Late Glacial Sea Level Minima in the Western British Isles

Lead Research Organisation: University of Ulster
Department Name: Sch of Environmental Sciences

Abstract

Relative sea level (RSL) change reflects the interplay between a large number of variables operating at scales from global to local. Changes in RSL around the British Isles (BI) since the height of the last glaciation (ca. 24 000 years ago), are dominated by two key variables (i) the rise of ocean levels caused by climate warming and the melting of land-based ice; and (ii) the vertical adjustment of the Earth's surface due to the redistribution of this mass (unloading of formerly glaciated regions and loading of the ocean basins and margins). As a consequence RSL histories vary considerably across the region once covered by the British-Irish Ice Sheet (BIIS). The variable RSL history means that the BI is a globally important location for studying the interactions between land, ice and the ocean during the profound and rapid changes that followed the last glacial maximum. The BI RSL record is an important yardstick for testing global models of land-ice-ocean interactions and this in turn is important for understanding future climate and sea level scenarios. At present, the observational record of RSL change in the British Isles is limited to shallow water areas because of accessibility and only the later part of the RSL curve is well studied. In Northern Britain, where the land has been rising most, RSL indicators are close to or above present sea level and the RSL record is most complete. In southern locations, where uplift has been less, sea level was below the present for long periods of time but there is very little data on RSL position. There are varying levels of agreement between models and existing field data and we cannot be certain of model projections of former low sea levels. Getting the models right is important for understanding the whole global pattern of land-ice-ocean interactions in the past and into the future. To gather the missing data and thus improve the utility of the British RSL curves for testing earth-ice-ocean models, we will employ a specialised, interdisciplinary approach that brings together a unique team of experts in a multidisciplinary team. We have carefully selected sites where there is evidence of former sea levels is definitely preserved and we will use existing seabed geological data in British and Irish archives to plan our investigations. The first step is marine geophysical profiling of submerged seabed sediments and mapping of surface geomorphological features on the seabed. These features include the (usually) erosional surface (unconformity) produced by the rise in sea level, and surface geomorphological features that indicate former shorelines (submerged beaches, barriers and deltas). These allow us to identify the position (but not the age) of lower than present sea levels. The second step is to use this stratigraphic and geomorphological information to identify sites where we will take cores to acquire sediments and organic material from low sea-level deposits. We will analyse the sediments and fossil content of the cores to find material that can be closely related to former sea levels and radiocarbon dated. The third step in our approach is to extend the observed RSL curves using our new data and compare this to model predictions of RSL. We can then modify the parameters in the model to obtain better agreement with observations and thus better understand the earth-ice-ocean interactions. These data are also important for understanding the palaeogeography of the British Isles. Our data will allow a first order reconstruction of former coastlines, based upon the modern bathymetry, for different time periods during the deglaciation. This is of particular importance to the presence or absence of potential landbridges that might have enabled immigration to Ireland of humans and animals. They will also allow us to identify former land surfaces on the seabed. The palaeogeography is crucial to understanding the evolving oceanographic circulation of the Irish Sea.

Publications

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Biausque M (2020) Multiple intertidal bars on beaches: A review in Earth-Science Reviews

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Hamon-Kerivel K (2020) Shoreface mesoscale morphodynamics: A review in Earth-Science Reviews

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Cooper J. Andrew (2014) New observations on lower than present relative sea-levels since the late Glacial from the British Isles in EGU General Assembly Conference Abstracts

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Callard S. Louise (2014) Offshore evidence of postglacial relative sea-level change from eastern Ireland. in EGU General Assembly Conference Abstracts

 
Description We have constrained the late glacial sea levels at several sites around the Irish Sea. This is providing a baseline for modelling investigations of earth-ice-ocean interactions. In addition, we have examined the relationship between sea level change and coastal evolution in several paraglacial environments (marine embayments, open sedimentary coast, open rocky coast and estuaries).
Exploitation Route Further refinement of sea level curves
Sectors Education,Energy,Environment,Culture, Heritage, Museums and Collections

 
Description We have created a display in the Titanic Belfast education centre, Northern Ireland's biggest indoor visitor attraction. This highlights our findings to a non-technical audience and describes the work of marine geologists.
First Year Of Impact 2015
Sector Education,Culture, Heritage, Museums and Collections
Impact Types Cultural,Societal

 
Description Coastal Geography Day Course for Geography Teachers, March 2011 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? Yes
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact The teachers acquired case studies that can be used in class.
A question and discussion session was included in the programme. The teachers were overwhelmingly positive in their appraisal.

After the engagement we were asked to make presentations at several schools' conferences
Year(s) Of Engagement Activity 2009
 
Description Session Organisation: Sea level in interglacials and the last deglaciation (including Milutin Milankovic Medal Lecture) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact The collection of talks encouraged discussion with other groups

It was agreed to co-convene a similar session in subsequent years
Year(s) Of Engagement Activity 2014