Page 3 - HydrographyReadMe

Introduction

Hydrography is the description of physical features of the ocean
and is the starting point for any analysis of water circulation and the
understanding of life within the ocean.

Standard hydrographic properties in the ocean include water
temperature, salinity, the dissolved oxygen content, total chlorophyll
(as a proxy for the total amount of microscopic plant life, or
phytoplankton, that grows in the upper 30m or so of the water
column where light can penetrate), and water clarity, which affects
the depth to which light penetrates.

Most of these properties, from the surface down to 150m, are
measured in the CitSci program by an electronic probe lowered
from a boat. Water clarity is measured be separately estimating the
Secchi depth.

The largest changes in the Strait of Georgia are seasonal, but over
longer periods, there are noticeable changes from year to year as
well in response to larger climatic variations such as El Nino cycles.
The seasonal cycle will provide some background for the changes
from year to year, and so sometimes we want to consider the
ANOMALIES relative to this mean seasonal cycle.

There are also regional differences. In order to show these, we have divided the Strait into 14
areas, and also provide averages in each of those areas.