Continuous Ice Cover Research Articles

Variability in Ice Cover Does Not Affect Annual Metabolism Estimates in a Small Eutrophic Reservoir

AbstractTemperate reservoirs and lakes worldwide are experiencing decreases in ice cover, which will likely alter the net balance of gross primary production (GPP) and respiration (R) in these ecosystems. However, most metabolism studies to date have focused on summer dynamics, thereby excluding winter dynamics from annual metabolism budgets. To address this gap, we analyzed 6 years of year‐round high‐frequency dissolved oxygen data to estimate daily rates of net ecosystem production (NEP), GPP, and R in a eutrophic, dimictic reservoir that has intermittent ice cover. Over 6 years, the reservoir exhibited slight heterotrophy during both summer and winter. We found winter and summer metabolism rates to be similar: summer NEP had a median rate of −0.06 mg O2 L−1 day−1 (range: −15.86 to 3.20 mg O2 L−1 day−1), while median winter NEP was −0.02 mg O2 L−1 day−1 (range: −8.19 to 0.53 mg O2 L−1 day−1). Despite large differences in the duration of ice cover among years, there were minimal differences in NEP among winters. Overall, the inclusion of winter data had a limited effect on annual metabolism estimates in a eutrophic reservoir, likely due to short winter periods in this reservoir (ice durations 0–35 days), relative to higher‐latitude lakes. Our work reveals a smaller difference between winter and summer NEP than in lakes with continuous ice cover. Ultimately, our work underscores the importance of studying full‐year metabolism dynamics in a range of aquatic ecosystems to help anticipate the effects of declining ice cover across lakes worldwide.

Interactions between Irregular Wave Fields and Sea Ice: A Physical Model for Wave Attenuation and Ice Breakup in an Ice Tank

Abstract Irregular, unidirectional surface water waves incident on model ice in an ice tank are used as a physical model of ocean surface wave interactions with sea ice. Results are given for an experiment consisting of three tests, starting with a continuous ice cover and in which the incident wave steepness increases between tests. The incident waves range from causing no breakup of the ice cover to breakup of the full length of ice cover. Temporal evolution of the ice edge, breaking front, and mean floe sizes are reported. Floe size distributions in the different tests are analyzed. The evolution of the wave spectrum with distance into the ice-covered water is analyzed in terms of changes of energy content, mean wave period, and spectral bandwidth relative to their incident counterparts, and pronounced differences are found between the tests. Further, an empirical attenuation coefficient is derived from the measurements and shown to have a power-law dependence on frequency comparable to that found in field measurements. Links between wave properties and ice breakup are discussed.

The status of the fur seal population (Arctocephalus gazelle) on the southern border of the distribution area (the Argentine Islands archipelago)

The study of the population status of Arctocephalus gazella (Peters, 1875) in waters of the Argentine Islands was carried out in the period from April 2015 to March 2016 in accordance with the objectives of the State Target Scientific and Technical Research Program of Ukraine in Antarctica for 2011–2020. The aim of the article is to study the population dynamics and distribution of the southern fur seal in waters of the Argentine Islands. Due to the lack of data on the specifics of the seal’s dispersal in different periods of the year and the dynamics of the species population at the southern border of the distribution range, the results of the research are relevant and of great importance. In the second half of the 20th century, some publications presented the results of monitoring of pinnipeds at the Argentine Islands and adjacent territories, but the objects of these studies usually were other seal species: Hydrurga leptonyx, Lobodon carcinophagus, Leptonychotes weddelli, and Mirounga leonina. In the early 21st century, monitoring of the fauna of the Argentine Islands was carried out by Ukrainian biologists. However, they focused on Leptonychotes weddelli and less on other species of pinnipeds. The field material was collected in waters of the Argentine Islands, which is located in the Pacific sector of Antarctica. The fur seal population census and distribution studies were conducted according to the generally accepted methods. After breeding season on the subantarctic islands, during the migration southwards, fur seals reach the Argentine Islands, usually in the third decade of January. In the summer of 2016, the first fur seal was recorded within the archipelago on 31 January. During the study period, the largest number of animals within the archipelago was recorded in March–April and it ranged from 300 to 400 individuals. On the islands of the archipelago, the main resting places of seals were identified. The movement of animals northwards starts in May, consequently a decrease in the number of animals in this region is observed at that time. The last individuals are recorded in the first half of August. In 2015, migration began in May and ended in early August. There are several periods that were characterized by intensive migration of the animals: late June, 5–8 July, and 29 July to 6 August. In winter, one individual was last found within the archipelago on 12 August. The migration is launched by the worsening of weather conditions, formation of a continuous ice cover, reduced availability of food, and other factors.

Age and duration of a MIS 3 interstadial in the Fennoscandian Ice Sheet core area – Implications for ice sheet dynamics

Previous assumptions of continuous ice cover of the core area of the Fennoscandian Ice Sheet, from Marine Isotope Stage 4 (ca. 70 ka) to the end of MIS 2 (ca. 12 ka), have been challenged by the discovery of several sites in central and northern Scandinavia with interstadial sediments of assumed MIS 3 age. The sequences have often been dated by Optically Stimulated Luminescence (OSL) and dates of around 55 ka are present at most sites, indicating ice-free conditions at this time. There is less consensus about the timing of the build-up and advance of the last (Late Weichselian) ice sheet after this ice-free stage. To address the duration of MIS 3 ice-free conditions in central Scandinavia, we reviewed available dating evidence. At the few sites where multiple OSL dates are available, ages indicate around 15 ka of ice-free conditions. Two studies employing cosmogenic nuclide dating of preserved interstadial ground surfaces both indicate a 20 ka long period of ice-free conditions during the last ice-free period before the Holocene. Our interpretation is that central Scandinavia became ice-free around 55 ka and remained so until c. 35 ka, when the Scandinavian Ice Sheet started to expand once again. Expansion started from a small-sized remnant ice sheet, or from separate remnant ice caps in Norway. Available data limits the size of any Scandinavian ice sheet remnant surviving the MIS 3 interstadial to less than 1 m of global sea-level equivalent.

АВТОКОЛЕБАНИЯ В ДРЕЙФУЮЩЕМ ЛЕДЯНОМ ПОКРОВЕ СЕВЕРНОГО ЛЕДОВИТОГО ОКЕАНА

During the monitoring of physical-mechanical state of the ice cover of the Arctic Ocean a wide spectrum of oscillation and wave processes was in the system ice-water studied. The investigations were carried out on the drifting stations “North Pole” with seismometers and tiltmeters. Vertical and horizontal displacements in the ice field characterize parameters of wave processes caused by compression and ridging of ice-mechanical self-excited oscillations. Mechanics of appearance and propagation of waves can be considered with an account of elastic-viscous properties of the ice cover. A phenomenological model is considered of appearance of periodic horizontal displacements on an extensive rupture in a continuous ice cover. At the fault of stresses on the rupture elastic horizontally polarized waves are emitted.

The influence of ice conditions when creating the hull for ice navigation

Mathematical model of the ice capable ship design and generalized optimization criteria that take into account the diversity of ice conditions in the area of operation are presented in the paper. The distribution of the duration of ice phenomena on inland waterways of the Russian Federation is shown. For the continuous ice cover, the dependencies of the expected ice thickness are presented. Classification of broken ice in the navigation areas of ships is shown

Ocean Floor Observation and Bathymetry System (OFOBS): A New Towed Camera/Sonar System for Deep-Sea Habitat Surveys

Towed camera systems are commonly used to collect photo and video images of the deep seafloor for a wide variety of purposes, from pure exploratory research to the development of management plans. Ongoing technological developments are increasing the quantity and quality of data collected from the deep seafloor. Despite these improvements, the area of seafloor, which towed systems can survey, optically remains limited by the rapid attenuation of visible wavelengths within water. We present an overview of a new towed camera platform integrating additional acoustical devices: the ocean floor observation and bathymetry system (OFOBS). The towed system maintains continuous direct communication via fiber optic cable with a support vessel, operational at depths up to 6000 m. In addition to collecting seafloor photo and video data, OFOBS gathers sidescan data over a 100-m swath width. OFOBS functionality is further augmented by a forward looking sonar, used to aid in hazard avoidance and real-time course correction. Data collected during the first field deployments of OFOBS, at a range of seamounts on the Langseth Ridge/Gakkel Ridge intersection (86° N, 61° E) in the high Arctic in September 2016, are presented to demonstrate the functionality of the system. Collected from a location with near continuous ice cover, this explanatory data set highlights the advantages of the system for deep-sea survey work in environments currently difficult to access for the majority of subsurface research platforms.

Air Pollution and Self-Purification by Precipitation in the Russian Arctic

Unusual precipitation fell out in the Russian Arctic. There were globally background concentrations of the main components (distilled water) with a ion sum of 1.1–3.6 mg/L, increased amount of chlorides (despite continuous ice cover), and high concentration of trace elements (the sum of heavy metals was 140 μg/L, i.e., 13% of the minimum ion sum, whereas the total mineral content was the lowest). Increased concentration of heavy metals in the Central Arctic was also observed at a higher ion sum (77 mg/L). The highest acidity was estimated at pH 4.7.

Crater degradation in the Noachian highlands of Mars: Assessing the hypothesis of regional snow and ice deposits on a cold and icy early Mars

The presence of valley networks and the highly degraded state of Noachian highland craters has led to the interpretation that Mars was once warmer and wetter. Recent climate models have suggested, however, that the extremely cold climate in the Noachian would be unlikely to support liquid water precipitation. The presence of a thicker atmosphere thermally coupled to the surface is predicted instead to concentrate surface snow and ice deposits in the higher-altitude southern highlands, producing a Late Noachian Icy Highlands (LNIH) characterized by hundreds of meters of relatively continuous ice cover. In this study we test this hypothesis by reevaluating the degradation state of Noachian highland craters to assess whether their degradation state might be attained in such a cold and icy climate. We review the characteristics of Amazonian-aged impact craters hypothesized to form in surface snow and ice layers (excess ejecta, EE; double-layered ejecta, DLE; and pedestal, Pd, craters) to provide the potential initial conditions of craters forming in Late Noachian surface snow and ice layers. We then examine modification processes active in the Amazonian that may have played a role in crater degradation in the Late Noachian. In addition, we examine the potential morphometric effects of impacting into a thick surface ice deposit, and the potential erosive effects of backwasting, top-down melting, basal ice melting, and atmospheric warming pulses on the morphology of Noachian highland craters. We find that several aspects of the highly degraded state of Noachian craters could be accounted for in the context of a cold and icy climate, and we outline further tests of the hypothesis.

Dynamic model constraints on oxygen-17 depletion in atmospheric O 2 after a snowball Earth

A large perturbation in atmospheric CO2 and O2 or bioproductivity will result in a drastic pulse of (17)O change in atmospheric O2, as seen in the Marinoan Oxygen-17 Depletion (MOSD) event in the immediate aftermath of a global deglaciation 635 Mya. The exact nature of the perturbation, however, is debated. Here we constructed a coupled, four-box, and quick-response biosphere-atmosphere model to examine both the steady state and dynamics of the MOSD event. Our model shows that the ultra-high CO2 concentrations proposed by the "snowball' Earth hypothesis produce a typical MOSD duration of less than 10(6) y and a magnitude of (17)O depletion reaching approximately -35‰. Both numbers are in remarkable agreement with geological constraints from South China and Svalbard. Moderate CO2 and low O2 concentration (e.g., 3,200 parts per million by volume and 0.01 bar, respectively) could produce distinct sulfate (17)O depletion only if postglacial marine bioproductivity was impossibly low. Our dynamic model also suggests that a snowball in which the ocean is isolated from the atmosphere by a continuous ice cover may be distinguished from one in which cracks in the ice permit ocean-atmosphere exchange only if partial pressure of atmospheric O2 is larger than 0.02 bar during the snowball period and records of weathering-derived sulfate are available for the very first few tens of thousands of years after the onset of the meltdown. In any case, a snowball Earth is a precondition for the observed MOSD event.

Hydrodynamic loads acting on an oscillating cylinder submerged in a stratified fluid with ice cover

The two-dimensional problem of steady oscillations of a horizontal cylinder submerged in a linearly stratified fluid layer whose upper boundary is ice cover is considered in a linear treatment using the Boussinesq approximation. The method of mass sources distributed along the body contour is used for the internal wave generation regime, and the integral equation for the disturbed pressure in the fluid is used for the regime of no internal waves. The hydrodynamic load acting on the body was calculated as a function of the oscillation frequency for the case of a continuous ice cover and for special cases (broken ice, free surface, and rigid lid).

Natural and anthropogenic influences on ice formation on various water bodies of the Silesian Upland (southern Poland)

Natural and anthropogenic influences on ice formation on various water bodies of the Silesian Upland (southern Poland)The aim of the study was to identify patterns of ice-related phenomena on 39 selected anthropogenic water bodies in the Silesian Upland in southern Poland. The core research was conducted in the winter season of 2009/2010, between December and March. Field measurements and observations were conducted every two days during the freezing and thawing phases and every four days at the time of continuous ice cover. Data were interpolated to cover days without observations. Differences in the ice cover phenology on these water bodies were caused by natural conditions (morphometric and hydro-meteorological) and human activity (thermal pollution). Two principal groups of anthropogenic water bodies were identified in terms of the ice phenomena: lakes and ponds with a natural or quasi-natural pattern of ice phenomena and water bodies featuring various degrees of human impact. The thickness of the ice-cover was found to vary, which was a source of great danger to the users of the water bodies in the winter season.

General stratigraphic framework of the Quaternary in Eastern Canada

In eastern Canada, inter-glacial and interstadial deposits have been reported from Nova Scotia and Québec, but in the other provinces only Wisconsinan deposits. In Nova Scotia, pollen from some organic deposits buried beneath one or more tills, indicates a warm, interglacial climate — presumably the Sangamon Interglacial Interval. Other buried organic deposits, in contrast, indicate a cool, boreal forest environment. As radiocarbon analyses have given 'greater than' dates the deposits are considered to be early Wisconsinan. The interval is tentatively correlated with the St. Pierre Interstadial of Québec. The only known mid-Wisconsinan deposit is at Salmon River on St. Mary's Bay, in southwestern Nova Scotia, where the marine shells have been dated at 38,600,4C years. Elsewhere in both coastal and interior Nova Scotia multiple till sections suggest a more or less continuous ice cover through-out the Wisconsinan. In central Nova Scotia, however, red tills have been considered late-Wisconsinan. In Québec, there is a very limited, but nevertheless important, record of the Sangamon Interglacial Interval. Compact clayey rhythmites in the Harricana River Basin, close to James Bay, appear to correlate with the lacustrine member of the Missinaibi Formation farther west in Ontario. In southern Québec, there is another indication of interglacial deposits for the oldest sediments exposed in the Sherbrooke region and in the Upper Chaudière River Valley beneath the lowest of three Wisconsinan tills. These deposits were weathered and cemented prior to deposition of the oldest till. As the gravels contain pebbles of Laurentian Shield gneiss there obviously was a pre-Sangamon glaciation. These two areas contain the most complete stratigraphie record of the Wisconsinan yet established in Québec.

Modeling the duration of intermittent ice cover on a lake for climate‐change studies

A generalized empirical approach to the problem of the prediction of intermittent lake ice cover for climate‐change studies is presented and applied to historical ice data from Muggelsee, a shallow lake in northern Germany that experiences either no ice cover, intermittent ice cover, or continuous ice cover, depending on the severity of the winter. The approach presented allows the total duration of ice cover in any winter to be estimated in terms of an air‐temperature probability function. Advantages over traditional empirical methods based on the mean air temperature during a fixed period or on the computed number of negative degree‐days are: (1) it is valid for both continuous and intermittent ice cover; (2) it is not necessary to specify a fixed time period for integration in advance; (3) the results emerge in time units, allowing them to be directly compared with the measured duration of ice cover without prior calibration; and (4) it is based on statistical properties of the ambient air temperature that are routinely forecast by climate models, making it easy to apply predictively. Regional climate model forecasts for northern Germany imply that for Muggelsee, the percentage of ice‐free winters will increase from ≪2% to over 60% by the end of the current century.

Beryllium isotopes in central Arctic Ocean sediments over the past 12.3 million years: Stratigraphic and paleoclimatic implications

The upper 200 m of the sediments recovered during IODP Leg 302, the Arctic Coring Expedition (ACEX), to the Lomonosov Ridge in the central Arctic Ocean consist almost exclusively of detrital material. The scarcity of biostratigraphic markers severely complicates the establishment of a reliable chronostratigraphic framework for these sediments, which contain the first continuous record of the Neogene environmental and climatic evolution of the Arctic region. Here we present profiles of cosmogenic 10Be together with the seawater‐derived fraction of stable 9Be obtained from the ACEX cores. The down‐core decrease of 10Be/9Be provides an average sedimentation rate of 14.5 ± 1 m/Ma for the uppermost 151 m of the ACEX record and allows the establishment of a chronostratigraphy for the past 12.3 Ma. The age‐corrected 10Be concentrations and 10Be/9Be ratios suggest the existence of an essentially continuous sea ice cover over the past 12.3 Ma.

The Influence of Cryogenic Processes on the Erosional Arctic Shoreface

Coastal dynamics and shoreface relief in ice-free seas are a function of hydrodynamic interactions between the sea and bottom sediments. In the Arctic, additional, cryogenic factors such as permafrost and the action of sea ice influence coastal processes. The goal of our paper is to assess this influence, mainly on the profile shape. Mathematical analyses of the shape of 63 shoreface profiles from the Laptev, Beaufort, and Chukchi Seas were carried out. The shapes of Arctic shoreface profiles and those of ice-free seas are compared. We found that large ice and silt content in perennially frozen sediments composing Arctic coasts favor their erosion. Sea ice plays an important role in sediment transport on the shoreface and correspondingly changes shoreface relief significantly. Some effects of ice intensify coastal erosion considerably, but others play a protective role. The overall influence of cryogenic processes on Arctic coasts composed of loose sediments is seen in that the average rate of coastal retreat is larger than in the temperate environments, even though Arctic coasts are protected by a continuous ice cover most of the year. The shape of the shoreface profile in the Arctic does not differ from that in ice-free seas, and is satisfactorily described by the Bruun/Dean equilibrium profile equation. The explanation of this fact is that all changes of the profile shape, caused by cryogenic processes, are short lived and quickly eliminated by wave action.

Glacial-Marine Sedimentation, Canadian Polar Margin, North of Axel Heiberg Island

Sediment cores, taken at depths of 140 to 300 m across the northwestern shelf of Axel Heiberg Island (82° N), record the deposition of sediments under perennial sea ice. Five sedimentary fades are recognized: (A) soft pebbly-sandy-mud with dropstone structures; (B) bioturbated silty muds; (C) wispy-laminated silty clay/clay; (D) laminated sands/silts and mud; (E) firm pebbly-sandy-mud with chaotic pebble fabrics. Other sediments include terrestrial bedrock of Paleogene Eureka Sound Group, and a younger Tertiary deposit, possibly the Beaufort Formation. Ages range from 1530 ± 60 BP (Fades A) to 9950 ± 80 BP (Fades D). Sedimentation rates vary as follows: - 0.8 cm ka-1, Fades B; 4 cm ka"\ Fades A; 90 cm ka-1, Fades C; 134 cm ka~', Fades D. The sedimentation history, as interpreted from the sedimentology, palynology and foraminiferal results, suggests intervals of more continuous ice cover, with a reduced influx of coarse ice-rafted detritus, alternating with more open water conditions, and high sediment input from meltwater and/or floating icebergs. Only marine sediments overlie Neogene bedrock in the cores. The absence of diamictons at the core sites suggests that grounded ice perhaps never occupied this part of the Axel Heiberg Island shelf. The interpreted history of sedimentation generally corresponds to the land-based record from Ellesmere Island, but differs significantly from marine-based studies in more southern latitudes.

Origins and assessment of snowball Earth hypotheses

Brian Harland was for many years an editor of this journal. He was also a seminal figure in the origins of the current ‘snowball Earth’ debate, having recognized in 1964 the significance of coupling emerging palaeomagnetic data on palaeolatitude with his interpretations of diamictites. Harland worked extensively in the Arctic and knew well many of the workers involved in the arguments surrounding the origin of diamictites. He thus had a unique perspective on the evidence and the disputes surrounding it. This was his last paper but he was not able to complete it before he died. However, with the help of Professor Ian Fairchild to whom we are indebted, the editors have lightly revised this work which is presented as the personal view of one of the key figures with a very broad stratigraphic appreciation of the problems of ‘snowball Earth’.Records of Precambrian glaciation onwards from the late nineteenth century led to the concept of one or more major ice ages. This concept was becoming well advanced by the mid 1930s, particularly through the compilation of Kulling in 1934. Even so tillite stratigraphy shows that glaciation was exceptional rather than typical of Earth history. Some Proterozoic tillites, sandwiched between warm marine facies, indicate low, even equatorial palaeolatitudes as determined magnetically, and more recently led to ideas of a snow- and ice-covered ‘snowball Earth’. However, interbedded non-glacial facies as well as thick tillite successions requiring abundant snowfall both militate against the hypothesis of extreme prolonged freezing temperatures referred to here as an ‘iceball Earth’ in which all oceans and seas were sealed in continuous ice cover. On the other hand tropical environments were interrupted by glaciation several times in the Proterozoic, something that did not recur in the Phanerozoic. The term ‘snowball Earth’ is consistent with the established view of extremely widespread Proterozoic glaciation, but the ‘iceball Earth’ version of this is not compatible with the geological record.

Effect of ice cover on the dynamics and energetics of surface and internal tides in the white sea: Model estimates

The effect of ice cover on the dynamics and energetics of surface and internal tides in the White Sea is investigated using the three-dimensional finite-element hudrothermodynamic model QUODDY-4. The sea ice is represented as a continuous and motionless ice cover that can move vertically but not horizontally. It is assumed that the resulting changes in the tidal regime are the maximum possible in reference to those occurring in real conditions when, in the cold season, a continuous and motionless ice cover is ubiquitous only in Kandalaksha, Dvina, and Onega bays, while drift ices prevail in all other areas of the White Sea. It is shown that the effect of sea ice does not lead to a qualitative restructuring of the tidal regime. However, its quantitative changes prove to be significant, which indicates that the ice-induced seasonal variation in tidal characteristics in the White Sea is important.

Neotectonically controlled fluvial features, Wałbrzych Upland, Middle Sudeten Mts, southwestern Poland

The landscape of the Wałbrzych Upland, Sudeten Mts, southwestern Poland, has developed over a long time involving three main stages: (I) the Oligocene-Early Pliocene, (II) the Late Pliocene-Early Pleistocene, and (III) the Middle-Late Pleistocene. Stage III is neotectonically controlled and is discussed in detail. The entire Wałbrzych Upland was covered by a continuous ice cover during the early Saalian and at least in its marginal part during the Elsterian. The pre-early Saalian fluvial landscape shows no evidence of tectonic activity in contrast with that of post-early Saalian time. The post-early Saalian valleys have been formed during the intensive and short-term uplift of the mountain upland with simultaneous re-activation of fault zones. The main geomorphological effects of this uplift are: abandonment of valleys; formation of deep river valleys cut within bedrock; varying shapes of newly incised valleys; highly irregular longitudinal profiles of channels; varying numbers of terraces and their heights along the valleys; tilting of terraces; and formation of fault scarps at some fault lines. The main geological effects are: variable thicknesses of alluvial deposits caused by rotation of bedrock blocks; synsedimentary increases of thickness of alluvial deposits at some fault lines; and breaking of the continuity of some alluvial surfaces at the major fault lines. The uplift of the Wałbrzych Upland was controlled by glacio-isostatic rebound after the early Saalian glaciation supplemented by localised extensional tectonics. Total tectonic uplift was about 40–50 m.