Sea level in time and space: revolutions and inconvenient truths

Abstract

In this paper we identify four 'revolutions' that in our view have shaped the study of sea-level changes in recent decades. (i) The search for 'eustasy'. One of the most hotly debated issues in the 1960s is still relevant as models of glacial isostatic adjustment (GIA) require input of the amount of meltwater transferred to the world's oceans following the demise of the large Pleistocene ice sheets. (ii) Resolution of sea-level archives. All sea-level archives have limitations in their resolving power but are we willing to define these? From studies of saltmarsh deposits and corals it is highly likely that climate-driven metre-scale sea-level fluctuations have not occurred during the middle and late Holocene. (iii) Rapid sea-level changes. Improved coring technology has resulted in the suggestion of meltwater pulses during the last deglaciation. Low-frequency high-magnitude events have been documented along seismically active shorelines and provide information on seismic hazards and storm impacts. (iv) Merging of empirical sea-level investigations and models. Much sea-level research in the past two decades has embraced the integration of models and field-derived data, providing testable hypotheses and insights into processes. We conclude with some reminders about the 'inconvenient truths' that keep the sea-level scientist honest.

Relative sea-level changes and crustal movements in Britain and Ireland since the Last Glacial Maximum

“…One of the most hotly debated topics, since at least the 1940s, focusses on the existence of decimetre-and centennial-scale oscillations in sea level and whether they occur at global, regional or local scales (Gehrels and Shennan, 2015). One line of argument centres on the interpretation of field evidence of horizontal shifts of coastal sedimentary environments recorded by transgressive and regressive overlaps between peat and clastic units, often mapped across many 10s of kilometres.…”

Review: Short-term sea-level changes in a greenhouse world — A view from the Cretaceous

“…Resulting high-amplitude, rapid sea-level changes are called glacio-eustatic and operate at rates of up to more than 40 mm a year (during melt water pulses, Gehrels and Shennan, 2015;Miller et al, 2011), on timescales between 10-100 thousand years, and at amplitudes of 50 to 250 m (e.g. Conrad, 2013;Cloetingh and Haq, 2015;see Figs.…”

Sea-level rise in Denmark: Bridging local reconstructions and global projections

“…It is projected to rise 74 ± 28 cm under the RCP8.5 scenario, which represents a 'business-as-usual' climate pathway (Box & Colgan 2017). These rates of recent and future sea-level rise are faster than those reconstructed for previous warm intervals, such as the Medieval Climatic Optimum (c. 1000 to 1400 CE) and the Holocene Thermal Maximum (c. 7000 to 3000 BCE) (Gehrels & Shennan 2015). Moreover, palaeo reconstructions indicate a global sea-level sensitivity of two metres per degree of warming (Levermann et al 2013).…”