Publication Details

This book chapter was originally published as Bryant, EA, Sea-level variability and its impact within the greenhouse scenario, In Pearman, G.I. (Ed) Greenhouse: Planning for climate change, CSIRO, Melbourne, 1988, 135-146.


The greenhouse scenario assumes that sea level will rise worldwide at uniform rates because of near-polar ice melting or because of thermal expansion of ocean waters. This view ignores the natural variability of existing sea-level behaviour that occurs globally over time. It also ignores the fact that some of this variability is related to changes in climatic parameters such as precipitation, barometric pressure and temperature that will be influenced by the greenhouse effect. This paper presents existing evidence on sea-level variability across the globe and links it to changes in atmospheric pressure, air temperature and precipitation for the period 1933-1980. Rapid fluctuations in rates of sea-level change occur over distances as little as 200 km. Additionally, sea-level directly responds to changes in climatic variables near areas of greatest seasonal climatic change, namely the coastlines affected by the Asian monsoon and beneath the path of the polar jet stream in the northern hemisphere. Aseasonal effects are greatest along coastlines bordering the Aleutian and Icelandic lows. The current postulated worldwide rise in sea-level of 1.0-1.5 mm y may be occurring concomitantly with increasing climatic trends in temperature, precipitation, surface pressure and intensity of pressure cells. These results will have a significant impact within the greenhouse scenario. An accelerated worldwide rise in sea-level will be difficult to detect because of the inherent variability that exists over time and space. Seasonal and inter-annual variability in tropical regions can exceed 40 cm and already poses a natural hazard that will only be exacerbated by the effects of a global rise due to greenhouse warming in these locations. In some temperate locations, rates of sea-level rise already exceed rates proposed within the scenario, while in parts of Scandinavia and northwestern North America negative rates will locally reduce the impact. Because of the linkages in behaviour between sea-level and climatic variables, negative and positive feedback will be superimposed at regional levels upon any global sea-level rise induced by the green¬house effect. This will add a degree of uncertainty to sea-level predictions at many locations.