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1. An 83 000-year-old ice core from Roosevelt Island, Ross Sea, Antarctica

Author

Lee, James E, Brook, Edward J, Bertler, Nancy AN, Buizert, Christo, Baisden, Troy, Blunier, Thomas, Ciobanu, V Gabriela, Conway, Howard, Dahl-Jensen, Dorthe, Fudge, Tyler J, Hindmarsh, Richard, Keller, Elizabeth D, Parrenin, Frederic, Severinghaus, Jeffrey P, Vallelonga, Paul, Waddington, Edwin D, and Winstrup, Mai

Subjects
Paleontology, Physical Geography and Environmental Geoscience
Abstract

Abstract. In 2013 an ice core was recovered from Roosevelt Island, an ice dome between two submarine troughs carved by paleo-ice-streams in the Ross Sea, Antarctica. The ice core is part of the Roosevelt Island Climate Evolution (RICE) project and provides new information about the past configuration of the West Antarctic Ice Sheet (WAIS) and its retreat during the last deglaciation. In this work we present the RICE17 chronology, which establishes the depth–age relationship for the top 754 m of the 763 m core. RICE17 is a composite chronology combining annual layer interpretations for 0–343 m (Winstrup et al., 2019) with new estimates for gas and ice ages based on synchronization of CH4 and δ18Oatm records to corresponding records from the WAIS Divide ice core and by modeling of the gas age–ice age difference. Novel aspects of this work include the following: (1) an automated algorithm for multiproxy stratigraphic synchronization of high-resolution gas records; (2) synchronization using centennial-scale variations in methane for pre-anthropogenic time periods (60–720 m, 1971 CE to 30 ka), a strategy applicable for future ice cores; and (3) the observation of a continuous climate record back to ∼65 ka providing evidence that the Roosevelt Island Ice Dome was a constant feature throughout the last glacial period.

Published
2020

2. An 83 000 year old ice core from Roosevelt Island, Ross Sea, Antarctica

Author

Lee, James E, Brook, Edward J, Bertler, Nancy AN, Buizert, Christo, Baisden, Troy, Blunier, Thomas, Ciobanu, V Gabriela, Conway, Howard, Dahl-Jensen, Dorthe, Fudge, Tyler J, Hindmarsh, Richard, Keller, Elizabeth D, Parrenin, Frédéric, Severinghaus, Jeffrey P, Vallelonga, Paul, Waddington, Edwin D, and Winstrup, Mai

Subjects
Climate Action
Abstract

Abstract. In 2013, an ice core was recovered from Roosevelt Island in the Ross Sea, Antarctica, as part of the Roosevelt Island Climate Evolution (RICE) project. Roosevelt Island is located between two submarine troughs carved by paleo-ice-streams. The RICE ice core provides new important information about the past configuration of the West Antarctic Ice Sheet and its retreat during the most recent deglaciation. In this work, we present the RICE17 chronology and discuss preliminary observations from the new records of methane, the isotopic composition of atmospheric molecular oxygen (δ18O-Oatm), the isotopic composition of atmospheric molecular nitrogen (δ15N-N2) and total air content (TAC). RICE17 is a composite chronology combining annual layer interpretations, gas synchronization, and firn modeling strategies in different sections of the core. An automated matching algorithm is developed for synchronizing the high-resolution section of the RICE gas records (60–720 m, 1971 CE to 30 ka) to corresponding records from the WAIS Divide ice core, while deeper sections are manually matched. Ice age for the top 343 m (2635 yr BP, before 1950 C.E.) is derived from annual layer interpretations and described in the accompanying paper by Winstrup et al. (2017). For deeper sections, the RICE17 ice age scale is based on the gas age constraints and the ice age-gas age offset estimated by a firn densification model. Novel aspects of this work include: 1) stratigraphic matching of centennial-scale variations in methane for pre-anthropogenic time periods, a strategy which will be applicable for developing precise chronologies for future ice cores, 2) the observation of centennial-scale variability in methane throughout the Holocene which suggests that similar variations during the late preindustrial period need not be anthropogenic, and 3) the observation of continuous climate records dating back to ∼ 65 ka which provide evidence that the Roosevelt Island Ice Dome was a constant feature throughout the last glacial period.

Published
2018

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

Author

Bertler, Nancy AN, Conway, Howard, Dahl-Jensen, Dorthe, Emanuelsson, Daniel B, Winstrup, Mai, Vallelonga, Paul T, Lee, James E, Brook, Ed J, Severinghaus, Jeffrey P, Fudge, Taylor J, Keller, Elizabeth D, Baisden, W Troy, Hindmarsh, Richard CA, Neff, Peter D, Blunier, Thomas, Edwards, Ross, Mayewski, Paul A, Kipfstuhl, Sepp, Buizert, Christo, Canessa, Silvia, Dadic, Ruzica, Kjær, Helle A, Kurbatov, Andrei, Zhang, Dongqi, Waddington, Edwin D, Baccolo, Giovanni, Beers, Thomas, Brightley, Hannah J, Carter, Lionel, Clemens-Sewall, David, Ciobanu, Viorela G, Delmonte, Barbara, Eling, Lukas, Ellis, Aja, Ganesh, Shruthi, Golledge, Nicholas R, Haines, Skylar, Handley, Michael, Hawley, Robert L, Hogan, Chad M, Johnson, Katelyn M, Korotkikh, Elena, Lowry, Daniel P, Mandeno, Darcy, McKay, Robert M, Menking, James A, Naish, Timothy R, Noerling, Caroline, Ollive, Agathe, Orsi, Anaïs, Proemse, Bernadette C, Pyne, Alexander R, Pyne, Rebecca L, Renwick, James, Scherer, Reed P, Semper, Stefanie, Simonsen, Marius, Sneed, Sharon B, Steig, Eric J, Tuohy, Andrea, Venugopal, Abhijith Ulayottil, Valero-Delgado, Fernando, Venkatesh, Janani, Wang, Feitang, Wang, Shimeng, Winski, Dominic A, Winton, V Holly L, Whiteford, Arran, Xiao, Cunde, Yang, Jiao, and Zhang, Xin

Subjects
Earth Sciences, Physical Geography and Environmental Geoscience, Geology, Climate Action, Paleontology, Climate change science
Abstract

Abstract. High-resolution, well-dated climate archives provide anopportunity to investigate the dynamic interactions of climate patternsrelevant for future projections. Here, we present data from a new, annuallydated ice core record from the eastern Ross Sea, named the Roosevelt IslandClimate Evolution (RICE) ice core. Comparison of this record with climatereanalysis data for the 1979–2012 interval shows that RICE reliably capturestemperature and snow precipitation variability in the region. Trends over thepast 2700 years in RICE are shown to be distinct from those in WestAntarctica and the western Ross Sea captured by other ice cores. For most ofthis interval, the eastern Ross Sea was warming (or showing isotopicenrichment for other reasons), with increased snow accumulation and perhapsdecreased sea ice concentration. However, West Antarctica cooled and thewestern Ross Sea showed no significant isotope temperature trend. Thispattern here is referred to as the Ross Sea Dipole. Notably, during theLittle Ice Age, West Antarctica and the western Ross Sea experienced colderthan average temperatures, while the eastern Ross Sea underwent a period ofwarming or increased isotopic enrichment. From the 17th century onwards, thisdipole relationship changed. All three regions show current warming, withsnow accumulation declining in West Antarctica and the eastern Ross Sea butincreasing in the western Ross Sea. We interpret this pattern as reflectingan increase in sea ice in the eastern Ross Sea with perhaps the establishmentof a modern Roosevelt Island polynya as a local moisture source for RICE.

Published
2018

4. The Ross Sea Dipole – Temperature, Snow Accumulation and Sea Ice Variability in the Ross Sea Region, Antarctica, over the Past 2,700 Years

Author

Bertler, Nancy AN, Conway, Howard, Dahl-Jensen, Dorthe, Emanuelsson, Daniel B, Winstrup, Mai, Vallelonga, Paul T, Lee, James E, Brook, Ed J, Severinghaus, Jeffrey P, Fudge, Taylor J, Keller, Elizabeth D, Baisden, W Troy, Hindmarsh, Richard CA, Neff, Peter D, Blunier, Thomas, Edwards, Ross, Mayewski, Paul A, Kipfstuhl, Sepp, Buizert, Christo, Canessa, Silvia, Dadic, Ruzica, Kjær, Helle A, Kurbatov, Andrei, Zhang, Dongqi, Waddington, Ed D, Baccolo, Giovanni, Beers, Thomas, Brightley, Hannah J, Carter, Lionel, Clemens-Sewall, David, Ciobanu, Viorela G, Delmonte, Barbara, Eling, Lukas, Ellis, Aja A, Ganesh, Shruthi, Golledge, Nicholas R, Haines, Skylar A, Handley, Michael, Hawley, Robert L, Hogan, Chad M, Johnson, Katelyn M, Korotkikh, Elena, Lowry, Daniel P, Mandeno, Darcy, McKay, Robert M, Menking, James A, Naish, Timothy R, Noerling, Caroline, Ollive, Agathe, Orsi, Anaïs, Proemse, Bernadette C, Pyne, Alexander R, Pyne, Rebecca L, Renwick, James, Scherer, Reed P, Semper, Stefanie, Simonsen, Marius, Sneed, Sharon B, Steig, Eric J, Tuohy, Andrea, Venugopal, Abhijith Ulayottil, Valero-Delgado, Fernando, Venkatesh, Janani, Wang, Feitang, Wang, Shimeng, Winski, Dominic A, Winton, Victoria HL, Whiteford, Arran, Xiao, Cunde, Yang, Jiao, and Zhang, Xin

Subjects
Climate Action
Abstract

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. Comparison of the Roosevelt Island Climate Evolution (RICE) ice core records with climate reanalysis data for the 1979–2012 calibration period shows that RICE records reliably capture temperature and snow precipitation variability of the region. RICE is compared with data from West Antarctica (West Antarctic Ice Sheet Divide Ice Core) and the western (Talos Dome) and eastern (Siple Dome) Ross Sea. For most of the past 2,700 years, the eastern Ross Sea was warming with perhaps increased snow accumulation and decreased sea ice extent. However, West Antarctica cooled whereas the western Ross Sea showed no significant temperature trend. From the 17th Century onwards, this relationship changes. All three regions now show signs of warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea, but increasing in the western Ross Sea. Analysis of decadal to centennial-scale climate variability superimposed on the longer term trend reveal that periods characterised by opposing temperature trends between the Eastern and Western Ross Sea have occurred since the 3rd Century but are masked by longer-term trends. This pattern here is referred to as the Ross Sea Dipole, caused by a sensitive response of the region to dynamic interactions of the Southern Annual Mode and tropical forcings.

Published
2017

5. RECCAP2 Future Component: Consistency and Potential for Regional Assessment to Constrain Global Projections

Author

Jones, Chris D., primary, Ziehn, Tilo, additional, Anand, Jatin, additional, Bastos, Ana, additional, Burke, Eleanor, additional, Canadell, Josep G., additional, Cardoso, Manoel, additional, Ernst, Yolandi, additional, Jain, Atul K., additional, Jeong, Sujong, additional, Keller, Elizabeth D., additional, Kondo, Masayuki, additional, Lauerwald, Ronny, additional, Lin, Tzu‐Shun, additional, Murray‐Tortarolo, Guillermo, additional, Nabuurs, Gert‐Jan, additional, O’Sullivan, Mike, additional, Poulter, Ben, additional, Qin, Xiaoyu, additional, von Randow, Celso, additional, Sanches, Marcos, additional, Schepaschenko, Dmitry, additional, Shvidenko, Anatoly, additional, Smallman, T. Luke, additional, Tian, Hanqin, additional, Villalobos, Yohanna, additional, Wang, Xuhui, additional, and Yun, Jeongmin, additional

Published
2023
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8. A comprehensive assessment of anthropogenic and natural sources and sinks of Australasia's carbon budget

Author

Villalobos, Yohanna, Canadell, Josep G., Keller, Elizabeth D., Briggs, Peter R., Bukosa, Beata, Giltrap, Donna L., Harman, Ian, Hilton, Timothy W., Kirschbaum, Miko U. F., Lauerwald, Ronny, Liang, Liyin L., Maavara, Taylor, Mikaloff-Fletcher, Sara E., Rayner, Peter J., Resplandy, Laure, Rosentreter, Judith, Metz, Eva M., Serrano, Oscar, Smith, Benjamin, Villalobos, Yohanna, Canadell, Josep G., Keller, Elizabeth D., Briggs, Peter R., Bukosa, Beata, Giltrap, Donna L., Harman, Ian, Hilton, Timothy W., Kirschbaum, Miko U. F., Lauerwald, Ronny, Liang, Liyin L., Maavara, Taylor, Mikaloff-Fletcher, Sara E., Rayner, Peter J., Resplandy, Laure, Rosentreter, Judith, Metz, Eva M., Serrano, Oscar, and Smith, Benjamin

Abstract

Regional carbon budget assessments attribute and track changes in carbon sources and sinks and support the development and monitoring the efficacy of climate policies. We present a comprehensive assessment of the natural and anthropogenic carbon (C-CO2) fluxes for Australasia as a whole, as well as for Australia and New Zealand individually, for the period from 2010 to 2019, using two approaches: bottom-up methods that integrate flux estimates from land-surface models, data-driven models, and inventory estimates; and top-down atmospheric inversions based on satellite and in situ measurements. Our bottom-up decadal assessment suggests that Australasia's net carbon balance was close to carbon neutral (−0.4 ± 77.0 TgC yr−1). However, substantial uncertainties remain in this estimate, primarily driven by the large spread between our regional terrestrial biosphere simulations and predictions from global ecosystem models. Within Australasia, Australia was a net source of 38.2 ± 75.8 TgC yr−1, and New Zealand was a net CO2 sink of −38.6 ± 13.4 TgC yr−1. The top-down approach using atmospheric CO2 inversions indicates that fluxes derived from the latest satellite retrievals are consistent within the range of uncertainties with Australia's bottom-up budget. For New Zealand, the best agreement was found with a national scale flux inversion estimate based on in situ measurements, which provide better constrained of fluxes than satellite flux inversions. This study marks an important step toward a more comprehensive understanding of the net CO2 balance in both countries, facilitating the improvement of carbon accounting approaches and strategies to reduce emissions.

Published
2023

9. RECCAP2 Future Component : Consistency and Potential for Regional Assessment to Constrain Global Projections

Author

Jones, Chris D., Ziehn, Tilo, Anand, Jatin, Bastos, Ana, Burke, Eleanor, Canadell, Josep G., Cardoso, Manoel, Ernst, Yolandi, Jain, Atul K., Jeong, Sujong, Keller, Elizabeth D., Kondo, Masayuki, Lauerwald, Ronny, Lin, Tzu Shun, Murray-Tortarolo, Guillermo, Nabuurs, Gert Jan, O’Sullivan, Mike, Poulter, Ben, Qin, Xiaoyu, von Randow, Celso, Sanches, Marcos, Schepaschenko, Dmitry, Shvidenko, Anatoly, Smallman, Luke, Tian, Hanqin, Villalobos, Yohanna, Wang, Xuhui, Yun, Jeongmin, Jones, Chris D., Ziehn, Tilo, Anand, Jatin, Bastos, Ana, Burke, Eleanor, Canadell, Josep G., Cardoso, Manoel, Ernst, Yolandi, Jain, Atul K., Jeong, Sujong, Keller, Elizabeth D., Kondo, Masayuki, Lauerwald, Ronny, Lin, Tzu Shun, Murray-Tortarolo, Guillermo, Nabuurs, Gert Jan, O’Sullivan, Mike, Poulter, Ben, Qin, Xiaoyu, von Randow, Celso, Sanches, Marcos, Schepaschenko, Dmitry, Shvidenko, Anatoly, Smallman, Luke, Tian, Hanqin, Villalobos, Yohanna, Wang, Xuhui, and Yun, Jeongmin

Abstract

Projections of future carbon sinks and stocks are important because they show how the world's ecosystems will respond to elevated CO2 and changes in climate. Moreover, they are crucial to inform policy decisions around emissions reductions to stay within the global warming levels identified by the Paris Agreement. However, Earth System Models from the 6th Coupled Model Intercomparison Project (CMIP6) show substantial spread in future projections—especially of the terrestrial carbon cycle, leading to a large uncertainty in our knowledge of any remaining carbon budget (RCB). Here we evaluate the global terrestrial carbon cycle projections on a region-by-region basis and compare the global models with regional assessments made by the REgional Carbon Cycle Assessment and Processes, Phase 2 activity. Results show that for each region, the CMIP6 multi-model mean is generally consistent with the regional assessment, but substantial cross-model spread exists. Nonetheless, all models perform well in some regions and no region is without some well performing models. This gives confidence that the CMIP6 models can be used to look at future changes in carbon stocks on a regional basis with appropriate model assessment and benchmarking. We find that most regions of the world remain cumulative net sources of CO2 between now and 2100 when considering the balance of fossil-fuels and natural sinks, even under aggressive mitigation scenarios. This paper identifies strengths and weaknesses for each model in terms of its performance over a particular region including how process representation might impact those results and sets the agenda for applying stricter constraints at regional scales to reduce the uncertainty in global projections.

Published
2023

11. Mahuika‐Auckland: A spatially and temporally resolved fossil fuel CO2 emissions data product for Auckland, New Zealand.

Author

Keller, Elizabeth D., Hilton, Timothy W., Benson, Adrian, Karalliyadda, Sapthala, Xie, Shanju, Gurney, Kevin R., and Turnbull, Jocelyn C.

Subjects
*EMISSION inventories, *GREENHOUSE gases, *INCINERATION, *FOSSIL fuels, *CARBON emissions, *WOOD waste
Abstract

Accurate, high‐resolution and sector‐specific greenhouse gas emissions information is increasingly needed for the development of local, targeted mitigation policies. We describe a detailed, spatially and temporally resolved CO2 emissions data product, Mahuika‐Auckland, for Auckland, New Zealand, based on Auckland's regional greenhouse gas and air emissions inventories. Emissions are provided at 500 m spatial resolution and at a 1‐hr time step, a level of detail not previously available for any New Zealand city. We divide fossil fuel emissions into six sectors that comprise the majority of Auckland Region's CO2 emissions profile: on‐road transport, industrial non‐point buildings and point sources, commercial non‐point buildings, residential non‐point buildings, air transport and sea transport. We also include separate layers representing biogenic CO2 emissions (primarily waste and wood burning), as these are significant sources in Auckland. We distribute emissions spatially and temporally based on activity data, energy and fuel consumption patterns, and population statistics. The code to generate Mahuika‐Auckland has been designed to be flexible so that updated information and/or data from more recent years can easily be incorporated. This data product improves upon New Zealand's current inventories that are only resolved at the regional and annual scale, providing a new level of detail that can be used as a prior estimate for atmospheric inversions, to inform emissions reduction policies and to guide the development of zero carbon pathways. [ABSTRACT FROM AUTHOR]

Published
2023
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12. Plausible Last Interglacial Antarctic Ice Sheet Changes Do Not Fully Explain Antarctic Ice Core Water Isotope Records

Author

Zou, Huiling, Sime, Louise C., Bertler, Nancy A. N., Keller, Elizabeth D., and Wolff, Eric W.

Abstract

Antarctic ice cores can help determine ice mass loss from the Antarctic Ice Sheet (AIS) during past warm periods. We compile Last Interglacial (LIG) δ18O${\delta }^{18}O$measurements from eight Antarctic cores and compare these to new isotope‐enabled LIG simulations, which explore three plausible LIG AIS elevation and extent scenarios. We find that these simulations capture less than 10% of East Antarctic core‐mean δ18O${\delta }^{18}O$changes. Although our simulations do not fully explain the changes, they capture some inter‐core geographical δ18O${\delta }^{18}O$variations. Some LIG AIS configurations show higher skill than PI AIS configurations in simulating the inter‐core differences. The remaining discrepancies between the simulated and observed core‐mean water isotope changes suggest that LIG simulations also need to include the influences of reduced Antarctic sea ice, a warmer Southern Ocean, and resultant shifts in vapor source regions to produce a more satisfactory match to δ18O${\delta }^{18}O$observed at ice core sites. Reconstructions of Antarctic Ice Sheet (AIS) retreat during past warm periods provide important constraints for projections of future ice mass loss and sea level rise. The Last Interglacial (LIG) is a particularly useful example, when global temperatures were 1±1oC$\pm {1}^{o}C$warmer than preindustrial (PI) conditions, to explore future sea level rise projections associated with the successful implementation of the Paris Agreement. Here, we use data from six East Antarctic ice cores and two new, unpublished records from West Antarctica that capture LIG conditions. Water isotopes in ice cores are sensitive to changes in temperature, AIS elevation, atmospheric circulation pattern, sea ice area, and ocean conditions. We compare model simulations of the LIG with ice core data and find that elevation changes, an important indicator of ice mass loss, explain only around 9% of the isotope change captured in East Antarctic ice cores. Due to the limitation of our simulations in the coastal regions, our West Antarctic coastal sites are more challenging. In summary, we find that while the range of our simulations does not fully explain average East Antarctic PI‐to‐LIG isotope changes, they do capture some of the geographical variations in isotope change patterns. A compilation of Last Interglacial δ18O${\delta }^{18}O$ice core records shows anomalies of +${+}$1.5‰ and +${+}$3.3‰ for 127 kyr BP and LIG‐peak core‐meanSimulations run with plausible LIG Antarctic Ice Sheet (AIS)configurations, alongside greenhouse gas and orbital changes, capture <${< } $10% of core‐mean differencesTwo LIG AIS configurations yield lower geographical errors at 127 kyr, compared to their PI configurations A compilation of Last Interglacial δ18O${\delta }^{18}O$ice core records shows anomalies of +${+}$1.5‰ and +${+}$3.3‰ for 127 kyr BP and LIG‐peak core‐mean Simulations run with plausible LIG Antarctic Ice Sheet (AIS)configurations, alongside greenhouse gas and orbital changes, capture <${< } $10% of core‐mean differences Two LIG AIS configurations yield lower geographical errors at 127 kyr, compared to their PI configurations

Published
2025
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13. Back to the Future: Using Long-Term Observational and Paleo-Proxy Reconstructions to Improve Model Projections of Antarctic Climate

Author

Bracegirdle, Thomas J., Colleoni, Florence, Abram, Nerilie J., Bertler, Nancy A. N., Dixon, Daniel A., England, Mark, Favier, Vincent, Fogwill, Chris J., Fyfe, John C., Goodwin, Ian, Goosse, Hugues, Hobbs, Will, Jones, Julie M., Keller, Elizabeth D., Khan, Alia L., Phipps, Steven J., Raphael, Marilyn N., Russell, Joellen, Sime, Louise, Thomas, Elizabeth R., van den Broeke, Michiel R., Wainer, Ilana, Sub Dynamics Meteorology, Marine and Atmospheric Research, Sub Dynamics Meteorology, Marine and Atmospheric Research, and UCL - SST/ELI/ELIC - Earth & Climate

Subjects
010504 meteorology & atmospheric sciences, 010502 geochemistry & geophysics, 01 natural sciences, Proxy (climate), Ice core, Paleoclimatology, paleoclimate, Antarctic climate, QE, 14. Life underwater, PMIP, Southern Ocean, climate, 0105 earth and related environmental sciences, projections, GE, PALEOCLIMATOLOGIA, lcsh:QE1-996.5, Oceanic climate, CMIP, lcsh:Geology, Geography, 13. Climate action, General Circulation Model, Climatology, General Earth and Planetary Sciences, Climate model, Observational study, Antarctic
Abstract

Quantitative estimates of future Antarctic climate change are derived from numerical global climate models. Evaluation of the reliability of climate model projections involves many lines of evidence on past performance combined with knowledge of the processes that need to be represented. Routine model evaluation is mainly based on the modern observational period, which started with the establishment of a network of Antarctic weather stations in 1957/58. This period is too short to evaluate many fundamental aspects of the Antarctic and Southern Ocean climate system, such as decadal-to-century time-scale climate variability and trends. To help address this gap, we present a new evaluation of potential ways in which long-term observational and paleo-proxy reconstructions may be used, with a particular focus on improving projections. A wide range of data sources and time periods is included, ranging from ship observations of the early 20th century to ice core records spanning hundreds to hundreds of thousands of years to sediment records dating back 34 million years. We conclude that paleo-proxy records and long-term observational datasets are an underused resource in terms of strategies for improving Antarctic climate projections for the 21st century and beyond. We identify priorities and suggest next steps to addressing this.

Published
2019
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14. An 83 000-year-old ice core from Roosevelt Island, Ross Sea, Antarctica

Author

Lee, James E., Brook, Edward J., Bertler, Nancy A. N., Buizert, Christo, Baisden, Troy, Blunier, Thomas, Ciobanu, V. Gabriela, Conway, Howard, Dahl-Jensen, Dorthe, Fudge, Tyler J., Hindmarsh, Richard, Keller, Elizabeth D., Parrenin, Frédéric, Severinghaus, Jeffrey P., Vallelonga, Paul, Waddington, Edwin D., Winstrup, Mai, Lee, James E., Brook, Edward J., Bertler, Nancy A. N., Buizert, Christo, Baisden, Troy, Blunier, Thomas, Ciobanu, V. Gabriela, Conway, Howard, Dahl-Jensen, Dorthe, Fudge, Tyler J., Hindmarsh, Richard, Keller, Elizabeth D., Parrenin, Frédéric, Severinghaus, Jeffrey P., Vallelonga, Paul, Waddington, Edwin D., and Winstrup, Mai

Abstract

In 2013 an ice core was recovered from Roosevelt Island, an ice dome between two submarine troughs carved by paleo-ice-streams in the Ross Sea, Antarctica. The ice core is part of the Roosevelt Island Climate Evolution (RICE) project and provides new information about the past configuration of the West Antarctic Ice Sheet (WAIS) and its retreat during the last deglaciation. In this work we present the RICE17 chronology, which establishes the depth–age relationship for the top 754 m of the 763 m core. RICE17 is a composite chronology combining annual layer interpretations for 0–343 m (Winstrup et al., 2019) with new estimates for gas and ice ages based on synchronization of CH4 and δ18Oatm records to corresponding records from the WAIS Divide ice core and by modeling of the gas age–ice age difference. Novel aspects of this work include the following: (1) an automated algorithm for multiproxy stratigraphic synchronization of high-resolution gas records; (2) synchronization using centennial-scale variations in methane for pre-anthropogenic time periods (60–720 m, 1971 CE to 30 ka), a strategy applicable for future ice cores; and (3) the observation of a continuous climate record back to ∼65 ka providing evidence that the Roosevelt Island Ice Dome was a constant feature throughout the last glacial period.

Published
2020

15. Global environmental consequences of 21st century ice sheet melt

Author

Golledge, Nicholas R, Keller, Elizabeth D, Gomez, Natalya, Naughten, Kaitlin, Bernales, Jorge, Trusel, Luke D, and Edwards, Tamsin L

Abstract

Government policies currently commit us to surface warming of three to four degrees Celsius above pre-industrial levels by 2100, which will lead to enhanced ice-sheet melt. Ice-sheet discharge was not explicitly included in Coupled Model Intercomparison Project phase 5, so effects on climate from this melt are not currently captured in the simulations most commonly used to inform governmental policy. Here we show, using simulations of the Greenland and Antarctic ice sheets constrained by satellite-based measurements of recent changes in ice mass, that increasing meltwater from Greenland will lead to substantial slowing of the Atlantic overturning circulation, and that meltwater from Antarctica will trap warm water below the sea surface, creating a positive feedback that increases Antarctic ice loss. In our simulations, future ice-sheet melt enhances global temperature variability and contributes up to 25 centimetres to sea level by 2100. However, uncertainties in the way in which future changes in ice dynamics are modelled remain, underlining the need for continued observations and comprehensive multi-model assessments.

Published
2019

16. A 2700-year annual timescale and accumulation history for an ice core from Roosevelt Island, West Antarctica

Author

Winstrup, Mai, primary, Vallelonga, Paul, additional, Kjær, Helle A., additional, Fudge, Tyler J., additional, Lee, James E., additional, Riis, Marie H., additional, Edwards, Ross, additional, Bertler, Nancy A. N., additional, Blunier, Thomas, additional, Brook, Ed J., additional, Buizert, Christo, additional, Ciobanu, Gabriela, additional, Conway, Howard, additional, Dahl-Jensen, Dorthe, additional, Ellis, Aja, additional, Emanuelsson, B. Daniel, additional, Hindmarsh, Richard C. A., additional, Keller, Elizabeth D., additional, Kurbatov, Andrei V., additional, Mayewski, Paul A., additional, Neff, Peter D., additional, Pyne, Rebecca L., additional, Simonsen, Marius F., additional, Svensson, Anders, additional, Tuohy, Andrea, additional, Waddington, Edwin D., additional, and Wheatley, Sarah, additional

Published
2019
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17. A 2700-year annual timescale and accumulation history for an ice core from Roosevelt Island, West Antarctica

Author

Winstrup, Mai, Vallelonga, Paul, Kjær, Helle A., Fudge, Tyler J., Lee, James E., Riis, Marie H., Edwards, Ross, Bertler, Nancy A.N., Blunier, Thomas, Brook, Ed J., Buizert, Christo, Ciobanu, Gabriela, Conway, Howard, Dahl-Jensen, Dorthe, Ellis, Aja, Emanuelsson, B. Daniel, Hindmarsh, Richard C.A., Keller, Elizabeth D., Kurbatov, Andrei V., Mayewski, Paul A., Neff, Peter D., Pyne, Rebecca L., Simonsen, Marius F., Svensson, Anders, Tuohy, Andrea, Waddington, Edwin D., Wheatley, Sarah, Winstrup, Mai, Vallelonga, Paul, Kjær, Helle A., Fudge, Tyler J., Lee, James E., Riis, Marie H., Edwards, Ross, Bertler, Nancy A.N., Blunier, Thomas, Brook, Ed J., Buizert, Christo, Ciobanu, Gabriela, Conway, Howard, Dahl-Jensen, Dorthe, Ellis, Aja, Emanuelsson, B. Daniel, Hindmarsh, Richard C.A., Keller, Elizabeth D., Kurbatov, Andrei V., Mayewski, Paul A., Neff, Peter D., Pyne, Rebecca L., Simonsen, Marius F., Svensson, Anders, Tuohy, Andrea, Waddington, Edwin D., and Wheatley, Sarah

Abstract

ice core, Ross Ice Shelf, West Antarctica. The core adds information on past accumulation changes in an otherwise poorly constrained sector of Antarctica. The timescale was constructed by identifying annual cycles in high-resolution impurity records, and it constitutes the top part of the Roosevelt Island Ice Core Chronology 2017 (RICE17). Validation by volcanic and methane matching to the WD2014 chronology from the WAIS Divide ice core shows that the two timescales are in excellent agreement. In a companion paper, gas matching to WAIS Divide is used to extend the timescale for the deeper part of the core in which annual layers cannot be identified. Based on the annually resolved timescale, we produced a record of past snow accumulation at Roosevelt Island. The accumulation history shows that Roosevelt Island experienced slightly increasing accumulation rates between 700 BCE and 1300 CE, with an average accumulation of 0.25±0.02 m water equivalent (w.e.) per year. Since 1300 CE, trends in the accumulation rate have been consistently negative, with an acceleration in the rate of decline after the mid-17th century. The current accumulation rate at Roosevelt Island is 0.210±0.002 m w.e. yr−1 (average since 1965 CE, ±2σ), and it is rapidly declining with a trend corresponding to 0.8 mm yr−2. The decline observed since the mid-1960s is 8 times faster than the long-term decreasing trend taking place over the previous centuries, with decadal mean accumulation rates consistently being below average. Previous research has shown a strong link between Roosevelt Island accumulation rates and the location and intensity of the Amundsen Sea Low, which has a significant impact on regional sea-ice extent. The decrease in accumulation rates at Roosevelt Island may therefore be explained in terms of a recent strengthening of the ASL and the expansion of sea ice in the eastern Ross Sea. The start of the rapid decrease in RICE accumulation rates observed in 1965 CE may thus mark the ons

Published
2019

18. Back to the Future: Using Long-Term Observational and Paleo-Proxy Reconstructions to Improve Model Projections of Antarctic Climate

Author

Sub Dynamics Meteorology, Marine and Atmospheric Research, Bracegirdle, Thomas J., Colleoni, Florence, Abram, Nerilie J., Bertler, Nancy A. N., Dixon, Daniel A., England, Mark, Favier, Vincent, Fogwill, Chris J., Fyfe, John C., Goodwin, Ian, Goosse, Hugues, Hobbs, Will, Jones, Julie M., Keller, Elizabeth D., Khan, Alia L., Phipps, Steven J., Raphael, Marilyn N., Russell, Joellen, Sime, Louise, Thomas, Elizabeth R., van den Broeke, Michiel R., Wainer, Ilana, Sub Dynamics Meteorology, Marine and Atmospheric Research, Bracegirdle, Thomas J., Colleoni, Florence, Abram, Nerilie J., Bertler, Nancy A. N., Dixon, Daniel A., England, Mark, Favier, Vincent, Fogwill, Chris J., Fyfe, John C., Goodwin, Ian, Goosse, Hugues, Hobbs, Will, Jones, Julie M., Keller, Elizabeth D., Khan, Alia L., Phipps, Steven J., Raphael, Marilyn N., Russell, Joellen, Sime, Louise, Thomas, Elizabeth R., van den Broeke, Michiel R., and Wainer, Ilana

Published
2019

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

Author

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, Zhang, X, Bertler, Nancy A. N., Conway, Howard, Dahl-Jensen, Dorthe, Emanuelsson, Daniel B., Winstrup, Mai, Vallelonga, Paul T., Lee, James E., Brook, Ed J., Severinghaus, Jeffrey P., Fudge, Taylor J., Keller, Elizabeth D., Troy Baisden, W., Hindmarsh, Richard C. A., Neff, Peter D., Blunier, Thomas, Edwards, Ross, Mayewski, Paul A., Kipfstuhl, Sepp, Buizert, Christo, Canessa, Silvia, Dadic, Ruzica, Kjær, Helle A., Kurbatov, Andrei, Zhang, Dongqi, Waddington, Edwin D., Baccolo, Giovanni, Beers, Thomas, Brightley, Hannah J., Carter, Lionel, Clemens-Sewall, David, Ciobanu, Viorela G., Delmonte, Barbara, Eling, Lukas, Ellis, Aja, Ganesh, Shruthi, Golledge, Nicholas R., Haines, Skylar, Handley, Michael, Hawley, Robert L., Hogan, Chad M., Johnson, Katelyn M., Korotkikh, Elena, Lowry, Daniel P., Mandeno, Darcy, McKay, Robert M., Menking, James A., Naish, Timothy R., Noerling, Caroline, Ollive, Agathe, Orsi, Anaïs, Proemse, Bernadette C., Pyne, Alexander R., Pyne, Rebecca L., Renwick, James, Scherer, Reed P., Semper, Stefanie, Simonsen, Marius, Sneed, Sharon B., Steig, Eric J., Tuohy, Andrea, Ulayottil Venugopal, Abhijith, Valero-Delgado, Fernando, Venkatesh, Janani, Wang, Feitang, Wang, Shimeng, Winski, Dominic A., Holly, Winton, Whiteford, Arran, Xiao, Cunde, Yang, Jiao, Zhang, Xin, 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, Zhang, X, Bertler, Nancy A. N., Conway, Howard, Dahl-Jensen, Dorthe, Emanuelsson, Daniel B., Winstrup, Mai, Vallelonga, Paul T., Lee, James E., Brook, Ed J., Severinghaus, Jeffrey P., Fudge, Taylor J., Keller, Elizabeth D., Troy Baisden, W., Hindmarsh, Richard C. A., Neff, Peter D., Blunier, Thomas, Edwards, Ross, Mayewski, Paul A., Kipfstuhl, Sepp, Buizert, Christo, Canessa, Silvia, Dadic, Ruzica, Kjær, Helle A., Kurbatov, Andrei, Zhang, Dongqi, Waddington, Edwin D., Baccolo, Giovanni, Beers, Thomas, Brightley, Hannah J., Carter, Lionel, Clemens-Sewall, David, Ciobanu, Viorela G., Delmonte, Barbara, Eling, Lukas, Ellis, Aja, Ganesh, Shruthi, Golledge, Nicholas R., Haines, Skylar, Handley, Michael, Hawley, Robert L., Hogan, Chad M., Johnson, Katelyn M., Korotkikh, Elena, Lowry, Daniel P., Mandeno, Darcy, McKay, Robert M., Menking, James A., Naish, Timothy R., Noerling, Caroline, Ollive, Agathe, Orsi, Anaïs, Proemse, Bernadette C., Pyne, Alexander R., Pyne, Rebecca L., Renwick, James, Scherer, Reed P., Semper, Stefanie, Simonsen, Marius, Sneed, Sharon B., Steig, Eric J., Tuohy, Andrea, Ulayottil Venugopal, Abhijith, Valero-Delgado, Fernando, Venkatesh, Janani, Wang, Feitang, Wang, Shimeng, Winski, Dominic A., Holly, Winton, Whiteford, Arran, Xiao, Cunde, Yang, Jiao, and Zhang, Xin

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
2018

22. The Ross Sea Dipole - temperature, snow accumulation and sea ice variability in the Ross Sea region, Antarctica, over the past 2700 Years

Author

Bertler, Nancy A.N., Conway, Howard, Dahl-Jensen, Dorthe, Emanuelsson, Daniel B., Winstrup, Mai, Vallelonga, Paul T., Lee, James E., Brook, Ed J., Severinghaus, Jeffrey P., Fudge, Taylor J., Keller, Elizabeth D., Baisden, W. Troy, Hindmarsh, Richard C.A., Neff, Peter D., Blunier, Thomas, Edwards, Ross, Mayewski, Paul A., Kipfstuhl, Sepp, Buizert, Christo, Canessa, Silvia, Dadic, Ruzica, Kjær, Helle A., Kurbatov, Andrei, Zhang, Dongqi, Waddington, Ed D., Baccolo, Giovanni, Beers, Thomas, Brightley, Hannah J., Carter, Lionel, Clemens-Sewall, David, Ciobanu, Viorela G., Delmonte, Barbara, Eling, Lukas, Ellis, Aja A., Ganesh, Shruthi, Golledge, Nicholas R., Haines, Skylar A., Handley, Michael, Hawley, Robert L., Hogan, Chad M., Johnson, Katelyn M., Korotkikh, Elena, Lowry, Daniel P., Mandeno, Darcy, McKay, Robert M., Menking, James A., Naish, Timothy R., Noerling, Caroline, Ollive, Agathe, Orsi, Anaïs, Proemse, Bernadette C., Pyne, Alexander R., Pyne, Rebecca L., Renwick, James, Scherer, Reed P., Semper, Stefanie, Simonsen, Marius, Sneed, Sharon B., Steig, Eric J., Tuohy, Andrea, Ulayottil Venugopal, Abhijith, Valero-Delgado, Fernando, Venkatesh, Janani, Wang, Feitang, Wang, Shimeng, Winski, Dominic A., Winton, Victoria H.L., Whiteford, Arran, Xiao, Cunde, Yang, Jiao, Zhang, Xin, Bertler, Nancy A.N., Conway, Howard, Dahl-Jensen, Dorthe, Emanuelsson, Daniel B., Winstrup, Mai, Vallelonga, Paul T., Lee, James E., Brook, Ed J., Severinghaus, Jeffrey P., Fudge, Taylor J., Keller, Elizabeth D., Baisden, W. Troy, Hindmarsh, Richard C.A., Neff, Peter D., Blunier, Thomas, Edwards, Ross, Mayewski, Paul A., Kipfstuhl, Sepp, Buizert, Christo, Canessa, Silvia, Dadic, Ruzica, Kjær, Helle A., Kurbatov, Andrei, Zhang, Dongqi, Waddington, Ed D., Baccolo, Giovanni, Beers, Thomas, Brightley, Hannah J., Carter, Lionel, Clemens-Sewall, David, Ciobanu, Viorela G., Delmonte, Barbara, Eling, Lukas, Ellis, Aja A., Ganesh, Shruthi, Golledge, Nicholas R., Haines, Skylar A., Handley, Michael, Hawley, Robert L., Hogan, Chad M., Johnson, Katelyn M., Korotkikh, Elena, Lowry, Daniel P., Mandeno, Darcy, McKay, Robert M., Menking, James A., Naish, Timothy R., Noerling, Caroline, Ollive, Agathe, Orsi, Anaïs, Proemse, Bernadette C., Pyne, Alexander R., Pyne, Rebecca L., Renwick, James, Scherer, Reed P., Semper, Stefanie, Simonsen, Marius, Sneed, Sharon B., Steig, Eric J., Tuohy, Andrea, Ulayottil Venugopal, Abhijith, Valero-Delgado, Fernando, Venkatesh, Janani, Wang, Feitang, Wang, Shimeng, Winski, Dominic A., Winton, Victoria H.L., Whiteford, Arran, Xiao, Cunde, Yang, Jiao, and Zhang, Xin

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. Comparison of the Roosevelt Island Climate Evolution (RICE) ice core records with climate reanalysis data for the 1979–2012 calibration period shows that RICE records reliably capture temperature and snow precipitation variability of the region. RICE is compared with data from West Antarctica (West Antarctic Ice Sheet Divide Ice Core) and the western (Talos Dome) and eastern (Siple Dome) Ross Sea. For most of the past 2,700 years, the eastern Ross Sea was warming with perhaps increased snow accumulation and decreased sea ice extent. However, West Antarctica cooled whereas the western Ross Sea showed no significant temperature trend. From the 17th Century onwards, this relationship changes. All three regions now show signs of warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea, but increasing in the western Ross Sea. Analysis of decadal to centennial-scale climate variability superimposed on the longer term trend reveal that periods characterised by opposing temperature trends between the Eastern and Western Ross Sea have occurred since the 3rd Century but are masked by longer-term trends. This pattern here is referred to as the Ross Sea Dipole, caused by a sensitive response of the region to dynamic interactions of the Southern Annual Mode and tropical forcings.

Published
2018

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

Author

Bertler, Nancy A. N., Conway, Howard, Dahl-Jensen, Dorthe, Emanuelsson, Daniel B., Winstrup, Mai, Vallelonga, Paul T., Lee, James E., Brook, Ed J., Severinghaus, Jeffrey P., Fudge, Taylor J., Keller, Elizabeth D., Baisden, W. Troy, Hindmarsh, Richard C. A., Neff, Peter D., Blunier, Thomas, Edwards, Ross, Mayewski, Paul A., Kipfstuhl, Sepp, Buizert, Christo, Canessa, Silvia, Dadic, Ruzica, Kjaer, Helle A., Kurbatov, Andrei, Zhang, Dongqi, Waddington, Edwin D., Baccolo, Giovanni, Beers, Thomas, Brightley, Hannah J., Carter, Lionel, Clemens-Sewall, David, Ciobanu, Viorela G., Delmonte, Barbara, Eling, Lukas, Ellis, Aja, Ganesh, Shruthi, Golledge, Nicholas R., Haines, Skylar, Handley, Michael, Hawley, Robert L., Hogan, Chad M., Johnson, Katelyn M., Korotkikh, Elena, Lowry, Daniel P., Mandeno, Darcy, McKay, Robert M., Menking, James A., Naish, Timothy R., Noerling, Caroline, Simonsen, Marius, Wang, Shimeng, Bertler, Nancy A. N., Conway, Howard, Dahl-Jensen, Dorthe, Emanuelsson, Daniel B., Winstrup, Mai, Vallelonga, Paul T., Lee, James E., Brook, Ed J., Severinghaus, Jeffrey P., Fudge, Taylor J., Keller, Elizabeth D., Baisden, W. Troy, Hindmarsh, Richard C. A., Neff, Peter D., Blunier, Thomas, Edwards, Ross, Mayewski, Paul A., Kipfstuhl, Sepp, Buizert, Christo, Canessa, Silvia, Dadic, Ruzica, Kjaer, Helle A., Kurbatov, Andrei, Zhang, Dongqi, Waddington, Edwin D., Baccolo, Giovanni, Beers, Thomas, Brightley, Hannah J., Carter, Lionel, Clemens-Sewall, David, Ciobanu, Viorela G., Delmonte, Barbara, Eling, Lukas, Ellis, Aja, Ganesh, Shruthi, Golledge, Nicholas R., Haines, Skylar, Handley, Michael, Hawley, Robert L., Hogan, Chad M., Johnson, Katelyn M., Korotkikh, Elena, Lowry, Daniel P., Mandeno, Darcy, McKay, Robert M., Menking, James A., Naish, Timothy R., Noerling, Caroline, Simonsen, Marius, and Wang, Shimeng

Published
2018

24. Precipitation isoscapes for New Zealand: enhanced temporal detail using precipitation-weighted daily climatology†

Author

W. Troy Baisden, Keller, Elizabeth D., Hale, Robert Van, Frew, Russell D., and Wassenaar, Leonard I.

Abstract

Predictive understanding of precipitation δ2H and δ18O in New Zealand faces unique challenges, including high spatial variability in precipitation amounts, alternation between subtropical and sub-Antarctic precipitation sources, and a compressed latitudinal range of 34 to 47 °S. To map the precipitation isotope ratios across New Zealand, three years of integrated monthly precipitation samples were acquired from >50 stations. Conventional mean-annual precipitation δ2H and δ18O maps were produced by regressions using geographic and annual climate variables. Incomplete data and short-term variation in climate and precipitation sources limited the utility of this approach. We overcome these difficulties by calculating precipitation-weighted monthly climate parameters using national 5-km-gridded daily climate data. This data plus geographic variables were regressed to predict δ2H, δ18O, and d-excess at all sites. The procedure yields statistically-valid predictions of the isotope composition of precipitation (long-term average root mean square error (RMSE) for δ18O = 0.6 ‰; δ2H = 5.5 ‰); and monthly RMSE δ18O = 1.9 ‰, δ2H = 16 ‰. This approach has substantial benefits for studies that require the isotope composition of precipitation during specific time intervals, and may be further improved by comparison to daily and event-based precipitation samples as well as the use of back-trajectory calculations.

Published
2016
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25. The Ross Sea Dipole – Temperature, Snow Accumulation and Sea Ice Variability in the Ross Sea Region, Antarctica, over the Past 2,700 Years

Author

Bertler, Nancy A. N., Conway, Howard, Dahl-Jensen, Dorthe, Emanuelsson, Daniel B., Winstrup, Mai, Vallelonga, Paul T., Lee, James E., Brook, Ed J., Severinghaus, Jeffrey P., Fudge, Taylor J., Keller, Elizabeth D., Baisden, W. Troy, Hindmarsh, Richard C. A., Neff, Peter D., Blunier, Thomas, Edwards, Ross, Mayewski, Paul A., Kipfstuhl, Sepp, Buizert, Christo, Canessa, Silvia, Dadic, Ruzica, Kjær, Helle A., Kurbatov, Andrei, Zhang, Dongqi, Waddington, Ed D., Baccolo, Giovanni, Beers, Thomas, Brightley, Hannah J., Carter, Lionel, Clemens-Sewall, David, Ciobanu, Viorela G., Delmonte, Barbara, Eling, Lukas, Ellis, Aja A., Ganesh, Shruthi, Golledge, Nicholas R., Haines, Skylar A., Handley, Michael, Hawley, Robert L., Hogan, Chad M., Johnson, Katelyn M., Korotkikh, Elena, Lowry, Daniel P., Mandeno, Darcy, McKay, Robert M., Menking, James A., Naish, Timothy R., Noerling, Caroline, Ollive, Agathe, Orsi, Anaïs, Proemse, Bernadette C., Pyne, Alexander R., Pyne, Rebecca L., Renwick, James, Scherer, Reed P., Semper, Stefanie, Simonsen, Marius, Sneed, Sharon B., Steig, Eric J., Tuohy, Andrea, Venugopal, Abhijith Ulayottil, Valero-Delgado, Fernando, Venkatesh, Janani, Wang, Feitang, Wang, Shimeng, Winski, Dominic A., Winton, Victoria H. L., Whiteford, Arran, Xiao, Cunde, Yang, Jiao, Zhang, Xin, Bertler, Nancy A. N., Conway, Howard, Dahl-Jensen, Dorthe, Emanuelsson, Daniel B., Winstrup, Mai, Vallelonga, Paul T., Lee, James E., Brook, Ed J., Severinghaus, Jeffrey P., Fudge, Taylor J., Keller, Elizabeth D., Baisden, W. Troy, Hindmarsh, Richard C. A., Neff, Peter D., Blunier, Thomas, Edwards, Ross, Mayewski, Paul A., Kipfstuhl, Sepp, Buizert, Christo, Canessa, Silvia, Dadic, Ruzica, Kjær, Helle A., Kurbatov, Andrei, Zhang, Dongqi, Waddington, Ed D., Baccolo, Giovanni, Beers, Thomas, Brightley, Hannah J., Carter, Lionel, Clemens-Sewall, David, Ciobanu, Viorela G., Delmonte, Barbara, Eling, Lukas, Ellis, Aja A., Ganesh, Shruthi, Golledge, Nicholas R., Haines, Skylar A., Handley, Michael, Hawley, Robert L., Hogan, Chad M., Johnson, Katelyn M., Korotkikh, Elena, Lowry, Daniel P., Mandeno, Darcy, McKay, Robert M., Menking, James A., Naish, Timothy R., Noerling, Caroline, Ollive, Agathe, Orsi, Anaïs, Proemse, Bernadette C., Pyne, Alexander R., Pyne, Rebecca L., Renwick, James, Scherer, Reed P., Semper, Stefanie, Simonsen, Marius, Sneed, Sharon B., Steig, Eric J., Tuohy, Andrea, Venugopal, Abhijith Ulayottil, Valero-Delgado, Fernando, Venkatesh, Janani, Wang, Feitang, Wang, Shimeng, Winski, Dominic A., Winton, Victoria H. L., Whiteford, Arran, Xiao, Cunde, Yang, Jiao, and Zhang, Xin

Published
2017

29. A 2700-year annual timescale and accumulation history for an ice core from Roosevelt Island, West Antarctica.

Author

Winstrup, Mai, Vallelonga, Paul, Kjær, Helle A., Fudge, Tyler J., Lee, James E., Riis, Marie H., Edwards, Ross, Bertler, Nancy A. N., Blunier, Thomas, Brook, Ed J., Buizert, Christo, Ciobanu, Gabriela, Conway, Howard, Dahl-Jensen, Dorthe, Ellis, Aja, Daniel Emanuelsson, B., Keller, Elizabeth D., Kurbatov, Andrei, Mayewski, Paul, and Neff, Peter D.

Abstract

We present a 2700-year annually resolved timescale for the Roosevelt Island Climate Evolution (RICE) ice core, and reconstruct a past snow accumulation history for the coastal sector of the Ross Ice Shelf in West Antarctica. The timescale was constructed by identifying annual layers in multiple ice-core impurity records, employing both manual and automated counting approaches, and constitutes the top part of the Roosevelt Island Ice Core Chronology 2017 (RICE17). The maritime setting of Roosevelt Island results in high sulfate influx from sea salts and marine biogenic emissions, which prohibits a routine detection of volcanic eruptions in the ice-core records. This led to the use of non-traditional chronological techniques for validating the timescale: RICE was synchronized to the WAIS Divide ice core, on the WD2014 timescale, using volcanic attribution based on direct measurements of ice-core acidity, as well as records of globally-synchronous, centennial-scale variability in atmospheric methane concentrations. The RICE accumulation history suggests stable values of 0.25m water equivalent (w.e.) per year until around 1260CE. Uncertainties in the correction for ice flow thinning of annual layers with depth do not allow a firm conclusion about long-term trends in accumulation rates during this early period but from 1260CE to the present, accumulation rate trends have been consistently negative. The decrease in accumulation rates has been increasingly rapid over the last centuries, with the decrease since 1950 CE being more than 7 times greater than the average over the last 300 years. The current accumulation rate of 0.22±0.06mw.e.yr-1 (average since 1950CE, ±1σ) is 1.49 standard deviations (86th percentile) below the mean of 50-year average accumulation rates observed over the last 2700 years. [ABSTRACT FROM AUTHOR]

Published
2017
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30. Atmospheric CO2 observations and models suggest strong carbon uptake by forests in New Zealand.

Author

Steinkamp, Kay, Mikaloff Fletcher, Sara E., Brailsford, Gordon, Smale, Dan, Moore, Stuart, Keller, Elizabeth D., Baisden, W. Troy, Hitoshi Mukai, and Stephens, Britton B.

Subjects
ATMOSPHERIC carbon dioxide, FORESTS & forestry, DISPERSION (Atmospheric chemistry), ATMOSPHERIC models, WEATHER forecasting, PHOTOSYNTHETIC rates
Abstract

A regional atmospheric inversion method has been developed to determine the spatial and temporal distribution of CO2 sinks and sources across New Zealand for 2011- 2013. This approach infers net air-sea and air-land CO2 fluxes from measurement records, using back-trajectory simulations from the Numerical Atmospheric dispersion Modelling Environment (NAME) Lagrangian dispersion model, driven by meteorology from the New Zealand Limited Area Model (NZLAM) weather prediction model. The inversion uses in situ measurements from two fixed sites, Baring Head on the southern tip of New Zealand's North Island (41.408- S, 174.871- E) and Lauder from the central South Island (45.038- S, 169.684- E), and ship board data from monthly cruises between Japan, New Zealand, and Australia. A range of scenarios is used to assess the sensitivity of the inversion method to underlying assumptions and to ensure robustness of the results. The results indicate a strong seasonal cycle in terrestrial land fluxes from the South Island of New Zealand, especially in western regions covered by indigenous forest, suggesting higher photosynthetic and respiratory activity than is evident in the current a priori land process model. On the annual scale, the terrestrial biosphere in New Zealand is estimated to be a net CO2 sink, removing 98 (-37) TgCO2 yr-1 from the atmosphere on average during 2011-2013. This sink is much larger than the reported 27 TgCO2 yr-1 from the national inventory for the same time period. The difference can be partially reconciled when factors related to forest and agricultural management and exports, fossil fuel emission estimates, hydrologic fluxes, and soil carbon change are considered, but some differences are likely to remain. Baseline uncertainty, model transport uncertainty, and limited sensitivity to the northern half of the North Island are the main contributors to flux uncertainty. [ABSTRACT FROM AUTHOR]

Published
2017
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31. Independent evaluation of point source fossil fuel CO2 emissions to better than 10%.

Author

Turnbull, Jocelyn Christine, Keller, Elizabeth D., Norris, Margaret W., and Wiltshire, Rachael M.

Subjects
*CARBON dioxide mitigation, *FOSSIL fuels, *POINT sources (Pollution), *EMISSION control, *CARBON isotopes, *ATMOSPHERIC transport, *FOSSIL fuel power plants
Abstract

Independent estimates of fossil fuel CO2 (CO2ff) emissions are key to ensuring that emission reductions and regulations are effective and provide needed transparency and trust. Point source emissions are a key target because a small number of power plants represent a large portion of total global emissions. Currently, emission rates are known only from self-reported data. Atmospheric observations have the potential tomeet the need for independent evaluation, but useful results from this method have been elusive, due to challenges in distinguishing CO2ff emissions from the large and varying CO2 background and in relating atmospheric observations to emission flux rates with high accuracy. Here we use time-integrated observations of the radiocarbon content of CO2 (14CO2) to quantify the recently added CO2ff mole fraction at surface sites surrounding a point source. We demonstrate that both fast-growing plant material (grass) and CO2 collected by absorption into sodium hydroxide solution provide excellent time-integrated records of atmospheric 14CO2. These timeintegrated samples allow us to evaluate emissions over a period of days to weeks with only a modest number of measurements. Applying the same time integration in an atmospheric transport model eliminates the need to resolve highly variable short-term turbulence. Together these techniques allow us to independently evaluate point source CO2ff emission rates from atmospheric observations with uncertainties of better than 10%. This uncertainty represents an improvement by a factor of 2 over current bottom-up inventory estimates and previous atmospheric observation estimates and allows reliable independent evaluation of emissions. [ABSTRACT FROM AUTHOR]

Published
2016
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32. Detecting long-term changes in point-source fossil CO2 emissions with tree ring archives.

Author

Keller, Elizabeth D., Turnbull, Jocelyn C., and Norris, Margaret W.

Subjects
POINT sources (Pollution), FOSSIL fuels, CARBON dioxide & the environment, EMISSIONS (Air pollution), TREE-rings
Abstract

We examine the utility of tree ring 14C archives for detecting long-term changes in fossil CO2 emissions from a point source. Trees assimilate carbon from the atmosphere during photosynthesis, in the process faithfully recording the average atmospheric 14C content in each new annual tree ring. Using 14C as a proxy for fossil CO2, we examine interannual variability over six years of fossil CO2 observations between 2004-2005 and 2011-2012 from two trees growing near the Kapuni Gas Treatment Plant in rural Taranaki, New Zealand. We quantify the amount of variability that can be attributed to transport and meteorology by simulating constant point-source fossil CO2 emissions over the observation period with the atmospheric transport model WindTrax. We compare model simulation results to observations and calculate the amount of change in emissions that we can detect with new observations over annual or multi-year time periods, given both the measurement uncertainty of 1ppm and the modelled variation in transport. In particular, we ask, what is the minimum amount of change in emissions that we can detect using this method, given a reference period of six years? We find that changes of 42% or more could be detected in a new sample from one year at the same observation location or 22% in the case of four years of new samples. This threshold is reduced and the method becomes more practical the more the size of the signal increases. For point sources 10 times larger than the Kapuni plant (a more typical size for power plants worldwide), it would be possible to detect sustained emissions changes on the order of 10%, given suitable meteorology and observations. [ABSTRACT FROM AUTHOR]

Published
2016
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