Sealevel Rise And Coastal Systems

Since the peak of the last glacial maximum about 20 000 a (years) ago, sea level has risen —125 m [11]. Geologic evidence indicates inundation of coastal lowlands and retreat of shorelines during periods of rapid sea-level rise, such as major meltwater pulses (Fig. 2). This pattern of sea-level rise was experienced around the world, driven by the melt of the large ice sheets

Years (x103) before present

Years (x103) before present

FIGURE 2 Sea level history since the peak of the last glacial maximum with arrows indicating the timing of meltwater pulses. Abbreviations: MWP meltwater pulse. MWP 1A0, c. 19 000 a ago, MWP 1A, 14600 13 500 a ago, MWP 1B, 11500 11000 a ago, MWP 1C, —8200 7600 a ago (Source: Ref. [12]).

which appears to have ceased 7500 6000 a ago. The level of the sea has risen less than 3 m over the past 6000 a and regional variations of sea level on time scales of a few 100 a or longer are likely to have been less than 0.3 0.5 m [13]. As sea level stabilised extensive coastal plains were formed, and the first evidence of early civilisations appeared on the plains [14,15].

Coastline location and stability is intimately linked with changes in mean sea level. However, even under conditions of relatively stable mean sea level, coasts are extremely dynamic systems, involving co-adjustment of form and process at different time and space scales, termed morphodynamics [16,17]. Hence, erosion and deposition of coasts are naturally occurring due to short-term wave and tide conditions, as well as seasonal and longer-term climatic variability. The El Nino phenomenon, for example, has been shown to influence wave processes that shape beaches in the southwest Pacific [18] and cliffs in the eastern Pacific [19].

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