Jochen Halfar

Jochen Halfar

Ph.D. | Professor | Earth Science | Paleoclimate and Paleontology

Research Areas:

Coralline Algal Paleoclimatology, Carbonate Sedimentology

Research Profile:

Halfar Research

Halfar‘s paleoclimate laboratory focuses on deciphering paleoclimates on different time scales ranging from the past centuries to 55 million years ago using sclerochronological, geochemical, and sedimentological multi-proxy approaches. Our highly interdisciplinary research is conducted in close collaboration with biologists, oceanographers, and climate physicists.

Currently, the group focuses on three main directions of research. First, we study crusty Arctic seafloor algae that can live up to 650 years while depositing annual tree-ring like layers. Using geochemical techniques we interpret past ocean climates and even sea-ice conditions from these layers. Another aspect of our current research focuses on modern shallow water marine carbonate environments in the tropics where we evaluate their adaptation to nutrient enrichment and the ongoing acidification of the ocean. Back on land we are studying exceptionally well-preserved fossil wood in volcanoclastic deposits associated with early Paleogene kimberlite pipes (55.1 million years) in the Northwest Territories, Canada, to explore terrestrial climate variability during a period of extreme  warmth.

Courses Taught:

ERS312H5, ERS315H5, ERS412H5, and ERS425H5 (undergraduate); ESS2303H1 (graduate)


Hetzinger, S., Grohganz, M., Halfar, J., Hathorne, E., Ballesteros, E., Kersting, D.K. (2023), Elemental cycles in the coralline alga Neogoniolithon mamillosum as a recorder of temperature variability in the Mediterranean Sea, Frontiers in Marine Sciences, DOI 10.3389/fmars.2023.1151592

*Gould, J., Halfar, J., Adey, W.H., Ries, J.B. (2022) Growth as a function of sea ice cover, light and temperature in the arctic/subarctic coralline Clathromorphum compactum: a year-long in situ experiment in the high Arctic, Frontiers in Marine Sciences, vol. 9 -2022,

*Leclerc N, Halfar J, Porter TJ, Black BA, Hetzinger S, Zulian M and Tsay A (2022) Utility of dendrochronology crossdating methods in the development of Arctic coralline red algae Clathromorphum compactum growth increment chronology for sea ice cover reconstruction. Fron

Porter, T. J. Anhaüser, T., Csank, A., Halfar, J., Keppler, F., Williams, C. J., (2022) Canadian Arctic Neogene temperatures reconstructed from hydrogen isotopes of lignin-methoxy groups from sub-fossil wood, Paleoceanography and Paleoclimatology, 37, e2021PA004345,

Leclerc, N., Halfar, J., Hetzinger, S., Chan, P.P.T.W., Adey, W., Tsay, A., et al. (2021). Sustainability of the coralline alga Clathromorphum compactum as an Arctic archive for past sea ice cover. Paleoceanography and Paleoclimatology, 36, e2021PA004286,

Hetzinger, S., Halfar, J., Zajacz, Z., Möller, M., Wisshak, M. (2021). Late 20th century increase in northern Svalbard glacier-derived runoff tracked by coralline algal Ba/Ca ratios, Climate Dynamics,,

Williams, B., Chan, P., Halfar, J., Hargan, K., Adey, W. (2021). Arctic crustose coralline alga resilient to environmental change, Limnology and Oceanography,

Rasher, D.B., Steneck, R.S., Halfar, J., Kroeker, K.J., Ries, J.B., Chan, P.T.W., Fietzke, J., Kamenos, N.A., Konar, B.H., Lefcheck, J.S., Norley, C.J., Weitzman, B.P., and Westfield, I.T., Estes, J.A., (2020). Keystone predators govern the pathway and pace of climate impacts in a subarctic marine ecosystem, Science, 369, 1351-1354

Chan, P., Halfar, J., Lebednik, P.A., Norley, C.J.D., Holdsworth, D.W. (2019).  Centennial record of subarctic coralline algal calcification rates, Geology,, C

Rahman, A., Halfar, J., Adey, W.H., Nash, M., Paulo, C., Dittrich, M. (2019). The role of chitin-rich skeletal organic matrix on the crystallization of calcium carbonate in the crustose coralline alga Leptophytum foecundum, Nature Scientific Reports, v. 9, 11869,, C

Hetzinger, S., Halfar, J. Zajacz, Z., Wisshak, M. (2019). Early start of 20th century Arctic sea ice decline recorded in Svalbard coralline algae, Geology, 47 (10): 963-967, 10.1130/G46507.1, C

Moffa-Sánchez, P., Moreno-Chamarro, E., Reynolds, D.J., Ortega, P., Cunningham, L., Swingedouw, D., Amrhein, D.E., Halfar, J., Jonkers, L., Jungclaus, J.H., Perner, K., Wanamaker, A., and Yeager, S. (2019). Variability in the northern North Atlantic and Arctic oceans across the last two millennia: A review, Palaeoceanography, Paleoclimatology, v. 34, 1399-1436, 10.1029/2018PA003508. C66.

Humphreys, A.F., Halfar, J., Ingle, J.C., Reymond, C.E., Westphal, H.; Riegl, B. (2019). Shallow water benthic foraminifera of the Galapagos Archipelago: Ecologically sensitive carbonate producers in an atypical tropical oceanographic setting, Journal of Foraminiferal Research, v. 49, no. 1, p. 48-65.

Williams, S., Adey, W., Halfar, J., Kronz, A., Gagnon, P., Belanger, D., Nash, M. (2018). Effects of light and temperature on Mg uptake, growth, and calcification in the proxy climate archive Clathromorphum compactum, Biogeosciences, 15, 5745-5759,

Humphreys, A.F., Halfar, J., Ingle, J.C., Manzello, D., Reymond, C.E., Westphal, H.; Riegl, B. (2018). Seawater temperature, pH, and nutrients influence character, distribution, and low abundance of shallow water benthic foraminifera in the Galápagos, PLoS ONE, 13(9): e0202746, 25p.

Williams, S., Halfar, J., Zack, T., Hetzinger, S., Blicher, M., Juul-Pedersen, T., Kronz, A., Noël, B., Van den Broeke, M., Van de Berg, W. (2018). Coralline algae archive Fjord surface water temperatures in Southwest Greenland, Journal of Geophysical Research – Biogeosciences, vol. 123, 8, 10p. 10.1029/2018JG004385.

Light, T., Williams, B., Halfar, J.,Hou, A., Zajacz, Z., Tsay, S., Adey, W. (2018). Advancing Mg/Ca analysis of coralline algae as a climate proxy by assessing LA-ICP-OES sampling and coupled Mg/Ca - δ18O analysis, Geochemistry, Geophysics, Geosystems, Vol 19, 9, 2876-2894, 10.1029/2018GC007504.

Anhaeuser, T., Hook, B., Halfar, J., Greule, M., F., Keppler, F. (2018). Early Eocene cold period and polar amplification - Insights from δ²H values of lignin methoxyl groups of mummified wood, Palaeogeography, Palaeoclimatology, Palaeoecology v. 505, p. 326-336.

Hou, A., Halfar, J., Adey, W., Wortmann, U., Zajaczc, Z., Tsayc, S., Williams, B., Chan, P. (2018). Long-lived coralline alga records multidecadal variability in Labrador Sea carbon isotopes, Chemical Geology

Williams, S., Halfar, J., Zack, T., Hetzinger, S., Blicher, M., Juul-Pedersen, T. (2018). Comparison of climate signals obtained from encrusting and free-living coralline algae. Chemical Geology476, p. 418-428,

Hetzinger, S., Halfar, J., Kronz, A., Simon, K., Adey, W., Steneck, R.S. (2018). Reproducibility of Clathromorphum compactum coralline algal Mg/Ca ratios and comparison to high-resolution sea surface temperature data, Geochimica et Cosmochimica Actav. 220, 96-109.

Chan, P., Halfar, J., Norley, C., Pollmann, S., Adey, W., Holdsworth, D. (2017). Micro-computed tomography: Applications for high-resolution skeletal density and calcification rate determinations. An example using annually-resolved crustose coralline algae, Geochemistry, Geophysics, Geosystems, 18, doi:10.1002/2017GC006966.

Sletten, H.R., Gillikin D., Halfar, J., Andrus, F.C., Guzman, H., (2017). Skeletal growth controls on Mg/Ca and P/Ca ratios in tropical Eastern Pacific rhodoliths (coralline red algae), Chemical Geology, 465, p. 1-10, doi: 10.1016/j.chemgeo.2017.05.010.

Chan, P., Halfar, J., Adey, W., Hetzinger, S., Zack, T., Moore, G.W.K., Wortmann, U.G. Williams, B., Hou, A. (2017). Multicentennial record of North Atlantic primary productivity and sea-ice variability archived in coralline algal barium, Nature Communications, 10.1038/NCOMMS1554

Williams, B., Halfar, J., DeLong, K.L., Smith, E., Steneck, R.S., Lebednik, P., Jacob, D., Fietzke, J., Moore, G.W.K. (2017). North Pacific 20th century decadal-scale variability is unique for the past 350 years, Geophysical Research Letters, 10.1002/2017GL073138

Moore, G.W.K., Halfar, J., Majeed, H., Adey, W., Kronz, A. (2017). Evidence for an Amplification of the Atlantic Multidecadal Oscillation associated with the onset of industrial-era warming, Scientific Reports, 7, 40861; doi: 10.1038/srep40861

Sletten, H.R., Andrus, F.T., Guzman, H., Halfar, J. (2017). Re-evaluation of using rhodolith growth patterns for paleoenvironmental reconstruction: An example from the Gulf of Panama. Palaeogeography, Palaeoclimatology, Palaeoecology, v. 465, Part A, Pages 264–277.

Ng, J., Williams, B., Thompson, D., Mayne, C., Halfar, J., Edinger, E., Johnson, K. (2016). Assessing multi-site δ18O-climate calibrations of the coralline alga Clathromorphum across the high-latitude Northern Hemisphere, Geochimica et Cosmochimica Acta, v. 194, 279-290,

Humphreys, A.F., Halfar, J., Rivera, F., Manzello, D., Reymond, C.E., Westphal, H., Riegl, B. (2016). Variable ENSO influence on biofacies dynamics of Eastern Pacific shallow water carbonate systems, Geology, doi:10.1130/G37745.

Jørgensbye, H. I. Ø., Halfar, J. (2016). Overview of coralline red algal crusts and rhodolith beds (Corallinales, Rhodophyta) and their ecological importance in Greenland, Polar Biology, 10.1007/s00300-016-1975-1.

Reymond, C.E., Zihrul, K.-S., Halfar, J., Riegl , B., Humphreys, A., Westphal, H. (2016). Heterozoan carbonates from the equatorial rocky reefs of the Galápagos Archipelago, Sedimentology, DOI: 10.1111/sed.12244.

Mallela, J., Hetzinger, S., Halfar, J. (2015). Thermal stress markers in Colpophyllia natans provide an archive of site-specific bleaching event, Coral Reefs, DOI 10.1007/s00338-015-1350-7.

Hook, B.A., Halfar, J., Gedalof, Z., Bollmann, J., and Schulze, D. (2015). Stable isotope paleoclimatology of the earliest Eocene using kimberlite-hosted mummified wood from the Canadian Subarctic. v. 12, 5899–5914, Biogeosciences, doi:10.5194/bg-12-5899-2015.

Hook, B.A., Halfar, J., Gedalof, Z., Bollmann, J., Rahman, Md.A., Reyes, J., Schulze, D. (2015). Extraction of α-cellulose from mummified wood for stable isotopic analysis, Chemical Geology, v. 405, 5, 19-27.

Bougeois, L., Williams, B., Halfar, J., Konar, B., Adey, W., Kronz, A., Wortmann, U. (2015). Does the coralline alga Leptophytum foecundum (Kjellman) capture paleoenvironmental variability in the Arctic Ocean? Arctic, Antarctic, and Alpine Research, 47, 2, 167-179, DOI:

Adey, W., Halfar, J., Humphreys, A., Suskiewicz, T., Belanger, D., Gagnon, P., Fox, M. (2015). Subarctic rhodolith beds promote longevity of crustose coralline algal buildups and their climate archiving potential, Palaios, 30, 281-293, DOI:

Fietzke, J., Ragazzola, F., Halfar, J., Dietze, H., Foster, L., Hansteen, T., Eisenhauer, A., Steneck, R.S. (2015). Century-scale trends and seasonality in pH and temperature for shallow zones of the Bering Sea, Proceedings National Academy of Sciences,