EPPEC Research

Paleoclimate history of the Equatorial South Atlantic from Rocas Atoll Corals

The National Geographic Society and the Waitt Foundation teamed up to fund the initial stages this project. The fundamental science goals are investigating the tropical Atlantic climate connections to global climate processes and learning more about a remarkable ecosystem as a basis for identifying future ecosystem changes. The funding is for an expedition to Rocas Atoll, Brazil with collaborator Ruy Kikuchi of the Universidade Federal da Bahia in Salvador, Brazil. Our joint expedition has two objectives:

1. Collect baseline coral reef community data from the unique ecosystem on Paleoclimate history of the Equatorial South Atlantic from Rocas Atoll to provide context for potential future global and regional anthropogenic impacts.

2. Obtain core samples for coral-geochemistry based climate reconstructions that extend the instrumental record of climate to understand decadal to century-scale variability of ocean circulation, temperature, and the tropical rain belt.

Paleoclimate Data Assimilation

Long records of past climate variability are needed to put recent changes into perspective and as validation data sets for predictive models because the modern instrumental record is too short to be useful for understanding multidecadal to century scale processes that are relevant to predicting the effects of anthropogenic climate change. Natural archives of climate information, known as paleoclimate proxies, can provide the necessary long records, but much work is needed to quantify the errors associated with these proxies and synthesize the many individual records into a coherent understanding of past climates. Additionally, we are realizing that in order to maximize the utility of the proxy data, it is important to interpret it in a way that leverages our understanding of climate physics and that quantifies proxy and reconstruction limitations. This project is designed to demonstrate a new data assimilation method that is a paleo-data adaptation to modern three dimensional variational data assimilation schemes. Dr. Kilbourne is working with collaborators at the NOAA Earth System Research laboratory to use a low-dimensional climate model derived from General Circulation Model (GCM) output to simplify the noisy climate system dynamics down to that which is predictable, and then use that model as a constraint to interpret a compilation of paleoclimate data.

Caribbean Paleoclimate of the last 1000 years

This project is a continuation my previous research into Caribbean paleoclimate using coral aragonite Sr/Ca and δ¹⁸O. We are extending the coral-based paleoclimate record for the northern Caribbean by using corals that grew between approximately 1200 C.E. and 1400 C.E. The coral specimens are part of an overwash deposit that brought coral heads from the coastal zone inland. This unique stratigraphic situation enables us to gather multiple specimens from a time period that is otherwise difficult to target since live corals are usually not so long lived. The time represented by these corals covers the late Medieval Climate Anomaly (MCA, ~900-1350C.E) and the transition to the Little Ice Age (LIA, ~1450-1850C.E), a period of great interest for understanding the causes of climate variability over the last 1000 years. We are generating coral-based climate records that overlap with existing central Pacific coral records, providing opportunity for rich inter-basin comparisons, and extension of northern Caribbean coral records which currently date back to 1444 C.E.

Developing paleoclimate records from the northern Caribbean during this time fills an important data gap in time and space. An increase in the tropical Indo-Pacific sea surface temperature (SST) gradient has been suggested by both modeling and paleoclimate proxy evidence as a proximal cause of observed paleoclimate patterns during the MCA (Graham et al. 2011). However, not all of the major patterns are explained by this mechanism and Atlantic sector processes may also be important. The Caribbean is a region where the modeling work predicts a strong influence by the Pacific, but current paleoclimate proxy data are insufficient to confirm or refute the model-based predictions. We will use our high-resolution paleoclimate record from the Caribbeanwill test the influence of the Pacific on the tropical Atlantic during the MCA , providing information on the relationship between climate in the two tropical basins over centennial to interannual timescales.

More project descriptions to come....