Characterizing seawater oxygen isotopic variability in a regional ocean modeling framework: Implications for coral proxy records

Details

• Journal Title:
  Paleoceanography
• Personal Author:
  Stevenson, S. ; Powell, B. S. ; Merrifield, M. A. ; Cobb, K. M. ; Nusbaumer, J. ; Noone, D.
• NOAA Program & Office:
  CoRIS (Coral Reef Information System) ; CIRES (Cooperative Institute for Research in Environmental Sciences)
• Description:
  Reconstructions of the El Niño–Southern Oscillation (ENSO) are often created using the oxygen isotopic ratio in tropical coral skeletons ( δ 18 O). However, coral δ 18 O can be difficult to interpret quantitatively, as it reflects changes in both temperature and the δ 18 O value of seawater. Small‐scale (10–100 km) processes affecting local temperature and seawater δ 18 O are also poorly quantified and contribute an unknown amount to intercoral δ 18 O offsets. A new version of the Regional Ocean Modeling System capable of directly simulating seawater δ 18 O (isoROMS) is therefore presented to address these issues. The model is used to simulate δ 18 O variations over the 1979–2009 period throughout the Pacific at coarse ( O (50 km)) resolution, in addition to 10 km downscaling experiments covering the central equatorial Pacific Line Islands, a preferred site for paleo‐ENSO reconstruction from corals. A major impact of downscaling at the Line Islands is the ability to resolve fronts associated with tropical instability waves (TIWs), which generate large excursions in both temperature and seawater δ 18 O at Palmyra Atoll (5.9°N, 162.1°W). TIW‐related sea surface temperature gradients are smaller at neighboring Christmas Island (1.9°N, 157.5°W), but the interaction of mesoscale features with the steep island topography nonetheless generates cross‐island temperature differences of up to 1°C. These nonlinear processes alter the slope of the salinity:seawater δ 18 O relationship at Palmyra and Christmas, as well as affect the relation between coral δ 18 O and indices of ENSO variability. Consideration of the full physical oceanographic context of reef environments is therefore crucial for improving δ 18 O‐based ENSO reconstructions.
• Source:
  Paleoceanography, 30(11), 1573-1593
• DOI:
  https://doi.org/10.1002/2015pa002824
• ISSN:
  0883-8305 ; 1944-9186
• Format:
  pdf
• Publisher:
  American Geophysical Union (AGU)
• Document Type:
  Journal Article
• Rights Information:
  Other
• Compliance:
  Library
• Main Document Checksum:
  urn:sha-512:c806b6143c50b59bfc611077f44cd8c24112739498dbef8a8c003d838b8885afac16b9ed8f329adfce6603567a08ebba7b2f8b589ba5d5c244832d17ff0edf02
• Download URL:
  https://repository.library.noaa.gov/view/noaa/68024/noaa_68024_DS1.pdf
• File Type:
  [PDF - 5.72 MB ]