the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 21 Feb 2025
Tropical temperature evolution across two glacial cycles derived from speleothem fluid inclusion microthermometry
Abstract. The evolution of tropical temperature across multiple glacial-interglacial cycles is mostly constrained with marine proxy records, which are associated with considerable uncertainties. Here we present a reconstruction of tropical land temperatures derived from fluid inclusions in stalagmite WR5_B from Whiterock Cave (Gunung Mulu National Park, Northern Borneo). The employed paleothermometer – nucleation-assisted microthermometry – is based on the density of the water trapped in fluid inclusions, i.e., on a well-known thermodynamic parameter and yields highly precise temperature estimates. The record consists of 49 temperature data points spanning a 127 kyr period from 460 to 333 ka including the glacial terminations T-V and T-IV. We find that Borneo temperature tracks Southern hemisphere temperature and atmospheric CO2 concentrations. Deglacial warming is accompanied by relatively dry conditions in Northern Borneo, indicated by pronounced enrichments in calcite δ18Occ and reconstructed drip water δ18Odw values. The amplitude of glacial-interglacial temperature changes amounts to 4.2 ± 0.4 °C (2SEM) between MIS 12 and the MIS 11 interglacial optimum and 4.3 ± 0.4 °C (2SEM) across T-IV. MIS 11 peak temperature was found to be 0.9 ± 0.4 °C warmer than late Holocene temperatures reconstructed for Whiterock Cave, whereas temperatures during MIS 12 and MIS 10 glacial maxima in our record are indistinguishable from those previously reconstructed for the Last Glacial Maximum. Both the present WR5_B record as well as the recently published record from Løland et al. (2022) covering the last glacial Termination exhibit a clear linear correlation with Antarctic temperature anomalies (R2 = 0.89 and 0.97, respectively), with practically identical slopes of the linear regression lines. Depending on the employed Antarctic ΔT reconstruction, Landais et al. (2021) and Jouzel et al. (2007), we found a polar amplification factor of 2.21 ± 0.22 and 2.42 ± 0.23 (95 % CI), respectively.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2025-668', Charlotte Honiat, 07 Apr 2025
I have read the manuscript « Tropical temperature evolution across two glacial cycles derived from speleothem fluid inclusion microthermometry » with great interest ; it was pleasant to read and well organised.
The authors present a reconstruction of tropical land temperatures derived from nucleation-assisted fluid inclusion microthermometry on a stalagmite (WR5_B) from northern Borneo. The record spans MIS 12 to MIS 9, covering two glacial terminations and one glacial inception (127 kyr in total). The authors analysed an extensive set of 2090 fluid inclusions in 49 different growth bands from that sample and an additional 146 fluid inclusions in 3 growth band from a late Holocene sample for comparaison. Previous work showed Borneo temperatures tracked CO₂ and Antarctic temperatures during the last termination. This study tests if that pattern holds for earlier terminations and glacial cycles.
The manuscript represent a significant contribution to the knowledge of past climate in the tropics over a long, less often studied timescale (from 460 to 333 ka) and the amount and replication of fluid inclusion (FI) microthermometry measurements give confidence in the results. The applied method of FI microthermometry on stalagmites is still regarded as novel in the field of speleothem science although it has been around for some time because it is not commonly use. To date, when it is applicable, it is the most accurate palaeothermometer available on speleothems.
The resulting temperature record is of high quality and precision and the discussion of the results is appropriate and well put into context. The only impair is the age model of stalagmite WR5_B resulting in uncertainty on the order of ±12 kyr. Although this can be regarded as large for speleothem chronology, it is comparable to other archives available for the time period (i.e. marine sediment) and taken into account into the discussion of climatic events. This new record shows that land temperatures closely followed Antarctic temperature changes during Terminations V and IV, consistent with previous findings from the last deglaciation. Deglacial warming began with Heinrich stadials, marked by drying in Borneo and Northern Hemisphere cooling, confirming a decoupling between temperature and hydroclimate in the region. Finally the authors have shown that a strong linear relationship between Antarctic temperature and Borneo records suggests a consistent polar amplification factor for the period of the LGM to the Holocene and MIS 12 to MIS 9.
I would therefore recommend the acceptance of this manuscript in Climate of the Past after a few minor corrections.
Minor comments :
Line 98 – 99 « Although the two temperature records do not cover the same time interval it is safe to assume that present-day cave temperature in Whiterock Cave closely reflects (multi) annual mean outside air temperature without seasonal bias. »
Here the argument could benefit or be supported by a check of the climatological reanalysis data for the same time interval.
Line 147 we additionally took into account
And « major hiatus (red dashed) » : is it the growth hiatus shown in Fig A1 ? If yes it would be good to refer to the figure ;
Figure 4 : is this inclusion from the studied stalagmite ? could you mention from which stalagmite it comes from ?
Line 320 : you mention the lapse rate uncertainty, could you give number ?
Line 349 : « we employed our temperature record to calculate the oxygen isotopic composition of the calcite supplying drip water d18Odw from which the stalagmite formed » I think this sentence need to be re-written ; isn’t the drip water supplying speleothem formation and not the calcite ?
Line 351 : Why did you use the empirical speleothem calibration for the calcite-water oxygen isotope fractionation proposed by Tremaine et al. (2011) ; and not other equations like Kim and O’neill (1997) ? I would be interesting to see the difference between the most commonly used equation in the litterature. Maybe this choice is based on modern monitoring data, if so, it would be worth mentionning it
Line 371 : « the previous interpretation of relative drying » not sure what « previous » refers to here ? Maybe a reference is needed
Line 392 : That is correct but it would be good to give estimates of uncertaities on both record
Line 459 : Give altitude difference in paranthesis
Figure 8 : You discuss above (between line 459 and 469) that you corrected for the difference in cave altitude between the Secret Chamber cave (Loland 2022) and Whiterock Cave (this study) so why not plotting a corrected version to make comparison easier for the reader ?
Why termination T-IV is not compared with T-I and T-V here ? I understand there is a hiatus during part of the glacial-interglacial transition but this hiatus also holds information ; is the timing of the hiatus comparable to an HS event-like ? A hiatus would fit with your argument of relative drying during Heinrich Stadials
Figure 9 : How did you select individual datapoint ? Is it based on each individual FI measured datapoint from your record and then the corresponding T° from the Antarctic record ? Or is at a point at a regular time interval from your interpolated record ? Could you clarify in the figure caption ?
Figure A4 : There are two different plot with Sample Pos. 29 (page 28 and 29)
Stalagmite WR5_B has previously been studied in a comparison study of different speleothem paleo thermometers (Meckler et al., 2015). I saw that the FI stable isotopes are plotted in figure 5 ; but what about the previous FI microthermometry data ? How does this newly produced data compare to the one in the study of Meckler et al. (2015) ? It could be briefly mentionned in the result section if uncertainty improvement have been made since that study, or shown in a supplementary figure in the appendix (showing the 2015 and 2025 data for the time period they overlap).
General comment : The notation of all temperature have to be made homogeneous (either space or no space between number and ±)
Citation: https://doi.org/10.5194/egusphere-2025-668-RC1 - AC1: 'Reply on RC1', Yves Krüger, 28 Jun 2025
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RC2: 'Comment on egusphere-2025-668', Anonymous Referee #2, 01 May 2025
Krüger et al. present a spectacular record of temperature reconstructions from Borneo spanning two glacial-interglacial cycles. The manuscript improves our understanding of tropical paleoclimate in a region where absolute temperature records are scarce. The authors present their findings with clarity and appropriate context. This paper will be of broad interest to the paleoclimate community and therefore merits publication. However, there are a few minor issues to address:
- Typo on Fig. A2: Cheng et al. 2016
- The authors may consider moving Fig. A2 to section 2.2, since many of the millennial-scale climate interpretations hinge on the detailed wiggle matching to Cheng et al. 2016
- Section 3.2 left me wondering how the globally averaged sea level reconstructions from Bintanja et al. compare to regional sea level reconstructions off the coast of Vietnam, New Guinea, etc. Do small differences in regional vs global sea level at, for example, the LGM yield significant differences in temperature corrections? If so, how can these differences be appropriately accounted for in the Tcorr uncertainties deeper in time?
- Although not my specialty, the term Polar Amplification is typically used to describe the enhanced polar temperature response relative to the tropics. This study presents data from the Western Pacific Warm Pool alone, which may not be representative of the broader tropical average. Clarifying this distinction will help avoid overgeneralization. The authors may also consider using the term Antarctic Amplification as opposed to polar.
Citation: https://doi.org/10.5194/egusphere-2025-668-RC2 - AC2: 'Reply on RC2', Yves Krüger, 28 Jun 2025
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EC1: 'Comment on egusphere-2025-668', Christo Buizert, 05 May 2025
Dear authors,
Your manuscript has now been reviewed by two experts. As you can see, they are overall very positive, yet they make some suggestions for improvement. Please respond to all reviewer comments in the open discussion. Based on the reviews I will most likely be inviting you to submit a revised manuscript, so feel free to write these comments in the form of proposed revisions to the text.
Please let me know if you have questions.
Best regards, Christo Buizert (CP editor)
Citation: https://doi.org/10.5194/egusphere-2025-668-EC1
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2025-668', Charlotte Honiat, 07 Apr 2025
I have read the manuscript « Tropical temperature evolution across two glacial cycles derived from speleothem fluid inclusion microthermometry » with great interest ; it was pleasant to read and well organised.
The authors present a reconstruction of tropical land temperatures derived from nucleation-assisted fluid inclusion microthermometry on a stalagmite (WR5_B) from northern Borneo. The record spans MIS 12 to MIS 9, covering two glacial terminations and one glacial inception (127 kyr in total). The authors analysed an extensive set of 2090 fluid inclusions in 49 different growth bands from that sample and an additional 146 fluid inclusions in 3 growth band from a late Holocene sample for comparaison. Previous work showed Borneo temperatures tracked CO₂ and Antarctic temperatures during the last termination. This study tests if that pattern holds for earlier terminations and glacial cycles.
The manuscript represent a significant contribution to the knowledge of past climate in the tropics over a long, less often studied timescale (from 460 to 333 ka) and the amount and replication of fluid inclusion (FI) microthermometry measurements give confidence in the results. The applied method of FI microthermometry on stalagmites is still regarded as novel in the field of speleothem science although it has been around for some time because it is not commonly use. To date, when it is applicable, it is the most accurate palaeothermometer available on speleothems.
The resulting temperature record is of high quality and precision and the discussion of the results is appropriate and well put into context. The only impair is the age model of stalagmite WR5_B resulting in uncertainty on the order of ±12 kyr. Although this can be regarded as large for speleothem chronology, it is comparable to other archives available for the time period (i.e. marine sediment) and taken into account into the discussion of climatic events. This new record shows that land temperatures closely followed Antarctic temperature changes during Terminations V and IV, consistent with previous findings from the last deglaciation. Deglacial warming began with Heinrich stadials, marked by drying in Borneo and Northern Hemisphere cooling, confirming a decoupling between temperature and hydroclimate in the region. Finally the authors have shown that a strong linear relationship between Antarctic temperature and Borneo records suggests a consistent polar amplification factor for the period of the LGM to the Holocene and MIS 12 to MIS 9.
I would therefore recommend the acceptance of this manuscript in Climate of the Past after a few minor corrections.
Minor comments :
Line 98 – 99 « Although the two temperature records do not cover the same time interval it is safe to assume that present-day cave temperature in Whiterock Cave closely reflects (multi) annual mean outside air temperature without seasonal bias. »
Here the argument could benefit or be supported by a check of the climatological reanalysis data for the same time interval.
Line 147 we additionally took into account
And « major hiatus (red dashed) » : is it the growth hiatus shown in Fig A1 ? If yes it would be good to refer to the figure ;
Figure 4 : is this inclusion from the studied stalagmite ? could you mention from which stalagmite it comes from ?
Line 320 : you mention the lapse rate uncertainty, could you give number ?
Line 349 : « we employed our temperature record to calculate the oxygen isotopic composition of the calcite supplying drip water d18Odw from which the stalagmite formed » I think this sentence need to be re-written ; isn’t the drip water supplying speleothem formation and not the calcite ?
Line 351 : Why did you use the empirical speleothem calibration for the calcite-water oxygen isotope fractionation proposed by Tremaine et al. (2011) ; and not other equations like Kim and O’neill (1997) ? I would be interesting to see the difference between the most commonly used equation in the litterature. Maybe this choice is based on modern monitoring data, if so, it would be worth mentionning it
Line 371 : « the previous interpretation of relative drying » not sure what « previous » refers to here ? Maybe a reference is needed
Line 392 : That is correct but it would be good to give estimates of uncertaities on both record
Line 459 : Give altitude difference in paranthesis
Figure 8 : You discuss above (between line 459 and 469) that you corrected for the difference in cave altitude between the Secret Chamber cave (Loland 2022) and Whiterock Cave (this study) so why not plotting a corrected version to make comparison easier for the reader ?
Why termination T-IV is not compared with T-I and T-V here ? I understand there is a hiatus during part of the glacial-interglacial transition but this hiatus also holds information ; is the timing of the hiatus comparable to an HS event-like ? A hiatus would fit with your argument of relative drying during Heinrich Stadials
Figure 9 : How did you select individual datapoint ? Is it based on each individual FI measured datapoint from your record and then the corresponding T° from the Antarctic record ? Or is at a point at a regular time interval from your interpolated record ? Could you clarify in the figure caption ?
Figure A4 : There are two different plot with Sample Pos. 29 (page 28 and 29)
Stalagmite WR5_B has previously been studied in a comparison study of different speleothem paleo thermometers (Meckler et al., 2015). I saw that the FI stable isotopes are plotted in figure 5 ; but what about the previous FI microthermometry data ? How does this newly produced data compare to the one in the study of Meckler et al. (2015) ? It could be briefly mentionned in the result section if uncertainty improvement have been made since that study, or shown in a supplementary figure in the appendix (showing the 2015 and 2025 data for the time period they overlap).
General comment : The notation of all temperature have to be made homogeneous (either space or no space between number and ±)
Citation: https://doi.org/10.5194/egusphere-2025-668-RC1 - AC1: 'Reply on RC1', Yves Krüger, 28 Jun 2025
-
RC2: 'Comment on egusphere-2025-668', Anonymous Referee #2, 01 May 2025
Krüger et al. present a spectacular record of temperature reconstructions from Borneo spanning two glacial-interglacial cycles. The manuscript improves our understanding of tropical paleoclimate in a region where absolute temperature records are scarce. The authors present their findings with clarity and appropriate context. This paper will be of broad interest to the paleoclimate community and therefore merits publication. However, there are a few minor issues to address:
- Typo on Fig. A2: Cheng et al. 2016
- The authors may consider moving Fig. A2 to section 2.2, since many of the millennial-scale climate interpretations hinge on the detailed wiggle matching to Cheng et al. 2016
- Section 3.2 left me wondering how the globally averaged sea level reconstructions from Bintanja et al. compare to regional sea level reconstructions off the coast of Vietnam, New Guinea, etc. Do small differences in regional vs global sea level at, for example, the LGM yield significant differences in temperature corrections? If so, how can these differences be appropriately accounted for in the Tcorr uncertainties deeper in time?
- Although not my specialty, the term Polar Amplification is typically used to describe the enhanced polar temperature response relative to the tropics. This study presents data from the Western Pacific Warm Pool alone, which may not be representative of the broader tropical average. Clarifying this distinction will help avoid overgeneralization. The authors may also consider using the term Antarctic Amplification as opposed to polar.
Citation: https://doi.org/10.5194/egusphere-2025-668-RC2 - AC2: 'Reply on RC2', Yves Krüger, 28 Jun 2025
-
EC1: 'Comment on egusphere-2025-668', Christo Buizert, 05 May 2025
Dear authors,
Your manuscript has now been reviewed by two experts. As you can see, they are overall very positive, yet they make some suggestions for improvement. Please respond to all reviewer comments in the open discussion. Based on the reviews I will most likely be inviting you to submit a revised manuscript, so feel free to write these comments in the form of proposed revisions to the text.
Please let me know if you have questions.
Best regards, Christo Buizert (CP editor)
Citation: https://doi.org/10.5194/egusphere-2025-668-EC1
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Yves Krüger
Leonardo Pasqualetto
Alvaro Fernandez
Kim M. Cobb
Anna Nele Meckler
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(10525 KB) - Metadata XML