Timing of emergence of modern rates of sea-level rise by 1863

Abstract

Sea-level rise is a significant indicator of broader climate changes, and the time of emergence concept can be used to identify when modern rates of sea-level rise emerged above background variability. Yet a range of estimates of the timing persists both globally and regionally. Here, we use a global database of proxy sea-level records of the Common Era (0-2000 CE) and show that globally, it is very likely that rates of sea-level rise emerged above pre-industrial rates by 1863 CE (P = 0.9; range of 1825 [P = 0.66] to 1873 CE [P = 0.95]), which is similar in timing to evidence for early ocean warming and glacier melt. The time of emergence in the North Atlantic reveals a distinct spatial pattern, appearing earliest in the mid-Atlantic region (1872-1894 CE) and later in Canada and Europe (1930-1964 CE). Regional and local sea-level changes occurring over different time periods drive the spatial pattern in emergence, suggesting regional processes underlie centennial-timescale sea-level variability over the Common Era.

Fig. 1. Time of emergence of global sea-level rise.

a Sixty-year average rates over the Common Era, where pre-industrial is 0–1700 CE. b Sixty-year average rates from 1700 to 2000 CE which increase concurrently with the probability that each 60-year interval and all subsequent 60-year intervals were greater than a random 60-year interval during the pre-industrial Common Era. The time of emergence year is given for 0.66, 0.90, and 0.95 probabilities. Model predictions are the mean with 1σ uncertainty.

Fig. 2. Spatial variability in the time of emergence of modern rates of relative sea level.

Time of emergence is shown for global sea level, null site (indicative generic site in northeast Asia (38°N, 127°E) with no instrumental data and far from available proxy data), and sites in the North Atlantic. Common Era rates for the periods 0–1700, 1700–2000, and 1940–2000 CE, as well as the distribution of mean estimates of pre-industrial 60-year rates, are also shown for each site by increasing longitude.

Fig. 3. Spatiotemporal model decomposition for New Jersey, Florida, and Scotland.

a Total, b global, c linear, and d regional and local nonlinear rates for three sites (New Jersey, Cheesequake; Florida, Nassau; Scotland, Kyle of Tongue) are shown with the time of emergence for each site. Model predictions are the mean with 1σ uncertainty. Note variable y-axes.