PERFORARE IL PASSATO PER COMPRENDERE IL CLIMA DEL FUTURO. FABIO FLORINDO Istituto Nazionale di Geofisica e Vulcanologia

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1 PERFORARE IL PASSATO PER COMPRENDERE IL CLIMA DEL FUTURO FABIO FLORINDO Istituto Nazionale di Geofisica e Vulcanologia

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3 COSA INFLUENZA IN CAMBIAMENTO CLIMATICO

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5 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

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7 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.

8 Seconda rivoluzione industriale - convenzionalmente dal introduzione dell'elettricità, dei prodotti chimici e del petrolio

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12 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...

13 Nell'ultima decade due enormi piattaforme di ghiaccio si sono disintegrate in pochissimi giorni: il Larsen B con 570 km quadrati di estensione la piattaforma di Wilkins con 3250 km quadrati

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16 Florindo and Pekar, in press

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18 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

19 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 ppm CO 2 in the atmosphere)

20 Collaborazione tra ricercatori, ingegneri, tecnici, studenti ed insegnanti di 4 nazioni : USA, Nuova Zelanda, Italia e Germania

21 Proximal records (high latitudes) ANDRILL s TARGET

22 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.

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24 Geological Setting

25 Rig 30m Riser 84m 850m 0.5m/day First geological drilling from ice shelf as a platform String Deepest geological borehole in Antarctica (MIS): ca 1285 m Longest geological rock core in Antarctica (98% recovery)! m

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28 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

29 McKay et al. GSA Bull in press Glacial-Interglacial cycles +7m sea level 0m sea level -5 m sea level

30 A long-duration period of warm, productive ocean without sea ice in the early Pliocene ( Ma)

31 A long-duration period of warm, productive ocean without sea ice in the early Pliocene ( Ma)

32 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 ANDRILL Core Naish et al., 2009 DeConto & Pollard, 2009

33 Obliquity-paced Early Pliocene WAIS oscillations Naish et al. Nature (2009)

34 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)

35 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

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