Transcript the student presentation

Abrupt Climate Change
?
Paleoceanography Presentation
4/13/2016
By Beth Hart
Abrupt Climate Cycles
Lockwood, J.G., 2001, Abrupt and sudden climatic transitions and
fluctuations: a review, International Journal of Climatology, 21: 1153-1179.
Abrupt Climate Cycles
Ivanochko, T.S.,et al., 2005, Variations in tropical convection as an amplifier
of global climate change at the millennial scale, Earth and Planetary
Science Letters, 235: 302-314.
The end of the present interglacial:
how and when?
Three Questions:
1. Were previous intervals of peak interglaciation
terminated by abrupt climate change?
2. How close are we to the end of the present
interval of peak interglaciation?
3. Will the ongoing buildup of greenhouse gases
alter the natural sequence of events?
Broecker, W.S., 1998, The end of the present interglacial: how and
when?, Quaternary Science Reviews, 17: 689-694.
Were previous intervals of peak interglaciation
terminated by abrupt climate change?
How do interglacials end?
Broecker, W.S., 1998, The end of the present interglacial: how and
when?, Quaternary Science Reviews, 17: 689-694.
Figure 14-20
(Ruddiman text)
Were previous intervals of peak interglaciation
terminated by abrupt climate change?
•Decreased insolation
•No evidence of
renewed ice growth
Broecker, W.S., 1998, The end of the present interglacial: how and
when?, Quaternary Science Reviews, 17: 689-694.
Were previous intervals of peak interglaciation
terminated by abrupt climate change?
Evidence of abrupt change:
• European pollen records
(Woillard, 1978)
• N. pachyderma forminifera go
“gang-buster” (McManus, 1996)
Broecker, W.S., 1998, The end of the present interglacial: how and
when?, Quaternary Science Reviews, 17: 689-694.
How close are we to the end of the present
interval of peak interglaciation?
Estimate the length of previous interglacials.
• 18O records for benthic foraminifera
• Warmth lasted ~11kyr (one half precession
cycle)
• Terminations occur at N.H. insolation peaks
and last ~11kyr
Length of present interglacial (11.5kyr – 17kyr)
• After Heinrich event #1 (17kyr)
• Beginning of Bölling warm interval (14.5kyr)
• Younger Dryas within glacial period (11.5kyr)
Broecker, W.S., 1998, The end of the present interglacial: how and
when?, Quaternary Science Reviews, 17: 689-694.
How close are we to the end of the present
interval of peak interglaciation?
Lockwood, J.G., 2001, Abrupt and sudden climatic transitions and
fluctuations: a review, International Journal of Climatology, 21: 1153-1179.
How close are we to the end of the present
interval of peak interglaciation?
If analogous to Eemian:
Ice cap growth should precede
Sea level fall has not begun
Interglacial will last more than several kyrs
From Broecker and Stocker (2006)
If analogous to stage 11:
Driven by precession
Interglacial much longer
Broecker, W.S., 1998, The end of the present interglacial: how and
when?, Quaternary Science Reviews, 17: 689-694.
How close are we to the end of the present
interval of peak interglaciation?
From Ruddiman (2005)
Will the ongoing buildup of greenhouse gases
alter the natural sequence of events?
THC – potential mode for abrupt climate switch
• Weakened NADW formation during glacial periods
• Requires the addition of fresh water (change in
density) in North Atlantic
• Interglacials end due to release of fresh water from
melting of newly formed ice caps
• Ice growth prior to end of Eemian warm
conditions
Broecker, W.S., 1998, The end of the present interglacial: how and
when?, Quaternary Science Reviews, 17: 689-694.
Will the ongoing buildup of greenhouse gases
alter the natural sequence of events?
Figure 15-13
(Ruddiman text)
Figure 15-20
(Ruddiman text)
Will the ongoing buildup of greenhouse gases
alter the natural sequence of events?
What about greenhouse gases?
• Cause a premature transition from between
modes
• Retard growth of ice sheets
No new ice sheets => no fresh water to North
Atlantic => no reorganization of THC
• Greenhouse gas buildup could be enough to
trigger an alteration of THC
Broecker, W.S., 1998, The end of the present interglacial: how and
when?, Quaternary Science Reviews, 17: 689-694.
Conclusions
Where do we go from here?
1. Monitor present-day deep water formation
2. Learn where and how deep water forms
3. Determine if THC reorganizations (induced by
greenhouse gas) would cause climatic
cooling
AND…….
Broecker, W.S., 1998, The end of the present interglacial: how and
when?, Quaternary Science Reviews, 17: 689-694.
We’re still in an interglacial cycle!
(Even in Ohio)
Surprised, anyone?
Broecker, W.S., 1998, The end of the present interglacial: how and
when?, Quaternary Science Reviews, 17: 689-694.
Timing and duration of Last Interglacial
conditions in Europe: a chronicle of a
changing chronology
1. The Last Interglacial
2. Current interpretation
3. Remaining issues
Figure 15-6c
(Ruddiman text)
Tzedakis, C., 2003, Timing and duration of Last Interglacial conditions
in Europe: a chronicle of a changing chronology, Quaternary
Science Reviews, 22: 763-768.
The Last Interglacial:
Why study the Last Interglacial?
• Most recent period with similar interglacial
conditions
• Minimal anthropogenic effects
Uncertainties
• Lack precise absolute timescales and
stratigraphic markers
• Correlation of terrestrial evidence with changes
in ice volume and sea level
• Timing and response of environment to the end
of interglacial periods
Tzedakis, C., 2003, Timing and duration of Last Interglacial conditions
in Europe: a chronicle of a changing chronology, Quaternary
Science Reviews, 22: 763-768.
Figure 15-8
(Ruddiman text)
The Last Interglacial:
The First Steps:
• Shackleton (1969) – Eemian equivalent to MIS 5e
Last Interglacial lasts ½ precessional cycle (not ½
eccentricity cycle)
• Agreed with Muller (1974) terrestrial evidence
from Germany
Involved annual laminations and extrapolation of
sedimentation rates
• No absolute dates
• Assumption of synchronous boundaries
Marine timescales assigned to terrestrial records
Tzedakis, C., 2003, Timing and duration of Last Interglacial conditions in
Europe: a chronicle of a changing chronology, Quaternary Science
Reviews, 22: 763-768.
The Last Interglacial:
Piecing it together:
• Many scientists attempted to correlate marine
timescales to terrestrial records.
• Terrestrial interglacial period extended into MIS 5d
• Evidence provided a range of times for Last
Interglacial duration (11kyr – 23kyr)
• Neither upper nor lower boundaries were
coincident between marine and terrestrial records
• Diachroneity between northern and southern
European terrestrial records
Tzedakis, C., 2003, Timing and duration of Last Interglacial conditions in
Europe: a chronicle of a changing chronology, Quaternary Science
Reviews, 22: 763-768.
Current Interpretation:
128ka – sea level at present height
127ka – peak insolation
126ka – full interglacial
120ka – decrease of temperatures
due to orbital changes; sea-ice
and tundra expand
~Increased albedo~
115ka – end interglacial in northern
Europe
110ka – end interglacial in southern
Europe
Tzedakis, C., 2003, Timing and duration of Last Interglacial conditions in
Europe: a chronicle of a changing chronology, Quaternary Science
Reviews, 22: 763-768.
Remaining Issues:
Timing and nature of Heinrich event 11
• Deglaciation complete by 128ka
• What is the cause of postulated icerafting event at 127ka?
Replication of marine patterns with other margins
• Is there a lagged SST and arboreal response
everywhere?
• Is response geographically dependent?
Large diachroneity in Europe
• When does glaciation begin in
intermediate areas?
Tzedakis, C., 2003, Timing and duration of Last Interglacial conditions in
Europe: a chronicle of a changing chronology, Quaternary Science
Reviews, 22: 763-768.
The Last Interglacial:
Piecing it together:
Tzedakis, et al., 1997
• Glacial-to-interglacial transitions used as tie points
Transitions represent rapid events
Vegetation response without significant delay
• Interglacial endpoints not fixed
Lacked evidence of abrupt elimination of vegetation
Created effect of terrestrial interglacials extending
after marine glacial conditions began
• Observed that forest (terrestrial interglacial) period
extended into MID 5d (marine stadial period)
Tzedakis, C., 2003, Timing and duration of Last Interglacial conditions in
Europe: a chronicle of a changing chronology, Quaternary Science
Reviews, 22: 763-768.
The Last Interglacial:
Piecing it together:
Kukla, et al., 1997
• Grande Pile pollen record with fixed beginning of
Last Interglacial (MIS 6/5) and Pleniglacial (MIS 5/4)
• Inferred duration of Last Interglacial (23 kyr)
• Terrestrial interglacial extends into MIS 5d and
concludes with major IRD
• MIS 5e to 5d transition occurs before IRD and polar
foraminifera N. pachyderma (McManus, et al., 1994)
Tzedakis, C., 2003, Timing and duration of Last Interglacial conditions in
Europe: a chronicle of a changing chronology, Quaternary Science
Reviews, 22: 763-768.