Abstract
Abstract The spatial and temporal distribution of relative sea-level change over the northwest European shelf seas has varied considerably since the Last Glacial Maximum, due to eustatic sea-level rise and a complex isostatic response to deglaciation of both near- and far-field ice sheets. Because of the complex pattern of relative sea level changes, the region is an ideal focus for modelling the impact of significant sea-level change on shelf sea tidal dynamics. Changes in tidal dynamics influence tidal range, the location of tidal mixing fronts, dissipation of tidal energy, shelf sea biogeochemistry and sediment transport pathways. Significant advancements in glacial isostatic adjustment (GIA) modelling of the region have been made in recent years, and earlier palaeotidal models of the northwest European shelf seas were developed using output from less well-constrained GIA models as input to generate palaeobathymetric grids. We use the most up-to-date and well-constrained GIA model for the region as palaeotopographic input for a new high resolution, three-dimensional tidal model (ROMS) of the northwest European shelf seas. With focus on model output for 1 ka time slices from the Last Glacial Maximum (taken as being 21 ka BP) to present day, we demonstrate that spatial and temporal changes in simulated tidal dynamics are very sensitive to relative sea-level distribution. The new high resolution palaeotidal model is considered a significant improvement on previous depth-averaged palaeotidal models, in particular where the outputs are to be used in sediment transport studies, where consideration of the near-bed stress is critical, and for constraining sea level index points.
Highlights
Since the Last Glacial Maximum (LGM), which occurred globally between ca. 26 and 20 ka BP (Clark et al, 2009), the changing ice mass balance between the oceans and land has had a significant role in driving changes in shelf sea tidal dynamics (e.g. Scott and Greenberg, 1983; Belderson et al, 1986; Austin, 1991; Austin and Scourse, 1997; Uehara et al, 2002, 2006; Egbert et al, 2004; Arbic et al, 2008; Neill et al, 2010)
The results presented within this paper focus on these new simulations, but we compare these Regional Ocean Modelling System (ROMS) þ Bradley simulations with two other palaeotidal models (Table 1)
Considerable differences were found between the palaeotidal models of the region which incorporated the glacial isostatic adjustment (GIA) models of Lambeck (1995) and Bradley et al (2011), not between different hydrodynamic models whose palaeotopographies were derived from the same GIA models (i.e. ROMS þ Lambeck, Kyushu University Tidal Model (KUTM) þ Lambeck)
Summary
Since the Last Glacial Maximum (LGM), which occurred globally between ca. 26 and 20 ka BP (Clark et al, 2009), the changing ice mass balance between the oceans and land has had a significant role in driving changes in shelf sea tidal dynamics (e.g. Scott and Greenberg, 1983; Belderson et al, 1986; Austin, 1991; Austin and Scourse, 1997; Uehara et al, 2002, 2006; Egbert et al, 2004; Arbic et al, 2008; Neill et al, 2010). The maximum volume of the LGM British-Irish Ice Sheet occurred between 27 and 21 ka BP (Chiverrell and Thomas, 2010; Clark et al, 2012; Everest et al, 2013), during which time the majority of the ice sheet was marine-based, extending into the present-day North Sea and the continental shelves of Britain and Ireland, with different sectors of the ice sheet reaching maximal extents at different times Changes in sea levels such as those that have occurred since the LGM have significant implications for tidal dynamics, including impacting upon tidal amplitudes (elevations and currents), sediment transport and upon sediment type and bedform distribution (Belderson et al, 1986; Van Landeghem et al, 2009b; Furze et al, 2014). Sea level changes influence seasonal stratification (Austin, 1991; Austin and Scourse, 1997; Scourse et al, 2002; Uehara et al, 2006) and shelf sea primary production and carbon dioxide uptake
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