Glaciation Of Antarctica Research Articles

ICE VELOCITY MEASUREMENT IN EAST ANTARCTICA FROM 1960s TO 1980s BASED ON ARGON AND LANDSAT IMAGERY

Abstract. Ice flow velocity is a vital parameter for estimating the ice mass balance of glaciers in Antarctica. Especially long time serial observation of the surface velocity is of great significance to assessing the relationship between Antarctic ice materials and global climate change. However, the existing research on Antarctic ice velocity based on remote sensing data since 1970s due to the harsh climate in Antarctica. This paper presents an ice flow velocity estimating method includes image pre-processing, geometric model reconstruction, image ortho-rectification and feature matching by using ARGON images token in 1963 and Landsat images collected form 1973 to 1989.Considering the temporal-spatial distributions of ARGON images and Landsat images in Antarctica, two different methods respectively based on ortho-photos pair and Non-Ortho photos are adopted in this paper. More specifically, when there exist two stereo pairs taken in different time in the glacier region, after being ortho-rectified, the stereo pairs can be used to calculate ice flow velocity based on feature matching method. Otherwise, a parallax decomposition method that separates the effect of the terrain relief from the ice flow motion is applied when there only exists one stereo pair with a certain time interval. With this method, glacier surface velocity is available in the glacier region lacked enough stereo pairs. The methods mentioned above for estimating ice flow velocity are applied in Totten, Amery and Fimbul, etc. in eastern Antarctica. Furthermore, a 1960-80s ice flow speed map in the main glaciers of East Antarctica is produced for the first time.

Obliquity-paced climate change recorded in Antarctic debris-covered glaciers

The degree to which debris-covered glaciers record past environmental conditions is debated. Here we describe a novel palaeoclimate archive derived from the surface morphology and internal debris within cold-based debris-covered glaciers in Antarctica. Results show that subtle changes in mass balance impart major changes in the concentration of englacial debris and corresponding surface topography, and that over the past ∼220 ka, at least, the changes are related to obliquity-paced solar radiation, manifest as variations in total summer energy. Our findings emphasize solar radiation as a significant driver of mass balance changes in high-latitude mountain systems, and demonstrate that debris-covered glaciers are among the most sensitive recorders of obliquity-paced climate variability in interior Antarctica, in contrast to most other Antarctic archives that favour eccentricity-paced forcing over the same time period. Furthermore, our results open the possibility that similar-appearing debris-covered glaciers on Mars may likewise hold clues to environmental change.

Carbon–ocean gateway links

A global cooling trend culminated in the glaciation of Antarctica during the Eocene–Oligocene transition. Simulations suggest that ocean circulation changes and enhanced drawdown of atmospheric carbon dioxide can explain this climate shift.

Temporal variations in the flow velocity for Shirase Glacier in Antarctica over a 20-year period

1996年から1998年のJapanese Earth Resources Satellite-1（JERS-1）衛星搭載のSynthetic Aperture Radar（SAR）の15 シーン，2007年から2010年のAdvanced Land Observing Satellite（ALOS）衛星搭載のPhased Array type L-band SAR（PALSAR）の17シーン，2014年から2015年のALOS-2衛星搭載のPALSAR-2の12シーンから，それぞれ12ペア，12ペア，11ペアの画像に対して画像相関法を適用し，南極・白瀬氷河の流動速度変動を調べた．2014年から2015年において，上流からGrounding line（GL）へと向かって流動速度が急激に速くなり，GLを挟む幅20kmの流域において一定となり，GLから下流そして浮氷舌へと再び流動速度がなだらかに速くなる傾向が見られた．この傾向は，1996年から1998年にJERS-1/SARおよび2007年から2009年にALOS/PALSARで観測された流動速度プロファイルから大局的には変化していないと考えられ，また流動速度も2.33kma−1（1996年）から2.26kma−1（2015年）で大きな変化は見られなかった．しかし，GLからの距離の関数として示した中央流線上では，上流域での速度に有意な経年変化が見られた．GLより5km上流から上流方向へ流動速度は増加しており，約18km上流では1996年から1998年を基準とした場合，2007年から2010年および2014年から2015年のそれぞれで0.57kma−1，0.72kma−1と最大の速度上昇に達した．30km上流ではそれぞれ0.25kma−1，0.35kma−1を示した．

Response of the Pacific inter-tropical convergence zone to global cooling and initiation of Antarctic glaciation across the Eocene Oligocene Transition.

Approximately 34 million years ago across the Eocene–Oligocene transition (EOT), Earth’s climate tipped from a largely unglaciated state into one that sustained large ice sheets on Antarctica. Antarctic glaciation is attributed to a threshold response to slow decline in atmospheric CO2 but our understanding of the feedback processes triggered and of climate change on the other contents is limited. Here we present new geochemical records of terrigenous dust accumulating on the sea floor across the EOT from a site in the central equatorial Pacific. We report a change in dust chemistry from an Asian affinity to a Central-South American provenance that occurs geologically synchronously with the initiation of stepwise global cooling, glaciation of Antarctica and aridification on the northern continents. We infer that the inter-tropical convergence zone of intense precipitation extended to our site during late Eocene, at least four degrees latitude further south than today, but that it migrated northwards in step with global cooling and initiation of Antarctic glaciation. Our findings point to an atmospheric teleconnection between extratropical cooling and rainfall climate in the tropics and the mid-latitude belt of the westerlies operating across the most pivotal transition in climate state of the Cenozoic Era.

The impact of glacier retreat from the Ross Sea on local climate: Characterization of mineral dust in the Taylor Dome ice core, East Antarctica

Recent declines in ice shelf and sea ice extent experienced in polar regions highlight the importance of evaluating variations in local weather patterns in response to climate change. Airborne mineral particles (dust) transported through the atmosphere and deposited on ice sheets and glaciers in Antarctica and Greenland can provide a robust set of tools for resolving the evolution of climatic systems through time. Here we present the first high time resolution radiogenic isotope (strontium and neodymium) data for Holocene dust in a coastal East Antarctic ice core, accompanied by rare earth element composition, dust concentration, and particle size distribution during the last deglaciation. We aim to use these combined ice core data to determine dust provenance, with variations indicative of shifts in either dust production, sources, and/or transport pathways. We analyzed a series of 17 samples from the Taylor Dome (77°47′47″S, 158°43′26″E) ice core, 113–391 m in depth from 1.1–31.4 ka. Radiogenic isotopic and rare earth element compositions of dust during the last glacial period are in good agreement with previously measured East Antarctic ice core dust records. In contrast, the Holocene dust dataset displays a broad range in isotopic and rare earth element compositions, suggesting a shift from long-range transported dust to a more variable, local input that may be linked to the retreat of the Ross Ice Shelf during the last deglaciation. Observed changes in the dust cycle inferred from a coastal East Antarctic ice core can thus be used to infer an evolving local climate.

Sheet, stream, and shelf flow as progressive ice-bed uncoupling: Byrd Glacier, Antarctica and Jakobshavn Isbrae, Greenland

Abstract. The first-order control of ice thickness and height above sea level is linked to the decreasing strength of ice-bed coupling along flowlines from an interior ice divide to the calving front of an ice shelf. Uncoupling progresses as a frozen bed progressively thaws for sheet flow, as a thawed bed is progressively drowned for stream flow, and as lateral and/or local grounding vanish for shelf flow. This can reduce ice thicknesses by 90 % and ice elevations by 99 % along flowlines. Original work presented here includes (1) replacing flow and sliding laws for sheet flow with upper and lower yield stresses for creep in cold overlying ice and basal ice sliding over deforming till, respectively, (2) replacing integrating the Navier–Stokes equations for stream flow with geometrical solutions to the force balance, and (3) including resistance to shelf flow caused by lateral confinement in a fjord and local grounding at ice rumples and ice rises. A comparison is made between our approach and two approaches based on continuum mechanics. Applications are made to Byrd Glacier in Antarctica and Jakobshavn Isbrae in Greenland.

Milankovitch cycles in the Juniata Formation, Late Ordovician, Central Appalachian Basin, USA

The Juniata Formation is a thick succession of prevalently red, cyclically bedded arenites, wackes, and mudrocks found in the Upper Ordovician of the Central Appalachian Basin, USA. In outcrops close to the study area, the Juniata cycles predominantly have the characteristics of regressive tidal flat deposits. Long and continuous well logs of the subsurface Juniata provide an unparalleled opportunity to investigate Milankovitch controls on the cyclic deposition. In the Preston 119 well, northern West Virginia, a 2700-ft long gamma-ray well log provides a high-resolution proxy of terrigenous siliciclastic flux to the northern Central Appalachian Basin shoreline, from the early Maysvillian (Reedsville Shale) to the Ordovician/Silurian transition (Tuscarora Sandstone). The gamma-ray cycles provide strong evidence for sea level oscillations forced by Milankovitch cycleswith a dominant obliquity component. The strong obliquity signal is reminiscent of the obliquity forcing of Oligocene climate and sea level following the glaciation of Antarctica. The Late Ordovician world analogously experienced glaciation of Gondwana, which straddled the South Pole; this may have involved ice sheet dynamics that generated obliquity-paced sea level oscillations that affected Late Ordovician shorelines worldwide. This Milankovitch-forced glacio-eustatic record from eastern North America joins other suspected Milankovitch-forced successions reported from the Late Ordovician of northern Africa, northwestern Australia, Scandinavia, and northeastern and eastern-central North America.

Atmospheric and oceanic impacts of Antarctic glaciation across the Eocene-Oligocene transition.

The glaciation of Antarctica at the Eocene-Oligocene transition (approx. 34 million years ago) was a major shift in the Earth's climate system, but the mechanisms that caused the glaciation, and its effects, remain highly debated. A number of recent studies have used coupled atmosphere-ocean climate models to assess the climatic effects of Antarctic glacial inception, with often contrasting results. Here, using the HadCM3L model, we show that the global atmosphere and ocean response to growth of the Antarctic ice sheet is sensitive to subtle variations in palaeogeography, using two reconstructions representing Eocene and Oligocene geological stages. The earlier stage (Eocene; Priabonian), which has a relatively constricted Tasman Seaway, shows a major increase in sea surface temperature over the Pacific sector of the Southern Ocean in response to the ice sheet. This response does not occur for the later stage (Oligocene; Rupelian), which has a more open Tasman Seaway. This difference in temperature response is attributed to reorganization of ocean currents between the stages. Following ice sheet expansion in the earlier stage, the large Ross Sea gyre circulation decreases in size. Stronger zonal flow through the Tasman Seaway allows salinities to increase in the Ross Sea, deep-water formation initiates and multiple feedbacks then occur amplifying the temperature response. This is potentially a model-dependent result, but it highlights the sensitive nature of model simulations to subtle variations in palaeogeography, and highlights the need for coupled ice sheet-climate simulations to properly represent and investigate feedback processes acting on these time scales.

Glacial Karst Aspects About the DeKalb Mounds in Illinois, USA

The glacial dead-ice origin of the DeKalb mounds in DeKalb County, Illinois, USA, is advanced in this study by discussing it within the context of late Wisconsinan glacial karst. Glacial karst is glacial dead-ice topography that resembles carbonate bedrock karst topography. The only difference here is that thermo-erosion or melting of ice by groundwater causes glacial karst, while dissolution of carbonates by groundwater causes bedrock karst. For example, bedrock karst such as haystack hills, dolines and entranceless caves analogously match up to stagnant glacial ice blocks with supraglacial ice pits and entranceless glacial caves. Entranceless bedrock caves are caves with no opening (entranceway) that is big enough for a human, yet contain water and/or accumulations of silt and clay. Although stagnant glacial ice blocks and supraglacial ice pits have been discussed in the literature, entranceless glacial caves is an undeveloped concept which is expounded in this study. An entranceless glacial cave is actually a subglacial/englacial, water-filled cavity formed by thermo-erosion due to active-layer groundwater/talik piping laterally seeping out of the adjoining terrain and into a body of glacial ice, as seen in modern glaciers of Antarctica. This type of water-filled cavity can also be classified as a subglacial or englacial lake. The study also discusses relationships to embryonic DeKalb mounds such as: why a localized part of the continental ice sheet degenerated into stagnant ice blocks; and the Wisconsinan creation of one or more steep depressions in the till plain underlying a DeKalb mound.

Message from the Business Office

These are great times for our organization and as ASLO President Jim Elser says, “ASLO is working on ASLO 2.0.” Of course, ASLO starts with you, our members. We hope that you have renewed your membership – and considered the multiyear option, as well as becoming a lifetime member. Exciting things are happening with the journals. We have a new Editor-in-Chief for Limnology & Oceanography, Bob Howarth, as well as a new publishing partner, Wiley, which offers exciting new platforms and features for all ASLO journals. Additionally, we are launching a new journal, L&O Letters. Many of these new initiatives were presented at the ASLO Aquatic Sciences Meeting in Granada, Spain in February. Granada was a wonderful host city and the University of Granada supported the meeting, including an opening by the University President D. Francisco Gonzalez Lodeiro. Over 2500 scientists presented their science, but also enjoyed visits to the Alhambra, tapas tours, morning runs, dinners in caves, and a rousing closing banquet. All continents were represented by 63 countries. A record 35% of those attending were students! ASLO also gained over 1000 new members – and to all of our new members, we hope you find ASLO as your new “society home” and continue your membership for many years to come. ASLO has much to offer all our members, including travel grants for Early Career Professionals and Students, discounts for developing countries, and reduced rates to ASLO meetings. One interesting website to check out – watch live streaming of 23 glaciers in Antarctica, Greenland, Iceland, Canada, Alaska, Austria, and the Rocky Mountains captured every 30 minutes through a project, Extreme Ice Survey (www.extremeicesurvey.org). Scientist James Balog and his team have turned this stunning video into a documentary, Chasing Ice. As it has been a tough winter for so many of us, I hope that spring has arrived where you are when you read this issue. P.S. Be sure to renew your membership – and continue your ASLO benefits! Business Office, 5400 Bosque Blvd., Suite 680, Waco, TX, 76710-4446, USA; business@also.org

Environmental and climate changes in Antarctica in the Geological Past

In the Cretaceous time, Antarctica was characterized by subtropical and tropical climate. The Early Eocene was warmest in the Antarctic history but this Climatic Optimum terminated with a long-term cooling trend that culminated in continental-scale glaciation of Antarctica at about 34 Ma ago. There is indirect evidence that small ice caps developed within central Antarctica in the Late Eocene (42−34 Ma). From the Early Oligocene to the Middle Miocene (34−13 Ma) ice sheet was wet-based and fluctuated considerably in volume, but about 14 m.y. ago it became dry-based and more stable. Seismic data collected on the East Antarctic margin give valuable information on dynamics of the past ice sheets. These data shows that the sedimentary cover of the western Wilkes Land margin includes a giant (c. 200 000 km 2 ) deep-water fan which formed between c. 43 and 34 Ma ago. The average rate of sedimentation in the central part of fan was 230–250 m/m.y. Active input of terrigenous sediments into deep-water denotes high-energy fluvial system within the Wilkes Land. Emergence of this fluvial system evidences earliest glaciation in the Antarctic interior which fed full-flowing rivers. The thickness of strata deposited during post-Early Oligocene glaciations on the Antarctic margin generally reflects the averaged energy of depositional environments. The thickest sediments (up to 2.0 km, i.e. almost twice more than in other parts of East Antarctic margin) and inferred highest energy are seen in the central Cooperation Sea, on the central Wilkes Land margin and in the D'Urville Sea. The areas with the thickest post-Early Oligocene strata correlate with places where present-day ice discharge is highest, such as via the Lambert, Totten and Mertz/Ninnis Glaciers. The correlation points to high ice (and sediment) flux in the same areas since the Early Oligocene.

Glacial Debris Hints at Ancient Climate Change

Interspersed layers of debris in some of Antarctica's glaciers give clues to ancient swings in climate.

Upper limit for sea level projections by 2100

We construct the probability density function of global sea level at 2100, estimating that sea level rises larger than 180 cm are less than 5% probable. An upper limit for global sea level rise of 190 cm is assembled by summing the highest estimates of individual sea level rise components simulated by process based models with the RCP8.5 scenario. The agreement between the methods may suggest more confidence than is warranted since large uncertainties remain due to the lack of scenario-dependent projections from ice sheet dynamical models, particularly for mass loss from marine-based fast flowing outlet glaciers in Antarctica. This leads to an intrinsically hard to quantify fat tail in the probability distribution for global mean sea level rise. Thus our low probability upper limit of sea level projections cannot be considered definitive. Nevertheless, our upper limit of 180 cm for sea level rise by 2100 is based on both expert opinion and process studies and hence indicates that other lines of evidence are needed to justify a larger sea level rise this century.

Productivity and sea-surface temperature changes recorded during the late Eocene–early Oligocene at DSDP Site 511 (South Atlantic)

This study investigates paleoenvironmental changes during the Eocene–Oligocene transition (EOT) at Deep Sea Drilling Project (DSDP) Site 511 (South Atlantic), as inferred from lipid biomarker (long-chain diols, alkenones) and calcareous nannofossil accumulation rates, as well as changes in sedimentation regime (i.e. relative contributions of total organic carbon-TOC-, calcium carbonate, and biogenic silica). Sea-surface temperatures (SSTs) reconstructed from the alkenone unsaturation index UK′37 indicate a progressive but significant cooling (~8°C) from 34.5Ma to 33.6Ma, consistent with estimates derived from other temperature proxies (TEX86; δ18O) at the same site and for the same time interval. This cooling is associated with a marked increase in primary productivity, as indicated by high accumulation rates of biogenic silica, TOC, alkenones, long-chain diols, and calcareous nannofossils. Together, these results are consistent with an enhancement of upwelling conditions favorable to the development of siliceous organisms at DSDP Site 511, possibly induced by the Oi-1 glaciation in Antarctica that occurred during this period.

Motion of the Lambert Glacier estimated by using differential Interferometric Synthetic Aperture Radar

Interferometric Synthetic Aperture Radar (InSAR) is one of the most promising remote sensing technologies and has been widely applied in constructing topographic information and estimating the deformation of the Earth's surface. Ice velocity is an important parameter for calculating the mass balance and modelling ice shelve dynamics. Ice velocity is also an important indicator for climate changes. Therefore, it plays an important role in studying the global climate change and global sea level rise. In this paper, the ERS-1/2 tandem data and the ASTER GDEM are combined together to obtained the deformation in line of sight by using the differential Interferometric SAR for the Lambert Amery glacier in Antarctica. Then the surface parallel assumption is adopted in order to achieve the ice flow velocity. The results showed that ice velocity would be increased along the Lambert glacier; the maximum ice velocity would be reach about 450m/year in the study area.

Cenozoic glaciation of Antarctica and sedimentation in the Southern Ocean

Literature pertaining to history of the Cenozoic glaciation in Antarctica and its influence on sedimentation in marginal areas of the continent and deep-water domains of the Southern Ocean are reviewed. Original data obtained by G.L. Leichenkov on seismostratigraphy of the East Antarctica margin are also used. Particular attention is paid to the history of silica accumulation, ice-rafted material deposition, and formation of contourites. The results make it possible to define the following main stages of Antarctic glaciation in the Cenozoic: (1) middle-late Eocene; (2) Oligocene; (3) early Miocene; (4) middle Miocene; (5) late Miocene-early Pliocene; and (6) late Pliocene-Holocene.

Strong Sensitivity of Pine Island Ice-Shelf Melting to Climatic Variability

Pine Island Glacier has thinned and accelerated over recent decades, significantly contributing to global sea-level rise. Increased oceanic melting of its ice shelf is thought to have triggered those changes. Observations and numerical modeling reveal large fluctuations in the ocean heat available in the adjacent bay and enhanced sensitivity of ice-shelf melting to water temperatures at intermediate depth, as a seabed ridge blocks the deepest and warmest waters from reaching the thickest ice. Oceanic melting decreased by 50% between January 2010 and 2012, with ocean conditions in 2012 partly attributable to atmospheric forcing associated with a strong La Niña event. Both atmospheric variability and local ice shelf and seabed geometry play fundamental roles in determining the response of the Antarctic Ice Sheet to climate.

Calculation of Greenland and Antarctica Glaciers' Weights Causing Some Earthquakes and Volcanic Activities

Global warming is very important subject for environmental physics. Although the earth seems like inanimate, it acts just like a live mechanism which is called as Glacial-Interglacial Ice. One can consider that there are three periods for this forming, say major (100,000 years), minor (12,000 years) and smaller (1000 years) ice ages. The temperature of the earth is a ected by increasing especially CO2 and other sera gases in the atmosphere. The solar radiation re ected from the earth surface cannot go back to the space due to the sera gases and is absorbed by the atmosphere. After the industrial revolution at the beginning of 20th century, especially in the last 30 years, the amount of CO2 and the other carbon gases emitted into the atmosphere has been increasing and causing natural disasters like irregular local temperature changes, oods, melting glaciers, and more powerful hurricanes. The solar radiations are mostly re ected by glaciers which are signi cant formations on the earth. Melting of these glaciers reduces the surface re ection and causes more absorption of solar radiation by the earth. In addition, sea level, amount of fresh water, and perceptible water vapor in the atmosphere may increase. In this study, Greenland and Antarctica glaciers' weights which press the plates downward are calculated. Melting the glaciers, the plates get rid of the pressure and rise upward over the mantle, and may cause some earthquakes, and volcanic activities such as Thoku earthquake in Japan and Eyjafjallajokull and Grimsvotn volcanos in Iceland.

Manifestation of characteristic periods of oscillations of the Earth’s orbital parameters in the paleoclimatic data

We performed a joint analysis of the fluctuations of the Earth's orbital parameters: eccentricity of the orbit, inclination of the Earth's axis to the plane of its orbit, and precession with variations in the indicators of the climate variations, such as reconstructions of temperature variations, CO2 and CH4 concentrations based on the drilling data of glaciers in Antarctica, and relative concentration of oxygen�18 in the benthic deposits on the sea floor (series LR04). The wavelet analysis of various paleoclimatic parameters demon� strated the existence and inphase properties of oscil� lation modes with periods of 100, 41, and 20 ky in the last 800 ka. Oscillations with a period of 41 ky distin� guished in the LR04 series are inphase with the fluc� tuations of the inclination of the Earth's axis in the last 2 Ma, and the oscillations with a period of 20 ky are correlated with the precession fluctuations in the last 1.25 Ma (at high amplitude values). In the last 700- 750 ka, synchronization is observed between the modes of 100 ky fluctuations in δ 18 O (and phase corre� lation of this mode with the other indicators of the cli� mate variations based on the Antarctic data) and eccentricity of the orbit. The transition to the regime of 100-120 ky glacialinterglacial cycles in the last 700 ka may be caused by the existence of such a corre� lation between the fluctuations of the climatic and orbital parameters. In the major part of the works related to studies of the Milankovitch cycles, the authors use calculated data on the solar irradiance flux that is incident at a specific latitude, in a specific season, and even on a specific day. Such data can be found for example, in (1). The calculated data on the variations in the Earth's orbital parameters can also be found there: eccentricity of the Earth's orbit, inclination of the Earth's axis, and precession during the last 5 Ma with a step of 1000 years. Time series LR04 was constructed in (2) on the basis of the composition data of sea floor drilling. The time series consists of δ 18 O in the fossil residuals of benthic marine organisms in the last 5.3 Ma with a step from 1 to 5 ky. To reach consistency between the evolution of largescale variations in the LR04 time series and the Earth's temperature varia� tions, we inverted the sign of variable δ 18 O. Then we calculated and excluded the nonlinear trend from the data and denoted the obtained time series as Δδ 18 O. The trend (Fig. 1) provides evidence that the Earth was cooling, which slowed down in the Middle Pleistocene and later. We used in this work the reconstructions of variations in the climatic parameters obtained from the analysis of ice cores at Antarctic stations Concor� dia, Dome C (3), and Vostok (4) including temperature T, carbon dioxide CO2, methane CH4, etc. The data from Dome C obtained within the EPICA project are for 800 ky, the other data from Vostok are for 415 ky with a time step of 500 years. We used the wavelet analysis with a real wavelet function of the Morlet type to study the amplitudes and phases of the data. This function uses a zero order discrete spheroid wave function instead of a Gaussian (5): , where the parameter is β = 3.5. We note that such choice of β, in particular, allows us to decrease the interval of distortions at the edges in the wavelet trans� form by a factor of 1.57-1.77 compared with the selection of the Morlet wavelet function where the selection of β is recommended within 5.5-6.2. The method of real wavelet analysis is described in (5). In this work it is adjusted for the analysis of data with gaps and uses the amplitude normalizing of the obtained modes. We note that distortions at the edges cover an interval equal to 1.75P, where P is the corresponding period. The range of periods in the wavelet analysis of data from Dome C is 5-115 ky. It is limited by the duration of the glacier data. The step over the period is 1000 years. The wavelet analysis applied to the Δδ 18 O time series (LR04), which covers an interval of 0 () ut