Water at intermediate depths of 2-3000m in the far north Pacific represents the end of the global thermohaline conveyor circulation, and is highly radiocarbon-depleted. Upwelling and mixing processes which bring this 14C-depleted water to the surface of the relatively small North Pacific Subarctic Gyre can therefore be expected to strongly influence radiocarbon levels in the mixed layer. Upwelling is stronger in west of the gyre than in the Gulf of Alaska, where vertical mixing is inhibited by stratification due to high precipitation and continental runoff.
Results of 14C measurements on known-age prebomb shell are broadly consistent with this overall picture. Radiocarbon was strongly depleted in coastal regions throughout the entire region in pre-bomb times, but the data show strong east-west gradients. Regional reservoir corrections (Delta R values) are 500 years for the western Bering sea, the Western Subarctic Gyre off Kamchatka, and the northern Sea of Okhotsk, and 300 years for the eastern Bering Sea and the Gulf of Alaska. Inshore locations (fjords and interisland passages) along the coast of British Columbia and southwestern Alaska show significantly stronger depletions than sites on the outer continental shelf.
See more of Reservoir Age Variability in the Marine Environment
See more of The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005)