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Werner, Niklas
Publications (3 of 3) Show all publications
Werner, N., Wang, Z., Werdelin, L. & Zhang, Q. (2025). East African uplift as a catalyst for Middle Miocene faunal transitions. Science advances, 11(42), Article ID eadx6569.
Open this publication in new window or tab >>East African uplift as a catalyst for Middle Miocene faunal transitions
2025 (English)In: Science advances, E-ISSN 2375-2548, Vol. 11, no 42, article id eadx6569Article in journal (Refereed) Published
Abstract [en]

The East African uplift during the Miocene played a crucial role in reshaping regional climates, ecosystems, and faunal communities, contributing to a shift from forested landscapes to widespread grasslands. Here, we use the high-resolution Earth System Model EC-Earth3, coupled with a dynamic vegetation model, to simulate climate and vegetation responses to East African uplift across three key Miocene intervals (25, 20, and 15 Ma) under varying atmospheric CO2 levels. Our results show that tectonic uplift, combined with declining CO2 during the Middle Miocene Climate Transition, substantially reduced forest cover and promoted grassland expansion across East and Central Africa. These environmental transitions likely facilitated faunal dispersals and ecological turnover, including among large mammals and early crown hominoids. By integrating geodynamic reconstructions, paleoclimate modeling, and fossil data, this study provides insight into how large-scale Earth system processes shaped Miocene biodiversity and altered the environmental context for mammalian evolution in Africa.

National Category
Physical Geography Other Earth Sciences
Identifiers
urn:nbn:se:su:diva-249010 (URN)10.1126/sciadv.adx6569 (DOI)001594864900024 ()41091858 (PubMedID)2-s2.0-105018892511 (Scopus ID)
Available from: 2025-11-05 Created: 2025-11-05 Last updated: 2025-11-05Bibliographically approved
Werner, N., Oehler, S., Rendlert, F. & Gunnarson, B. E. (2024). Reduced accuracy in dendroglaciological mass balance reconstruction of Storglaciären since the 1980s. The Holocene, 34(3), 366-372
Open this publication in new window or tab >>Reduced accuracy in dendroglaciological mass balance reconstruction of Storglaciären since the 1980s
2024 (English)In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 34, no 3, p. 366-372Article in journal (Refereed) Published
Abstract [en]

Recent studies have raised concerns regarding the reconstruction of glacier mass balance using tree-ring data. The method relies on a stable relationship between both variables and summer (June-August) or melt season (May-September) temperature. However, with recent anthropogenic climate change the stability of this relationship is challenged by both, a divergence between tree-ring and temperature, as well as mass balance and temperature data. Establishing to what extent this divergence influences the reconstruction of mass balance using tree-ring data is important to assess the future viability and applicability of the method. In this paper we analyze the relationship between the Tornetrask tree-ring and Storglaciaren mass balance records, their response to climate change, and investigate changes in the relationship. We provide evidence for a sensitivity loss in the Tornetrask record and quantify its impact on the reconstruction of summer mass balance of Storglaciaren. We find that by including years post 1980, the amplitude of reconstructed variability is reduced, but it remains possible to explain the variance of the record significantly. Our results suggest that for glaciers without an extensive mass balance record the applicability of the method is challenged.

Keywords
climate change, dendroglaciology, divergence problem, mass balance reconstruction, Storglaciaren, tree-ring analysis
National Category
Physical Geography
Identifiers
urn:nbn:se:su:diva-224668 (URN)10.1177/09596836231211873 (DOI)001105699200001 ()2-s2.0-85177605490 (Scopus ID)
Available from: 2023-12-19 Created: 2023-12-19 Last updated: 2024-04-26Bibliographically approved
Langhamer, L., Sauter, T., Temme, F., Werner, N., Heinze, F., Arigony-Neto, J., . . . Schneider, C. (2024). Response of lacustrine glacier dynamics to atmospheric forcing in the Cordillera Darwin. Journal of Glaciology, 70, Article ID e8.
Open this publication in new window or tab >>Response of lacustrine glacier dynamics to atmospheric forcing in the Cordillera Darwin
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2024 (English)In: Journal of Glaciology, ISSN 0022-1430, E-ISSN 1727-5652, Vol. 70, article id e8Article in journal (Refereed) Published
Abstract [en]

Calving glaciers respond quickly to atmospheric variability through ice dynamic adjustment. Particularly, single weather extremes may cause changes in ice-flow velocity and terminus position. Occasionally, this can lead to substantial event-driven mass loss at the ice front. We examine changes in terminus position, ice-flow velocity, and calving flux at the grounded la-custrine Schiaparelli Glacier in the Cordillera Darwin using geo-referenced time-lapse camera images and remote sensing data (Sentinel-1) from 2015 to 2022. Lake-level records, lake discharge measurements, and a coupled energy and mass balance model provide insight into the subglacial water discharge. We use downscaled reanalysis data (ERA-5) to identify climate extremes and track land-falling atmospheric rivers to investigate the ice-dynamic response on possible atmospheric drivers. 

Meltwater controls seasonal variations in ice-flow velocity, with an efficient subglacial drainage system developing during the warm season and propagating up-glacier. Calving accounts for 4.2% of the ice loss. Throughout the year, warm spells, wet spells, and landfalling atmospheric rivers promote calving. The progressive thinning of the ice destabilizes the terminus position, highlighting the positive feedback between glacier thinning, near-terminus ice-flow acceleration, and calving flux.

Keywords
applied glaciology, calving, ice/atmosphere interactions, ice dynamics, ice velocity
National Category
Geophysics
Identifiers
urn:nbn:se:su:diva-228097 (URN)10.1017/jog.2024.14 (DOI)001174083300001 ()2-s2.0-85184005381 (Scopus ID)
Available from: 2024-04-24 Created: 2024-04-24 Last updated: 2025-02-20Bibliographically approved
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