Wednesday, August 3, 2011

Pass the salt

En route between the Nahatlatch River and the mouth of the Fraser, we made a brief stop at Lytton to observe the mixing of the blue Thompson, the largest tributary of the Fraser River, with the muddy Fraser. The swirling eddies clearly visible at this point provided a natural platform for our resident physical oceanographer, Rocky Geyer, to pontificate on the dynamics of mixing. The two streams remain separate for a considerable distance downstream despite the turbulent flow of the river.

After following the mighty Fraser from its icy beginnings at the base of Rocky Mountain glaciers through raging tributaries of the Cariboo and Coast Mountains, we finally concluded our journey at the estuary near Vancouver, where muddy river water first meets the ocean in the Strait of Georgia. We chartered a whale watching boat to take us across the freshwater-saltwater transition at different tidal stages. Using CTD casts, we watched a wedge of saltwater at depth creep upstream with the rising tide, then retreat with the ebb. We also collected grab samples of bottom sediments, which will inform us about what types of sediment (small clay and mud particles versus large sand grains) are deposited at different points across this transition.

Our time in Vancouver was graced by beautiful sunshine, which made exploring the city on our last day all the more enjoyable. Despite nursing cuts, sunburns, twisted ankles, blisters, and colds on our return trip to Boston, I'm sure we were all sufficiently distracted by pleasant memories of the gorgeous surroundings we enjoyed over the last 10 days and the exciting science that infused all our adventures. Thanks to everyone who organized and participated in this year's Geodynamics trip, and thanks for reading!