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Lund Andersen, J., Newall, J. C., Fredin, O., Glasser, N. F., Lifton, N. A., Stuart, F. M., . . . Stroeven, A. P. (2023). A topographic hinge-zone divides coastal and inland ice dynamic regimes in East Antarctica. Communications Earth & Environment, 4, Article ID 9.
Open this publication in new window or tab >>A topographic hinge-zone divides coastal and inland ice dynamic regimes in East Antarctica
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2023 (English)In: Communications Earth & Environment, E-ISSN 2662-4435, Vol. 4, article id 9Article in journal (Refereed) Published
Abstract [en]

The impact of late Cenozoic climate on the East Antarctic Ice Sheet is uncertain. Poorly constrained patterns of relative ice thinning and thickening impair the reconstruction of past ice-sheet dynamics and global sea-level budgets. Here we quantify long-term ice cover of mountains protruding the ice-sheet surface in western Dronning Maud Land, using cosmogenic Chlorine-36, Aluminium-26, Beryllium-10, and Neon-21 from bedrock in an inverse modeling approach. We find that near-coastal sites experienced ice burial up to 75–97% of time since 1 Ma, while interior sites only experienced brief periods of ice burial, generally <20% of time since 1 Ma. Based on these results, we suggest that the escarpment in Dronning Maud Land acts as a hinge-zone, where ice-dynamic changes driven by grounding-line migration are attenuated inland from the coastal portions of the East Antarctic Ice Sheet, and where precipitation-controlled ice-thickness variations on the polar plateau taper off towards the coast.

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-214356 (URN)10.1038/s43247-022-00673-6 (DOI)000909510000002 ()2-s2.0-85145718538 (Scopus ID)
Available from: 2023-02-02 Created: 2023-02-02 Last updated: 2023-02-02Bibliographically approved
Dulfer, H. E., Margold, M., Darvill, C. M. & Stroeven, A. P. (2022). Reconstructing the advance and retreat dynamics of the central sector of the last Cordilleran Ice Sheet. Quaternary Science Reviews, 284, Article ID 107465.
Open this publication in new window or tab >>Reconstructing the advance and retreat dynamics of the central sector of the last Cordilleran Ice Sheet
2022 (English)In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 284, article id 107465Article in journal (Refereed) Published
Abstract [en]

The advance of the Cordilleran Ice Sheet (CIS) towards its Last Glacial Maximum (LGM) configuration and its subsequent retreat remain poorly understood. We use the glacial landform record to determine ice dynamics for the central sector of the CIS in northern British Columbia, Canada, beneath the LGM ice divide. We classify seventy ice-flow indicator flowsets based on morphology, elevation, orientation and cross-cutting relationships into one of three stages, whereby stage 1 is oldest and stage 3 youngest. Combined with ice-contact geomorphology, our reconstruction highlights complex changes in ice flow over time as a result of ice divide migrations through the LGM and deglacial phases. The orientation and distribution of landforms indicates active post-LGM ice retreat westward through the Cassiar and Omineca mountains. We map the regional distribution of independent mountain glaciers, ice caps, and ice fields that regrew during a cooling event in the Late Glacial and show that some of these readvance glaciers were subsequently overrun by advancing outlet glaciers of the CIS. We use the cross-cutting relationship between readvance glaciers and CIS outlet glaciers and available chronological data to reconstruct the eastern CIS margin during the Late Glacial for the first time.

Keywords
Glacial geomorphology, North America, Paleoglaciology, Pleistocene
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-206243 (URN)10.1016/j.quascirev.2022.107465 (DOI)000805168800002 ()2-s2.0-85129322418 (Scopus ID)
Available from: 2022-06-13 Created: 2022-06-13 Last updated: 2022-08-16Bibliographically approved
Suganuma, Y., Kaneda, H., Mas e Braga, M., Ishiwa, T., Koyama, T., Newall, J. C., . . . Abe-Ouchi, A. (2022). Regional sea-level highstand triggered Holocene ice sheet thinning across coastal Dronning Maud Land, East Antarctica. Communications Earth & Environment, 3, Article ID 273.
Open this publication in new window or tab >>Regional sea-level highstand triggered Holocene ice sheet thinning across coastal Dronning Maud Land, East Antarctica
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2022 (English)In: Communications Earth & Environment, E-ISSN 2662-4435, Vol. 3, article id 273Article in journal (Refereed) Published
Abstract [en]

The East Antarctic Ice Sheet stores a vast amount of freshwater, which makes it the single largest potential contributor to future sea-level rise. However, the lack of well-constrained geological records of past ice sheet changes impedes model validation, hampers mass balance estimates, and inhibits examination of ice loss mechanisms. Here we identify rapid ice-sheet thinning in coastal Dronning Maud Land from Early to Middle Holocene (9000–5000 years ago) using a deglacial chronology based on in situ cosmogenic nuclide surface exposure dates from central Dronning Maud Land, in concert with numerical simulations of regional and continental ice-sheet evolution. Regional sea-level changes reproduced from our refined ice-load history show a highstand at 9000–8000 years ago. We propose that sea-level rise and a concomitant influx of warmer Circumpolar Deep Water triggered ice shelf breakup via the marine ice sheet instability mechanism, which led to rapid thinning of upstream coastal ice sheet sectors.

National Category
Geology
Identifiers
urn:nbn:se:su:diva-211114 (URN)10.1038/s43247-022-00599-z (DOI)000885084000001 ()
Available from: 2022-11-10 Created: 2022-11-10 Last updated: 2022-12-06Bibliographically approved
Mas e Braga, M., Jones, R. S., Newall, J. C. H., Rogozhina, I., Andersen, J. L., Lifton, N. A. & Stroeven, A. P. (2021). Nunataks as barriers to ice flow: implications for palaeo ice sheet reconstructions. The Cryosphere, 15(10), 4929-4947
Open this publication in new window or tab >>Nunataks as barriers to ice flow: implications for palaeo ice sheet reconstructions
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2021 (English)In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 15, no 10, p. 4929-4947Article in journal (Refereed) Published
Abstract [en]

Numerical models predict that discharge from the polar ice sheets will become the largest contributor to sea-level rise over the coming centuries. However, the predicted amount of ice discharge and associated thinning depends on how well ice sheet models reproduce glaciological processes, such as ice flow in regions of large topographic relief, where ice flows around bedrock summits (i.e. nunataks) and through outlet glaciers. The ability of ice sheet models to capture long-term ice loss is best tested by comparing model simulations against geological data. A benchmark for such models is ice surface elevation change, which has been constrained empirically at nunataks and along margins of outlet glaciers using cosmogenic exposure dating. However, the usefulness of this approach in quantifying ice sheet thinning relies on how well such records represent changes in regional ice surface elevation. Here we examine how ice surface elevations respond to the presence of strong topographic relief that acts as an obstacle by modelling ice flow around and between idealised nunataks during periods of imposed ice sheet thinning. We find that, for realistic Antarctic conditions, a single nunatak can exert an impact on ice thickness over 20 km away from its summit, with its most prominent effect being a local increase (decrease) of the ice surface elevation of hundreds of metres upstream (downstream) of the obstacle. A direct consequence of this differential surface response for cosmogenic exposure dating is a delay in the time of bedrock exposure upstream relative to downstream of a nunatak summit. A nunatak elongated transversely to ice flow is able to increase ice retention and therefore impose steeper ice surface gradients, while efficient ice drainage through outlet glaciers produces gentler gradients. Such differences, however, are not typically captured by continent-wide ice sheet models due to their coarse grid resolutions. Their inability to capture site-specific surface elevation changes appears to be a key reason for the observed mismatches between the timing of ice-free conditions from cosmogenic exposure dating and model simulations. We conclude that a model grid refinement over complex topography and information about sample position relative to ice flow near the nunatak are necessary to improve data-model comparisons of ice surface elevation and therefore the ability of models to simulate ice discharge in regions of large topographic relief.

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-198761 (URN)10.5194/tc-15-4929-2021 (DOI)000711009900001 ()2-s2.0-85118279760 (Scopus ID)
Available from: 2021-11-16 Created: 2021-11-16 Last updated: 2022-11-21Bibliographically approved
Schneider, R. A. A., Blomdin, R., Fu, P., Xu, X. K. & Stroeven, A. P. (2021). Paleoglacial footprint and fluvial terraces of the Shaluli Shan, SE Tibetan Plateau. Journal of Maps, 17(2), 439-452
Open this publication in new window or tab >>Paleoglacial footprint and fluvial terraces of the Shaluli Shan, SE Tibetan Plateau
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2021 (English)In: Journal of Maps, E-ISSN 1744-5647, Vol. 17, no 2, p. 439-452Article in journal (Refereed) Published
Abstract [en]

This study provides mapping of glacial and fluvial geomorphology in the Shaluli Shan region on the eastern margin of the south-eastern Tibetan Plateau. Based on TanDEM-X 12 m elevation data and GoogleEarth imagery, glacial valleys, ice-marginal moraines, glacial lineations, scoured terrain and fluvial terraces were mapped. Covering around 11,000 km2, this map is the first for this region to display geomorphology at a spatial resolution of 0.4 arcsec (= c. 11 m) and to include fluvial terraces. Its glacial landform distribution is largely consistent with previous mapping. The substantially higher level of detail in this study is reflected in an approximately tenfold number and smaller median sizes of individual landforms such as moraines and glacial lineations. These results underscore the importance of high-resolution DEM data such as TanDEM-X for the identification of glacial and fluvial geomorphology. The map presented here will be used for detailed paleoglacial reconstructions and landscape evolution studies combining both glacial and fluvial landforms. 

Keywords
TanDEM-X, SE Tibetan Plateau, paleoglaciology, fluvial terrace, ice-marginal moraine, glacial valley
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-197050 (URN)10.1080/17445647.2021.1946443 (DOI)000681188800001 ()
Available from: 2021-09-27 Created: 2021-09-27 Last updated: 2023-10-03Bibliographically approved
Mas e Braga, M., Bernales, J., Prange, M., Stroeven, A. P. & Rogozhina, I. (2021). Sensitivity of the Antarctic ice sheets to the warming of marine isotope substage 11c. The Cryosphere, 15(1), 459-478
Open this publication in new window or tab >>Sensitivity of the Antarctic ice sheets to the warming of marine isotope substage 11c
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2021 (English)In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 15, no 1, p. 459-478Article in journal (Refereed) Published
Abstract [en]

Studying the response of the Antarctic ice sheets during periods when climate conditions were similar to the present can provide important insights into current observed changes and help identify natural drivers of ice sheet retreat. In this context, the marine isotope substage 11c (MIS11c) interglacial offers a suitable scenario, given that during its later portion orbital parameters were close to our current interglacial. Ice core data indicate that warmer-than-present temperatures lasted for longer than during other interglacials. However, the response of the Antarctic ice sheets and their contribution to sea level rise remain unclear. We explore the dynamics of the Antarctic ice sheets during this period using a numerical ice sheet model forced by MIS11c climate conditions derived from climate model outputs scaled by three glaciological and one sedimentary proxy records of ice volume. Our results indicate that the East and West Antarctic ice sheets contributed 4.0-8.2 m to the MIS11c sea level rise. In the case of a West Antarctic Ice Sheet collapse, which is the most probable scenario according to far-field sea level reconstructions, the range is reduced to 6.7-8.2 m independently of the choices of external sea level forcing and millennialscale climate variability. Within this latter range, the main source of uncertainty arises from the sensitivity of the East Antarctic Ice Sheet to a choice of initial ice sheet configuration. We found that the warmer regional climate signal captured by Antarctic ice cores during peak MIS11c is crucial to reproduce the contribution expected from Antarctica during the recorded global sea level highstand. This climate signal translates to a modest threshold of 0.4 degrees C oceanic warming at intermediate depths, which leads to a collapse of the West Antarctic Ice Sheet if sustained for at least 4000 years.

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-191335 (URN)10.5194/tc-15-459-2021 (DOI)000614266000004 ()
Available from: 2021-03-16 Created: 2021-03-16 Last updated: 2022-11-21Bibliographically approved
Hall, A. M., Krabbendam, M., van Boeckel, M., Goodfellow, B. W., Hättestrand, C., Heyman, J., . . . Näslund, J.-O. (2020). Glacial ripping: geomorphological evidence from Sweden for a new process of glacial erosion. Geografiska Annaler. Series A, Physical Geography, 102(4), 333-353
Open this publication in new window or tab >>Glacial ripping: geomorphological evidence from Sweden for a new process of glacial erosion
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2020 (English)In: Geografiska Annaler. Series A, Physical Geography, ISSN 0435-3676, E-ISSN 1468-0459, Vol. 102, no 4, p. 333-353Article in journal (Refereed) Published
Abstract [en]

In low relief Precambrian gneiss terrain in eastern Sweden, abraded bedrock surfaces were ripped apart by the Fennoscandian Ice Sheet. The resultantboulder spreadsare covers of large, angular boulders, many with glacial transport distances of 1-100 m. Boulder spreads occur alongside partly disintegrated roches moutonnees and associated fracture caves, and are associated withdisrupted bedrock, which shows extensive fracture dilation in the near surface. These features are distributed in ice-flow parallel belts up to 10 km wide and extend over distances of >500 km. Our hypothesis is that the assemblage results from (1) hydraulic jacking and bedrock disruption, (2) subglacial ripping and (3) displacement, transport and final deposition of boulders. Soft sediment fills indicate jacking and dilation of pre-existing bedrock fractures by groundwater overpressure below the ice sheet. Overpressure reduces frictional resistance along fractures. Where ice traction overcomes this resistance, the rock mass strength is exceeded, resulting in disintegration of rock surfaces and ripping apart into separate blocks. Further movement and deposition create boulder spreads and moraines. Short boulder transport distances and high angularity indicate that glacial ripping operated late in the last deglaciation. The depths of rock mobilized in boulder spreads are estimated as 1-4 m. This compares with 0.6-1.6 m depths of erosion during the last glaciation derived from cosmogenic nuclide inventories of samples from bedrock surfaces without evidence of disruption. Glacially disrupted and ripped bedrock is also made ready for removal by future ice sheets. Henceglacial rippingis a highly effective process of glacial erosion.

Keywords
Glacial ripping, groundwater overpressure, Fennoscandian ice sheet
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-183665 (URN)10.1080/04353676.2020.1774244 (DOI)000545025400001 ()
Available from: 2020-07-24 Created: 2020-07-24 Last updated: 2022-02-26Bibliographically approved
Andersen, J. L., Newall, J. C., Blomdin, R., Sams, S. E., Fabel, D., Koester, A. J., . . . Stroeven, A. P. (2020). Ice surface changes during recent glacial cycles along the Jutulstraumen and Penck Trough ice streams in western Dronning Maud Land, East Antarctica. Quaternary Science Reviews, 249, Article ID 106636.
Open this publication in new window or tab >>Ice surface changes during recent glacial cycles along the Jutulstraumen and Penck Trough ice streams in western Dronning Maud Land, East Antarctica
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2020 (English)In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 249, article id 106636Article in journal (Refereed) Published
Abstract [en]

Reconstructing past ice-sheet surface changes is key to testing and improving ice-sheet models. Data constraining the past behaviour of the East Antarctic Ice Sheet are sparse, limiting our understanding of its response to past, present and future climate change. Here, we report the first cosmogenic multinuclide (Be-10, Al-26, Cl-36) data from bedrock and erratics on nunataks along the Jutulstraumen and Penck Trough ice streams in western Dronning Maud Land, East Antarctica. Spanning elevations between 741 and 2394 m above sea level, the samples have apparent exposure ages between 2 ka and 5 Ma. The highest-elevation bedrock sample indicates (near-) continuous minimum exposure since the Pliocene, with a low apparent erosion rate of 0.15 +/- 0.03 m Ma(-1), which is similar to results from eastern Dronning Maud Land. In contrast to studies in eastern Dronning Maud Land, however, our data show clear indications of a thicker-than-present ice sheet within the last glacial cycle, with a thinning of similar to 35-120 m during the Holocene (similar to 2-11 ka). Difficulties in separating suitable amounts of quartz from the often quartz-poor rock-types in the area, and cosmogenic nuclides inherited from exposure prior to the last deglaciation, prevented robust thinning estimates from elevational profiles. Nevertheless, the results clearly demonstrate ice-surface fluctuations of several hundred meters between the current grounding line and the edge of the polar plateau for the last glacial cycle, a constraint that should be considered in future ice-sheet model simulations.

Keywords
Antarctica, Glaciation, Quaternary, Cosmogenic isotopes, Dronning Maud Land
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-188102 (URN)10.1016/j.quascirev.2020.106636 (DOI)000589909900002 ()
Available from: 2021-01-11 Created: 2021-01-11 Last updated: 2022-02-25Bibliographically approved
Moon, S., Perron, J. T., Martel, S. J., Goodfellow, B. W., Ivars, D. M., Hall, A., . . . Stroeven, A. P. (2020). Present-Day Stress Field Influences Bedrock Fracture Openness Deep Into the Subsurface. Geophysical Research Letters, 47(23), Article ID e2020GL090581.
Open this publication in new window or tab >>Present-Day Stress Field Influences Bedrock Fracture Openness Deep Into the Subsurface
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2020 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 47, no 23, article id e2020GL090581Article in journal (Refereed) Published
Abstract [en]

Fracturing of bedrock promotes water‐rock interactions and influences the formation of the life‐sustaining layer of soil at Earth's surface. Models predict that present‐day stress fields should influence bedrock fracture openness, but testing this prediction has proven difficult because comprehensive fracture data sets are rarely available. We model the three‐dimensional present‐day stress field beneath the deglaciated, low‐relief landscape of Forsmark, Sweden. We account for ambient regional stresses, pore pressure, topography, sediment weight, and seawater loading. We then compare the modeled stresses to a data set of ~50,000 fractures reaching depths of 600 m at Forsmark. We show that modeled failure proxies correlate strongly with the fraction of observed open fractures to depths of ~500 m. This result implies that the present‐day regional stress field, affected by surface conditions and pore pressure, influences fracture openness in bedrock hundreds of meters beneath the surface, thereby preparing the rock for further weathering.

Keywords
fractures, stress, critical zone, subsurface surface interaction, weathering
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-190340 (URN)10.1029/2020GL090581 (DOI)000598677000034 ()
Available from: 2021-02-16 Created: 2021-02-16 Last updated: 2022-02-25Bibliographically approved
Newall, J. C. H., Dymova, T., Serra, E., Blomdin, R., Fredin, O., Glasser, N. F., . . . Stroeven, A. P. (2020). The glacial geomorphology of western Dronning Maud Land, Antarctica. Journal of Maps, 16(2), 468-478
Open this publication in new window or tab >>The glacial geomorphology of western Dronning Maud Land, Antarctica
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2020 (English)In: Journal of Maps, E-ISSN 1744-5647, Vol. 16, no 2, p. 468-478Article in journal (Refereed) Published
Abstract [en]

Reconstructing the response of present-day ice sheets to past global climate change is important for constraining and refining the numerical models which forecast future contributions of these ice sheets to sea-level change. Mapping landforms is an essential step in reconstructing glacial histories. Here we present a new map of glacial landforms and deposits on nunataks in western Dronning Maud Land, Antarctica. Nunataks are mountains or ridges that currently protrude through the ice sheet and may provide evidence that they have been wholly or partly covered by ice, thus indicating a formerly more extensive (thicker) ice sheet. The map was produced through a combination of mapping from Worldview satellite imagery and ground validation. The sub-metre spatial resolution of the satellite imagery enabled mapping with unprecedented detail. Ten landform categories have been mapped, and the landform distributions provide evidence constraining spatial patterns of a previously thicker ice sheet.

Keywords
Antarctica, Glacial geomorphology, Nunatak, Paleoglaciology, WorldView
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-183923 (URN)10.1080/17445647.2020.1761464 (DOI)000544456100001 ()
Available from: 2020-08-19 Created: 2020-08-19 Last updated: 2023-10-03Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-8812-2253

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