2004 LOM Workshop Tuesday 3:40 - 4:00 p.m.
Investigation of the Temporal and Spatial Variability of the North Atlantic Subtropical Mode Water Using Float Data and Numerical Model Results
Ge Peng, Eric Chassignet, Young-Oh Kwon, Stephen Riser
RSMAS/University of Miami
gpeng@rsmas.miami.edu
ABSTRACT
The properties of the North Atlantic Subtropical Mode Water (STMW), i.e., the 18-degree water (EDW), are calculated with float profiling observational data and ocean circulation model results. The basic characteristics of STMW are well documented in the literature from one time hydrographic sections or long term measurements at one location. Since the summer of 1997, up to 71 profiling floats were launched in the Western Subtropical North Atlantic region. The broad coverage in both time and space of the float profiles enables us to investigate the spatial and temporal variability of the STMW. In this study, we evaluate the performance of a North Atlantic numerical simulation against these float data, using the Miami Isopycnic Coordinate Ocean Model (MICOM). The good agreement between the two allows us to discuss the sensitivities of the float-derived results to observational sampling area and data coverage. Float-derived STMW properties are found to display more spatial variation when compared to the model-derived ones, even with the float profiles binned and mapped onto the model grid. Most variability of the model-derived STMW properties occurs at the northeast portion of the STMW domain and the least in the southeast. The spatial and temporal variability of model subduction rates and ventilation patterns will be described. The time series of domain averaged STMW temperature in both the model and observations do not show statistically significant seasonal and interannual variabilities while that of STMW volume displays a primary peak in the spring (March to May) each year and a secondary peak at October. Multi-year and decadal variabilities of the North Atlantic STMW properties (temperature, volume, subduction rate, etc.), and their relationship to the NAO will also be discussed using the model results.
LOM Users' Workshop, February 9-11, 2004