Interglacials are warm intervals in Earth's climatic history characterized by high global average temperatures, reduced ice sheet extent, and higher-than-present sea levels. Geological records from many sites around the globe allow the identification of several interglacials that have occurred since the late Pliocene, each different in height and duration of peak sea level and wave intensity. Studying these periods is particularly pertinent for unravelling sea-level oscillations and wave regime variations and refining models of polar ice melting in the near future. The relative sea level (RSL) and wave conditions are reconstructed using geological and biological sea-level proxies, which are formed in relation to the past position of the sea level. Although we comprehensively understand global sea-level dynamics during the current interglacial (Holocene), our knowledge of these dynamics during past interglacials remains limited. Hence, a compendium of sea-level and wave condition proxies, over the multi-millennial scale of multiple interglacials, will help in assessing sea-level impacts in a future warmer world.

This special issue invites the international sea-level community to present studies broadly related to sea level and coastal geological processes during the Plio-Pleistocene interglacials. We welcome studies presenting new field data and re-analysis of previously published data with new techniques and new models of coastal processes in the past including hydrodynamics and geodynamics. We also welcome contributions to geochronology methods and remote sensing techniques applied to constrain sea-level proxies in both active and steady tectonic settings.

Ice cores have revolutionized our understanding of Earth's climatic and environmental evolution through detailed and well-dated records of polar climate and atmospheric composition and aerosols. The ice cores and boreholes further provide a valuable glaciological laboratory for studying ice dynamics, microstructure, and subglacial processes. The International Partnership in Ice Core Sciences (IPICS) is an expert group of scientists and engineers from over 20 nations that aims to coordinate international collaboration in ice core sciences.

The North American ice core community is proud to host the Fourth IPICS Open Science Conference in Banff, Canada, in October 2026. This meeting brings together experts in environmental reconstruction, ice dynamics, climate and ice sheet modeling, and ice drilling. Networking and professional development activities are organized for and by early career researchers. Many nations have taken up the IPICS "Oldest Ice Challenge" to extend the ice core record further back in time beyond the 800,000 year limit of traditional continuous ice cores. The 2026 IPICS conference will feature new results from continuous cores extending back as far as perhaps 1.5 million years, and discontinuous cores going back as far as six million years.

This IPICS 2026 special issue between Climate of the Past and The Cryosphere invites contributions from all aspects of ice core related sciences.

The glacial–interglacial cyclicity of the climate system varied in the past, most notably during the transition from a 40 ka to a 100 ka world in the mid-Pleistocene. Gases trapped in Antarctic ice are the most direct access available to investigate the composition of the paleo-atmosphere of that age and processes related to climate variability. The International Partnerships in Ice Core Sciences (IPICS) Oldest Ice endeavour aims at obtaining an undisturbed ice-core record older than 1 Ma. In addition to ice cores, time slices of paleo-records, available, for example, in Antarctic blue-ice fields, provide further valuable information, which complements continuous time series based on ice cores. This special issue will assemble contributions dedicated to the preparatory phase of this global effort to obtain ice samples and time series older than 700 000 years. This includes a consideration of glaciogical and geophysical settings which allow the presence of old ice, results from pre-site surveys and modelling studies, aspects of ice-core and other sampling techniques and analyses, and requirements for drilling and core handling.

Two closely coordinated groups (one from the USA and the other from Europe) are revisiting the Camp Century sub-ice sediment and the silty ice zone just above it using a wide variety of analytical techniques to make inferences about ice sheet behaviour, palaeo-climate, and palaeo-ecology as well as sediment transport and sourcing. The paper that kicked this off was in Proceedings of the National Academy of Sciences (PNAS) 2 years ago: "A multi-million-year-old record of Greenland vegetation and glacial history preserved in sediment beneath 1.4 km of ice at Camp Century" (Christ et al., 2021).

Talking among the 20+ lead investigators, we decided that the papers coming out of multiple, coordinated investigations of this historic (and still unique) ice core would be very useful to the broader community if they could be gathered into a special issue. Having these papers together would increase their impact and accessibility. Because of the wide variety of investigations being conducted on the core materials, a combined special issue including papers from both The Cryosphere and Climate of the Past will generate the most contributions and the largest readership.

Reference:

Christ, A. J., Bieman, P. R., Schaefer, J. M., Dahl-Jensen, D., Steffensen, J. P, Corbett, L. B., Peteet, D. M., Thomas, E. K., Steig, E. J., Rittenour, T. M., Tison, J.-L., Blard, P.-H., Perdrial, N., Dethier, D. P., Lini, A., Hidy, A. J., Caffee, M. W., and Southon, J.: A multi-million-year-old record of Greenland vegetation and glacial history preserved in sediment beneath 1.4 km of ice at Camp Century, P. Natl. Acad. Sci. USA, 118, e2021442118, https://doi.org/10.1073/pnas.2021442118, 2021.

The climate history since the Last Interglacial (~ 130 000 years ago) is marked by profound transitions, ranging from abrupt events to gradual reorganizations of the Earth system. This period offers a unique testing ground for evaluating and refining Earth system models across a wide spectrum of boundary conditions, from glacial extremes to interglacial warmth.

Simulating the climate dynamics of the last glacial cycle – including transitions, feedbacks, and tipping elements – enables us to assess the structural robustness of Earth system models used for future projections. Such model–data comparisons are critical not only to constrain uncertainties, but also to understand possible regime shifts in climate variability, the emergence of nonlinear behaviour, and the relevance of long-term feedbacks under anthropogenic forcing.

Ice cores have revolutionized our understanding of Earth's climatic and environmental evolution through detailed and well-dated records of polar climate and atmospheric composition and aerosols. The ice cores and boreholes further provide a valuable glaciological laboratory for studying ice dynamics, microstructure, and subglacial processes. The International Partnership in Ice Core Sciences (IPICS) is an expert group of scientists and engineers from over 20 nations that aims to coordinate international collaboration in ice core sciences.

The North American ice core community is proud to host the Fourth IPICS Open Science Conference in Banff, Canada, in October 2026. This meeting brings together experts in environmental reconstruction, ice dynamics, climate and ice sheet modeling, and ice drilling. Networking and professional development activities are organized for and by early career researchers. Many nations have taken up the IPICS "Oldest Ice Challenge" to extend the ice core record further back in time beyond the 800,000 year limit of traditional continuous ice cores. The 2026 IPICS conference will feature new results from continuous cores extending back as far as perhaps 1.5 million years, and discontinuous cores going back as far as six million years.

This IPICS 2026 special issue between Climate of the Past and The Cryosphere invites contributions from all aspects of ice core related sciences.

The climate history since the Last Interglacial (~ 130 000 years ago) is marked by profound transitions, ranging from abrupt events to gradual reorganizations of the Earth system. This period offers a unique testing ground for evaluating and refining Earth system models across a wide spectrum of boundary conditions, from glacial extremes to interglacial warmth.

Simulating the climate dynamics of the last glacial cycle – including transitions, feedbacks, and tipping elements – enables us to assess the structural robustness of Earth system models used for future projections. Such model–data comparisons are critical not only to constrain uncertainties, but also to understand possible regime shifts in climate variability, the emergence of nonlinear behaviour, and the relevance of long-term feedbacks under anthropogenic forcing.

Interglacials are warm intervals in Earth's climatic history characterized by high global average temperatures, reduced ice sheet extent, and higher-than-present sea levels. Geological records from many sites around the globe allow the identification of several interglacials that have occurred since the late Pliocene, each different in height and duration of peak sea level and wave intensity. Studying these periods is particularly pertinent for unravelling sea-level oscillations and wave regime variations and refining models of polar ice melting in the near future. The relative sea level (RSL) and wave conditions are reconstructed using geological and biological sea-level proxies, which are formed in relation to the past position of the sea level. Although we comprehensively understand global sea-level dynamics during the current interglacial (Holocene), our knowledge of these dynamics during past interglacials remains limited. Hence, a compendium of sea-level and wave condition proxies, over the multi-millennial scale of multiple interglacials, will help in assessing sea-level impacts in a future warmer world.

This special issue invites the international sea-level community to present studies broadly related to sea level and coastal geological processes during the Plio-Pleistocene interglacials. We welcome studies presenting new field data and re-analysis of previously published data with new techniques and new models of coastal processes in the past including hydrodynamics and geodynamics. We also welcome contributions to geochronology methods and remote sensing techniques applied to constrain sea-level proxies in both active and steady tectonic settings.

Two closely coordinated groups (one from the USA and the other from Europe) are revisiting the Camp Century sub-ice sediment and the silty ice zone just above it using a wide variety of analytical techniques to make inferences about ice sheet behaviour, palaeo-climate, and palaeo-ecology as well as sediment transport and sourcing. The paper that kicked this off was in Proceedings of the National Academy of Sciences (PNAS) 2 years ago: "A multi-million-year-old record of Greenland vegetation and glacial history preserved in sediment beneath 1.4 km of ice at Camp Century" (Christ et al., 2021).

Talking among the 20+ lead investigators, we decided that the papers coming out of multiple, coordinated investigations of this historic (and still unique) ice core would be very useful to the broader community if they could be gathered into a special issue. Having these papers together would increase their impact and accessibility. Because of the wide variety of investigations being conducted on the core materials, a combined special issue including papers from both The Cryosphere and Climate of the Past will generate the most contributions and the largest readership.

Reference:

Christ, A. J., Bieman, P. R., Schaefer, J. M., Dahl-Jensen, D., Steffensen, J. P, Corbett, L. B., Peteet, D. M., Thomas, E. K., Steig, E. J., Rittenour, T. M., Tison, J.-L., Blard, P.-H., Perdrial, N., Dethier, D. P., Lini, A., Hidy, A. J., Caffee, M. W., and Southon, J.: A multi-million-year-old record of Greenland vegetation and glacial history preserved in sediment beneath 1.4 km of ice at Camp Century, P. Natl. Acad. Sci. USA, 118, e2021442118, https://doi.org/10.1073/pnas.2021442118, 2021.

The glacial–interglacial cyclicity of the climate system varied in the past, most notably during the transition from a 40 ka to a 100 ka world in the mid-Pleistocene. Gases trapped in Antarctic ice are the most direct access available to investigate the composition of the paleo-atmosphere of that age and processes related to climate variability. The International Partnerships in Ice Core Sciences (IPICS) Oldest Ice endeavour aims at obtaining an undisturbed ice-core record older than 1 Ma. In addition to ice cores, time slices of paleo-records, available, for example, in Antarctic blue-ice fields, provide further valuable information, which complements continuous time series based on ice cores. This special issue will assemble contributions dedicated to the preparatory phase of this global effort to obtain ice samples and time series older than 700 000 years. This includes a consideration of glaciogical and geophysical settings which allow the presence of old ice, results from pre-site surveys and modelling studies, aspects of ice-core and other sampling techniques and analyses, and requirements for drilling and core handling.