PERFORARE IL PASSATO PER COMPRENDERE IL CLIMA DEL FUTURO

FABIO FLORINDO

Istituto Nazionale di Geofisica e Vulcanologia

COSA INFLUENZA IN CAMBIAMENTO CLIMATICO

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

AD 950 to 1250

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

°C/decade

East Antarctic Ice Sheet (65 m)

West Antarctic Ice Sheet (5 m)

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

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)

The IPCC Imperative

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

Riser

String

Angie Fox

0.5m/day

84m

850m

1284.87m

30m

First geological drilling from ice shelf as a platform

Deepest geological borehole in Antarctica (MIS): ca 1285 m

Longest geological rock core in

Antarctica (98% recovery)!

60 glacial-interglacial cycles 38 in the last 5 million years

Naish et al. (2008) McKay et al. (2009)

5-2 million

years ago

Naish et al., 2008

Glacial-Interglacial cycles

McKay et al. GSA Bull in press

+7m sea level

-5 m sea level

0m sea level

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

ANDRILL

Core

Naish et al., Nature, 2009

DeConto & Pollard, 2009

Naish et al., 2009

Naish et al. Nature (2009)

Obliquity-paced Early Pliocene WAIS oscillations

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