# Introduction

Definitions of Gulf Stream location sometimes centre on thermal signature, but it might make sense to work with dynamic height $\eta$ instead. This is illustrated here, using a $\tanh$ model for $\eta=\eta(x)$, with $x$ the distance along the transect. The idea is to select $x_ 0$, the halfway point in the $\tanh()$ function, where the slope is maximum and where therefore the inferred geostrophic velocity peaks.

# Exercises

From the map, work out a scale factor for correcting geostrophic velocity from cross-section to along-stream, assuming the Drinkwater (1994) climatology to be relevant.

# Resources

• Source code: 2014-06-22-gulf-stream-center.R

• K. F. Drinkwater, R. A Myers, R. G. Pettipas and T. L. Wright, 1994. Climatic data for the northwest Atlantic: the position of the shelf/slope front and the northern boundary of the Gulf Stream between 50W and 75W, 1973-1992. Canadian Data Report of Fisheries and Ocean Sciences 125. Department of Fisheries and Oceans, Canada.

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