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.

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.

The global vegetation distribution determines the physical properties of the land surface, such as the roughness, albedo or water conductivity, and is a key player in the terrestrial carbon cycle. Hence, the vegetation directly affects the climate on Earth. In turn, the global climate controls the large-scale spatial vegetation distribution. Biogeophysical and biogeochemical interactions between vegetation and climate have contributed to past climate changes and will affect the future. Understanding past vegetation dynamics and their role in the climate system is thus of utmost importance.

The increasing publication of large-scale syntheses of vegetation reconstructions and the steadily growing ability to perform long-term transient and sophisticated past time-slice Earth system model simulations allow for more and more detailed analyses of the large-scale vegetation transitions and their effect on climate. However, previous studies also reveal that new metrics are needed to quantitatively compare the more complex reconstructions and model results.

With this special issue, we would like to bundle reconstructions, vegetation simulations and comparison tools. We invite all papers on the broad theme of past vegetation dynamics and their interaction with climate. This includes (a) vegetation simulations of various time intervals, (b) regional to global data–model or model–model comparison studies, (c) development of data–model comparison tools and techniques, and (d) vegetation–climate dynamics inferred from compilations of regional to global vegetation records. Any other related topic (past land use or past fire dynamics) is also welcome. Data compilation products may also be considered if the compiled data are integrated and used to address specific questions about past vegetation dynamics.

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.

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 global vegetation distribution determines the physical properties of the land surface, such as the roughness, albedo or water conductivity, and is a key player in the terrestrial carbon cycle. Hence, the vegetation directly affects the climate on Earth. In turn, the global climate controls the large-scale spatial vegetation distribution. Biogeophysical and biogeochemical interactions between vegetation and climate have contributed to past climate changes and will affect the future. Understanding past vegetation dynamics and their role in the climate system is thus of utmost importance.

The increasing publication of large-scale syntheses of vegetation reconstructions and the steadily growing ability to perform long-term transient and sophisticated past time-slice Earth system model simulations allow for more and more detailed analyses of the large-scale vegetation transitions and their effect on climate. However, previous studies also reveal that new metrics are needed to quantitatively compare the more complex reconstructions and model results.

With this special issue, we would like to bundle reconstructions, vegetation simulations and comparison tools. We invite all papers on the broad theme of past vegetation dynamics and their interaction with climate. This includes (a) vegetation simulations of various time intervals, (b) regional to global data–model or model–model comparison studies, (c) development of data–model comparison tools and techniques, and (d) vegetation–climate dynamics inferred from compilations of regional to global vegetation records. Any other related topic (past land use or past fire dynamics) is also welcome. Data compilation products may also be considered if the compiled data are integrated and used to address specific questions about past vegetation dynamics.

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.