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1. Global ocean heat content in the Last Interglacial

Author

Shackleton, S., Baggenstos, D., Menking, J. A., Dyonisius, M. N., Bereiter, B., Bauska, T. K., Rhodes, R. H., Brook, E. J., Petrenko, V. V., McConnell, J. R., Kellerhals, T., Häberli, M., Schmitt, J., Fischer, H., and Severinghaus, J. P.

Published
2020
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3. Millennial‐Scale Changes in Terrestrial and Marine Nitrous Oxide Emissions at the Onset and Termination of Marine Isotope Stage 4.

Author

Menking, J. A., Brook, E. J., Schilt, A., Shackleton, S., Dyonisius, M., Severinghaus, J. P., and Petrenko, V. V.

Subjects
*NITROUS oxide, *ATMOSPHERIC nitrous oxide, *GLOBAL cooling, *GLACIATION, *ISOTOPES, *STABLE isotopes, *ICE cores
Abstract

Ice core measurements of the concentration and stable isotopic composition of atmospheric nitrous oxide (N2O) 74,000–59,000 years ago constrain marine and terrestrial emissions. The data include two major Dansgaard‐Oeschger (D‐O) events and the N2O decrease during global cooling at the Marine Isotope Stage (MIS) 5a‐4 transition. The N2O increase associated with D‐O 19 (~73–71.5 ka) was driven by equal contributions from marine and terrestrial emissions. The N2O decrease during the transition into MIS 4 (~71.5–67.5 ka) was caused by gradual reductions of similar magnitude in both marine and terrestrial sources. A 50 ppb increase in N2O concentration at the end of MIS 4 was caused by gradual increases in marine and terrestrial emissions between ~64 and 61 ka, followed by an abrupt increase in marine emissions at the onset of D‐O 16/17 (59.5 ka). This suggests that the importance of marine versus terrestrial emissions in controlling millennial‐scale N2O fluctuations varied in time. Plain Language Summary: Nitrous oxide is a powerful greenhouse gas that is produced naturally in soils and oceans. An important unresolved question is the extent to which anthropogenic warming will stimulate additional emissions from these sources, further adding to the warming. Past variations in the abundance of nitrous oxide have been observed using ice core reconstructions, but the reasons for the variations are not well understood. Nitrous oxide produced in soils is isotopically distinct from nitrous oxide produced in oceans. New measurements of the isotopes of atmospheric nitrous oxide provide constraints on how marine and terrestrial sources must have changed, driving fluctuations in nitrous oxide concentration during two intervals of rapid warming and a prolonged period of global cooling. The reconstructed changes in nitrous oxide sources provide insights into relationships between marine and terrestrial ecosystems and climate. Key Points: Stable isotopes of nitrous oxide constrain marine versus terrestrial production 74,000–59,000 years agoMarine and terrestrial sources varied similarly across Dansgaard‐Oeschger 19 and during the Marine Isotope Stage 5‐4 transitionMarine emissions dominated across Dansgaard‐Oeschger 16/17; thus, abrupt N2O increases were not all identical during the last glacial period [ABSTRACT FROM AUTHOR]

Published
2020
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5. Optimized method for black carbon analysis in ice and snow using the Single Particle Soot Photometer.

Author

Wendl, I. A., Menking, J. A., Färber, R., Gysel, M., Kaspari, S. D., Laborde, M. J. G., and Schwikowski, M.

Subjects
*PHOTOMETERS, *SOOT, *ATOMIZERS, *CALIBRATION, *ICE cores
Abstract

In this study we attempt to optimize the method for measuring black carbon (BC) in snow and ice using a single particle soot photometer (SP2). Beside the previously applied ultrasonic (CETAC) and Collison-type nebulizers we introduce a jet (APEX-Q) nebulizer to aerosolize the aqueous sample for SP2 analysis. Both CETAC and APEXQ require small sample volumes (few milliliters) which makes them suitable for ice core analysis. The APEX-Q shows the least size-dependent nebulizing efficiency in the BC particle diameter range of 100-1000 nm. The CETAC has the advantage that air and liquid flows can be monitored continuously. All nebulizer-types require a calibration with BC standards for the determination of the BC mass concentration in unknown aqueous samples.We found Aquadag to be a suitable material for preparing calibration standards. Further, we studied the influence of different treatments for fresh discrete snow and ice samples as well as the effect of storage. The results show that samples are best kept frozen until analysis. Once melted, they should be sonicated for 25 min, immediately analyzed while being stirred and not be refrozen. [ABSTRACT FROM AUTHOR]

Published
2014
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6. Global ocean heat content in the Last Interglacial

Author

Shackleton, S., Baggenstos, Daniel, Menking, J. A., Dyonisius, M. N., Bereiter, Bernhard, Bauska, T. K., Rhodes, R. H., Brook, E. J., Petrenko, V. V., McConnell, J. R., Kellerhals, T., Häberli, M., Schmitt, J., Fischer, Hubertus, and Severinghaus, J. P.

Subjects
13. Climate action, 530 Physics, 550 Earth sciences & geology, 14. Life underwater
Abstract

The Last Interglacial (129–116 thousand years ago (ka)) represents one of the warmest climate intervals of the past 800,000 years and the most recent time when sea level was metres higher than today. However, the timing and magnitude of the peak warmth varies between reconstructions, and the relative importance of individual sources that contribute to the elevated sea level (mass gain versus seawater expansion) during the Last Interglacial remains uncertain. Here we present the first mean ocean temperature record for this interval from noble gas measurements in ice cores and constrain the thermal expansion con-tribution to sea level. Mean ocean temperature reached its maximum value of 1.1 ± 0.3 °C warmer-than-modern values at the end of the penultimate deglaciation at 129 ka, which resulted in 0.7 ± 0.3 m of thermosteric sea-level rise relative to present level. However, this maximum in ocean heat content was a transient feature; mean ocean temperature decreased in the first several thousand years of the interglacial and achieved a stable, comparable-to-modern value by ~127 ka. The synchroneity of the peak in mean ocean temperature with proxy records of abrupt transitions in the oceanic and atmospheric circulation suggests that the mean ocean temperature maximum is related to the accumulation of heat in the ocean interior during the preceding period of reduced overturning circulation.

7. Old carbon reservoirs were not important in the deglacial methane budget

Author

Dyonisius, M. N., Petrenko, V. V., Smith, A. M., Hua, Q., Yang, B., Schmitt, J., Beck, J., Seth, B., Bock, M., Hmiel, B., Vimont, I., Menking, J. A., Shackleton, S. A., Baggenstos, D., Bauska, T. K., Rhodes, R. H., Sperlich, P., Beaudette, R., Harth, C., Kalk, M., Brook, E. J., Fischer, H., Severinghaus, J. P., and Weiss, R. F.

Subjects
13. Climate action, 530 Physics, 550 Earth sciences & geology, 15. Life on land
Abstract

Permafrost and methane hydrates are large, climate-sensitive old carbon reservoirs that have the potential to emit large quantities of methane, a potent greenhouse gas, as the Earth continues to warm. We present ice core isotopic measurements of methane (D14C, d13C, and dD) from the last deglaciation, which is a partial analog for modern warming. Our results show that methane emissions from old carbon reservoirs in response to deglacial warming were small (

8. The Ross Sea Dipole – temperature, snow accumulation and sea ice variability in the Ross Sea region, Antarctica, over the past 2700 years

Author

N. A. N. Bertler, H. Conway, D. Dahl-Jensen, D. B. Emanuelsson, M. Winstrup, P. T. Vallelonga, J. E. Lee, E. J. Brook, J. P. Severinghaus, T. J. Fudge, E. D. Keller, W. T. Baisden, R. C. A. Hindmarsh, P. D. Neff, T. Blunier, R. Edwards, P. A. Mayewski, S. Kipfstuhl, C. Buizert, S. Canessa, R. Dadic, H. A. Kjær, A. Kurbatov, D. Zhang, E. D. Waddington, G. Baccolo, T. Beers, H. J. Brightley, L. Carter, D. Clemens-Sewall, V. G. Ciobanu, B. Delmonte, L. Eling, A. Ellis, S. Ganesh, N. R. Golledge, S. Haines, M. Handley, R. L. Hawley, C. M. Hogan, K. M. Johnson, E. Korotkikh, D. P. Lowry, D. Mandeno, R. M. McKay, J. A. Menking, T. R. Naish, C. Noerling, A. Ollive, A. Orsi, B. C. Proemse, A. R. Pyne, R. L. Pyne, J. Renwick, R. P. Scherer, S. Semper, M. Simonsen, S. B. Sneed, E. J. Steig, A. Tuohy, A. U. Venugopal, F. Valero-Delgado, J. Venkatesh, F. Wang, S. Wang, D. A. Winski, V. H. L. Winton, A. Whiteford, C. Xiao, J. Yang, X. Zhang, Victoria University of Wellington, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Bertler, N, Conway, H, Dahl-Jensen, D, Emanuelsson, D, Winstrup, M, Vallelonga, P, Lee, J, Brook, E, Severinghaus, J, Fudge, T, Keller, E, Troy Baisden, W, Hindmarsh, R, Neff, P, Blunier, T, Edwards, R, Mayewski, P, Kipfstuhl, S, Buizert, C, Canessa, S, Dadic, R, Kjær, H, Kurbatov, A, Zhang, D, Waddington, E, Baccolo, G, Beers, T, Brightley, H, Carter, L, Clemens-Sewall, D, Ciobanu, V, Delmonte, B, Eling, L, Ellis, A, Ganesh, S, Golledge, N, Haines, S, Handley, M, Hawley, R, Hogan, C, Johnson, K, Korotkikh, E, Lowry, D, Mandeno, D, Mckay, R, Menking, J, Naish, T, Noerling, C, Ollive, A, Orsi, A, Proemse, B, Pyne, A, Pyne, R, Renwick, J, Scherer, R, Semper, S, Simonsen, M, Sneed, S, Steig, E, Tuohy, A, Ulayottil Venugopal, A, Valero-Delgado, F, Venkatesh, J, Wang, F, Wang, S, Winski, D, Holly, W, Whiteford, A, Xiao, C, Yang, J, and Zhang, X

Subjects
Arctic sea ice decline, 010504 meteorology & atmospheric sciences, lcsh:Environmental protection, Stratigraphy, Antarctic ice sheet, Antarctic sea ice, 010502 geochemistry & geophysics, 01 natural sciences, Physical Geography and Environmental Geoscience, lcsh:Environmental pollution, Sea ice, Cryosphere, lcsh:TD169-171.8, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, lcsh:Environmental sciences, 0105 earth and related environmental sciences, lcsh:GE1-350, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Global and Planetary Change, geography, geography.geographical_feature_category, Paleontology, Future sea level, 15. Life on land, Arctic ice pack, Climate Action, Oceanography, 13. Climate action, lcsh:TD172-193.5, Ice sheet, Geology
Abstract

High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually dated ice core record from the eastern Ross Sea, named the Roosevelt Island Climate Evolution (RICE) ice core. Comparison of this record with climate reanalysis data for the 1979–2012 interval shows that RICE reliably captures temperature and snow precipitation variability in the region. Trends over the past 2700 years in RICE are shown to be distinct from those in West Antarctica and the western Ross Sea captured by other ice cores. For most of this interval, the eastern Ross Sea was warming (or showing isotopic enrichment for other reasons), with increased snow accumulation and perhaps decreased sea ice concentration. However, West Antarctica cooled and the western Ross Sea showed no significant isotope temperature trend. This pattern here is referred to as the Ross Sea Dipole. Notably, during the Little Ice Age, West Antarctica and the western Ross Sea experienced colder than average temperatures, while the eastern Ross Sea underwent a period of warming or increased isotopic enrichment. From the 17th century onwards, this dipole relationship changed. All three regions show current warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea but increasing in the western Ross Sea. We interpret this pattern as reflecting an increase in sea ice in the eastern Ross Sea with perhaps the establishment of a modern Roosevelt Island polynya as a local moisture source for RICE.

Published
2019
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