Erin L. McClymont Department of Geography, Durham University Aurora Elmore (Durham University), Benjamin Petrick (Newcastle University), Sev Kender (British Geological Survey), Harry Elderfield (Cambridge University), Antoni Rosell-Mele (Autonomous University of Barcelona), Sindia Sosdian (Cardiff University), Yair Rosenthal (Rutgers University) Palaeo-ocean proxies: reconstructing 4 million years of ocean temperature fluctuations.
15
Embed
Palaeo-ocean proxies: reconstructing 4 million years of ocean temperature fluctuations.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Erin L. McClymont
Department of Geography, Durham University
Aurora Elmore (Durham University), Benjamin Petrick (Newcastle University),
Sev Kender (British Geological Survey), Harry Elderfield (Cambridge University),
Antoni Rosell-Mele (Autonomous University of Barcelona), Sindia Sosdian (Cardiff University),
Yair Rosenthal (Rutgers University)
Palaeo-ocean proxies: reconstructing 4 million years of ocean temperature fluctuations.
Palaeo-ocean proxies and their application
• Motivation: why is it important to understand climate evolution
over the last 4 million years?
• How can we use marine sediments?– Climate “proxies”
• What role does the ocean play in climates of the past?– Ocean / ice-sheet interaction
– Global or regional climate changes
• New developments and future research directions
• What drives climate transitions?
• Which parts of the climate system are sensitive to change?
• How can climate change impacts be amplified?
Why did the Earth shift from global warmth in the Pliocene to the “ice
ages” in the Quaternary?
Climate change during the last 4 million years is important:
Why did the Earth shift from global warmth in the Pliocene to the “ice ages” in the Quaternary?
• “Onset of northern hemisphere glaciation” (ONHG) ~2.7 Ma
• The “mid-Pleistocene transition” (MPT) ~1 Ma: development of
larger ice-sheets which also survived for longer
Homo erectus(Am.Mus.Nat.Hist.)
Australopithecus boisei(Univ.Minnesota Duluth)
Marine sediments record the oceans through time
Marine sediments record the oceans through time
• Use of “proxies”: indirect measures of key climate variables e.g.
Foraminifera
DiatomsCoccolithophores
O
O
O
8
15
22
29
37:2
37:3
37:4
Biomarkers(organic components)
Marine sediments record the oceans through time
• Use of “proxies”: indirect measures of key climate variables e.g.
Coccolithophores
O
O
O
8
15
22
29
37:2
37:3
37:4
Biomarkers(organic components)
60°S – 60°N
Müller et al. (1998)
983
1087
806 849
882
1090
Q1: did surface ocean temperatures change during the expansion of the ice-sheets from 1 million years ago?
Mean annual SSTs (Levitus, 1994)
McClymont & Rosell-Mele (2005) Geology; McClymont et al. (2005) QSR; McClymont et al. (2008) Paleoceanography; Martínez-Garcia et al. (2010) Science; McClymont et al. (under review).
McClymont et al. (under review) Earth Science Reviews
• Sea-surface temperature records produced at high temporal resolution
• Long-term mean calculated by removing the high frequency variability
Was there a long-term cooling over the last 2 million years?
Approach
SST (°C)
Age (ka)
Tem
per
atu
re c
han
ge
(rel
ativ
e to
th
e m
axim
um
rec
ord
ed
; °C
)
McClymont et al. (under review) Earth Science Reviews
• Our data identify cooling in
the surface ocean ~1.2 million
years ago
• But the ice-sheets expanded
at ~ 1 million years ago
We suggest that cooler global
climate and evolving ocean
circulation were conducive to
the later ice-sheet growth
Results: all sites
983
1087
806 849
882
1090
Q2: did the ocean below the sea surface cool over the last 4 million years?