DOI: 10.25921/p03w-tf08
title: NOAA/WDS Paleoclimatology - MARGO Project Last Glacial Maximum SST Reconstructions

description: Observation-based reconstructions of sea surface temperature from relatively stable periods in the past, such as the Last Glacial Maximum, represent an important means of constraining climate sensitivity and evaluating model simulations. The first quantitative global reconstruction of sea surface temperatures during the Last Glacial Maximum was developed by the Climate Long-Range Investigation, Mapping and Prediction (CLIMAP) project in the 1970s and 1980s.  Since that time, several shortcomings of that earlier effort have become apparent. Here we present an updated synthesis of sea surface temperatures during the Last Glacial Maximum, rigorously defined as the period between 23 and 19 thousand years before present, from the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) project.  We integrate microfossil and geochemical reconstructions of surface temperatures and include assessments of the reliability of individual records. Our reconstruction reveals the presence of large longitudinal gradients in sea surface temperature in all of the ocean basins, in contrast to the simulations of the Last Glacial Maximum climate available at present.
description: An updated synthesis of sea surface temperature reconstructions 
at the Last Glacial Maximum (23 - 19 KYrBP), from the Multiproxy 
Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) 
project.  Microfossil and geochemical reconstructions of SST are
included, plus assessments of the reliability of individual records. 
These data are also archived at PANGEA: 
http://doi.pangaea.de/10.1594/PANGAEA.733406 

MARGO Project Members: 
C. Waelbroeck, A. Paul, M. Kucera, A. Rosell-Melé, M. Weinelt, 
R. Schneider, A.C. Mix, A. Abelmann, L. Armand, E. Bard, S. Barker, 
T.T. Barrows, H. Benway, I. Cacho, M.-T. Chen, E. Cortijo, X. Crosta, 
A. de Vernal, T. Dokken, J. Duprat, H. Elderfield, F. Eynaud, 
R. Gersonde, A. Hayes, M. Henry, C. Hillaire-Marcel, C.-C. Huang, 
E. Jansen, S. Juggins, N. Kallel, T. Kiefer, M. Kienast, L. Labeyrie, 
H. Leclaire, L. Londeix, S. Mangin, J. Matthiessen, F. Marret, 
M. Meland, A.E. Morey, S. Mulitza, U. Pflaumann, N.G. Pisias, 
T. Radi, A. Rochon, E.J. Rohling, L. Sbaffi, C. Schäfer-Neth, 
S. Solignac, H. Spero, K. Tachikawa, and J.-L. Turon. 


NGS-2008-09-00905 Supplementay Information

Definition of the quality flags used in the computation of the 
mean reliability index. 
1. Quality flag for number of samples, qnum
qnum = 1 when the number of samples within the LGM interval is > 4
= 2 when the number of samples within the LGM interval is 2 to 4
= 3 when there is only 1 sample within the LGM interval 

2. SST reconstruction reliability flag, qrel
2.a. Planktonic foraminifera abundances
qrel = 1 when the maximum difference in SST estimates among the 4 techniques < 2°C
= 2 when the maximum difference in SST estimates among the 4 techniques is 2 to 4°C
= 3 when the maximum difference in SST estimates among the 4 techniques > 4°C or
when samples are dominated by only one species (relative abundance > 95%) 

2.b. Diatoms and radiolarians abundances
The full definition is given in 1. It can be summarized as follows.
For Imbrie and Kipp2 derived SST estimates based on diatom and radiolarian assemblages
three quality levels have been defined using the communality value obtained for the downcore
samples.
qrel = 1 communality >0.8. For diatom estimates only: SST difference between radiolarian and
diatom based estimate <1.5°C
= 2 communality = 0.7 to 0.8. For diatom estimates only: SST difference between
radiolarian and diatom based estimate <1.5°C
= 3 communality <0.7. For diatom estimates only: SST difference between radiolarian and
diatom based estimate > 1.5°C
For Modern Analog Technique3 derived estimates of SST and sea ice extent based on the
diatom record three quality levels have been defined taking into account the dissimilarity
index.
qrel = 1 dissimilarity < 0.1
= 2 dissimilarity = 0.1 to 0.2
= 3 dissimilarity = 0.2 to 0.25
Samples with dissimilarity values above 0.25 indicate no-analog situations and have been
discarded. 

2.c. Dinoflagellate cysts abundances
The full definition is given in 4. It can be summarized as follows.
qrel = 1 distance between sample and best analog < 37
= 2 distance between sample and best analog = 37 to 74
= 3 distance between sample and best analog > 74 

2.d. Alkenones unsaturation ratio
qrel = 3 for core depths shallower than 100m, or sites with present day annual mean SST
higher than 28.5°C, or colder than 4°C
= 2 for core depths shallower than 1000m, or Mediterranean Sea sites, or sites with
present day annual mean SST higher than 27.5°C
= 1 in other cases 

2.e. Planktonic foraminifera Mg/Ca
qrel = 1 for near-surface dwelling species (G. ruber, G. sacculifer, N. pachyderma s.) AND
core depth shallower than 3000m in Atlantic or shallower than 2000m elsewhere
= 2 for non-near surface dwelling species OR core depth larger than 3000m in Atlantic or
larger than 2000m elsewhere
= 3 for non-near surface dwelling species AND core depth larger than 3000m in Atlantic
or larger than 2000m elsewhere 



DATA: 
Supplementary data tables S1 through S9, archived in text and Excel format. 
Data files archived at WDC Paleo and PANGEA:
https://www.ncei.noaa.gov/pub/data/paleo/contributions_by_author/margo2009/ 
http://doi.pangaea.de/10.1594/PANGAEA.733406
 

Table S1. Comparison of MARGO and PMIP2 mean annual SST anomalies (modern - LGM) 
for key regions. 

Table S2. Comparison of MARGO and PMIP2 mean northern hemisphere winter SST
anomalies (modern - LGM) for Southern Ocean key regions. 

Table S3. Diatoms-based LGM SST anomalies. The file header contains a 
description of the columns content. All SST proxies in the MARGO compilation 
have been calibrated to pre-1998 long-term average SST (ref.7) and the LGM SST 
anomalies are here calculated as the differences between WOA98 climatology (ref.5)
and the reconstructed values. 

Table S4. Radiolarians-based LGM SST anomalies. As in Table S1.

Table S5. Dinocysts-based LGM SST anomalies. As in Table S1. 

Table S6. Foraminifera-based LGM SST anomalies. As in Table S1. 

Table S7. Alkenone-based LGM SST anomalies. As in Table S1. 

Table S8. Mg/Ca-based LGM SST anomalies. As in Table S1. 

Table S9. 5°x5° block weighted mean values. The file header contains 
a description of the columns content. By convention (International 
Hydrographic Bureau 1953), the meridian of Cape Agulhas (20°E) was taken 
as the boundary between the Atlantic and Indian Oceans, the meridian of 
the southern cape of Tasmania (147°E) was taken as the boundary between 
the Indian and Pacific Oceans and the meridian of Cape Horn (68°W) was 
taken as the boundary between the Pacific and Indian Oceans. The Nordic 
Seas and Arctic Ocean were included in the Atlantic Ocean.  


Supplementary figures, archived in PDF format.

Fig. S1. Map of reconstructed minimum LGM SST anomalies. 
Anomalies are computed as LGM - WOA985 values. 
(a) Northern hemisphere summer (July-August-September). 
(b) Northern hemisphere winter (January-February-March). 
(c) Annual mean. Symbols show the location and proxy-type 
    of the original available data (see Fig. 1). 
    Note the uneven spacing of the diverging colour scheme 6 and isotherms.
Fig. S2. Map of reconstructed maximum LGM SST anomalies. (a), (b), (c) As in Figure S1.
Fig. S3. Comparison of MARGO and PMIP2 mean annual SST anomalies (modern - LGM).
Fig. S4. Comparison of MARGO and PMIP2 mean northern hemisphere winter SST
         anomalies (modern - LGM).
Fig. S5. Comparison of MARGO and PMIP2 mean northern hemisphere summer SST
         anomalies (modern - LGM).