termination, because the dating uncertainty associated with older terminations is too large to allow phase relationships to be determined. Here we present a new chronology of Antarctic climate change over the past 360,000 years that is based on the ratio of oxygen to nitrogen molecules in air trapped in the Dome Fuji and Vostok ice cores. This ratio is a proxy for local summer insolation, and thus allows the chronology to be constructed by orbital tuning without the need to assume a lag between a climate record and an orbital parameter. The accuracy of the chronology allows us to examine the phase relationships between climate records from the ice cores and changes in insolation. Our results indicate that orbital-scale Antarctic climate change lags Northern Hemisphere insolation by a few millennia, and that the increases in Antarctic temperature and atmospheric carbon dioxide concentration during the last four terminations occurred within the rising phase of Northern Hemisphere summer insolation. These results support the Milankovitch theory that Northern Hemisphere summer insolation triggered the last four deglaciations. [ABSTRACT FROM AUTHOR]

A high-resolution deuterium profile is now available along the entire European Project for Ice Coring in Antarctica Dome C ice core, extending this climate record back to marine isotope stage 20.2, ∼800,000 years ago. Experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation. We assessed the general correspondence between Dansgaard-Oeschger events and their smoothed Antarctic counterparts for this Dome C record, which reveals the presence of such features with similar amplitudes during previous glacial periods. We suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records. [ABSTRACT FROM AUTHOR]

Precise knowledge of the phase relationship between climate changes in the two hemispheres is a key for understanding the Earth’s climate dynamics. For the last glacial period, ice core studies have revealed strong coupling of the largest millennial-scale warm events in Antarctica with the longest Dansgaard–Oeschger events in Greenland through the Atlantic meridional overturning circulation. It has been unclear, however, whether the shorter Dansgaard–Oeschger events have counterparts in the shorter and less prominent Antarctic temperature variations, and whether these events are linked by the same mechanism. Here we present a glacial climate record derived from an ice core from Dronning Maud Land, Antarctica, which represents South Atlantic climate at a resolution comparable with the Greenland ice core records. After methane synchronization with an ice core from North Greenland, the oxygen isotope record from the Dronning Maud Land ice core shows a one-to-one coupling between all Antarctic warm events and Greenland Dansgaard–Oeschger events by the bipolar seesaw6. The amplitude of the Antarctic warm events is found to be linearly dependent on the duration of the concurrent stadial in the North, suggesting that they all result from a similar reduction in the meridional overturning circulation. [ABSTRACT FROM AUTHOR]

We propose that from ∼3 to 1 million years ago, ice volume changes occurred in both the Northern and Southern Hemispheres, each controlled by local summer insolation. Because Earth's orbital precession is out of phase between hemispheres, 23,000-year changes in ice volume in each hemisphere cancel out in globally integrated proxies such as ocean δ18O or sea level, leaving the in-phase obliquity (41,000 years) component of insolation to dominate those records. Only a modest ice mass change in Antarctica is required to effectively cancel out a much larger northern ice volume signal. At the mid-Pleistocene transition, we propose that marine-based ice sheet margins replaced terrestrial ice margins around the perimeter of East Antarctica, resulting in a shift to in-phase behavior of northern and southern ice sheets as well as the strengthening of 23,000-year cyclicity in the marine δ18O record. [ABSTRACT FROM AUTHOR]

Marine and rift sediments exert a fundamental control on ice stream flow in the West Antarctic Ice Sheet, and hence on its mass balance and stability. In contrast, most ice streams in the much larger East Antarctic Ice Sheet are thought to be relatively stable features resting on till, perhaps underlain by crystalline rock. Any geological controls on East Antarctic Ice Sheet enhanced flow remain largely unknown. We present aerogeophysical evidence indicating that a region of enhanced ice flow in the interior of the East Antarctic Ice Sheet is underlain by subglacial sediments ∼3 km thick and that these are influencing the flow regime of the overlying ice. We show that subglacial sediments are important in modulating ice dynamics, not just for the West Antarctic Ice Sheet, but also for its much larger neighbor, and suggest that the sedimentary basin identified here may contain information on the Neogene glacial history of this part of the East Antarctic Ice Sheet. [ABSTRACT FROM AUTHOR]

Since the first evidence of low algal productivity during ice ages in the Antarctic Zone of the Southern Ocean was discovered, there has been debate as to whether it was associated with increased polar ocean stratification or with sea-ice cover, shortening the productive season. The sediment concentration of biogenic barium at Ocean Drilling Program site 882 indicates low algal productivity during ice ages in the Subarctic North Pacific as well. Site 882 is located southeast of the summer sea-ice extent even during glacial maxima, ruling out sea-ice-driven light limitation and supporting stratification as the explanation, with implications for the glacial cycles of atmospheric carbon dioxide concentration. [ABSTRACT FROM AUTHOR]

The Antarctic Vostok ice core provided compelling evidence of the nature of climate, and of climate feedbacks, over the past 420,000 years. Marine records suggest that the amplitude of climate variability was smaller before that time, but such records are often poorly resolved. Moreover, it is not possible to infer the abundance of greenhouse gases in the atmosphere from marine records. Here we report the recovery of a deep ice core from Dome C, Antarctica, that provides a climate record for the past 740,000 years. For the four most recent glacial cycles, the data agree well with the record from Vostok. The earlier period, between 740,000 and 430,000 years ago, was characterized by less pronounced warmth in interglacial periods in Antarctica, but a higher proportion of each cycle was spent in the warm mode. The transition from glacial to interglacial conditions about 430,000 years ago (Termination V) resembles the transition into the present interglacial period in terms of the magnitude of change in temperatures and greenhouse gases, but there are significant differences in the patterns of change. The interglacial stage following Termination V was exceptionally long-28,000 years compared to, for example, the 12,000 years recorded so far in the present interglacial period. Given the similarities between this earlier warm period and today, our results may imply that without human intervention, a climate similar to the present one would extend well into the future. [ABSTRACT FROM AUTHOR]

The question of how stable the climate in Antarctica has been during the last few million years compared to the rest of the planet is still controversial. This study attempts to add new information to the discussion by reconstructing the timing and spatial extent of glacial advances in northern Victoria Land over tens of thousands to millions of years. In Terra Nova Bay region, surface exposure ages and erosion rates of glacially rounded bedrock and glacial erratics have been determined using the cosmogenic nuclides ³He, [sup10]Be and [sup21]Ne. Three morphological units have been analysed. They yield minimum ages of 11 to 34 ka, 309 ka, and 2.6 Ma, respectively. Erosion rates were as low as 20 cm Ma[sup-1] since middle Pliocene time. Taking erosion into account, the oldest surface is 5.3 Ma old. Pleistocene glacier advances had considerable extent, reaching up to 780 m above modem ice levels, but have been restricted to the valleys since at least mid-Pliocene. The existence of landscapes of mid-Pliocene age in northern Victoria Land implies that the climatic stability of the McMurdo Dry Valleys is not unique within the Transantarctic Mountains, but rather the expression of a constantly cold and hyperarid climate regime in entire Victoria Land. [ABSTRACT FROM AUTHOR]

Recent ice core studies have raised the disturbing possibility that glacial-interglacial climate changes may be non-uniform across Antarctica. These findings have been confined to records from the Ross Sea sector of the continent, but significant deviations in other areas would call into question the widely assumed validity of the climate record obtained from Vostok, East Antarctica, on large spatial scales. Here we present an isotopic profile from a core drilled at Dome Fuji, situated 1,500?km from Vostok in a different sector of East Antarctica. The two records show remarkable similarities over the past three glacial cycles (the extent of the Dome Fuji record) in both large-amplitude changes, such as terminations, interglacials and interstadials and more subtle glacial events, even when the origin of precipitation is accounted for. Our results indicate that Antarctic climate is essentially homogeneous at the scale of the East Antarctic Plateau, possibly as a consequence of the symmetry of the plateau and the adjacent ocean. [ABSTRACT FROM AUTHOR]

abstract A deep ice core drilled at Dome Fuji, East Antarctica was analyzed for the CO2 concentration using a wet extraction method in order to reconstruct its atmospheric variations over the past 320 kyr, which includes three full glacial–interglacial climatic cycles, with a mean time resolution of about 1.1 kyr. The CO2 concentration values derived for the past 65 kyr are very close to those obtained from other Antarctic ice cores using dry extraction methods, although the wet extraction method is generally thought to be inappropriate for the determination of the CO2 concentration. The comparison between the CO2 and Ca2+ concentrations deduced from the Dome Fuji core suggests that calcium carbonate emitted from lands was mostly neutralized in the atmosphere before reaching the central part of Antarctica, or that only a small part of calcium carbonate was involved in CO2 production during the wet extraction process. The CO2 concentration for the past 320 kyr deduced from the Dome Fuji core varies between 190 and 300 ppmv, showing clear glacial–interglacial variations similar to the result of the Vostok ice core. However, for some periods, the concentration values of the Dome Fuji core are higher by up to 20 ppmv than those of the Vostok core. There is no clear indication that such differences are related to variations of chemical components of Ca2+ , microparticle and acidity of the Dome Fuji core. [ABSTRACT FROM AUTHOR]

The sudden, widespread glaciation of Antarctica and the associated shift towards colder temperatures at the Eocene/Oligocene boundary (∼34 million years ago) (refs 1-4) is one of the most fundamental reorganizations of global climate known in the geologic record. The glaciation of Antarctica has hitherto been thought to result from the tectonic opening of Southern Ocean gateways, which enabled the formation of the Antarctic Circumpolar Current and the subsequent thermal isolation of the Antarctic continent[SUP5]. Here we simulate the glacial inception and early growth of the East Antarctic Ice Sheet using a general circulation model with coupled components for atmosphere, ocean, ice sheet and sediment, and which incorporates palaeogeography, greenhouse gas, changing orbital parameters, and varying ocean heat transport. In our model, declining Cenozoic CO[SUB2] first leads to the formation of small, highly dynamic ice caps on high Antarctic plateaux. At a later time, a CO[SUB2] threshold is crossed, initiating ice-sheet height/mass-balance feedbacks that cause the ice caps to expand rapidly with large orbital variations, eventually coalescing into a continental-scale East Antarctic Ice Sheet. According to our simulation the opening of Southern Ocean gateways plays a secondary role in this transition, relative to CO[SUB2] concentration. [ABSTRACT FROM AUTHOR]

The sudden, widespread glaciation of Antarctica and the associated shift towards colder temperatures at the Eocene/Oligocene boundary (∼34 million years ago) (refs 1-4) is one of the most fundamental reorganizations of global climate known in the geologic record. The glaciation of Antarctica has hitherto been thought to result from the tectonic opening of Southern Ocean gateways, which enabled the formation of the Antarctic Circumpolar Current and the subsequent thermal isolation of the Antarctic continent[SUP5]. Here we simulate the glacial inception and early growth of the East Antarctic Ice Sheet using a general circulation model with coupled components for atmosphere, ocean, ice sheet and sediment, and which incorporates palaeogeography, greenhouse gas, changing orbital parameters, and varying ocean heat transport. In our model, declining Cenozoic CO[SUB2] first leads to the formation of small, highly dynamic ice caps on high Antarctic plateaux. At a later time, a CO[SUB2] threshold is crossed, initiating ice-sheet height/mass-balance feedbacks that cause the ice caps to expand rapidly with large orbital variations, eventually coalescing into a continental-scale East Antarctic Ice Sheet. According to our simulation the opening of Southern Ocean gateways plays a secondary role in this transition, relative to CO[SUB2] concentration. [ABSTRACT FROM AUTHOR]

Features a record of atmospheric carbon dioxide concentration during the transition from the Last Glacial Maximum to the Holocene, obtained from the Dome Concordia, Antarctica, ice core. Increase of 76 parts per million by volume over a period of 6000 years in four clearly distinguishable intervals; Correlation between carbon dioxide concentration and Antarctic temperature.

The article reports on Antarctic ice-core data offering insights into interhemispheric climatic changes during the last glacial period in the Northern Hemisphere. The authors discuss warming trends known as Dansgaard–Oeschger (DO) events, explore the presence of hemispheric climate coupling, and examine the Atlantic meridional overturning circulation (AMOC).

The article focuses on the study conducted by L. C. Sime and colleagues describing the ways on how they have used climate- model simulations to re-examine the temperature history that has been recorded by the isotopic composition of three long ice cores from Antarctica. The researchers conclude that the previous estimates of the southern-polar warmth during the Eemian and other interglacials have been underestimates. Sime along with his colleagues suggest that temperatures that have peaked at about 6 kelvin higher than at present, about double the usually accepted figure.

The article discusses two research papers concerning the generating of data to allow human knowledge of climatic conditions in past epochs to serve as a model for future sea-level rise resulting from global warming. The papers focus on the early to middle Pliocene Period to reconstruct Antarctica's glacial history. Observational evidence was obtained from a sediment core taken from beneath the Ross Ice Shelf, providing the authors with insight about cycles dictating summer sea ice and tectonic forces.

The article explores how the Antarctic ice sheet has changed in recent years by tracking mass changes. The methods for measuring mass changes mentioned in the article include subtracting the melt and ice flow from the total snowfall, sensing changes in the strength of gravity using pairs of satellites, and repeat mapping of surface elevations from satellites. A study cited in this article, which applied the repeated mapping method, showed that a correction must be made for changes in the density of the firn layer on the ice sheet surface.

Reveals a record of Earth's climate over the eight past ice ages and their associated interglacial periods from an ice core in Antarctica. Evidence for the past climatic instability of the last glacial cycle; Dome C record; Shift in the pattern of glacial cycles that occurred without changes in the varying seasonal distribution of sunlight that is believed to pace the ice ages.

Examines research that studied the cores of large polar ice sheets to describe glacial-interglacial cycles. Extent of the core record; Research by Petit et al in this issue; Previous research; Details about the four transitions from glacial to warm epochs evident from Vostok drillings in Antarctica; Interplay between greenhouse gases and climate; Role of CO2 in temperature increases; Mechanisms governing global climate change. INSET: Box 1: Ice cores south and north.

The article presents an interview with Eric Wolff, a scientist from the British Antarctic Survey in Great Britain. When ask about his working experienced in Antarctica, he answered that it was exciting to work in that international program. Wolff urged that his job in chopping up the ice into different sections had spent a lot of time. He also explains how he have derived for the eight glacial cycles.