High-centered polygons in the Sør Rondane Mountains, East Antarctica: Possible effect of ice wedge sublimation

Small high-centered polygons, 3-15m in diameter, dominate moraine fields in an inland cold desert of the Sør Rondane Mountains, Antarctica. They mainly occur on moraine fields at two stages younger than 1Ma. The polygons on the younger moraine (<0.5Ma) generally have an ice wedge surrounded by ice-cemented permafrost, although the ice wedge cracking is inactive or too slow to be detectable. The polygons on the older moraine (0.5-1Ma) have either an ice wedge or ice-free wedge. The ice-free wedge underlies a subsided trough and consists entirely of loose and coarse sediments with vertically-oriented clasts, which represents an ice-wedge cast probably originating from long-term sublimation of an ice wedge. These observations suggest that flat-top polygons with ice wedges form in wet permafrost when located close to the ice sheet surface, but that the subsequent ice sheet lowering separates the polygons from the moisture source, and finally long-term ice sublimation leads to domed polygons with ice-wedge casts enclosed in dry permafrost

Die Packeisküste Japans

Die Küsten des nördlichen Hokkaidos gehören zu den äquatornächsten Bereichen, die in saisonalem Wechsel einer wellen- und strömungsdominierten Sommerformung (8—10 Monate) und einer packeis- und frostinduzierten Winterformung (2—4 Monate) unterliegen. Es werden für diesen Raum die typischen Prozesse der Sommer- und Wintermonate beschrieben. Im Sommer werden die Küsten wesentlich stärker geformt als im Winter und die durch Eispressung entstandenen Formen an den Stränden und Dünen überdauern nur in Relikten. Dennoch kann die Zone der saisonal vereisten Küsten klimageomorphologisch von den Küsten wärmerer Breiten abgegrenzt werden, da nur hier ein derart großer Kontrast zwischen Sommer- und Winterformung existiert. Diese Grenze ist allerdings ein breiter Saum und kein schmaler Übergang, wie es für solche physisch geographischen Grenzen die Regel ist.researc

Antarctic Glacial History Since the Last Glacial Maximum: An Overview of the Record on Land

This overview examines available circum-Antarctic glacial history archives on land, related to developments after the Last Glacial Maximum (LGM). It considers the glacial-stratigraphic and morphologic records and also biostratigraphical information from moss banks, lake sediments and penguin rookeries, with some reference to relevant glacial marine records. It is concluded that Holocene environmental development in Antarctica differed from that in the Northern Hemisphere. The initial deglaciation of the shelf areas surrounding Antarctica took place before 10000 C-14 yrs before present(sp), and was controlled by rising global sea level. This was followed by the deglaciation of some presently ice-free inner shelf and land areas between 10000 and 8000 yr sp. Continued deglaciation occurred gradually between 8000 yr sp and 5000 yr sp. Mid-Holocene glacial readvances are recorded from various sites around Antarctica. There are strong indications of a circum-Antarctic climate warmer than today 4700-2000 yr sp. The best dated records from the Antarctic Peninsula and coastal Victoria Land suggest climatic optimums there from 4000-3000 yr sp and 3600-2600 yr sp, respectively. Thereafter Neoglacial readvances are recorded. Relatively limited glacial expansions in Antarctica during the past few hundred years correlate with the Little Ice Age in the Northern Hemisphere

Circum-Antarctic Coastal Environmental Shifts During the Late Quaternary Reflected by Emerged Marine Deposits

This review assesses the circumpolar occurrence of emerged marine macrofossils and sediments from Antarctic coastal areas in relation to Late Quaternary climate changes. Radiocarbon ages of the macrofossils, which are interpreted in view of the complexities of the Antarctic marine radiocarbon reservoir and resolution of this dating technique, show a bimodal distribution. The data indicate that marine species inhabited coastal environments from at least 35000 to 20000 yr sp, during Marine Isotope Stage 3 when extensive iceberg calving created a \u27meltwater lid\u27 over the Southern Ocean. The general absence of these marine species from 20000 to 8500 yr sp coincides with the subsequent advance of the Antarctic ice sheets during the Last Glacial Maximum. Synchronous re-appearance of the Antarctic marine fossils in emerged beaches around the continent, all of wh ich have Holocene marine-limit elevations an order of magnitude lower than those in the Arctic, reflect minimal isostatic rebound as relative sea-level rise decelerated. Antarctic coastal marine habitat changes around the continent also coincided with increasing sea-ice extent and outlet glacial advances during the mid-Holocene. in view of the diverse environmental changes that occurred around the Earth during this period, it is suggested that Antarctic coastal areas were responding to a mid-Holocene climatic shift associated with the hydrological cycle. This synthesis of Late Quaternary emerged marine deposits demonstrates the application of evaluating circum-Antarctic phenomena from the glacial-terrestrial-marine transition zone

Tsunami run-up heights of the 2003 Tokachi-oki earthquake

Tsunami height survey was conducted immediately after the 2003 Tokachi-oki earthquake. Results of the survey show that the largest tsunami height was 4 m to the east of Cape Erimo, around Bansei-onsen, and locally at Mabiro. The results also show that the tsunami height distribution of the 2003 Tokachi-oki earthquake is clearly different from that of the 1952 Tokachi-oki earthquake, suggesting the different source areas of the 1952 and 2003 Tokachioki earthquakes. Numerical simulation of tsunami is carried out using the slip distribution estimated by Yamanaka and Kikuchi (2003). The overall pattern of the observed tsunami height distribution along the coast is explained by the computed ones although the observed tsunami heights are slightly smaller. Large later phase observed at the tide gauge in Urakawa is the edge wave propagating from Cape Erimo along the west coast of the Hidaka area.The 2003 Tokachi-oki earthquak

Solifluction resulting from one-sided and two-sided freezing: Field data from Svalbard

Two years of observation of soil movement on three Arctic slopes underlain by permafrost demonstrate convex downslope profiles at two depths, corresponding respectively to the middle and basal parts of the active layer The absence of superficial movement reflects the paucity of diurnal freeze-thaw action throughout the year and soil desiccation in summer The middle layer movement is attributed to annual frost creep/gelifluction associated mainly with frost heave during downward freezing and subsequent thaw subsidence This type of movement prevails where the lower part of the active layer is composed of coarse materials that reject ice lensing, and over the long term eventually develops typical solifluction sheets or lobes In contrast, the basal layer movement represents plug-like flow originating from thawing of ice lenses developed during upward freezing from the top of permafrost Plug-like flow occurs where the whole active layer consists of muddy sediments Such a deep movement is rarely accompanied by a specific surface feature, despite causing large mass transpor

Downslope movement of solifluction lobes in iceland: a tephrostratigraphic approach

Excavatins of the turf-banked solifluction lobe at 28 localities in Iceland have revealed dislocated and deformed volcanic ash layers composing solifluction lobes. Tephrostratigraphy and tephrochronology present much information about the rate and the mechanism of downslope movement of solifluction lobe which probably extends over the last 7,000 years. Downslope movement during the period between ca. 4,000 yBP and 2,000 yBP was faster than that in the last 900 years. The rate of downslope movement of solifluction lobe front is strongly associated with the gradients of slopes. However, environmental conditions, particularly those related to the existence of permafrost may have been favorable for the downslope movement. Concerning the mechanism of movement, the solifluction lobes have not moved as a slab slide, but as a viscous flows, because no shear plane was found

Development of palsa bog in central highland, iceland

Topography and deposits in two selected bogs with permafrost in the central highland of Iceland are described. Radiocarbon dates and tephrochronological observation reaveal that development of permafrost in the bog started around 4,000 to 3,000 years B.P., succeeding to the formation of almost all deposits of bogs during the Atlantic time. Present irregularly undulating topography with slightly hilly microlandforms and varied depressions indicates that a thermokarst resulted from the more extensive development of former permafrost. That has occurred during these several hundred years since the beginning of the Middle Ages. Typical palsa, mineral palsas in most cases, formed only in such thermokarst depressions have occurred after the partial disappearence of the extensive permafrost