Holocene climate and oceanography of the Western United States and California Current System
Anthropogenic climate change is altering global climate processes with critical implications for marine and terrestrial ecosystems and human communities. Investigation of climate records from the Holocene (11.75 ka to present) provides critical insights into contextualizing modern climate change and understanding biogeochemical, ecosystem, and societal responses to environmental change. In this study, we present the most comprehensive multi-proxy Holocene climate reconstruction of the Western United States and California Current System to date. We identify phases of linked marine-terrestrial climate change over the last 11.75 ka and examine the drivers of change through time. A notable feature of this paper is the inclusion of human-environment interactions and ecosystem responses to change in addition to climate changes.
Palmer, HM., Hill, TM., Padilla Vriesman, V., Livsey, C., Fish, C. A review of Holocene climate and oceanography of the Western United States and Northeast Pacific. Climate of the Past Discussions. 3 September 2021. 3:1-55. 10.5194/cp-2021-10 |
Geochemical tracing of wildfire: implications for paleofire reconstruction and wildfire pollutant distribution
Quantifying the relative impact of climate change, fuel sources, and fire management in determining fire frequency and severity remains a critical research question. Novel geochemical charcoal analysis techniques now make it possible to quantify the relative temperature and intensity of a fire. In this work, I aim to identify the impacts of wildfire intensity and fuel type on geochemical signatures of pyrogenic carbon following wildfires in California. This work will be the focus of my postdoctoral research at UC Merced. More information to come soon! |
Ocean oxygenation through the Holocene
Modern climate change is causing expansions of low oxygen zones, with detrimental impacts to marine life. To better predict future ocean oxygen change, I study past expansions and contractions of low oxygen zones using microfossils of seafloor organisms (including foraminifera). This work included both spatial analysis in the modern to understand relationships between community assemblages and spatial hydrographic gradients and temporal analysis to identify changes in the oxygen minimum zone through time.
Palmer, HM., Hill TM, Roopnarine PR, Myhre SM, Donnefield JT, Reyes, KR. Southern California margin benthic foraminiferal assemblages record recent centennial-scale changes in oxygen minimum zone. Biogeosciences. 03 June 2020. Vol 17, 2923–2937. DOI: 10.5194/bg-17-2923-2020. Palmer, HM., Hill, TM., Kennedy, E., Roopnarine, PD., Langlois, S., Reyes, KR., and Stott, L., Oxygenation of offshore Southern California marine basins through the Holocene. In Review. Preprint available: https://www.essoar.org/doi/10.1002/essoar.10508818.1 |
Understanding nearshore-offshore oceanographic change through time
To fill a knowledge gap in linking nearshore-offshore oceanography, I collaborated with researchers at the California Academy of Sciences and University of California Museum of Paleontology to build a database of published oxygen and carbon stable isotope measurements from nearshore molluscs along the coast of the Northeast Pacific through the Holocene (Palmer et al., 2021, PANGEA). This novel database provides multi-site, seasonal archives of nearshore conditions and can test geochemical questions across ecological, spatial, temporal, and taxonomic gradients (Palmer et al., 2021, In review). Palmer, H. M., Padilla Vriesman, V., Banker, R. M., & Bean, J. R. (2021). A database of Holocene nearshore marine mollusc shell geochemistry from the Northeast Pacific. Earth System Science Data Discussions, 1-13. doi.org/10.5194/essd-14-1695-2022 Palmer, HM., Padilla Vriesman, V., Banker, R.M.W, Bean, J.R. (2021): A database of Holocene nearshore marine mollusc shell geochemistry from the Northeast Pacific. PANGAEA, doi.org/10.1594/PANGAEA.932671 |
