EGU22-5745, updated on 08 Jan 2023
https://doi.org/10.5194/egusphere-egu22-5745
EGU General Assembly 2022
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Reconstruction of intermediate water temperature in the tropical North Atlantic since the Little Ice Age using cold-water corals 

Qian Liu1, Laura F. Robinson1, Erica Hendy1, Si-Yuan Sean Chen2,3, Joseph A. Stewart1, Timothy Knowles4, Tao Li5, and Ana Samperiz Vizcaino6
Qian Liu et al.
  • 1University of Bristol, School of Earth Sciences, United Kingdom of Great Britain – England, Scotland, Wales (qian.liu@bristol.ac.uk)
  • 2Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, MA 02139 U.S.A (osean@mit.edu)
  • 3Department of Physical Oceanography, Woods Hole Oceanographic Institution, MA 02543 U.S.A (osean@mit.edu)
  • 4Bristol Radiocarbon Accelerator Mass Spectrometry, University of Bristol, Bristol, BS8 1UU, UK (Tim.Knowles@bristol.ac.uk)
  • 5Department of Earth and Planetary Sciences, Nanjing University, Nanjing, 210023, China (taoli.es.nju@gmail.com)
  • 6School of Earth and Ocean Sciences, Cardiff University, Cardiff, CF10 3AT, UK (SamperizVizcainoA@cardiff.ac.uk)

Long-lived colonial cold-water corals have the potential to provide robust continuous archives of environmental change. These high-resolution records of the subsurface ocean are particularly valuable, especially at understudied intermediate water depths. Yet, to understand the anthropogenic impacts on the sub-surface ocean and better predict future changes, it is critical to establish the natural variation of temperature and circulation of the ocean system prior to the Industrial Revolution.

Here we combine temperature proxy and radiocarbon data from specimens of two taxa of cold-water coral that grew in intermediate water depths (~1500 m) in the tropical North Atlantic. In 2013, specimens of the bamboo coral Lepidisis spp. and scleractinian coral Enallopsammia rostrata were collected from sites currently situated in the boundary of North Atlantic Deep Water and Antarctic Intermediate Water to reconstruct the temperature and circulation history of the region. We demonstrate that bamboo corals can be used to reconstruct ambient seawater radiocarbon content when independently dated by organic node annual band counting. Radiocarbon was also analysed in Enallopsammia rostrata to develop age models for both the radial section and from discrete corallites (polyps) along a branch. Dating results show that this coral is about 500 years old, allowing us to generate a temperature record as far back as the Little Ice Age. Trace metal ratios were analysed along the growth axis of the coral, and the Li/Mg ratio was used as a temperature proxy. We find that the Li/Mg derived temperature of the most recent polyps is consistent with modern ambient temperature. The overall temperature record shows a general increasing trend since the Little Ice Age, while the radiocarbon record indicates no significant change until the late 20th century. Combining these records allows us to reconstruct potential ocean circulation changes in the central tropical North Atlantic over last 500 years.

How to cite: Liu, Q., Robinson, L. F., Hendy, E., Chen, S.-Y. S., Stewart, J. A., Knowles, T., Li, T., and Samperiz Vizcaino, A.: Reconstruction of intermediate water temperature in the tropical North Atlantic since the Little Ice Age using cold-water corals , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5745, https://doi.org/10.5194/egusphere-egu22-5745, 2022.

Displays

Display file