Introducing Sea Level Change

Dawson Alastair

Description

One of the most important issues in current debates on climate change is sea level rise. Hardly a day goes by when there is not a newspaper article, TV or radio presentation on the topic. Nearly half of the worlds population live on or near the coast, so there is real concern about the impact that future sea level rise may have. Yet media predictions of future changes tend to be depicted in a sensationalist manner and quite often the explanations of the science of sea level change bear little relation to reality. This book details the history of scientific discoveries that have explained the patterns of sea level change that have taken place across the Earth in the past. Alastair Dawson introduces the many complex processes, some of which are not well-known, that influence patterns and rates of relative sea level change. Using this knowledge, the reader is much better placed to form a clearer perspective on what the future is likely to have in store for sea levels on Earth.Alastair Dawson first addresses some of the most important misconceptions about the topic of sea level change. He then explains the principal causes of sea level change focusing on the key issues of vertical land movements and changes in global ocean volume. He explores the key areas of science that we need to understand in order to evaluate competing assertions of how sea level is likely to change in the future. He also shows how, remarkably, the melting history of the last great ice sheets on Earth is still playing an important part in contributing to present patterns of sea level change. The book concludes with a consideration of the rates and patterns of sea level change that have occurred over the last century and demonstrates how satellite technology is presently contributing new ways of understanding of present patterns of change.

Sujets

• Histoire
• Historical geology
• History

Informations

• Publié par: Dunedin Academic Press
• Date de parution: 01 décembre 2018
• Nombre de lectures: 0
• EAN13: 9781780466002
• Langue: English
• Poids de l'ouvrage: 2 Mo

Extrait

INTRODUCING
SEA LEVEL CHANGE
Alastair Dawson
For Sue, Greg, Laura and Euan. Particular gratitude is expressed to the late Brian Sissons who inspired me to study sea level change.

Contents
Preface
List of illustrations and tables
1 What does ‘sea level’ mean?
2 Evidence for former relative sea level changes
3 Long-term chronologies of relative sea level change
4 Reconstructing past changes in relative sea level
5 Response of the Earth’s crust to surface loads
6 Processes of relative sea level change
7 Ancient and modern ice sheets and relative sea level changes
8 Relative sea level change during the last glacial maximum
9 Ice sheets and meltwater pulses
10 Abandoning global sea level curves
11 Present and future relative sea level change
12 Understanding sea level change
Glossary
Selected further reading
Preface
One of the most important issues in current debates on climate change is sea level rise. Not a day goes by when there is not a newspaper article, TV or radio presentation on the topic. With millions of people around the world living at the coast there is real concern that a future dramatic rise in sea level will cause chaos to coastal towns and cities. Yet, the world has experienced many dramatic changes of relative sea level in the past. In this book I give an account of the remarkable history of these past changes. It is a story that takes us from the last ice age on Earth to the effects of present-day climate changes on the world’s glaciers, ice sheets and oceans. I describe the rates and patterns of sea level change that have occurred over the last century and show how scientific advances are being used to measure present-day patterns of relative sea level change. This book provides the reader with the key scientific information that is needed om which to base an informed discussion on the topic of ‘sea level rise’. It is hoped that it will be of value, not only to students as an educational textbook, but also to a wide range of non-governmental organisations as well as to the general public wishing to understand the subject.
Alastair Dawson Dundee, October 2018
* Note: all terms initially highlighted in bold are defined in the Glossary at the end of the book.
List of illustrations and tables Figure 1.1 The Barbados view of relative sea level from the beach Figure 1.2 The Potzdam gravity ‘potato’ Figure 1.3 Tide gauge, Reykjavik, Iceland Figure 1.4 Rates of land subsidence, Jefferson Parish, New Orleans Figure 1.5 Artist’s impression of twin GRACE (GRACE-FO) satellites Figure 1.6 An ARGO aquatic robot Figure 1.7 Sea level departures for 2011 from long-term (1993–2011) average Figure 2.1 Shoreline notch produced by preferential erosion of Holocene emerged reef beneath igneous boulder Figure 2.2 Ice-moulded strandflat surfaces, Lofoten Isles, northern Norway Figure 2.3 Raised Late Pleistocene rock platform and cliff cut in limestone, Isle of Lismore, western Scotland Figure 2.4 Storm beach ridge, Pollochar, South Uist, Scottish Outer Hebrides, deposited during a major storm, 11 January 2005 Figure 2.5 Raised marine terrace of Late Pleistocene age, Glenbatrick, western Jura, Scottish Inner Hebrides Figure 2.6 Sequence of four elevated Pleistocene reef terraces, north coast of Bonaire, Dutch Caribbean Figure 2.7 Coral reef complex, American Samoa. Dating of individual submerged coral species can be used to reconstruct past patterns of relative sea level change Figure 2.8 Holocene tree stumps in present intertidal zone, Borth, south Wales Figure 2.9 Sediment core sampling using the transfer function approach from a salt marsh, Nanortalik, western Greenland Figure 2.10 Three microfossils used in sea level change research Figure 2.11 Marine fossil assemblage in uplifted Pleistocene marine terrace, Coelha, north San Nicolau, Cape Verde Figure 3.1 Generalised oxygen isotope curve for the world’s oceans compared with Milankovitch insolation curve Figure 3.2 Respective enrichments and depletions of oxygen isotopes 16 and 18 during glacial and interglacial cycles Figure 3.3 Oxygen isotope curve of inferred global sea level history for last c .140,000 years compared with pattern of relative sea level change reconstructed by John Chappell for New Guinea Figure 4.1 Illustration of Ulf Hafsten model of use of isolation basins in order to reconstruct past patterns of relative sea level change Figure 4.2 Brian Sissons’ classic representation of surface and buried morphology and stratigraphy of upper Forth valley, eastern Scotland Figure 4.3 Example from Scotland of concentric shoreline uplift isobases around a single dome of glacio-isostatic rebound Figure 4.4 Holocene raised beach ridges, Cape Krusenstern, Kivalina, NW Alaska Figure 4.5 Example of shoreline height–distance diagram Figure 5.1 Internal structure of the Earth Figure 6.1 Illustration of interaction of glacial eustasy and glacial isostasy Figure 6.2 Emerged shoreline notches, Milokopi Bay, Perochora peninsula, eastern Gulf of Corinth, Greece Figure 6.3 ‘Temple of Serapis’, Pozzuoli, Naples Figure 6.4 Emerged shoreline notches in an aseismic region, S Gigante Island, Philippines Figure 6.5 Patterns of geoidal sea surface lowering (m) associated with an instantaneous melting of the last Fennoscandian ice sheet Figure 6.6 Schematic illustration of geoidal sea surface changes associated with the melting of an ice sheet Figure 6.7 Glacio-isostatic depression and forebulge development associated with ice-sheet growth Figure 6.8 Raised shorelines of NE Islay, Scotland Figure 6.9 Patterns and rates of lithospheric rebound (mmyr -1 ) Figure 6.10 Schematic illustration of key relationships between long-term crustal movements and changes in ocean mass Figure 6.11 Numerical relationship between ocean temperature, density and salinity Figure 6.12 Tide gauge record for San Francisco Figure 7.1 Marine oxygen isotope variations over last c .1Myr Figure 7.2 Marine oxygen isotope variations over last c .300,000yr Figure 7.3 Reconstruction of dimensions of Eurasian ice sheet during last glacial maximum Figure 7.4 Emerged reef platform, Spelonk lighthouse, NE Bonaire, Dutch Caribbean dated to last interglacial (substage 5e) Figure 7.5 NASA reconstruction of areas of Antarctica that have experienced the greatest surface warming between 1957 and 2006 Figure 7.6 Illustration of ice sheet grounding line migration Figure 8.1 Modelled reconstruction by Glenn Milne of the geoidal sea surface for the last glacial maximum Figure 8.2 Predicted relative sea level history for Barbados using the ICE-5G (VM2) model of Dick Peltier Figure 8.3 Generalised map of ice cover across the northern hemisphere during the last glacial maximum Figure 8.4 One of several possible scenarios of maximum ice cover extent across Antarctica for last glacial maximum Figure 8.5 Image of Asian continent giving general indication of potential areas of land bridges during last glacial maximum Figure 8.6 Reconstruction of Beringia for last glacial maximum Figure 9.1 Timing of global meltwater pulses since the last glacial maximum based on analysis of submerged coral data Figure 9.2 Glacial lake Agassiz-Ojibway drained northward through a network of subglacial tunnels underneath areas of the Laurentide ice sheet Figure 10.1 Schematic representation of three competing graphs of Holocene relative sea level change, each promoted by different groups of research scientists during the late 20th century Figure 10.2 Emerged Holocene beach ridge staircase, Bathurst Inlet, Nunavut, northern Canada Figure 10.3 Trend of relative sea level change, southern Vancouver Island Figure 10.4 Evolution of Baltic Ice Lake, Yoldia Sea, Ancylus Lake and Litorina Sea Figure 10.5 Suite of theoretical relative sea level curves for western Norway derived from shoreline height–distance diagram data Figure 10.6 Mid-Holocene emerged notch, south coast of Vanua Levu, Savusavu, Fiji Figure 11.1 Whereas the East Antarctic ice sheet is relatively stable, the West Antarctic ice sheet (WAIS) is in many areas a marine ice sheet and much more sensitive to climate change Figure 11.2 The sub-ice topography across the Antarctic Figure 11.3 A 6000km cross-profile across Antarctica extending from the Amundsen Sea and Pine Island glacier area in the west to Prydz Bay in the east Figure 11.4 The Greenland ice sheet, and its bedrock topography with the ice sheet removed Figure 11.5 Theoretical modelling of regional sea level changes caused by annual contributions of 0.5mmyr -1 from both the Greenland and Antarctic ice sheets Figure 11.6 Monitoring of the Franz Josef Glacier, New Zealand, between April 2012 and January 2017 Figure 12.1 Coastal archaeological remains in the Shetland Isles Figure 12.2 Plot of future IPCC sea level rise scenarios with qualitative comments on probabilities of specific changes taking place Table 3.1 Classical scheme of fourfold glaciation based on Penck and Bruckner Table 3.2 Nomenclature used for Late Pleistocene chronology of Canada, USA and Russia Table 9.1 Generalised chronology for Lateglacial across NW Europe Table 11.1 Observed contributions to global mean sea level rise, 1993–2010 according to IPCC 5th report (2014)
Unless otherwise acknowledged in the captions all illustrations are the work of the author.
1 What does ‘sea level’ mean?
Introduction
To many, the issues of sea level change and sea level rise, together with the dangers that society may face in the future, are very simple – global warming caused by climate change is melting glaciers, and this is causing sea level to rise uniformly worldwide. This view, as we shall see, is light years away from reality. Although based on good intentions to save our planet from the effects of climate change, this interpretation of sea level change is at best misinformed and at worst just plain wrong. This book is essentially a rough guide to the science of sea level change. It attempts to provide a relatively simple and straightforward e