Dr. Paul Aharon

Paul Aharon

Professor|Ray E. Loper Endowed Chair in Geology

paharon@ua.edu
(205) 348-0818
2023 Bevill

Education

BS, The Hebrew University of Jerusalem (HUJ), Israel, 1972

MS, The Hebrew University of Jerusalem (HUJ), Israel, 1974

PhD, The Australian National University (ANU), Canberra, Australia, 1980

Post-Doctoral, Queen’s Fellow in Marine Sciences, Research School of Earth Sciences (RSES), The Australian National University (ANU), Canberra, Australia, 1980-1982

Research Interests

My research addresses questions of broad geologic implications concerning changing Earth Systems through time. The research tools are primarily light stable isotopes, radioactive isotopes, trace metals and some of their heavy stable isotopes that allow greater capability to exploit marine and land-based sediments as high-resolution geologic archives. These archives contain the records of present and past changes of atmosphere, ocean, land, climate and biota and their complex interactions. Retrieval of these records requires skill, understanding of their geologic context, and development of archive-specific proxies. The proxy records are essential for improving our ability to understand variability and determine their societal impacts and vulnerability.

Current Research Projects

1. El-Niño/Southern Oscillation (ENSO)-Controlled Rainfall Variability Records Archived in Tropical Stalagmites from the Mid-Ocean Island of Niue, South Pacific

Objectives of the Study:

ENSO is an ocean and atmosphere coupling phenomenon occurring in the tropical Pacific, and is presently the main energy source and sink of global climate variability whose periodicity ranges from 2.4 to 6 years. Records of past and present climate variability from the tropical Pacific region directly impacted by ENSO were derived so far only from corals via sea-surface temperature proxies. Living corals, however, offer records whose continuity is limited to few centuries at best, and there are only fragmentary records further back in time.
The principal objective of this study is to acquire continuous high-resolution proxy rainfall records from stalagmites in caves located on the island of Niue in the Southwest Tropical Pacific whose annual and multi-decadal rainfall variability is directly controlled by the ENSO phenomenon. Stalagmites offer the advantage of continuous long-lived archives of ENSO-controlled atmosphere variability, and fill an essential gap in our understanding of the coupled ocean-atmosphere interaction. The “Pacific” team working with me on the project consists of three PhDs (Mike Rasbury; Val Murgulet; Montana Puscas) and two undergraduate majors (Lane Lambert and Gwendolyn M. Yaden).

Questions Addressed in the Ongoing Study:

(i) How different are the ambient conditions and stalagmite deposition styles in flank-margin and phreatic caves? How does dripwater chemistry compare with that of rainfall and the island phreatic lens? What is the crystal fabric and petrography of the layered stalagmites?
(ii) Are the past two centuries climate proxy records in the stalagmites matching contemporaneous ENSO instrumental records?
(iii) Were there ENSO periodicity and intensity shifts during known cold (e.g., Little Ice Age, Early Medieval Cold Event) and warm (Medieval Warm Period) episodes of the past two millennia? How did these shifts affect the fall and rise of contemporaneous civilizations?
(iv) Did sub-orbital climate forcing factors (e.g., solar variability, cosmic rays; volcanic activity, forest fires) play a role in the documented climate shifts of the past two millennia?
(iv) Do stalagmites forming in the flank-margin caves contain the imprints of catastrophic cyclones in their trace metal chemistry?
(v) Was ENSO shut down during past glaciation/interglaciation transitions?

2. Investigation of abrupt climate events in the Southeastern USA and Gulf Coast during the last glaciation maximum (LGM) and the last deglaciation from stalagmites in the DeSoto Cave, Alabama

Objectives of the Study

The detailed history of the North American Laurentide Ice Sheet (LIS) in the last glacial cycle is a subject of considerable interest because its growth and decay was punctuated by abrupt climate shifts whose controlling factors are subject of heated debate. The DeSoto Cave is conveniently located between the Gulf of Mexico, one of the principal sources of moisture feeding the ice sheet, and LIS, and as such it has intercepted the changes in the atmospheric circulation occurring during the transition between the glacial and interglacial modes.
Working with me on the DeSoto project is PhD student Joe Lambert and our objectives are as follows:
(i) Acquisition of a multi-year record of rainfall and dripwater oxygen, carbon and hydrogen isotope compositions at the cave site.
(ii) Dripwater rate automated monitoring and its relation to rainfall amount.
(iii) Development of climate proxies in stalagmites spanning the LGM and last deglaciation and containing an expanded interval of the Younger Dryas (YD) cold event that has recently been the subject of renewed interest and speculation about its cause/s.

3. A study of marine-based gas hydrate dissociation event in the Mediterranean during the end-Miocene interval.

Objective of Study

Recent investigations of end-Miocene age sediments in the Mediterranean satellite basins (e.g., Sorba Basin in Spain) have suggested that a gas-hydrate dissociation event occurred there during the pre-evaporitic Messinian stage. In collaboration with Italian geoscientists we are testing the hypothesis that tectonic upheaval during the marine Messinian led to destabilization of gas hydrates in the Vena-del-Gesso basin of northern Italy that left marks in the alternating euxinic shales/carbonate layers outcropping there. Working with me on this project is PhD student Sandip Bordoloi. The study forms a part of Sandip’s recently completed dissertation and consists of:

(i) Petrography, petrology and isotope geochemistry of the limestone units.

(ii) Up-section distribution of macro and micro fossil fauna.

(iii) Trace-metal geochemistry that is diagnostic of anoxic- environments in the black shales.

(iv) Biomarkers of AMO/BSR (Anaerobic Methane Oxidation/

Bacterial Sulfate Reduction) in the intercalated euxinic shales.

Representative Publications

In Peer-Reviewed Journals (Asterisk denotes student author)

*W. Joe Lambert, Paul Aharon and Antonio B. Rodriguez. Catastrophic Hurricane History by Organic Geochemical Proxies in Coastal Lake Sediments: A Case Study of Lake Shelby, Alabama (USA). J. Paleolimnology, 39: 117-131, doi: 10.1007/ s10933-007- 9101-6 (2008)

Williams, M., Talbot, M., Aharon, P., Abdl Salaam, Y., Williams, F., and Brendeland, K. I. Abrupt return of the summer monsoon 15,000 years ago: New supporting evidence from the lower White Nile valley and Lake Albert. Quat. Sci. Rev. 25: 2651-1665 (2006)

*Rasbury, M. and Aharon, P. ENSO-controlled rainfall variability records archived in tropical stalagmites from the mid-ocean island of Niue, South Pacific. Geochemistry, Geophysics, Geosystems, v. 7 (7), doi: 10.1029/2005GC001232 (2006)

Aharon, P., *Rasbury M., *Murgulet, V. Caves of Niue island, South Pacific: Speleothems and Water Chemistry. In Harmon, R. S. and Wicks, C. (eds.), Perspectives on Karst Geomorphology, Hydrology and Geochemistry-A tribute volume to Derek C. Ford and William B. White. Geol. Soc. of Am. Spec. Paper 404, Chapter 24, doi: 10.1130/2006.2404 (24) (2006)

Aharon, P. Entrainment of meltwaters in hyperpycnal flows during deglaciation superfloods in the Gulf of Mexico. Earth and Planetary Science Letters 241: 260-270 (2006)
Aharon, P.. Redox stratification and anoxia of the early Precambrian oceans: Implications for carbon isotope excursions and oxidation events. Precambrian Research 137: 207-222 (2005)

Peckmann, J., Thiel, V., Reitner, J., Taviani, M., Aharon, P. and Michaelis, W. A microbial mat of a large sulfur bacterium preserved in a Miocene methane-seep limestone. Geomicrobiology Journal 21: 247-255 (2004)

*Lambert, W. J., Aharon, P. and Rodriguez, A. B. An assessment of the late Holocene record of severe storm impacts from Lake Shelby, Alabama. GCAGS Trans. 53: 443-452 (2003)

Aharon, P. Is drilling in deepwater Gulf of Mexico uncorking bad genies? GCAGS Trans. 53: 1-10 (2003)

Aharon, P. Meltwater flooding events in the Gulf of Mexico revisited: Implications for rapid climate changes during the last deglaciation. Paleoceanography 18 (4), 1079, doi: 1029/2002PA000840: 3-1 to 3-14 (2003)

Van Dover, C. L., Aharon, P. and 17 co-authors. Blake Ridge methane seeps: Characterization of a soft sediment, chemosynthetically based ecosystem. Deep-Sea Res. I 50: 281-300 (2003)

Aharon, P. and *Fu, B. Sulfur and oxygen isotopes of coeval sulfate-sulfide in pore fluids of cold seep sediments with sharp redox gradients. Chem. Geol. 195: 201-218 (2003)

Aharon, P. Microbial processes and products fueled by hydrocarbons at submarine seeps. In: Microbial Sediments (eds. R.E. Riding and S.M. Awramik), Springer-Verlag Berlin, Ch. 29: 270-281 (2000)

Aharon, P. and *Fu B. Microbial sulfate reduction rates and sulfur and oxygen isotope fractionations at oil and gas seeps in deepwater Gulf of Mexico. Geochim. Cosmochim. Acta 64 (2): 233-246 (2000)

 

Abstracts in Proceeding Volumes
(Asterisk denotes student author)

S. *Bordoloi, P. Aharon and T. Pape. Hot and Cold: Complex Biochemical Processes in a Mud Volcano Setting on the Northern Gulf of Mexico. Am. Geophys. Union Fall Meeting, B11D-03 (2006)

V. *Murgulet and P. Aharon. Imprints of Catastrophic Cyclones in the Trace Element Records (Mg, Na, S, P) of Tropical Stalagmites. Am. Geophys. Union Fall Meeting, PP51D-1171 (2006)

S. *Bordoloi, P. Aharon, M. Taviani, G. B. Vai. Trace Metal Records of Rapid Anoxia Development in a Mediterranean Satellite Basin During the Pre-Evaporitic Messinian Stage. Geol. Soc. Am. Abstracts with Programs, 38 (7), p. 125 (2006)

B. Ghaleb and Paul Aharon. Excess 226Ra dating of young stalagmites: An example from Niue Island, South Pacific. Goldshmidt Intl. Conf. Melbourne, Australia (2006)

Valeriu *Murgulet, Paul Aharon, Michael G. Bersch. Rainfall Seasonality in Tropical Stalagmites Discerned from Magnesium and Phosphorus Partitioning in Sub-Annual Couplets. Fourth Intl. Conf. Climate Change: “The Karst Record”, Romania, May 26-29 (2006)

Michael G. Bersch, Valeriu *Murgulet, and Paul Aharon. X-ray Mapping of a Stalagmite from Niue Island, South Pacific: Visualizing Element Distribution. Fourth Intl. Conf. Climate Change: “The Karst Record”, Romania, May 26-29 (2006)

Michael *Rasbury, Paul Aharon, and William J. *Lambert. A two Centuries Long Annual Record of Rainfall and ENSO Variability Archived in the Oxygen Isotope Profiles of South Pacific Stalagmites. Fourth Intl. Conf. Climate Change: “€œThe Karst Record”€, Romania, May 26-29 (2006)

W. Joe *Lambert and Paul Aharon. Paleoclimate Reconstructions for the Southeastern U.S.A. from Speleothems in DeSoto Caverns, Alabama. Fourth Intl. Conf. Climate Change: “The Karst Record”€, Romania, May 26-29 (2006)

Paul Aharon, M. S. *Rasbury, W. J. *Lambert, Lane *Lambert and B. Ghaleb. Is Solar Forcing a Controlling Factor of ENSO Variability? Fourth Intl. Conf. Climate Change: “€œThe Karst Record”€, Romania, May 26-29 (2006)

*Bordoloi, S., Aharon. P., Pape, T., Taviani, M., Vai, G.B., Sen Gupta, B., *Platon, E. Geochemistry of Anoxic Marine Sediments of Late-Miocene Age: Vena del Gesso Basin, Northern Apennines, Italy. Earth System Processes 2, GSA Speciality Meetings, Abstracts with Programs, No. 1, p.45 (2005)

*Rasbury, M, Aharon, P. and Harry, D. Pluviometry and ENSO variability over the past two centuries recorded in mid-ocean island stalagmites from the South Pacific. Alexander von Humboldt Int. Conf. Ecuador, Guayaquil: The El-Niño Phenomenon and its Global Impact. AVH1-A-00058 (2005)

Aharon, P. and *Rasbury, M. The imprints of ENSO and PDO in mid-ocean island stalagmites: examples from Niue Island, South Pacific. Alexander von Humboldt Int. Conf. Ecuador, Guayaquil: The El-Niño Phenomenon and its Global Impact. AVH1-A-00111 (2005)

Aharon, P., *Rasbury, M. S., *Lambert, W. J., Ghaleb, B. and *Lambert, L. A millennial record of rainfall and ENSO variability in a stalagmite from the island of Niue in the South Pacific. . EOS Trans. AGU, Fall Meet. Suppl., PP53A-05 (2005)

*Lambert, W. J., Aharon, P. and Rodriguez, A. B. Pnicaut Storm: Alabama lake sediment preserves forgotten catastrophic hurricane disaster. SE Geol. Soc. Am. Abstracts with Programs: 14-3 (2005)

*Murgulet, V. and Aharon, P. A groundwater chemical drill explains cave formation on Niue Island, South Pacific. SE Geol. Soc. Am. Abstracts with Programs: 17-1 (2005)
Aharon, P. Episodic meltwater discharges into the Gulf of Mexico during the last deglaciation: The benthic isotope record. SE Geol. Soc. Am. Abstracts with Programs: 14-1 (2005)

*Lambert, W. J. and Aharon, P. Climate change recorded in aragonite speleothems from central Alabama. EOS Trans. AGU, Fall Meet. Suppl., PP43A-0610 (2004)

*Rasbury, M., Aharon, P. and Harry, D. Records of rainfall and ENSO in the South Pacific from speleothem growth bands. EOS Trans. AGU, Fall Meet. Suppl., PP43A-0609 (2004)

Aharon, P. Entrainment of meltwaters in hyperpycnal flows during deglaciation superfloods in the Gulf of Mexico: Implications for freshwater outflows in the climate system. EOS Trans. AGU, Fall Meet. Suppl., PP431A-0889 (2004)

*Bordoloi, S., Aharon, P., Taviani, M. and Vai, G. B. Hydrocarbon-derived limestones interbedded with lower Messinian euxinic shales (Northern Apennines, Italy). Geol. Soc. Am. Abstracts with Programs 34 (7): A-620 (2003)

*Murgulet, V., Aharon, P. and *Wheeler, C. W. Hydrogeochemistry of cave dripwaters from a tropical ocean island karst. Geol. Soc. Am. Abstracts with Programs 34 (7): A-452 (2003)

*Rasbury, M., Aharon, P. and Harry, D. Power spectra analysis of annually laminated stalagmites from Pacific island caves. Geol. Soc. Am. Abstracts with Programs 34 (7): A-415 (2003)

Taviani, M., Roveri, M., Aharon, P. Pliocene chemoherm formation within deep-sea reducing environments, Italian northern Apennines. Geol. Soc. Am. Abstracts with Programs 34 (7): A-382 (2003)

*Lambert, W. J., Aharon, P. and Rodriguez, A. B. A high resolution geochemical record of severe storms from Lake Shelby, Alabama, USA. Geol. Soc. Am. Abstracts with Programs 34 (7): A-294 (2003)

Aharon, P. and Van Gent, D. Growth rates of bathymodiolids from gas seeps in the Gulf of Mexico derived from Polonium-210/Radium-226 ratios. Geol. Soc. Am. Abstracts with Programs 34 (7): A-287 (2003)

*Hackworth, M. and Aharon, P. Determination of sedimentation rates in the Gulf of Mexico gas hydrate-bearing sediments using radiocarbon and stable carbon isotopes. Geol. Soc. Am. Abstracts with Programs 34: A-15 (2002)

Aharon, P. and *Rasbury, M. Extracting ENSO records from speleothems: A new initiative in the South Pacific. EOS Trans. AGU, 83 (47), Fall Meet. Suppl., Abstract PP51A-0282 (2002)

Aharon, P. and *Hackworth, M. Anomalous carbon isotope fractionations in hydrate-bearing sediments from the Gulf of Mexico: Are bacteria to be blamed? EOS, Am. Geophys. Union Trans. 82 (47): F-174 (2001)

Sen Gupta, B. K., *Platon, E., *Hackworth, M. S. and Aharon, P. Historical records of benthic foraminiferal species at a methane-hydrate dissociation site, Green Canyon, Gulf of Mexico. Geol. Soc. Am. Abstracts with Programs 33 (6): A-161 (2001)

Aharon, P., *Hackworth, M. S., *Platon, E., Wheeler, C. and Sen Gupta, B. Isotope records of recent benthic foraminifera from hydrate-bearing sediments: Methane hydrate dissociation effects. Geol. Soc. Am. Abstracts with Programs 33 (6): A-162 (2001)

*Hackworth, M. and Aharon, P. Pore fluids and authigenic carbonate products from biogenic and thermogenic sourced gas hydrates in the Gulf of Mexico. Geol. Soc. Am. Abstracts with Programs 33 (6): A-224 (2001)

Schiebout, J. A., Ting, S., Aharon, P., Chu, M., Stromberg, C., Hinds, D., *White, P., and Wrenn, J. The Fort Polk Miocene vertebrate sites (Louisiana, USA): Implications for local and global paleoenvironmental changes. Geol. Soc. Am. Abstracts with Programs 33 (6): A-445 (2001)

Aharon, P. and *Hackworth, M. Geochemical complexity of gas hydrates setting in the Gulf of Mexico. Geol. Soc. Am. Abstracts with Programs 32 (7): A-101 (2000)

*Hackworth, M. and Aharon, P. Carbonates as recorders of gas hydrate dissociation in the Gulf of Mexico. Geol. Soc. Am. Abstracts with Programs 32 (7): A-101 (2000)

Campbell, K. A., Aharon, P. and Marincovich, L. Paleo-gas hydrates in the Arctic Ocean: Evidence from late Neogene Nuwok strata, Northern Alaska. Geol. Soc. Am. Abstracts with Programs 32 (7): A-102 (2000)

*Wheeler, C. W. and Aharon, P. Evidence of ENSO-driven climatic variations during the last glaciation from speleothems in the tropical western Pacific: Initial results. Geol. Soc. Am. Abstracts with Programs 32 (7): A-218 (2000)

*Hackworth, M. and Aharon, P. Authigenic carbonate precipitation driven by episodic gas hydrate sublimation: Evidence from the Gulf of Mexico. VI Inter. Conf. on Gas in Marine Sediments, Abstracts Book, St. Petersburg (Russia) Sept. 5-9: 46-47 (2000)

Aharon, P., *Hackworth, M. and *Fu, B. On the geochemical complexity of gas hydrates setting in the Gulf of Mexico. VI Inter. Conf. on Gas in Marine Sediments, Abstracts Book, St. Petersburg (Russia) Sept. 5-9: 1-2 (2000)