An official website of the United States government
Abstract Tropical Pacific seawater and precipitation stable oxygen isotope data aid in understanding modern oceanic and atmospheric interactions, and these data are particularly valuable as they are archived in isotope‐based paleoclimate records. However, the absence of modern seawater isotope time series limits the ability to identify the atmospheric influences on these data, precluding robust paleoclimate interpretations. We present a new 10 year sub‐monthly record of seawater and precipitation stable oxygen isotope values (δ18Oswand δ18Op) from Koror, Palau. Our dataset indicates that temporally, δ18Oswis strongly influenced by local δ18Op.Both monthly δ18Oswand δ18Opare highly correlated with outgoing longwave radiation across the tropical Pacific, reflecting a Walker Circulation imprint on the surface ocean. Changes in the Palau δ18Osw—salinity relationship correspond to NINO3.4 variability, indicating a difference in how these variables record El Niño Southern Oscillation (ENSO) information, but demonstrating the utility of δ18Oswto reconstruct ENSO variability in the western tropical Pacific.
more »
« less
Oxygen Isotopic Signatures of Major Climate Modes and Implications for Detectability in Speleothems
Abstract Natural and social systems worldwide are impacted by climate modes such as the El Niño/Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO), making it imperative to understand their sensitivity to climate change. Paleoclimate studies extend the observational climate baseline, and speleothem records (δ18Ospel) are a common data source. However, relationships between δ18Ospeland climate modes are uncertain; climate models provide a way to test the strength and stability of these relationships. Here, we use the isotope‐enabled Community Earth System Model's Last Millennium Ensemble combined with a forward proxy model to delineate the global expression of modal variability in “pseudo‐stalagmite” (δ18Ospel) records worldwide. The modeled δ18Ospelspatially correlates with modal signatures. However, substantial changes in modal variance only modestly affect individual δ18Ospelvariance. A network of δ18Ospelrecords, particularly one that straddles the Pacific, significantly improves the reconstructability of ENSO variance.
more »
« less
- PAR ID:
- 10452588
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 48
- Issue:
- 1
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Recent studies have revealed robust in‐phase relationships between El Niño–Southern Oscillation (ENSO) and Asian Monsoon precipitation δ18O values (i.e., warm ENSO events with high δ18O values), and this relationship has been used in an attempt to reconstruct past ENSO activity. However, whether this relationship holds in the past is unknown. Here we use precipitation δ18O data from Hong Kong (East Asia) and Bangkok (Southeast Asia) and an ice core δ18O record from Dasuopu glacier (South Asia) to examine the δ18O‐ENSO relationship across two recent climate shifts that occurred during the winters of 1976/1977 and 1988/1989. On an annual scale, the δ18O‐ENSO relationship is weak prior to 1977 and strongest after 1988. We show that the changing δ18O‐ENSO relationship mainly originates from changes in the dry season isotope/climate relationship (which is significant only after 1988), whereas the rainy season relationship is relatively stable. We confirm that, consistent with earlier work on the rainy season, the significant δ18O‐ENSO relationship in the dry season post‐1988 is associated with ENSO's influence on regional convection (Bay of Bengal to South China Sea region). We suggest the insignificant dry season relationship prior to 1989 is due to limited ENSO impacts on convection in the Bay of Bengal to South China Sea region, which is supported by the insignificant relationship between ENSO and vertical velocity at 500 hPa. These findings suggest that without additional constraints, systematic variability in isotope/climate relationships will lead to large uncertainties in ENSO reconstructions based on Asian Monsoon region δ18O data.more » « less
-
Abstract Hydroclimate variability in tropical South America is strongly regulated by the South American Summer Monsoon (SASM). However, past precipitation changes are poorly constrained due to limited observations and high‐resolution paleoproxies. We found that summer precipitation and the El Niño‐Southern Oscillation (ENSO) variability are well registered in tree‐ring stable oxygen isotopes (δ18OTR) ofPolylepis tarapacanain the Chilean and Bolivian Altiplano in the Central Andes (18–22°S, ∼4,500 m a.s.l.) with the northern forests having the strongest climate signal. More enrichedδ18OTRvalues were found at the southern sites likely due to the increasing aridity toward the southwest of the Altiplano. The climate signal ofP. tarapacana δ18OTRis the combined result of moisture transported from the Amazon Basin, modulated by the SASM, ENSO, and local evaporation, and emerges as a novel tree‐ring climate proxy for the southern tropical Andes.more » « less
-
Abstract Tropical South American climate is influenced by the South American Summer Monsoon and the El Niño Southern Oscillation. However, assessing natural hydroclimate variability in the region is hindered by the scarcity of long-term instrumental records. Here we present a tree-ringδ18O-based precipitation reconstruction for the South American Altiplano for 1700–2013 C.E., derived fromPolylepis tarapacanatree rings. This record explains 56% of December–March instrumental precipitation variability in the Altiplano. The tree-ringδ18O chronology shows interannual (2–5 years) and decadal (~11 years) oscillations that are remarkably consistent with periodicities observed in Altiplano precipitation, central tropical Pacific sea surface temperatures, southern-tropical Andean ice coreδ18O and tropical Pacific coralδ18O archives. These results demonstrate the value of annual-resolution tree-ringδ18O records to capture hydroclimate teleconnections and generate robust tropical climate reconstructions. This work contributes to a better understanding of global oxygen-isotope patterns, as well as atmospheric and oceanic processes across the tropics.more » « less
-
Abstract Coral oxygen isotopes (δ18O) from the central equatorial Pacific provide monthly resolved records of El Niño‐Southern Oscillation activity over past centuries to millennia. However, calibration studies usingin situdata to assess the relative contributions of warming and freshening to coral δ18O records are exceedingly rare. Furthermore, the fidelity of coral δ18O records under the most severe thermal stress events is difficult to assess. Here, we present six coral δ18O records andin situtemperature, salinity, and seawater δ18O data from Kiritimati Island (2°N, 157°W) spanning the very strong 2015/16 El Niño event. Local sea surface temperature (SST) anomalies of +2.4 ± 0.4°C and seawater δ18O anomalies of −0.19 ± 0.02‰ contribute to the observed coral δ18O anomalies of −0.58 ± 0.05‰, consistent with a ∼70% contribution from SST and ∼30% from seawater δ18O. Our results demonstrate that Kiritimati coral δ18O records can provide reliable reconstructions even during the largest class of El Niño events.more » « less
