Links between tropical rainfall and North Atlantic climate during the last glacial period
Summary (1 min read)
Methods
- Colour reflectance logging has been used successfully as a proxy for changes in sediment composition and for correlation with other palaeo-proxy records5,7,17.
- Further details of the data acquisition and the agemodel can be found in the Supplementary Information.
- To mimic Heinrich conditions and a weakened AMOC, an idealized freshwater forcing of 1.0 Sv (1 Sv= 106 m3 s−1) was applied under Last Glacial Maximum boundary conditions for 100 years28.
Author contributions
- G.D. performed the reflectance analyses, interpreted the data and wrote the first version of the manuscript.
- Y.H. and U.R. supervised taking the pictures at the ETH Zürich and the MARUM, University of Bremen.
- All the authors discussed the results and provided significant input to the final manuscript.
Additional information
- Supplementary information is available in the online version of the paper.
- Reprints and permissions information is available online at www.nature.com/reprints.
- Correspondence and requests for materials should be addressed to G.D. or G.H.H.
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Citations
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...This accords with the Cariaco Basin and Arabian Sea records, which also do not register strong cooling at this time, possibly indicating that interstadials 9 and 10 could be considered parts of the same interstadial period (Deplazes et al., 2013), as also appears to be the case with respect to GI-14/GI-13 and GI-23/GI-22, discussed below....
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...Some of these events have already been noted in ice-core records (“precursor events” by Capron et al. (2010a) and Vallelonga et al. (2012)) and equivalent events have also been recognised in speleothems (Boch et al., 2011) and in marine records (Deplazes et al., 2013)....
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...…Sea records, which also do not register strong cooling at this time, possibly indicating that interstadials 9 and 10 could be considered parts of the same interstadial period (Deplazes et al., 2013), as also appears to be the case with respect to GI-14/GI-13 and GI-23/GI-22, discussed below....
[...]
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293 citations
Cites background from "Links between tropical rainfall and..."
...Similarity of millennial event features in the GM record with Antarctic temperature records could also result from the mechanism that modulates Antarctic temperatures such as the SST adjustment (Deplazes et al., 2013) and a possible thermal reservoir effect (Stocker and Johnsen, 2003)....
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References
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Related Papers (5)
Frequently Asked Questions (17)
Q2. What is the effect of warming in the North Atlantic?
During interstadial periods, warming in the North Atlantic has two effects on tropical precipitation: as a result of higher air temperatures, the atmosphere can hold more moisture, which leads to increased precipitation in regions of mean convergence; weakening of the trade winds, in response to the reduced cross-equatorial SST gradient, leads to an anomalous convergence in the northern tropical Atlantic.
Q3. What is the effect of the remineralization of organic material on the sediments?
Limited deep-water renewal and oxygen demand driven by organic material remineralization result in present-day anoxic conditions leading to minimal bioturbation and preservation of sediment recordswith exceptional temporal resolution5,17–19.
Q4. What is the effect of low oxygen on the L record?
If the climatologic seasonal march of the ITCZ crosses the Cariaco Basin, and low oxygen conditions preserve sediment laminations, the L∗ record captures interannual to multidecadal variations of hydroclimate.
Q5. What is the effect of an intense oxygen minimum zone on the sediments?
An intense oxygen minimum zone inhibits bioturbation, hence preserving annually laminated, high-resolution sediment archives of monsoon conditions7,8,20,21.
Q6. What is the role of colour reflectance logging in the palaeo-proxy?
Colour reflectance logging has been used successfully as a proxy for changes in sediment composition and for correlation with other palaeo-proxy records5,7,17.
Q7. What is the description of the idealized climate model experiment?
The idealized climate model experiment yields a substantial reduction in rainfall over the Cariaco Basin and the Arabian Sea (by about 80% at both sites), as well as a pronounced decrease in interannual rainfall variance.
Q8. What is the effect of the migration of the ITCZ?
The migration of the ITCZ leads to seasonally varying inputs of terrigenous and biogenic components that are recorded as light/dark coloured laminations in the sediments at the sea floor17,19.
Q9. What is the earliest evidence of the precursor-type events?
The abrupt onset/end of the precursor-type events within decades might have been caused by the fast melting/growth of sea ice that in turn led to a rapid northward/southward shift of the ITCZ.
Q10. How long does it take to reach the darkest sediment?
After the initial abrupt step, it generally takes decades to centuries until the darkest sediment is reached; this dark colour is thenmaintained over centuries until a centennial-scale lightening at the beginningof the following stadial.
Q11. What were the main factors that caused the increased rainfall?
increased oxygen availability, low productivity, reduced rainfall and a southerly position of the ITCZ, occurred mostly during the late stages of stadials or Heinrich events (see colouring in Fig. 2a).
Q12. What is the effect of the NGRIP 18O on the tropical North Atlantic?
The overall decadal adjustment time of tropical North Atlantic SSTs to high-latitude forcing may by itself lead to considerable smoothing of the tropical response to high-latitude signals.
Q13. What is the link between the Dansgaard– Oeschger sawtooth structure?
Following previous studies25 the authors propose that the Dansgaard– Oeschger sawtooth structure in Greenland δ18O is related to changes in sea-ice coverage in the Nordic seas and regional changes in precipitation.
Q14. What is the relationship between the L records and the climate model?
By analogy with present-day seasonalvariations8,17,19,20, and on the basis of the strong correspondence of the records, the L∗ records are interpreted to indicate that warm Greenland interstadials are consistently associated with a more northerly annual position of the ITCZ over the tropical Americas and a stronger summer monsoon over India, supporting previous inferences from climate modelling13,23.
Q15. What model was used to study the variability of tropical hydroclimate during Heinrich?
To investigate tropical hydroclimate variability during Heinrich conditions, the authors analysed a water-hosing experiment that was conducted with the state-of-the art coupled general circulation model CCSM3 (ref. 28; Fig. 3).
Q16. What is the current area of seasonal migration of the western Atlantic intertropical convergence zone?
The Cariaco Basin sits within the present area of seasonal migration of the western Atlantic intertropical convergence zone (ITCZ), which controls the rainfall distribution over Central and northern South America (Supplementary Fig. S1).
Q17. What is the L record from the Arabian Sea?
The L∗ record from the northeastern Arabian Sea (SO130-289KL; 23◦ 07.34′ N, 66◦ 29.84′ E; water depth of 571m) spans the time period of ∼79.5–1.8 kyr before ad 2000 (ref. 21).