Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events...
-
Upload
beverley-harris -
Category
Documents
-
view
216 -
download
0
Transcript of Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events...
![Page 1: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/1.jpg)
Climate Variability on Millennial Time Scales
• Introduction
• Dansgaard-Oeschger events
• Heinrich events
• Younger Dryas event
• Deglacial meltwater
• Meridional overturning circulation
![Page 2: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/2.jpg)
Introduction
• Some proxy records provide evidence of substantial climate variability at time scales that are considerable shorter than those of orbital forcing.
• Typical time scales are O(103) years
• Only certain natural archives have sufficient temporal resolution to record such variability.
![Page 3: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/3.jpg)
Ice Core Paleoclimatology
• As snow falls on very cold glaciers or ice sheets and gradually is converted to ice, air is trapped in bubbles.
• This “fossil air” can be chemically analyzed to determine past atmospheric composition.
• Other paleoclimatic proxies (isotopes, dust, acidity) can also be determined from the ice, providing information about temperature, sulfate aerosols, precipitation.
![Page 4: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/4.jpg)
GISP2 Drilling Project
![Page 5: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/5.jpg)
Extracting An Ice Core
![Page 6: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/6.jpg)
Annual Layers In Ice Core
![Page 7: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/7.jpg)
Dansgaard-Oeschger Events
• Analysis of rapidly accumulating ice cores in Greenland yielded evidence of “rapid” shifts in isotopic composition.
• Source: Dansgaard et al. (1982)
![Page 8: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/8.jpg)
Glacials, Interglacials, Stadials and Interstadials
• Glacials: Cold phases of 100-kyr cycles
• Interglacials: Warm phases of 100-kyr cycles.
• Stadials: Relatively cold periods during glacials.
• Interstadials: Relatively warm periods during glacials.
![Page 9: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/9.jpg)
Glacials, Interglacials, Stadials and Interstadials
stadial
interstadial
Interglacial
Glacial
Interglacial
![Page 10: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/10.jpg)
Methane Variations DuringD-O Events
• Methane is regarded as an index of tropical wetland variations.
• Methane covaries with isotopes in Greenland ice cores.
• Source: Brook et al. (2000)
![Page 11: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/11.jpg)
Global Extent?
• Millennial-scale climate variations have been found in a number of records.
• Most are in or near the North Atlantic region, but there is some evidence elsewhere.
![Page 12: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/12.jpg)
Heinrich Events
• Ice-rafted material appears in marine sediments in North Atlantic every several thousand years.
• Events appear to be correlated with D-O events in Greenland ice cores.
• Source: Bond and Lotti (1995)
![Page 13: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/13.jpg)
![Page 14: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/14.jpg)
A Heinrich Event Sediment Core
• In this image, a Heinrich event is represented by the light-colored sediment in the bottom half of this core segment.
• The black patches within the light-colored section is probably due to bioturbation, the mixing of sediments by living organisms such as deep sea worms.
![Page 15: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/15.jpg)
Evidence of Heinrich Events
Site withice-rafteddebris
Site withoutice-rafteddebris
![Page 16: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/16.jpg)
Heinrich Event
Chronology
![Page 17: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/17.jpg)
• Possible effects of Heinrich events have been found outside of the region of ice-rafted debris. (Bard et al. 2000)
![Page 18: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/18.jpg)
Heinrich Events in Florida?
![Page 19: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/19.jpg)
The relative magnitude of Heinrichand Dansgaard-Oeschger eventsvaries with location.
Only Heinrich events are evidentin Fe/Ca (continental runoff proxy)from Brazilian Margin.
![Page 20: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/20.jpg)
A Pervasive 1500-Year Climate Cycle?
![Page 21: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/21.jpg)
Source: Bond et al. (1997)
![Page 22: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/22.jpg)
![Page 23: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/23.jpg)
Source: deMenocal et al. (2000)
![Page 24: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/24.jpg)
Solar Forcing of 1500-Year Cycle?
![Page 25: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/25.jpg)
The Younger Dryas
• During the last deglaciation, a dramatic climate “flip-flop” occurred in which the deglacial warming was interrupted by a return to near-glacial conditions.
• This “flip-flop” in known as the Younger Dryas, deriving its name from a cold-loving plant species whose pollen reappeared during this interval.
![Page 26: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/26.jpg)
Schematic Deglaciation History
![Page 27: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/27.jpg)
Younger Dryas Climate Records
![Page 28: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/28.jpg)
Greenland Accumulation Rates
![Page 29: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/29.jpg)
Younger Dryas Climate Records
Proxy for NorthAtlantic DeepWater formation
![Page 30: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/30.jpg)
Cariaco Basin (Venezuela)
![Page 31: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/31.jpg)
Cariaco Basin Bathymetry
• Water exchange with the open Caribbean Sea is restricted• Intense seasonal productivity and high sedimentation rate• Anoxic below 300 m• Limited bioturbation (post-depositional mixing of sediments by marine life)
![Page 32: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/32.jpg)
The Younger Dryas in the
Cariaco Basin
![Page 33: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/33.jpg)
The Younger Dryasin the AmazonBasin
![Page 34: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/34.jpg)
Deglacial Meltwater
• As the Pleistocene ice sheets melted, meltwater collected in large postglacial lakes, such as Glacial Lake Agassiz.
• As crustal rebound occurred, these lakes discahrged into the ocean.
![Page 35: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/35.jpg)
Meltwater Discharge Paths
![Page 36: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/36.jpg)
Barbados Sea Level Changes
![Page 37: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/37.jpg)
![Page 38: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/38.jpg)
Schematic of Meridional Overturning Circulation
![Page 39: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/39.jpg)
Meridional Overturning Streamfunction
meanzonal
zv
yw
Units of ψ are Sverdrups; 1 Sv = 106 m3s-1
![Page 40: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/40.jpg)
Temperature-Salinity Diagram
• At low temperatures, salinity has a large effect on the density of sea water.
• Higher salinity → more dense.
• Lower salinity → less dense.
![Page 41: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/41.jpg)
![Page 42: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/42.jpg)
Meltwater Discharge Paths
![Page 43: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/43.jpg)
Younger Dryas Climate Records
Meltwater RoutingHudson R./St. Lawrence R.Hudson Strait
![Page 44: Climate Variability on Millennial Time Scales Introduction Dansgaard-Oeschger events Heinrich events Younger Dryas event Deglacial meltwater Meridional.](https://reader036.fdocuments.us/reader036/viewer/2022081515/56649ccf5503460f9499aaa4/html5/thumbnails/44.jpg)
Meltwater Routing OscillatorClark et al. (2001)