Late Quaternary sea ice evolution in the Arctic

Supervisors: Margit Simon (Main); Sitjn De Schepper (Co), Project Enquiries: msim@norceresearch.no; stde@norceresearch.no

Project Background

Sea ice is a critical component of the Earth system, regulating air–sea heat exchange, ocean circulation, albedo, and polar amplification. In the Nordic Seas, changes in sea ice affect Atlantic heat transport, deep-water formation, and European climate (Årthun et al., 2025). Although satellites show rapid recent sea ice decline (Jahn et al., 2024), its behaviour under very different climate states remains poorly understood. The Last Glacial Maximum (LGM; ~23–19 ka BP) was one of the coldest periods of the late Quaternary and provides a key case for studying sea ice under expanded ice sheets and altered circulation (Larkin et al., 2022). However, LGM sea ice extent and seasonality in the Nordic Seas are still uncertain and sometimes contradictory in proxy records (Simon et al., 2023). Rapid retreat during the deglaciation (~18–11 ka BP) offers insight into sea ice responses to abrupt warming (Mayers et al., 2026; Müller et al., 2009). This PhD project contributes to a broader effort to improve Earth System Models by integrating paleoclimate constraints, producing robust quantitative reconstructions of high-latitude sea ice to better understand past ocean conditions and test climate models across contrasting climate states

Project Aims and Methods

This PhD project will reconstruct the spatial extent and seasonality of sea ice in the Nordic Seas since the LGM using organic geochemical proxies (notably IP_25, (Brown et al., 2014)) and palaeogenomic tools (ddPCR of a sea ice dinoflagellate (e.g. Mayers et al. 2026)) applied to strategically selected marine sediment cores (Fig.1).

The project will:

• Generate high-resolution sea-ice reconstructions using IP₂₅ combined with productivity biomarkers.
• Produce complementary reconstructions of first-year sea ice from palaeogenomic records.
• Establish robust age models using radiocarbon dating and isotope stratigraphy.
• Apply quantitative, uncertainty-aware calibration methods (Fu et al., 2025) to estimate sea-ice concentration.
• Synthesize site records into regional reconstructions suitable for Earth System Model integration.

Laboratory work includes biomarker analyses by chromatography–mass spectrometry, ancient DNA work at NORCE, and Bayesian-based uncertainty assessment. The resulting datasets will support future model–data integration within the Arctic Ocean 2050 research framework.

• A strong academic background in Earth Sciences, Oceanography, Climate Science, or a related field (MSc/MSci level).

• Laboratory experience (e.g., geochemistry or molecular ecology) is an advantage.

• Experience with statistical analysis is an advantage.

• Ability to work independently, in a structured manner, and collaboratively.

• Good written and oral English skills.

• Personal qualities, ambition, and potential will be emphasized.

• Good understanding of paleoceanography and/or paleoclimatology

• The project requires motivation for laboratory-based work, quantitative analysis, and critical scientific interpretation, as well as strong communication skills in English.

Training

The student will receive training in biomarker and palaeogenomic methods, proxy calibration, and uncertainty analysis within the research environment at NORCE and the Bjerknes Centre. Conference participation, publishing, and transferable-skills training are encouraged.

References:

Årthun, M. et al., 2025. Atlantification drives recent strengthening of the Arctic overturning circulation. Sci. Adv. 11, eadu1794;

Brown, T.A. et al., 2014. Source identification of the Arctic sea ice proxy IP25. Nat. Commun. 5, 4197;

Fu, C.Y. et al., 2025. Bayesian calibration for the Arctic sea ice biomarker IP25. Paleoceanogr. Paleoclimatol. 40, e2024PA005048;

Jahn, A. et al., 2024. Projections of an ice-free Arctic Ocean. Nat. Rev. Earth Environ. 5, 164–176.
Mayers, K.M.J. et al., 2026. First-year sea ice history from ancient DNA. Earth Planet. Sci. Lett. 678, 119809; Müller, J. et al., 2009. Sea-ice variability in the Fram Strait over 30 ka. Nat. Geosci. 2, 772–776;

Müller, J. et al., 2011. Quantitative sea ice reconstructions in the N North Atlantic. Earth Planet. Sci. Lett. 306, 137–148.

Navarro-Rodriguez, A. et al., 2013. Mapping recent Barents Sea ice using IP25. Quat. Sci. Rev. 79, 26–39;

Sadatzki, H. et al., 2020. Nordic Seas sea ice variability during abrupt glacial changes. PNAS 117, 202005849.

Xiao, X. et al., 2015. Modern Arctic sea-ice distribution from biomarkers. Geochim. Cosmochim. Acta 155, 16–29.