Marine Glacier Research Articles

Sea ice in the western Antarctic Peninsula region: Spatio-temporal variability from ecological and climate change perspectives

The Antarctic Peninsula region is undergoing rapid change: a warming in winter of almost 6 °C since 1950, the loss of six ice shelves, the retreat of 87% of the marine glaciers, and decreases in winter sea-ice duration. Concurrently, there is evidence of ecosystem change along the western Antarctic Peninsula (wAP). Since the life histories of most polar marine species are synchronized with the seasonal cycle of sea ice, we assess how the seasonal sea-ice cycle is changing in the wAP region. Four new metrics of seasonal sea-ice variability were extracted from spatial maps of satellite derived daily sea-ice concentration: (a) day of advance, (b) day of retreat, (c) the total number of sea-ice days (between day of advance and retreat), and (d) the percent time sea-ice was present (or sea-ice persistence). The spatio-temporal variability describes distinct on-to-offshore and alongshore differences in ice–ocean marine habitats, characterized overall by a longer sea-ice season in coastal regions (6.8–7.9 months) versus a shorter sea-ice season over the shelf (4.1–5.3 months), with on-to-offshore differences increasing south-to-north. Large perturbations in the seasonality of the marine habitat occur in association with ENSO and Southern Annular Mode (SAM) variability. The local atmospheric response to these climate modes is largely a strengthening of the meridional winds during spring-to-autumn, which in turn affect the timing of the sea-ice retreat and subsequent advance. These perturbations are embedded in overall trends towards a later sea-ice advance, earlier retreat and consequently shorter sea-ice season, the impacts of which are expected to affect ecosystem functionality in the wAP region. A suite of ocean–atmosphere–ice interactions are described that are consistent with the amplified warming in late autumn, early winter.

Retreating Glacier Fronts on the Antarctic Peninsula over the Past Half-Century

The continued retreat of ice shelves on the Antarctic Peninsula has been widely attributed to recent atmospheric warming, but there is little published work describing changes in glacier margin positions. We present trends in 244 marine glacier fronts on the peninsula and associated islands over the past 61 years. Of these glaciers, 87% have retreated and a clear boundary between mean advance and retreat has migrated progressively southward. The pattern is broadly compatible with retreat driven by atmospheric warming, but the rapidity of the migration suggests that this may not be the sole driver of glacier retreat in this region.

Dynamics of marine glacier termini read from moraine architecture

Research Article| March 01, 2001 Dynamics of marine glacier termini read from moraine architecture Ida Lønne Ida Lønne 1The University Courses on Svalbard (UNIS), P.O. Box 156, N-9171 Longyearbyen, Norway Search for other works by this author on: GSW Google Scholar Geology (2001) 29 (3): 199–202. https://doi.org/10.1130/0091-7613(2001)029<0199:DOMGTR>2.0.CO;2 Article history received: 07 Aug 2000 rev-recd: 20 Nov 2000 accepted: 01 Dec 2000 first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Ida Lønne; Dynamics of marine glacier termini read from moraine architecture. Geology 2001;; 29 (3): 199–202. doi: https://doi.org/10.1130/0091-7613(2001)029<0199:DOMGTR>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Allostratigraphic mapping of the internal facies architecture of marine moraines reveals the development history of ice-contact sedimentary systems. The new method for a high-resolution analysis of the dynamic stratigraphy of moraines provides important information on the ice-front behavior, glacier dynamics, and regional climatic conditions. Based on a series of case studies of the moraines of temperate glaciers in Norway, an allostratigraphic model is suggested as a conceptual guide for the field analysis of ice-contact deposits based on outcrop sections as well as seismic or ground-penetrating radar profiles. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Evaluation of conditions along the grounding line of temperate marine glaciers: an example from Muir Inlet, Glacier Bay, Alaska

In the marine environment, stability of the glacier terminus and the location of subglacial streams are the dominant controls on the distribution of grounding-line deposits within morainal banks. A morainal bank complex in Muir Inlet, Glacier Bay, SE Alaska, is used to develop a model of terminus stability and location of subglacial streams along the grounding line of temperate marine glaciers. This model can be used to interpret former grounding-line conditions in other glacimarine settings from the facies architecture within morainal bank deposits. The Muir Inlet morainal bank complex was deposited between 1860 A.D. and 1899 A.D., and historical observations provide a record of terminus positions, glacial retreat rates and sedimentary sources. These data are used to reconstruct the depositional environment and to develop a correlation between sedimentary facies and conditions along the grounding line. Four seismic facies identified on the high-resolution seismic-reflection profiles are used to interpret sedimentary facies within the morainal bank complex. Terminus stability is interpreted from the distribution of sedimentary facies within three distinct submarine geomorphic features, a grounding-line fan, stratified ridges, and a field of push ridges. The grounding-line fan was deposited along a stable terminus and is represented on seismic-reflection profiles by two distinct seismic facies, a proximal and a distal fan facies. The proximal fan facies was deposited at the efflux of subglacial streams and indicates the location of former glacifluvial discharges into the sea. Stratified ridges formed as a result of the influence of a quasi-stable terminus on the distribution of sedimentary facies along the grounding line. A field of push ridges formed along the grounding line of an unstable terminus that completely reworked the grounding-line deposits through glacitectonic deformation. Between 1860 A.D. and 1899 A.D. (39 years), 8.96×10 8 m 3 of sediment were deposited within the Muir Inlet morainal bank complex at an average annual sediment accumulation rate of 2.3×10 7 m 3/a. This rate represents the annual sediment production capacity of the glacier when the Muir Inlet drainage basin is filled with glacial ice.

Patterns of late Palaeozoic deglaciation in the Paraná Basin, Brazil

Abstract The Itarare Subgroup (Middle Carboniferous-Early Permian) of the Parana Basin of southeastern Brazil contains the thickest, most extensive and one of the longest records of late Palaeozoic glaciation in all of the Gondwana supercontinent. Glacially controlled deposition started as early as the Middle Carboniferous when lobate termini of ice streams from the Windhoek Ice Sheet (WIS), and Rio Grande do Sul and Asuncion ice caps moved into the Parana Basin. Lobes reached sea-level and advanced grounded at least as far as 200 km into the basin, stabilizing as tidal/intertidal margins. Glaciation and glacial sedimentation occurred penecontemporaneously with the transgressive phase of the late Palaeozoic tectonic cycle of the Parana Basin, while Gondwana was gradually moving away from the South Pole. Evolution involved complex interaction of tectonic, palaeogeographic and palaeoclimatic factors. Initial flooding of the basin by an epicontinental sea in the Middle Carboniferous may have provided moisture necessary for the growth of glaciers. Conversely, episodes of sea-level rise probably affected the stability of marine glaciers. The palaeoclimatic setting for the WIS and other ice masses at the margins of the Parana Basin was mostly temperate. Multiple ice advances are evidenced by subglacial tillites resting on striated and/or glaciotectonized basement and deformed glacigenic sediments identified at different stratigraphic levels in the Itarare Subgroup. Glaciation reached its maximum expansion sometime between the Late Carboniferous and Early Permian, gradually diminishing and vanishing in the late Early Permian. The reconstructed palaeogeographic evolution favors a model of irregular melt back of ice masses, particularly along the eastern margin of the Parana Basin, in analogy with the deglacial pattern of the Pleistocene Laurentide ice sheet, in North America. Retreat of marine glaciers was mostly associated with relatively simple accumulations, or complex build-ups of ice contact/proglacial facies associations in glacial estuarine embayments. Fast retreat was mainly controlled by decoupling associated with sea-level rise and intense calving. In the terrestrial environment, more fragmentary evidence shows that retreat may have involved several mechanisms including downwasting of stagnant/inactive ice margins and destabilization by surging of glaciers moving over deformable sediments. Highstand sea-level following ice wastage is often marked by widespread deposition of relatively thin marine beds. At least four stratigraphically different basinwide marine “horizons” are recognized. Isostatic rebound of deglaciated margins of the Parana Basin is recorded by transition from deep marine beds to shallowing/coarsening upward, prograding sequences of littoral/fluvio-deltaic facies basinwards, sourced from raised basin margins. Eventually, upon emersion, these constituted platforms for interglacial and postglacial peat development. Although glaciation lasted for a long time, glacial sedimentation alternated with relatively long periods of intense and widespread subaerial and subaquatic (submarine) reworking of previously deposited glacigenic sediments and deposition of “normal”, non-glacial sediments, that comprise the bulk of the Itarare Subgroup sequence. Thin coal beds, which locally rest on fossil soils, denote climatic amelioration during these interglacial phases.

Modelling of a marine glacier and ice-sheet-ice-shelf transition zone based on asymptotic analysis

All parts of a two-dimensional, isothermal, stationary marine glacier (grounded ice sheet, ice shelf and transition zone) with constant viscosity are analysed by perturbation methods. In so doing, all zones of different flow patterns can be considered separately. Correlations between spatial scales for all parts can be expressed in terms of the typical ice-surface slope distant from the ocean, which reflects exterior conditions of the glacier’s existence. In considering the ice-sheet–ice-shelf transition zone, a small parameter characterizing the difference between ice and water densities is used. Such an analysis allows us to find boundary conditions at the grounding line for the grounded ice mass. Glacier-surface profiles are determined by numerical methods. The grounding-line position found by using the boundary conditions derived in this paper differs from that obtained by using Thomas and Bentley’s (1978) boundary conditions by about 10% of the grounded ice-stream length.

Modelling of a marine glacier and ice-sheet-ice-shelf transition zone based on asymptotic analysis

All parts of a two-dimensional, isothermal, stationary marine glacier (grounded ice sheet, ice shelf and transition zone) with constant viscosity are analysed by perturbation methods. In so doing, all zones of different flow patterns can be considered separately. Correlations between spatial scales for all parts can be expressed in terms of the typical ice-surface slope distant from the ocean, which reflects exterior conditions of the glacier’s existence. In considering the ice-sheet–ice-shelf transition zone, a small parameter characterizing the difference between ice and water densities is used. Such an analysis allows us to find boundary conditions at the grounding line for the grounded ice mass. Glacier-surface profiles are determined by numerical methods. The grounding-line position found by using the boundary conditions derived in this paper differs from that obtained by using Thomas and Bentley’s (1978) boundary conditions by about 10% of the grounded ice-stream length.

Push‐moraines and glacier‐contact fans in marine and terrestrial environments

ABSTRACT The local climatic regime and the mass balance state are important determinants of the dynamics of terrestrial and marine glacier fronts, which in turn determine the sediments and landforms produced at the glacier front. Many modern glaciers undergoing overall retreat in areas of‘maritime’climate produce winter push moraines during a late winter readvance, followed by a summer retreat, whilst in more‘continental’regions no significant winter readvance occurs and annual push‐moraines are absent. The frontal dynamics which lead to these changes are analysed and the form, structure, sequence and field relations of both terrestrial and marine push‐moraines are described from Iceland, Spitsbergen and Baffin Island.Long‐term changes in mass balance leading to major glacier advances or readvances also generate large push‐moraines. In terrestrial environments push‐moraine formation is accompanied by uplift, rejuvenation and down‐cutting of outwash systems whose sediments become closely associated with glaciotectonic structures, which permit pre‐, syn‐ and post‐tectonic sequences to be identified.The development of ice marginal fan/moraine complexes is modelled as a function of the relative magnitude of two parameters: the velocity of ice movement and the calving rate. A high ice velocity just exceeded by the calving rate gives closely spaced push‐moraines and confluent ice marginal fans. A high velocity far exceeded by the calving rate produces closely spaced moraines but separate ice marginal fans. A low ice velocity in combination with a high calving rate results in well separated and feebly developed push‐moraines, while a low ice velocity and a low calving rate produces feeble push‐moraines and coalescent fans.

Glaciomarine sediments of the Isle of Man as a key to late Pleistocene stratigraphic investigations in the Irish Sea Basin

The northern part of the Isle of Man in the central Irish Sea Basin is identified as a raised marine foreland containing the largest subaerial exposure of last glaciation marine and glaciomarine sediments yet recognized on the British continental shelf. A large push ridge that crosses the foreland identifies a major ice limit. The ridge divides the foreland stratigraphy into a coarsening-upward marine sequence of pelagic muds with dropstones, sand, and gravel to the south from offlapping stratified and massive sandy diamict assemblages overlying glaciotectonized marine sediments to the north. Coarse-grained diamicts are argued to form part of a push-ridge-subaqueous-outwash depositional system deposited when processes of suspension deposition, density underflow, ice rafting, highly variable traction-current activity, and sediment gravity flow were operative adjacent to a grounded marine ice margin. The identification of large offshore submarine banks aligned parallel to the Bride moraine suggests that construction of the push-ridge-subaqueous-outwash depositional system may have been repeated during ice recession. This and published descriptions of other “Irish Sea tills” indicate that analogous structures and sediments are present offshore and around the Irish Sea Basin.