Testing competing GIA models against field observations along the Tyrrhenian coasts of Italy.

Citation:

Ruggieri G, Spada G, Evelpidou N, Pirazzoli P, Vassilopoulos A. Testing competing GIA models against field observations along the Tyrrhenian coasts of Italy. In: XVIII INQUA Congress. Bern; 2011.

Date Presented:

20-27 July

Abstract:

Global models of glacio-isostatic adjustment (GIA) depend critically on assumptions
about the rheology of the mantle and the history of ice melting since the Last
Glacial Maximum. Here we employ different viscosity profiles in the range of 0.4 x
10^21 Pa.s for upper mantle and 4 x 10^21Pa.s for lower mantle and several late-
Pleistocene ice sheets chronologies to interpret relative sea level (RSL) observations collected along the Tyrrhenian coasts. Neglecting the tectonic contributions to sea level variations and supposing a laterally uniform rheology, in these regions, RSL curves depart from eustasy mainly because of the effects of melt water loading, responsible for a widespread subsidence reaching its largest amplitude in the bulk of the basin. We reassess the importance of archaeological sea level indicators along the Tyrrhenian coasts of Italy (Lazio, Italy), recently revisited within the European COST Action ES0701. It appears that the local sea level rise since 2000 y ears ago can be estimated of the order of about half a meter, that agrees with the classical literature about this topic, rather than ~1.35 m, as recently proposed. The mismatch between observations from field data and model predictions can be partly attributed to the poor knowledge of the visco-elastic property of the mantle and to uncertainties of the details of the melting history. By forward modelling based on a modified ICE5G chronology, and using data from Tyrrhenian coast of Italy and SE Tunisia, we also evaluate the effects of a melt water pulse of the history of RSL, according to distinct assumptions about its origin
(Antarctic or Northern Hemispheric).