Presentation on theme: "Abrupt climate change: something to worry about? ocorrências climáticas bruscas: algo para se preocupar? Dr. Hilde Snoeckx University of West Florida."— Presentation transcript:
Abrupt climate change: something to worry about? ocorrências climáticas bruscas: algo para se preocupar? Dr. Hilde Snoeckx University of West Florida
From Bradley, 1990; based on data from Le Roy Ladurie and Baulant, historical grape harvest dates historical grape harvest dates Burgundy (1370 – 1879) used to reconstruct summer temperatures
Ice Skating near a Village, c. 1610, by Hendrick Avercamp (via wikimedia commons) Woolly mammoths died out around 10,000 years ago. Photo: Alamy Thinking of ice age… Pensando em idade de gelo...
Deep sea drilling Credit: Ocean Drilling Program
Sediment cores Ross Ice Shelf, Antarctica.. Source: ANDRILL. Credit: Alan Mix Scientists sampling a deep-sea sediment core
DM Sigman et al. Nature 466, (2010) doi: /nature09149 Records of changing climate, atmospheric CO 2, and Southern Ocean conditions over the last 800 thousand years. benthic foraminiferal δ 18 O continental glaciation and deep ocean temperature phytoplankton shells: productivity in the surface ocean deuterium content in Antarctic ice core air temperature in ice core
Encyclopedia of the Earth Milankovitch cycles. Source: UCARhttp://www.eoearth.org Three variables of Earth’s orbit affect global climate. Eccentricity distance between Earth and Sun. Obliquity strength of seasons. Precession timing of seasons. = Astronomical control of solar radiation
. Source: Global Warming Art Slow cooling Fast warming ~100 ky Milankovitch cycles over the past years
Assumes climate changes slowly and smoothly Ice Volume Planktonic Foraminifera O18 as Proxy More ice Less ice δ18O GGGGGGG
Porcupine Abyssal Plain, northeast Atlantic An Echinocrepis rostrata urchin moving across the abyssal seafloor (Image: MBARI) NOVA Ocean explorer Bioturbation
Ruddiman, Earth’s Climate, 2001 Bioturbation
Ice core locations North Greenland Ice Core Project members Nature 431, U.S. International Trans Antarctic Scientific Expedition
GISP2 drill from inside the drilling dome Photo Credits: Mark Twickler, GISP2 SMO, University of New Hampshire GISP Drill Dome
Summer and winter core layers Photo Credits: Anthony Gow United States Army Corps of Engineers, Cold Regions Research and Engineering Laboratory.
earthobservatory.nasa.gov/Features/Paleoclimatology_IceCores / Air bubbles in ice: record of past atmospheric composition. - levels of CO 2 and CH 4 highest level in past 400,000 years. (Photo redit: U.S. National Ice Core Laboratory) Temperature of ice sheet: temperature measured directly by lowering thermometer into borehole. (Graph based on data provided by Gary Clow, USGS)
ice in a core from North Greenland Ice Core Project annual layers of the ice from about 1800 m depth (~ years picture Søren Wedel. From North Greenland Ice core Project, photos from North Greenland Ice core Projectphotos from
VOSTOK ice core (Antarctica) Notice stable climate during Holocene - unstable climate before! stepwise cooling and rapid warming Temperature ICE
Climate variability over the past 80 ky 9°C 15°C 16°C amplitude
Abrupt climate change
Abrupt Climate Change: Inevitable surprises Committee on Abrupt Climate Change, National Research Council, 2002 An abrupt climate change occurs when the climate system is forced to cross some threshold, triggering a transition to a new state at a rate determined by the climate system itself and faster than the cause threshold state 1 state 2 Gradual push Fast transition
A large-scale change in the climate system that takes place over a few decades or less, persists for at least a few decades, and causes disruptions in human and natural systems.
In 2004 Jack Hall, paleo-climatologist Global warming causes break up of Larsen B ice shelf
Climate conference New Delhi, North Atlantic Current may shut down in years Leads to very successful ‘documentary’
Oceanic shutdown triggers super-storm in northern hemisphere
In the eye of super-cyclones extremely cold air is sucked down from the upper troposphere to the surface
After the storm… most of the northern hemisphere is snow-covered snow-albedo feedback leads to new ice age Stefan Rahmstorf
SCIENCE – FICTION? Is there any science in this fiction?
Larsen Ice Shelf Collapse Colored lines mark the Larsen B Ice Shelf edge in 1947,1961, 1993, and —NASA MODIS image courtesy of Ted Scambos, National Snow and Ice Data Center, University of Colorado, Boulder. Larson Ice Shelf on February 21, 2000 (Credit: Image courtesy Landsat 7 Science Team and NASA GSFC)
Can the North Atlantic Current shut down and cause an ice age?
Surface Ocean Circulation Ruddiman, Earth’s Climate, 2001 North Atlantic Current Solar radation
Global conveyor Schematic map of thermohaline circulation of the world ocean. Purple ovals indicate ventilation areas, which feed the flow of deep dense waters (blue lines with arrows). These waters flow into all of the oceans and slowly ascend throughout them. From there, they return to the ventilation areas as warm compensating currents (red lines with arrows) in the upper layers. Science 13 August 2004: vol. 305 no
Atlantic Meridional Overturning Circulation (AMOC) Source: R. Curry, Woods Hole Oceanographic Institution/Science/USGCRP Surface currents (solid curves) and deep currents (dashed curves) Colors of curves indicate approximate temperatures. North Atlantic Deep Water North Atlantic Current
From The Once and Future Circulation of the Ocean.The Once and Future Circulation of the Ocean (Illustration by E. Paul Oberlander, Woods Hole Oceanographic Institution)
Glacial deposits- ice rafted debris Photo Credits: Kendrick Taylor, Desert Research Institute (DRI), University of Nevada-Reno. ice rafted debris Edge of the Greenland Ice Sheet iceberg_armada Freshwater cap
Top: δ18O record from GISP2 ice core Greenland, showing 20 of the 25 observed Dansgaard-Oeschger events during the last glacial period (Grootes et al., 1993). Bottom: A record of ice-rafted debris during Heinrich events from a deep-sea core in the North Atlantic (Bond and Lotti, 1995).
HEINRICH EVENTS Where do they come from?
Marshall and Koutnik, 2006, Paleoceanography, Vol. 21, pa2021, fig. 3 IRD belt
North Atlantic Ocean and surrounding continental geology Bailey et al., EPSL 2012
Armadas of icebergs from the Laurentide ice sheet
Snoeckx et al., 1999
Top: δ18O record GISP2 ice core Greenland, showing Dansgaard-Oeschger events Bottom: Bottom: Ice-rafted debris in deep-sea core in the North Atlantic, showing Heinrich events (Grootes et al., 1993), (Bond and Lotti, 1995).
[Sr] 87 Sr/ 86 Sr Ɛ Nd (o) Dissolve in HF+HClO 4 + HNO3 IRD Sample 50 mg size >63μ Too big for wind transport Too far for rivers ICP-MS TIMS
Hemming, 2004 fig 4 Stalagmite growth "rings" Credit: Paul Williams temperature and rainfall rate weaker Monsoon
Caverna de Botuverá wet dry wet dry Hulu, China Botuvera, Brazil South American Monsoon anti-correlated with Asian Monsoon D/Ooscillation H-events
Global climate anomalies during Heinrich events Ocean-Atmosphere Interaction Compilation by Overpeck and Cole (2006).
Left: Recent times: stable circulation, polar front allows warm water to penetrate beyond Norway. Center: Last ice age, periodic surges of icebergs and reduced meridional overturning circulation cause polar front to move southward Bottom: rough indication of temperature in the region, but the scales are not the same
Spatial patterns of millennial-scale climate change events Caverna Botuverá Cariaco Basin caves HULU
Should we be worried?
Oceans under surveillance Strength of AMOC monitored since April 2009 30% drop in average current strength less heat to N Atlantic. Result: unusually harsh winter in Europe in 2009–10. strength of AMOC monitored since future now December 2013
Do We Expect an Abrupt Change in the Atlantic Meridional Overturning Circulation? VERY LIKELY strength of AMOC decreases 25–30% over 21st century Europe and North America will warm over 21st century even with weaker AMOC VERY UNLIKELY: collapse of AMOC or abrupt transition to weaker AMOC during the 21st century. But IF it did: severe consequences southward shift of the tropical rainfall belts additional sea level rise around the North Atlantic disruptions to marine ecosystems. US Climate Change Program, 2008
Conclusions Paleoclimatic evidence shows that major regional and global shifts happen abruptly (in just a few years to decades) Tropical climates are sensitive to northern hemisphere ice sheet instabilities Abrupt climate change probably will occur but not in the next 100 years Understanding abrupt climate change is a work-in- progess