El Niño Activities
The first Research Coordination Meeting (RCM) of the CRP took place at the IAEA Marine Environment Laboratories in Monaco during 25-29 October 2004 and was attended by 19 representatives from 10 countries. The meeting was held in parallel to the Aquatic Forum 2004 organized by IAEA-MEL during 25-29 October in the Grimaldi Forum (Monaco).
The first project web page was launched. This page received the “Best Website for Specific Theme in 2005” by the Department of Nuclear Applications of the IAEA.
In the framework of the PALEOPECES project (IMARPE-IRD), sediment multicores and long gravity cores were collected during the Galathea-3 Expedition in the Pisco Mud Lens. Sedimentary archives from the upper Peruvian margin in the Pisco Mud Lens (14ºS) are characterized by the presence of laminated sequences, providing high-resolution records that potentially reflect the imprint of ENSO variability. Based on this previous knowledge, these archives are analyzed to reveal the evolution and variability of the climate and oceanographic conditions during at least the late Holocene, in order to explore changes in the frequency or intensity of the ENSO-related variability mode. Other CRP members participate in the analysis of diverse proxies.
First Mission of the CRP – Palmyra Coral Collection Variability of climate and circulation in the tropical Pacific using radiocarbon. In June 2007, members of the CRP (Dunbar, Sanchez-Cabeza, Druffel) surveyed reefs at Palmyra Atoll located in the tropical Pacific (6°N, 162°W), which is influenced by ENSO events. Cores were collected from five coral heads that were among the largest identified at this atoll (Figure 2). We have completed radiocarbon measurements of annual coral bands that grew from 1895-2005 and results were reported at the 2007 Fall Meeting of the AGU (Druffel-Rodriguez et al. 2007). These data reveal that bomb 14C is present at levels in between those present in mid-gyre waters of the North Pacific (Hawaii) and upwelling waters of the eastern equatorial Pacific (Galapagos) (Figure 3). Additionally, the reduction of 14C during the first half of the 20th century (Suess Effect) is evident in the Palmyra 14C record.
The 2nd Project meeting was held at the IAEA Headquarters (Vienna, Austria) during 28 – 30 November 2007 and was attended by 7 CRP Members from 5 Member States (Australia, Jordan, Monaco, New Zealand and the USA), 1 UNEP staff and 4 IAEA staff.
The 2nd coral sampling mission of the CRP took place in Republic of Palau, during 25th November to 4th December 2008 and 5 scientists from 4 countries participated. The objective of the mission was to recover drill cores from large colonies of Porites lutea or Diploastrea sp. for climate / environmental reconstruction over the past 200 years. The mission was carried out aboard the Reel Time. The mission was extremely successful and a total of 13 coral cores were sampled, amounting to more than 15 meters in total. The longest core was 272 cm, what might represent close to 200 years, potentially a major achievement in this region. Once slabbed and X-rayed, samples will be distributed by Stanford University to CRP members, including IAEA-MEL, for specific analysis.
Climate records from corals for the past 400 years from the Galapagos Islands. We analyzed radiocarbon in annual coral bands from Urvina Bay in the Galapagos Islands in the tropical east Pacific. Our objective was to understand natural variability of past ocean circulation associated with climate change, and to compare the radiocarbon data with the ENSO record from δ18O for this coral sequence (Dunbar et al. 1994). Variability was observed on El Niño timescales (3-7 years) as well as at decadal and multi-decadal periods (Figure 1). Low radiocarbon levels persisted for nearly two decades during the early 1800s, coincident with a period of high volcanic aerosol loading in the atmosphere from two massive eruptions (e.g. Tambora in AD 1815 and an unknown eruption in Indonesia in 1809). Intensification of tropical circulation at this time may be linked to climatically-controlled changes in the structure of the tropical thermocline that is responsible for delivering cool, upwelled waters to the tropical east Pacific.
We are also conducting 14C analyses of monthly samples from this Galapagos coral in collaboration with Rob Dunbar. Variability of circulation in the tropical Pacific, specifically the strength of entrainment of Sub-Antarctic Mode Water into the Equatorial Undercurrent, is a major goal of this work.
For a proposed activity of the CRP, we would like to update the radiocarbon record at Galapagos by collecting small cores of the past 25 years of growth. This would be one of the studies to result from a mission to the Galapagos Islands in 2009 or 2010. Ideally, we would like to collect samples from a transect between the islands from 2.5°N (Wenman Island) to 1°S (Punta Pitt).
The third Research Coordination meeting of the CRP “Nuclear and Isotopic Studies of the El Niño Phenomenon in the Ocean” took place in Lima, Peru, from 14 to 17 April 2009. The meeting was held at the premises of IMARPE (Instituto del Mar del Peru), the National Marine Institution in Lima, Peru and was attended by seven CRP members from six Member States, and fifteen scientists from IMARPE.