rise in sea level of over 120 m that occurred from 15 000 to 6000 years ago.
This was related to significant global warming and melting of large ice caps
situated in the northern hemisphere. Now, human-induced climate change
threatens a renewed global rise in sea level.
Sea-level components. The local change in sea level at any coastal location
depends on the sum of global, regional and local factors and is termed relative
sea-level change. Therefore, the global-mean sea-level rise does not translate
into a uniform rise in sea level around the world. The relative (or local) level of the
sea to the land can change for a number of reasons and over a range of timescales
from seconds to millions of years. Here we are interested in mean sea level, so
the time period of wave and tides can be disregarded, while the upper time bound
is 10—10 years. Over this period, relative sea level is the sum of several
components:
E Global-mean sea-level rise, which is due to an increase in the global volume of
the ocean. In the 20th/21st century, this is primarily due to thermal
expansion of upper ocean as it warms and the melting of small ice caps due to
human-induced global warming. The contribution of Greenland is less
certain, while the Antarctica ice sheet is expected to grow in size due to
increased snowfall. This will produce a relative sea-level fall, offsetting any
positive contribution from Greenland. Beyond 2100, Greenland and
Antarctica could become significant contributors to sea-level rise. Direct
human influence is also possible due to modifications to the hydrological
cycle [e.g. increased terrestrial storage of water (causing sea-level fall), versus
increased groundwater mining (causing sea-level rise)].
E Regional meteo-oceanographic factors such as spatial variation in thermal
expansion effects, changes to long-term wind fields and atmospheric
pressure, and changes in ocean circulation such as the Gulf Stream. These
effects could be significant, with regional effects equal to the magnitude of
the global-mean thermal expansion term. A possible example of this type of
effect is an apparent fall of the Mediterranean since 1960. This observation
might be linked to decreased freshwater inputs to the Mediterranean and
M. S. Kearney, Late holocene sea level variations, in B. C. Douglas, M. S. Kearney and S. P.
Leatherman (eds.), Sea-level Rise: History and Consequences, Academic Press, London, 2000, pp.
13—36.
J. A. Church, J. M. Gregory, P. Huybrechts, M. Kuhn, K. Lambeck, M. T. Nhuan, D. Qin and P. L.
Woodworth, Changes in sea level, in D. J. Houghton, Y. Ding, D. J. Griggs, M. Noguer, P. J. van
der Linden and D. Xiaosu (eds.), Climate Change 2001. The Scientific Basis, Cambridge University
Press, Cambridge, 2001, pp. 639—693.
R. J. Nicholls and S. P. Leatherman, Adapting to sea-level rise: relative sea level trends to 2100 for
the USA, Coastal Manage., 1996, 24(4), 301—324.
R. J. N. Devoy, Sea Surface Studies: A Global View, Croom Helm, London, 1987, 650 pp.
D. Smith, S. B. Raper, S. Zerbini and A. Sanchez-Arcilla, (eds.), Sea Level Change and Coastal
Processes. Implications for Europe, EUR 19337, European Commission, Brussels, 2000, 247 pp.
J. M. Gregory, Sea-level changes under increasing atmospheric CO
in a transient coupled
ocean-atmosphere GCM experiment, J. Clim., 1993, 6, 2247—2262.
M. N. Tsimplis and T. F. Baker, Sea level drop in the Mediterranean Sea: an indicator of deep
water salinity and temperature changes?, Geophys. Res. Lett., 2000, 27, 1731—1734.
Rising Sea Levels: Potential Impacts and Responses
85
This was related to significant global warming and melting of large ice caps
situated in the northern hemisphere. Now, human-induced climate change
threatens a renewed global rise in sea level.
Sea-level components. The local change in sea level at any coastal location
depends on the sum of global, regional and local factors and is termed relative
sea-level change. Therefore, the global-mean sea-level rise does not translate
into a uniform rise in sea level around the world. The relative (or local) level of the
sea to the land can change for a number of reasons and over a range of timescales
from seconds to millions of years. Here we are interested in mean sea level, so
the time period of wave and tides can be disregarded, while the upper time bound
is 10—10 years. Over this period, relative sea level is the sum of several
components:
E Global-mean sea-level rise, which is due to an increase in the global volume of
the ocean. In the 20th/21st century, this is primarily due to thermal
expansion of upper ocean as it warms and the melting of small ice caps due to
human-induced global warming. The contribution of Greenland is less
certain, while the Antarctica ice sheet is expected to grow in size due to
increased snowfall. This will produce a relative sea-level fall, offsetting any
positive contribution from Greenland. Beyond 2100, Greenland and
Antarctica could become significant contributors to sea-level rise. Direct
human influence is also possible due to modifications to the hydrological
cycle [e.g. increased terrestrial storage of water (causing sea-level fall), versus
increased groundwater mining (causing sea-level rise)].
E Regional meteo-oceanographic factors such as spatial variation in thermal
expansion effects, changes to long-term wind fields and atmospheric
pressure, and changes in ocean circulation such as the Gulf Stream. These
effects could be significant, with regional effects equal to the magnitude of
the global-mean thermal expansion term. A possible example of this type of
effect is an apparent fall of the Mediterranean since 1960. This observation
might be linked to decreased freshwater inputs to the Mediterranean and
M. S. Kearney, Late holocene sea level variations, in B. C. Douglas, M. S. Kearney and S. P.
Leatherman (eds.), Sea-level Rise: History and Consequences, Academic Press, London, 2000, pp.
13—36.
J. A. Church, J. M. Gregory, P. Huybrechts, M. Kuhn, K. Lambeck, M. T. Nhuan, D. Qin and P. L.
Woodworth, Changes in sea level, in D. J. Houghton, Y. Ding, D. J. Griggs, M. Noguer, P. J. van
der Linden and D. Xiaosu (eds.), Climate Change 2001. The Scientific Basis, Cambridge University
Press, Cambridge, 2001, pp. 639—693.
R. J. Nicholls and S. P. Leatherman, Adapting to sea-level rise: relative sea level trends to 2100 for
the USA, Coastal Manage., 1996, 24(4), 301—324.
R. J. N. Devoy, Sea Surface Studies: A Global View, Croom Helm, London, 1987, 650 pp.
D. Smith, S. B. Raper, S. Zerbini and A. Sanchez-Arcilla, (eds.), Sea Level Change and Coastal
Processes. Implications for Europe, EUR 19337, European Commission, Brussels, 2000, 247 pp.
J. M. Gregory, Sea-level changes under increasing atmospheric CO
in a transient coupled
ocean-atmosphere GCM experiment, J. Clim., 1993, 6, 2247—2262.
M. N. Tsimplis and T. F. Baker, Sea level drop in the Mediterranean Sea: an indicator of deep
water salinity and temperature changes?, Geophys. Res. Lett., 2000, 27, 1731—1734.
Rising Sea Levels: Potential Impacts and Responses
85