Torbjörn E. Törnqvist

Dr. Törnqvist's research interests include Quaternary geology, Sea-level change, Coastal sustainability, Fluvial and deltaic sedimentology, Sequence stratigraphy, Applied geochronology and Paleoclimatology

Research Directions

Holocene ice sheet‒sea level connections.
The sedimentary record of the Mississippi Delta offers unique opportunities to investigate Holocene relative sea-level (RSL) change at very high resolution, and to develop connections with paleoclimate records. Our past efforts have focused, among others, on an abrupt sea-level rise associated with the 8.2 ka cooling event that was likely caused by the final drainage of proglacial Lake Agassiz. More recent work has pushed this record back beyond 10 ka, providing one of the first high-resolution RSL curves for the early Holocene. Combined with glacial isostatic adjustment (GIA) modeling, this sheds light on the relative contribution of the North American and Antarctic ice sheets to global sea-level rise during the second half of the last deglaciation.

Mechanisms and rates of subsidence in low-elevation coastal zones.
Subsidence in rapidly urbanizing, low-lying coastal environments is evolving into a “slow-motion catastrophe.” Our primary focus is on coastal Louisiana and involves the collection and analysis of field data (both geological and instrumental) that is combined with various modeling approaches (GIA models, compaction models) which involves several collaborators. Our Holocene RSL records are a cornerstone of this work, more recently augmented by surface-elevation table – marker horizon data available from the unparalleled Coastwide Reference Monitoring System. A recent addition is the “subsidence superstation” near Myrtle Grove, Louisiana, where a wide range of instrumental and geological methods are integrated to gain a more fundamental understanding about subsidence mechanisms and rates over a range of depth and timescales.

Holocene delta evolution.
There is a resurgence of interest in delta evolution over timescales longer than the instrumental record, motivated by the increasing challenge to successfully manage deltas throughout this century and beyond. Our research involves a variety of projects concerned with rates of delta growth (both vertically and horizontally) as well as patterns of sediment dispersal in the Mississippi Delta. This work relies heavily on geochronology as provided by 14C dating (including novel methods such as ramped PyrOx 14C) and optically stimulated luminescence dating. Much of this research is closely tied to questions that emanate from coastal restoration efforts, such as deciphering the patterns and rates of fluviodeltaic deposition that can serve as analogs for coastal restoration projects by means of river diversions.

Coastal wetland sustainability.
The wetland loss problem in coastal Louisiana is widely documented and there is an enormous interest in the future fate of these highly valuable ecosystems. Our research attempts to determine, among others, which rates of RSL rise coastal wetlands can withstand. Our work has shown that marsh collapse in this area occurs at rates of RSL rise of 3-7 mm/yr, not unlike recent findings for coastal ecosystems worldwide. Many intriguing questions remain, including the need for a better understanding of the conditions that cause marsh drowning and subsequent re-emergence (including possible hysteresis effects), both in coastal Louisiana and elsewhere.

Carbon in the coastal zone.
Coastal plains are increasingly recognized as important repositories of organic carbon, commonly referred to as “blue carbon.” However, the rates and mechanisms of carbon burial are inadequately understood, contributing to uncertainties around the terrestrial sink in global carbon models. Our work examines both modern carbon accumulation rates as well as the ultimate burial of carbon in the stratigraphic record, and relies on a combination of instrumental records, sediment core analysis, and geochronology in a variety of deltaic, coastal, and marine environments.

For more information, please visit the website of the Quaternary Research Group.

Selected Recent Publications

Saintilan, N., Horton, B., Törnqvist, T.E., Ashe, E.L., Khan, N.S., Schuerch, M., Perry, C., Kopp, R.E., Garner, G.G., Murray, N., Rogers, K., Albert, S., Kelleway, J., Shaw, T.A., Woodroffe, C.D., Lovelock, C.E., Goddard, M.M., Hutley, L.B., Kovalenko, K., Feher, L. and Guntenspergen, G., 2023. Widespread retreat of coastal habitat is likely at warming levels above 1.5 °C. Nature 621, 112-119.

Nienhuis, J.H., Kim, W., Milne, G., Quock, M., Slangen, A.B.A. and Törnqvist, T.E., 2023. River deltas and sea-level rise. Annual Review of Earth and Planetary Sciences, 51: 79-104.

Dangendorf, S., Hendricks, N., Sun, Q., Klinck, J., Ezer, T., Frederikse, T., Calafat, F.M., Wahl, T. and Törnqvist, T.E., 2023. Acceleration of U.S. Southeast and Gulf coast sea-level rise amplified by internal climate variability. Nature Communications, 14: 1935.

Törnqvist, T.E., Cahoon, D.R., Morris, J.T. and Day, J.W., 2021. Coastal wetland resilience, accelerated sea-level rise, and the importance of timescale. AGU Advances, 2: e2020AV000334.

Shirzaei, M., Freymueller, J., Törnqvist, T.E., Galloway, D.L., Dura, T. and Minderhoud, P.S.J., 2021. Measuring, modelling and projecting coastal land subsidence. Nature Reviews Earth & Environment, 2: 40-58.

Törnqvist, T.E., Jankowski, K.L., Li, Y.-X. and González, J.L., 2020. Tipping points of Mississippi Delta marshes due to accelerated sea-level rise. Science Advances, 6: eaaz5512.

Nienhuis, J.H., Ashton, A.D., Edmonds, D.A., Hoitink, A.J.F., Kettner, A.J., Rowland, J.C. and Törnqvist, T.E., 2020. Global-scale human impact on delta morphology has led to net land area gain. Nature, 577: 514-518.

You can find these as well as my other papers at ResearchGate.