Physical drivers of biogeochemical cycles in the North Atlantic Subtropical Gyre.

摘要

The biological carbon pump, the ocean's biologically driven carbon sequestration from the atmosphere to the deep ocean, is a major component in global biogeochemical cycles. In the North Atlantic Subtropical Gyre (NASG), a mechanistic understanding of this carbon cycling across both space and time is still largely lacking, and thus limits our fidelity in projecting future carbon exchange in between ocean and atmosphere under changing climate. One fundamental challenge centers on a puzzle that nutrient supply from large-scale physical forcing can only support ∼50% of the estimated biological productivity. Episodic nutrient injection by mesoscale eddies and submesoscale fronts are potential mechanisms to balance the needed nutrients, but their large-scale impact has not been well explored with observations.;In this thesis, I aim to bridge the knowledge gap by addressing three fundamental but complementary questions: (Q1) Are satellite data useful for detecting physical features (i.e. eddy types, fronts, and edges) in the NASG? (Q2) Which physical features are responsible for the NASG's primary productivity across space, and to what extent is each responsible? and (Q3) In the vertical dimension, what biological/physical mechanisms mediate the NASG's summertime primary productivity? By solving these questions, I aim to improve our mechanistic understanding of biological/physical drivers in controlling upper ocean carbon dynamics in the NASG.