C ocean warming, up to + 8m sea

PERFORARE IL PASSATO
PER COMPRENDERE IL CLIMA DEL FUTURO
FABIO FLORINDO
Istituto Nazionale di Geofisica e Vulcanologia
COSA INFLUENZA IN CAMBIAMENTO CLIMATICO
AD 950 to 1250
I vichinghi sfruttando l’optimum climatico medioevale riescono ad esplorare tutto
l’Atlantico Settentrionale, colonizzano la Groenlandia e raggiungono il nord America
Erik il rosso
Locally, sea level can rise because the land is sinking. Globally, it rises because the
total volume of seawater is increasing. Global warming drives that in two basic ways:
(1) by warming the ocean and (2) by melting ice on land, which adds more water.
Since 1900 global sea level has risen about 20 cm. It’s now rising at about an height of
3 cm a year and accelerating.
Seconda rivoluzione industriale
- convenzionalmente dal 1870-1880 introduzione dell'elettricità, dei prodotti chimici e del petrolio
West
Antarctic Ice
Sheet (5 m)
East Antarctic
Ice Sheet (65 m)
°C/decade
Continent-wide warming trend from 1957 through 2006 (Steig et al., Nature, 2009).
Antarctic ice sheet is losing mass at a rate of 250 gigatonnes yearly ...
Nell'ultima decade due enormi piattaforme di
ghiaccio si sono disintegrate in pochissimi giorni:
- 2002 il Larsen B con 570 km quadrati di
estensione
- 2008 la piattaforma di Wilkins con 3250 km
quadrati
Florindo and Pekar, in press
Come la storia dell’uomo, così anche la storia del clima è
registrata e conservata negli archivi
Principali tipi di archivi:
 CORALLI
(centinaia di anni)
 ANELLI DEGLI ALBERI
(migliaia di anni)
 GHIACCIO
(fino a circa 1 Ma)
 ROCCE SEDIMENTARIE E SEDIMENTI
The IPCC Imperative
How is the International Scientific community addressing the
uncertainty surrounding the future contribution of the polar ice sheets
to sea-level rise?

Improved observational data from satellites

Improved computer ice sheet models that capture dynamic processes

Geological drilling records that capture past physical changes to the ice
sheets when Earth’s climate was warmer and similar to what it may be
by 2100 (e.g. 2-3°C warmer and 400-500 ppm CO2 in the atmosphere)
Collaborazione tra ricercatori, ingegneri, tecnici, studenti ed
insegnanti di 4 nazioni : USA, Nuova Zelanda, Italia e
Germania
Proximal records (high latitudes)
ANDRILL’s TARGET
Nel corso della prima stagione di perforazione di ANDRILL, ci siamo
concentrati in un intervallo di tempo che va da 5 a 3 milioni di anni fa
(Pliocene inferiore-medio) quando l’atmosfera del pianeta aveva valori di
concentrazione di CO2 e di temperature simili a quelle previste dall’ IPCC
entro la fine del XXI secolo a causa dell’aumento antropogenico della
temperatura.
Geological Setting
Rig
30m
84m
0.5m/day
Riser
First geological drilling from ice
shelf as a platform
850m
String
Deepest geological borehole in
Antarctica (MIS): ca 1285 m
Longest geological rock core in
Antarctica (98% recovery)!
1284.87m
60 glacial-interglacial cycles
38 in the last 5 million years
5-2 million
years ago
Naish et al. (2008)
McKay et al. (2009)
Naish et al., 2008
Glacial-Interglacial
cycles
+7m sea level
0m sea level
-5 m sea level
McKay et al. GSA Bull in press
A long-duration period of warm, productive ocean
without sea ice in the early Pliocene (4.5-3.5 Ma)
A long-duration period of warm, productive ocean
without sea ice in the early Pliocene (4.5-3.5 Ma)
Collapse of the West Antarctic Ice sheet 4 million years ago
400ppm atmospheric carbon dioxide, +5°C ocean warming, up to + 8m sea-level rise
Naish et al.,
Nature, 2009
Naish et al., 2009
DeConto &
Pollard, 2009
ANDRILL
Core
Obliquity-paced Early Pliocene WAIS oscillations
Naish et al. Nature (2009)
During interglacials, southward expansion of westerly winds creates divergence
across the polar front and northward export of cold surface and intermediate
water enhancing advection of CO2-rich, warm circumpolar deep waters onto the
Antarctic continental shelf that melt the marine margin of ice sheets
(Toggweiler et al. 2007, Paleoceanography)
IN CONCLUSION
We identified 38 sedimentary cycles, each of about 40,000 years'
duration, during the Pliocene, in which the grounding line moved
back and forth across the seafloor between glacial and interglacial
states, punctuated by periodic ice-sheets collapses with open
ocean conditions during super-integlacials.
For the first time we have a direct evidence for orbitally induced
oscillations in the WAIS, resulting in a switch from grounded ice,
or ice shelves, to open water in the Ross embyment when
planetary temperatures were up to 3°C warmer than today and
atmospheric CO2 concentration was as high as ca. 400 p.p.m.v