TY - JOUR
T1 - North–south palaeohydrological contrasts in the central Mediterranean during the Holocene
T2 - tentative synthesis and working hypotheses
AU - Magny, M.
AU - Combourieu Nebout, N.
AU - de Beaulieu, J. L.
AU - Bout-Roumazeilles, V.
AU - Colombaroli, D.
AU - Desprat, S.
AU - Francke, A.
AU - Joannin, S.
AU - Peyron, O.
AU - Revel, M.
AU - Sadori, L.
AU - Siani, G.
AU - Sicre, M. A.
AU - Samartin, S.
AU - Simonneau, A.
AU - Tinner, W.
AU - Vannière, B.
AU - Wagner, B.
AU - Zanchetta, G.
AU - Anselmetti, F.
AU - Brugiapaglia, E.
AU - Chapron, E.
AU - Debret, M.
AU - Desmet, M.
AU - Didier, J.
AU - Essallami, L.
AU - Galop, D.
AU - Gilli, A.
AU - Haas, J. N.
AU - Kallel, N.
AU - Millet, L.
AU - Stock, A.
AU - Turon, J. L.
AU - Wirth, S.
PY - 2013/4/5
Y1 - 2013/4/5
N2 - On the basis of a multi-proxy approach and a strategy combining
lacustrine and marine records along a north-south transect, data
collected in the Central Mediterranean within the framework of a
collaborative project have led to reconstruction of high-resolution and
well-dated palaeohydrological records and to assessment of their spatial
and temporal coherency. Contrasting patterns of palaeohydrological
changes have been evidenced in the Central Mediterranean: south (north)
of around 40° N of latitude, the middle part of the Holocene was
characterised by lake-level maxima (minima), during an interval dated to
ca. 10 300-4500 cal BP to the south and 9000-4500 cal BP to the north.
Available data suggest that these contrasting palaeohydrological
patterns operated throughout the Holocene, both on millennial and
centennial scales. Regarding precipitation seasonality, maximum humidity
in the Central Mediterranean during the middle part of the Holocene was
characterised by humid winters and dry summers north of ca. 40° N,
and humid winters and summers south of ca. 40° N. This may explain
an apparent conflict between palaeoclimatic records depending on the
proxies used for reconstruction as well as the synchronous expansion of
tree species taxa with contrasting climatic requirements. In addition,
south of ca. 40° N, the first millennium of the Holocene was
characterised by very dry climatic conditions not only in the Eastern,
but also in the Central and the Western Mediterranean zones as reflected
by low lake levels and delayed reforestation. These results suggest
that, in addition to the influence of the Nile discharge reinforced by
the African monsoon, the deposition of Sapropel 1 has been favoured (1)
by an increase in winter precipitation in the northern Mediterranean
borderlands, and (2) by an increase in winter and summer precipitation
in the southern Mediterranean area. The climate reversal following the
Holocene climate optimum appears to have been punctuated by two major
climate changes around 7500 and 4500 cal BP. In the Central
Mediterranean, the Holocene palaeohydrological changes developed in
response to a combination of orbital, ice-sheet and solar forcing
factors. The maximum humidity interval in the south-central
Mediterranean started at ca. 10 300 cal BP, in correlation with the
decline (1) of the possible blocking effects of the North Atlantic
anticyclone linked to maximum insolation, and/or (2) of the influence of
the remnant ice sheets and fresh water forcing in the North Atlantic
Ocean. In the north-central Mediterranean, the lake-level minimum
interval began only around 9000 cal BP when the Fennoscandian ice-sheet
disappeared and a prevailing positive NAO-type circulation developed in
the North Atlantic area. The major palaeohydrological oscillation around
4500-4000 cal BP may be a non-linear response to the gradual decrease,
with additional key seasonal and interhemispherical changes, in
insolation. On a centennial scale, the successive climatic events which
punctuated the entire Holocene in the central Mediterranean coincided
with cooling events associated with deglacial outbursts in the North
Atlantic area and decreases in solar activity during the interval 11
700-7000 cal BP, and to a possible combination of NAO-type circulation
and solar forcing since ca. 7000 cal BP onwards. Thus, regarding the
centennial-scale climatic oscillations, the Mediterranean Basin appears
to have been strongly linked to the North Atlantic area and affected by
solar activity over the entire Holocene. In addition to
model experiments, a better understanding of forcing factors and past
atmospheric circulation patterns behind the Holocene palaeohydrological
changes in the Mediterranean area will require further investigation to
establish additional high-resolution and well-dated records in selected
locations around the Mediterranean Basin and in adjacent regions.
Special attention should be paid to greater precision in the
reconstruction, on millennial and centennial time scales, of changes in
the latitudinal location of the limit between the northern and southern
palaeohydrological Mediterranean sectors, depending on (1) the intensity
and/or characteristics of climatic periods/oscillations (e.g. Holocene
thermal maximum versus Neoglacial, as well as, for instance, the 8.2 ka
event versus the 4 ka event or the Little Ice Age), and (2) on varying
geographical conditions from the western to the eastern Mediterranean
areas (longitudinal gradients).
AB - On the basis of a multi-proxy approach and a strategy combining
lacustrine and marine records along a north-south transect, data
collected in the Central Mediterranean within the framework of a
collaborative project have led to reconstruction of high-resolution and
well-dated palaeohydrological records and to assessment of their spatial
and temporal coherency. Contrasting patterns of palaeohydrological
changes have been evidenced in the Central Mediterranean: south (north)
of around 40° N of latitude, the middle part of the Holocene was
characterised by lake-level maxima (minima), during an interval dated to
ca. 10 300-4500 cal BP to the south and 9000-4500 cal BP to the north.
Available data suggest that these contrasting palaeohydrological
patterns operated throughout the Holocene, both on millennial and
centennial scales. Regarding precipitation seasonality, maximum humidity
in the Central Mediterranean during the middle part of the Holocene was
characterised by humid winters and dry summers north of ca. 40° N,
and humid winters and summers south of ca. 40° N. This may explain
an apparent conflict between palaeoclimatic records depending on the
proxies used for reconstruction as well as the synchronous expansion of
tree species taxa with contrasting climatic requirements. In addition,
south of ca. 40° N, the first millennium of the Holocene was
characterised by very dry climatic conditions not only in the Eastern,
but also in the Central and the Western Mediterranean zones as reflected
by low lake levels and delayed reforestation. These results suggest
that, in addition to the influence of the Nile discharge reinforced by
the African monsoon, the deposition of Sapropel 1 has been favoured (1)
by an increase in winter precipitation in the northern Mediterranean
borderlands, and (2) by an increase in winter and summer precipitation
in the southern Mediterranean area. The climate reversal following the
Holocene climate optimum appears to have been punctuated by two major
climate changes around 7500 and 4500 cal BP. In the Central
Mediterranean, the Holocene palaeohydrological changes developed in
response to a combination of orbital, ice-sheet and solar forcing
factors. The maximum humidity interval in the south-central
Mediterranean started at ca. 10 300 cal BP, in correlation with the
decline (1) of the possible blocking effects of the North Atlantic
anticyclone linked to maximum insolation, and/or (2) of the influence of
the remnant ice sheets and fresh water forcing in the North Atlantic
Ocean. In the north-central Mediterranean, the lake-level minimum
interval began only around 9000 cal BP when the Fennoscandian ice-sheet
disappeared and a prevailing positive NAO-type circulation developed in
the North Atlantic area. The major palaeohydrological oscillation around
4500-4000 cal BP may be a non-linear response to the gradual decrease,
with additional key seasonal and interhemispherical changes, in
insolation. On a centennial scale, the successive climatic events which
punctuated the entire Holocene in the central Mediterranean coincided
with cooling events associated with deglacial outbursts in the North
Atlantic area and decreases in solar activity during the interval 11
700-7000 cal BP, and to a possible combination of NAO-type circulation
and solar forcing since ca. 7000 cal BP onwards. Thus, regarding the
centennial-scale climatic oscillations, the Mediterranean Basin appears
to have been strongly linked to the North Atlantic area and affected by
solar activity over the entire Holocene. In addition to
model experiments, a better understanding of forcing factors and past
atmospheric circulation patterns behind the Holocene palaeohydrological
changes in the Mediterranean area will require further investigation to
establish additional high-resolution and well-dated records in selected
locations around the Mediterranean Basin and in adjacent regions.
Special attention should be paid to greater precision in the
reconstruction, on millennial and centennial time scales, of changes in
the latitudinal location of the limit between the northern and southern
palaeohydrological Mediterranean sectors, depending on (1) the intensity
and/or characteristics of climatic periods/oscillations (e.g. Holocene
thermal maximum versus Neoglacial, as well as, for instance, the 8.2 ka
event versus the 4 ka event or the Little Ice Age), and (2) on varying
geographical conditions from the western to the eastern Mediterranean
areas (longitudinal gradients).
U2 - 10.5194/cpd-9-1901-2013
DO - 10.5194/cpd-9-1901-2013
M3 - Article
VL - 9
SP - 1901
EP - 1967
JO - Climate of the Past Discussions
JF - Climate of the Past Discussions
ER -