EGU2020-14805
https://doi.org/10.5194/egusphere-egu2020-14805
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

The southern North Sea as a natural palaeo-laboratory to reconstruct the coastal response to Last Interglacial sea-level rise

Natasha Barlow1, Victor Cartelle1, Oliver Pollard1, Lauren Gregoire1, Natalya Gomez2, David Hodgson1, Stephen Eaton1, Freek Busschers3, Kim Cohen4, Carol Cotterill5, Claire Mellett6, and Ivan Haigh7
Natasha Barlow et al.
  • 1School of Earth and Environment, University of Leeds, Leeds, UK (n.l.m.barlow@leeds.ac.uk)
  • 2Department of Earth & Planetary Sciences, McGill University, Montreal, Canada
  • 3Geological Survey of the Netherlands (TNO), Utrecht, The Netherlands
  • 4School of Geosciences, University of Utrecht, Utrecht, The Netherlands
  • 5British Geological Survey, Edinburgh, UK
  • 6Wessex Archaeology, Salisbury, UK
  • 7Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, UK

Current models that project sea-level rise beyond 2100 have large uncertainties because recent observation encompass a too limited range of climate variability to provide robust tests against which to simulate future changes. It is crucial to turn to the geological record where there are large-scale changes in climate, but the current interglacial provides limited evidence for how the Earth-system responds to increased temperatures, and therefore it is necessary to study previous climatically-warm periods. Global temperatures during the Last Interglacial were ~1oC warmer than pre-industrial values and 3-5oC warmer at polar latitudes, during which time global mean sea level was likely 6-9 m above present. Though the drivers of warming during the Last Interglacial are different to those of today, it is the amplified warming at polar latitudes, the primary locations of the terrestrial ice masses likely to contribute to long term sea-level rise, which makes the Last Interglacial an ideal palaeo-laboratory to understand coastal response to sea-level rise.  However, our understanding of Last Interglacial sea level change is primarily limited to tropical and sub-tropical latitudes and it is important to understand the response of temperate estuarine settings to rising sea level.

The ERC-funded RISeR project (Rates of Interglacial Sea-level Change, and Responses) focuses on specifically targeting palaeo shorelines buried within the southern North Sea, preserved beyond the limit of the Last Glacial Maximum ice sheets. Buried Last Interglacial sequences in this area provide a valuable record of marine transgression and are being unveiled in new geophysical and geotechnical datasets acquired to support the offshore renewable energy development. This offshore sedimentary archives offer significant advantages over the geomorphologically restricted onshore records allowing us to trace the transgression over a much large area, and should capture the earliest flooding of the Last Interglacial North Sea basin, when the far-field data suggests ice sheet melt was at it maximum. By integrating the already available datasets with newly acquired samples as part of the project, we aim to develop new palaeoenvironmental reconstructions of the Last Interglacial sea-level change from northwest Europe, providing the first chronological constraints on timing, and therefore rates. This has the potential to allow us to ‘fingerprint’ the source of melt (Greenland and/or Antarctica) during the interglacial sea-level highstand.

How to cite: Barlow, N., Cartelle, V., Pollard, O., Gregoire, L., Gomez, N., Hodgson, D., Eaton, S., Busschers, F., Cohen, K., Cotterill, C., Mellett, C., and Haigh, I.: The southern North Sea as a natural palaeo-laboratory to reconstruct the coastal response to Last Interglacial sea-level rise, EGU General Assembly 2020, Online, 4–8 May 2020, https://doi.org/10.5194/egusphere-egu2020-14805, 2020

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Presentation version 2 – uploaded on 01 May 2020
Scale bar label added on slide 8
  • CC1: Comment on EGU2020-14805, Francesco Mascioli, 06 May 2020

    Hello, I am Francesco Mascioli from NLWKN-Coastal Research Station Norderney (Lower Saxony).

    - Did you observe any outcrop of the Pre-Eemians deposits or are they alway covered by Eemian and Late-Eemian ones?

    - Could you please provide some detail on lithology/sediments types and depositional environments within the three units you identified?

    Thanks

    • AC1: Reply to CC1, Victor Cartelle, 06 May 2020

      In the wind farms we have studied by now, pre-Eemian sediments are always covered by at least young Holocene sediments, but not always by Eemian deposits. In some sites, these pre-Eemian deposits are only covered by a few meters of sediments. However, the chronological constraint is still weak and age attribution is based on correlation with the regional stratigraphic framework and some pollen stratigraphies.

       

      Regarding sediment types, most pre-Eemian deposits in KHZ are sands (in some cases with some silt and clay interbeds), although there are also some deeper and older clay/peat deposits. We have not analysed in detail these deposits to discern the depositional environment. Eemian deposits include sands, clays and peat: they are sandier to the south and west of the wind far, while to the east clayely deposits and peats are more common. The early results point to an estuarine environment in a coastal plain, but more work is underway. The youngest unit mainly corresponds to sandy sediments. I am sorry, but the detailed depositional history is not yet finished.

      • AC2: Reply to AC1, Kim Cohen, 06 May 2020

        In addtion: in some places, pre-Eemian deposits offshore the Holland coast (not saying anything on HKZ specifically, but for the wider area of the southernmost Saalian limit) are glacio-tectonically (ice-pushing) displaced and then they form subcrops (below the Holocene). In other places they have not been (much) displaced by the penultimate glaciation, and overthere, where the older levels have preserved they tend to be buried by Eemian strata (and also Late Saalian and Weichselian strata) - understandably given the long-term subsiding  current tectonic setting of the North Sea Basin. In yet other places, erosian surfaces of the Penultimate glaciation and deglaciation, the Eemian transgression, the Early Weichselian sea-level fall, the Weichselian have interupted and removed the sequence, which is a third reason why some areas do have pre-Eemian subcrop, miss the Eemian stata, and have Holocene superficial cover. So: there are two reasons why pre-eemian strata locally are subcrop: (1) ice pushing during the penultimate glaciation, (2) erosion-sedimentation dynamics since that glaciation.

        • CC2: Reply to AC2, Francesco Mascioli, 06 May 2020

          Thanks for your reply.

          We are working on similar topic in the Lower Saxony North Sea, where hard-substrates (?Saalian?) outcrop but unfortunately we still have no chronological constrains.

          Just another question. Do you know which sound velocity has been used to calculate the depth of the sparker profiles?

Presentation version 1 – uploaded on 30 Apr 2020
  • CC1: Comment on EGU2020-14805, Alessio Rovere, 01 May 2020

    Just a curiosity: are there any good geological constraints on the MIS 6 Eurasian Ice Sheet margins?

    • AC1: Reply to CC1, Natasha Barlow, 01 May 2020

      Its limited, as the chronology is a real problem (particularly with the idea of the Saalain in Europe likely a complex of three glacials).  We have been using the compilation limit put together in the Batchelor 2019 paper for the GIA modelling, thus far, but this assumes a synchronous maximum.  At a local scale Victor has been working on a revised local margin in the eastern North Sea.

    • AC5: Reply to CC1, Victor Cartelle, 01 May 2020

      As Natasha pointed out, we have found some evidence in another wind farm site to the North (HKN) that we interpret as the imprint of MIS 6 ice advance and retreat, however, chronological information is limited. There are deformation ridges and erosional features useful to redefine the ice limit at a local scale.

  • AC2: Comment on EGU2020-14805, Kim Cohen, 01 May 2020

    @Alessio Rovere

    For MIS-6 the reconstructions are very reasonable and developed over
    - mainland Netherlands, Germany, Poland, into Russia (not overprinted by LGM)
    - a little bit more difficult in remote NW Russia (overprinted by LGM glaciation)
    - a little bit more difficult over Britain and Ireland (underprinted by older and overprinted by LGM glaciation)
    - a bit more difficult in the offshore southern north sea (data density/different type of primary data) - but doable [direct contribution by RISEr / this presentaion - the further authors may well want to comment on this]
    - a bit more difficult in the offshore of Russia / Kara Sea (data density/non-disclosed data)
    - a bit more difficult in the offshore NW Atlantic (off Norway, off Scotland)... but not too difficult since the shelf-break is about the limit.


  • AC4: Shear Stress Map Units, Oliver Pollard, 01 May 2020

    Please note that, due to a formatting error, the unit and label on the shear stress map colourbar have been hidden. They should read: "Shear Stress (106Pa)".

  • AC6: Comment on EGU2020-14805, Freek Busschers, 01 May 2020

    Agree. I think that onshore the Netherlands, Germany and Poland the max limit is very, very well know. In the UK there is more discussion but evidence of a clear MIS6 line is also compelling (Norfolk). The exact timing of max expansion within MIS6 is less well know but likely occuring during the second part after ~170ka. Keep in mind that the term Saalian s.s. is the entire period between the Holsteinian and Eemian and includes multiple glacial phases, although MIS6 is likely the biggest. The older ones are much more difficult to reconstruct, partially due to mix-up of with presumed 'Elsterian' stratigraphy and very difficult dating stuff. We are progressing fast (Corona related ;-)) with a new study on these older ice limits in the northern Netherlands and intercalated transgressional MIS11-7 sequences (you guys will like them for future SLR reconstructions).