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1

The decline of Svalbard land-fast sea ice extent as a result of climate change

Urbański Jacek A., Litwicka Dagmara

Oceanologia

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2022

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No. 64 (3)

535--547

EN

The Svalbard Archipelago has experienced some of the most severe temperature increases in the Arctic in the last three decades. This temperature rise has accelerated sea-ice melting along the coast of the archipelago, thus bringing changes to the local environment. In view of the importance of the near-future distribution of land-fast sea ice along the Svalbard coast, the available observation data on the ice extent between 1973 and 2018 are used herein to create a random forest (RF) model for predicting the daily ice extent and its spatial distribution according to the cumulative number of freezing and thawing degree days and the duration of the ice season. Two RF models are constructed by using either regression or classification algorithms. The regression model makes it possible to estimate the extent of land-fast ice with a root mean square error (RMSE) of 800 km2, while the classification model creates a cluster of submodels in order to forecast the spatial distribution of land-fast ice with less than 10% error. The models also enable the reconstruction of the past ice extent, and the prediction of the near-future extent, from standard meteorological data, and can even analyze the real-time spatial variability of land-fast ice. On average, the minimum two-monthly extent of land-fast sea ice along the Svalbard coast was about 12,000 km2 between 1973 and 2000. In 2005–2019, however, the ice extent declined to about 6,000 km2. A further increase in mean winter air temperatures by two degrees, which is forecast in 10 to 20 years, will result in a minimum two-monthly land-fast ice extent of about 1,500 km2, thus indicating a trend of declining land-fast ice extent in this area.

2

The erratic rocks of the Upper Cretaceous Chalk of England: how did they get there, ice transport or other means?

Jeans Christopher V., Platten Ian M.

Acta Geologica Polonica

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2021

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Vol. 71, no. 3

287--304

EN

Rare erratic clasts - extraneous rock types - occur in the Upper Cretaceous Chalk, including a local basal facies, the Cambridge Greensand. The underlying Upper Albian Gault Clay and the Hunstanton Red Chalk Formations have also yielded erratics. The discovery of these erratics, their description and the development of hypotheses to explain their origins and significance are reviewed. They became the subject of scientific interest with the interpretation of a particularly large example “The Purley Boulder” by Godwin-Austen (1858) as having been transported to its depositional site in the Chalk Sea by drifting coastal ice. Thin section petrography (1930–1951) extended knowledge of their diverse provenance. At the same time the Chalk Sea had become interpreted as warm, so drifting ice was considered out of context, and the preferred agents of transport were entanglement in the roots of drifting trees, as holdfasts of floating marine algae, or as stomach stones of marine reptiles or large fish. Reconsideration of their occurrence, variable nature and sedimentary setting suggests that there are three zones in the English Chalk where erratics may be less rare (1) near the base of the Cenomanian in the Cambridge area, (2) the Upper Cenomanian-Middle Turonian in Surrey, and (3) the Upper Coniacian and Lower Santonian of Kent. The assemblage from each level and their sedimentary setting is subtly different. Present evidence suggests that the erratics found in the Upper Albian-Lower Cenomanian and the Upper Cenomanian-Middle Turonian zones represent shallow water and shoreline rocks that were transported into the Chalk Sea by coastal ice (fast-ice) that enclosed coastal marine sediments as it froze. The Upper Coniacian and Lower Santonian erratics from Rochester and Gravesend in Kent are gastroliths.

3

Kriokonity i kriojamy w przylepie lodowej Antarktyki

Rakusa-Suszczewski S.

Problemy Klimatologii Polarnej

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2015

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Nr 25

119--125

PL

Kriokonity są cylindrycznymi otworami powstałymi w wyniku topnienia na lodowcu w otoczeniu ziarn mineralnych. Takie formy obserwowano na powierzchni przylepy lodowej powstałej na morzu w sąsiedztwie oazy Thala Hills na Ziemi Enderby w Antarktydzie Wschodniej. Otwory kriokonitów są większe przy brzegu niż dalej od brzegu w wyniku selekcji cząstek mineralnych wynoszonych przez wiatr z oazy. W przylepie lodowej powstają też kriojamy jako efekt topnienia lodu wokół fragmentów makroglonów, które przylgnęły do dna powstającego lodu, często wraz z lodem dennym. Kriojamy i kriokonity są więc różnego pochodzenia. Prezentowane są warunki środowiskowe i tworzenie się zespołu podlodowego.

EN

Cryoconite are cylindrical melt holes on glacial surface. Such creature were observed on surface of landfast sea ice near Thala Hills oasis in Antarctic. Holes are larger near shore than off shore depend of size of minerals selected by winds. In the land fast ice cryocavernes vere observed as effect of melting water around of macroalge attached bottom of ice. Cryocavernes are different orginate than cryoconites. Subfast ice community and environmental changes are presented.