Long- -Term Changes in Global Term Changes in Global Long Sea - PowerPoint PPT Presentation

Public Policy Forum Public Policy Forum 10 March 2010 10 March 2010 Long- -Term Changes in Global Term Changes in Global Long Sea Level Sea Level Craig S. Fulthorpe Craig S. Fulthorpe University of Texas Institute for Geophysics University of Texas Institute for Geophysics John A. and Katherine G. Jackson School of Geosciences John A. and Katherine G. Jackson School of Geosciences

Causes and Effects of Global Sea- -Level Change Level Change Causes and Effects of Global Sea Growth and decay of continental ice Growth and decay of continental ice Miller et al. (2005) sheets has been the primary cause of sheets has been the primary cause of large sea- -level changes (e.g., ~120 m level changes (e.g., ~120 m large sea lower at last glacial maximum) for at lower at last glacial maximum) for at least the last 40 million years least the last 40 million years Total potential sea- -level rise cause by level rise cause by Total potential sea melting of onshore ice sheets is ~70 m. melting of onshore ice sheets is ~70 m. • All of Antarctica: ~57 All of Antarctica: ~57- -60 m (IPCC) 60 m (IPCC) • • West Antarctic Ice Sheet West Antarctic Ice Sheet • alone: up to ~7 m alone: up to ~7 m • Greenland: ~7 m Greenland: ~7 m • Principal methods for estimating long- -term changes in sea term changes in sea- -level: level: Principal methods for estimating long 1) Oxygen isotopic record from deep Oxygen isotopic record from deep- -sea sediments sea sediments 1) 2) Continental margin sedimentary sequences Continental margin sedimentary sequences 2)

1. Oxygen Isotopic Record of Ice Volume and Temperature 1. Oxygen Isotopic Record of Ice Volume and Temperature • DSDP/ODP/IODP drilling of pelagic sediments DSDP/ODP/IODP drilling of pelagic sediments • has revolutionized climate studies by providing has revolutionized climate studies by providing long long- -term oxygen isotopic records. term oxygen isotopic records. • High High- -frequency (40 frequency (40 ky ky – – 100 100 ky ky), ), orbitally orbitally forced forced • climate change is modulated by long- -term term climate change is modulated by long changes in plate motion, oceanic gateways and changes in plate motion, oceanic gateways and atmospheric CO 2 . atmospheric CO 2 . Abrupt Events Abrupt Events • PETM (55 Ma): 5 PETM (55 Ma): 5- -6 6° °C rise in deep C rise in deep- -sea sea • temperature in <10 ky ky (release of methane from (release of methane from temperature in <10 marine gas hydrates?) marine gas hydrates?) • Cooling events: Oi Cooling events: Oi- -1 (34 Ma), Mi 1 (34 Ma), Mi- -1 (23 Ma) 1 (23 Ma) • Climate, and sea level, do not always Climate, and sea level, do not always respond linearly to forcing respond linearly to forcing Record from >40 scientific ocean drilling sites Record from >40 scientific ocean drilling sites (Zachos Zachos et al., 2001) et al., 2001) (

Early Pliocene Warm Period Early Pliocene Warm Period • • No Northern Hemisphere No Northern Hemisphere After Lisiecki Lisiecki and and Raymo Raymo (2005). Figure by R. Rohde, Global Warming Art project. (2005). Figure by R. Rohde, Global Warming Art project. ice, periodic (40 ky ky) collapse ) collapse After ice, periodic (40 of West Antarctic Ice Sheet. of West Antarctic Ice Sheet. • 7 7- -10 m sea 10 m sea- -level level • equivalent. equivalent. • • CO CO 2 2 similar to present, but: similar to present, but: • ~3 ~3° °C warmer (IPCC C warmer (IPCC • estimate this would estimate this would require a doubling of require a doubling of CO 2 ) CO 2 ) • Sea level ~25 m higher. Sea level ~25 m higher. • • So climate and sea level So climate and sea level • were more sensitive to CO were more sensitive to CO 2 2 variation than today. variation than today. • • Provides a glimpse of the Provides a glimpse of the future Earth system. future Earth system. Schweitzer and Thompson (1996); USGS Open- Schweitzer and Thompson (1996); USGS Open -File Report 96 File Report 96- -000 000

2. Estimating Sea- -Level Change Using Level Change Using 2. Estimating Sea Continental Margin Drilling Transects Continental Margin Drilling Transects • Targets the environment directly affected by sea Targets the environment directly affected by sea- -level change level change • Expedition 317: Expedition 317: Canterbury Basin, Canterbury Basin, New Zealand New Zealand • Thick early Thick early • Pliocene section Pliocene section

Climatic and Global Sea- -Level Records Level Records Climatic and Global Sea Figure by A. Droxler Droxler, , Stratigraphic signature of the signature of the Neogene Neogene Figure by A. Stratigraphic Rice University Rice University (Bartek Bartek et al., 1991) et al., 1991) ( 1) Late Oligocene 1) Late Oligocene- -early Miocene aggradation, backstepping and partial drowning early Miocene aggradation, backstepping and partial drowning 2) Late early Miocene 2) Late early Miocene- -early middle Miocene vertical growth or aggradation early middle Miocene vertical growth or aggradation 3) Earliest middle Miocene downward shift of deposition 3) Earliest middle Miocene downward shift of deposition 4) Late middle Miocene systematic lateral growth (progradation) 4) Late middle Miocene systematic lateral growth (progradation) 5) Late Miocene 5) Late Miocene- -early Pliocene re early Pliocene re- -flooding and aggradation flooding and aggradation

Importance of Studying Past Sea- -Level Change Level Change Importance of Studying Past Sea • • The geologic record provides an opportunity to quantify the tim The geologic record provides an opportunity to quantify the timing, amplitudes, ing, amplitudes, rates, mechanisms/controls, and effects of global sea- -level change. level change. rates, mechanisms/controls, and effects of global sea • This record can tell us: This record can tell us: • • How the earth system has operated during past abrupt climate ch How the earth system has operated during past abrupt climate changes and anges and • under past conditions of extreme climate forcing. under past conditions of extreme climate forcing. • • The potential sea The potential sea- -level response (rates and amplitudes) to elevated CO level response (rates and amplitudes) to elevated CO 2 2 levels. levels. • • Improved understanding of the long Improved understanding of the long- -term record of global sea term record of global sea- -level change: level change: • Enables critical evaluation of computer model predictions. Enables critical evaluation of computer model predictions. • • • Improves our ability to predict the societal impact of future s Improves our ability to predict the societal impact of future sea ea- -level change level change and allow us to better assess the contribution of greenhouse gases. es. and allow us to better assess the contribution of greenhouse gas craig@ig.utexas.edu craig@ig.utexas.edu www.ig.utexas.edu www.ig.utexas.edu