Recent Inflexions in Proxy Records of Sea-Level Change and Their Possible Fingerprint
Abstract
The small number of long northern European tide-gauge records shows evidence of accelerations in sea level between the 19th and 20th centuries. However, their limited duration precludes efforts to compare modern rates of sea-level rise with those in preceding centuries. Recent advances in sea-level reconstruction techniques mean that it is now possible to extract high resolution sea-level records, up to several centuries in length, from salt-marsh sediments. These 'proxy tide gauges' can overlap and extend existing tide-gauge records and also create new time series for sites where observations are lacking. Recently developed proxy sea-level records reveal sea-level inflexions in Iceland around AD 1820 and in W. Atlantic and S.W. Pacific sites around AD 1900 (dating error ~20 years). These inflexions are also found in the longest N. Atlantic tide-gauge records (e.g., Amsterdam, New York City). HADCM3 model runs of global sea-level change show increases in the rates of sea-level rise around these times, but they fall short in producing the magnitude of observed trends and decadal variability. They do indicate, however, that 19th century sea-level rise was controlled by natural factors, whereas anthropogenic forcing dominates 20th century sea-level rise. Sea-level fingerprint theory predicts that Greenland ice melt should produce zero (or negative) sea-level rise in the near field (e.g., our Iceland site) and a higher rate of sea-level rise in the S.W. Pacific than in the N. Atlantic. In the W. Atlantic, excess sea-level rise during the 20th century, as compared with preceding centuries, was 1.6-1.8 mm/yr. In New Zealand, it was 2.3-3.2 mm/yr. Elsewhere records are fragmented, but comparisons between tide-gauge data and late Holocene sea-level trends show that in Australia excess sea- level rise during the 20th century was high (~2-3 mm/yr), it was lower along the east coast of N. America (~1.5-2 mm/yr) and lowest in N.W. Europe (~1-1.5 mm/yr). These data support the hypothesis that Greenland ice melt was responsible for the sea-level acceleration between the 19th and the 20th century and that its sea-level fingerprint exceeded signals produced by regional steric change.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFMGC54A..07G
- Keywords:
-
- 1223 Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions (0762;
- 1218;
- 3319;
- 4550);
- 1605 Abrupt/rapid climate change (4901;
- 8408);
- 1621 Cryospheric change (0776);
- 1641 Sea level change (1222;
- 1225;
- 4556)