Having said that this should only be considered as a preliminary first attempt, the mutual comparison of the maps shows a first phase (1530-1592) of delta lobe progradation speed not directly correlated to the LIA beginning, and a second, sudden one (1592-1599) of severe coastal regression. Other maps under study can confirm the above-mentioned erosional phase. This fact is quite astonishing if one bears in mind that for many decades the Republic of Venice tried to divert the Po riverbed, declaring that the high sedimentation rates at the river mouth were a real hazard for the southernmost Venice lagoon tidal inlet. It was not due to an actual lowering of the water discharge or to a consistent change in Ql/Qs discharge but probably to the development of more energetic conditions in the Adriatic Sea basin. Indeed, it was an episode of real coastal erosion that cut more than an half of the northeastern corner of the delta, furthermore displaying a beautiful, large submerged coastal bar ending in a southward directed spit. This could mean that the main causative agent may well have been an highly energetic content mainly of the Bura wind. Even if the indicated values may be partially affected by errors due to methodological problems, the erosion rates order of magnitude characterizing that phenomenon (about 500 m/y) were 5 to 10 times higher than the former progradation rates: the latter grew higher only after 1604 A.D. during the growth of the new Po delta apparatus. That severe erosion of the coastal Po delta lobe is the most striking evidence, having a term of comparison, to some extent, e.g. in today’s delta coast evolutionary trends (Simeoni et al. 2007). This kind of interpretation is consistent with the sea basin climate in 1594, various other very cold winters (Penzar, Penzar 1997) and also with a low order (bidecadal) climatic oscillation characterized by a -1°C temperature anomaly in respect to the 1901-1995 A.D. winter mean value (Lutherbacher et al. 2004, fig 1), i.e., -2.2°C as compared with the year 2000.
Climatic suggestions from the Po river delta coastline (Italy) at the beginning of the Little Ice Age / Cremonini S.. - STAMPA. - (2010), pp. 114-119. (Intervento presentato al convegno China-Italy bilateral Symposium on the Coastal Zone and Continental Shelf evolution trend tenutosi a ISMAR-CNR, Bologna, Italy nel October 5-8, 2010).
Climatic suggestions from the Po river delta coastline (Italy) at the beginning of the Little Ice Age.
CREMONINI, STEFANO
2010
Abstract
Having said that this should only be considered as a preliminary first attempt, the mutual comparison of the maps shows a first phase (1530-1592) of delta lobe progradation speed not directly correlated to the LIA beginning, and a second, sudden one (1592-1599) of severe coastal regression. Other maps under study can confirm the above-mentioned erosional phase. This fact is quite astonishing if one bears in mind that for many decades the Republic of Venice tried to divert the Po riverbed, declaring that the high sedimentation rates at the river mouth were a real hazard for the southernmost Venice lagoon tidal inlet. It was not due to an actual lowering of the water discharge or to a consistent change in Ql/Qs discharge but probably to the development of more energetic conditions in the Adriatic Sea basin. Indeed, it was an episode of real coastal erosion that cut more than an half of the northeastern corner of the delta, furthermore displaying a beautiful, large submerged coastal bar ending in a southward directed spit. This could mean that the main causative agent may well have been an highly energetic content mainly of the Bura wind. Even if the indicated values may be partially affected by errors due to methodological problems, the erosion rates order of magnitude characterizing that phenomenon (about 500 m/y) were 5 to 10 times higher than the former progradation rates: the latter grew higher only after 1604 A.D. during the growth of the new Po delta apparatus. That severe erosion of the coastal Po delta lobe is the most striking evidence, having a term of comparison, to some extent, e.g. in today’s delta coast evolutionary trends (Simeoni et al. 2007). This kind of interpretation is consistent with the sea basin climate in 1594, various other very cold winters (Penzar, Penzar 1997) and also with a low order (bidecadal) climatic oscillation characterized by a -1°C temperature anomaly in respect to the 1901-1995 A.D. winter mean value (Lutherbacher et al. 2004, fig 1), i.e., -2.2°C as compared with the year 2000.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
