TOSST Research Themes

TOSST’s interdisciplinary research and training environment assembles broad disciplinary expertise to tackle common questions and topics effectively. Research projects within the research school address key issues facing the North Atlantic Ocean, such as external forcing and resource exploitation, within three themes: 4D Ocean-Atmosphere Dynamics, Ecosystem Hotspots, and Seafloor Structures. Individual projects focus along a conceptual “transatlantic transect” from West Africa (Cape Verde) to the Labrador Sea/Baffin Bay, crossing over the Mid-Atlantic Ridge, and emphasize interdisciplinary studies of these regions to attain an understanding of the whole system.

4D Ocean-Atmosphere Dynamics

The ocean is a three-dimensional system evolving through time, as ocean materials and energy are exchanged with both the atmosphere and the seafloor. For instance, the ocean surface acts as a major source and sink for long-lived, radiatively active gases, such as CO2. Interfacial fluxes (gas or dissolved chemical exchanges at the water-atmosphere and sediment-water interfaces) are governed by physical, chemical and biological transport and transformation processes, most of which are closely coupled to the pelagic, or open ocean, biosphere. Past and present climate change and chemical additions alter processes at the atmosphere-seawater transition, affecting chemical and biological processes as well as ocean circulation dynamics. The transatlantic transect includes two key regions. First, the NW Atlantic is particularly important because of the large and variable exchanges associated with heat loss, convection, and massive seasonal phytoplankton blooms. Second the coast off NW Africa, with strong and variable wind-driven upwelling and intense biological productivity, is subject to high air-sea fluxes of gases such as CO2, N2O, and organohalogens.

Ecosystem Hotspots

Life originated in the sea and the oceans harbor a tremendous diversity of life forms. The North Atlantic Ocean is host to a range of hotspots which are subject to human pressure. The globally significant primary production associated with deep, winter-time mixing and restratification (the “Spring Bloom”) is climate- sensitive, as is coastal upwelling along, for example, the NW African coast. In addition to supporting major fish populations (and heavily exploited fisheries), biological activity is also an important source of nitrogen for the oceans via nitrogen fixation which, in turn, is impacted by Saharan dust deposition. Coastal regions surrounding the Atlantic are becoming hotspots with the advance of commercial aquaculture. Important ecosystem hotspots on the Atlantic seafloor include seamounts and hydrothermal vents along spreading axes. Seamounts are hotspots of biodiversity due to the availability of a variety of substrates at a range of depths, their effects on the ocean circulation system, and their geographical isolation. In contrast, the ecosystems of hydrothermal vents are unique in their reliance on reduced substances produced by the interaction of seawater with the oceanic crust and mantle.

Seafloor Structures

The structure of the seafloor is created by volcanic, tectonic, and sedimentary processes operating over millions of years. Various structures serve as oases for marine biodiversity, are the source of both geohazards (volcanic, slope instability, and mass wasting at passive margins) and mineral resources (e.g. manganese crusts), or directly influence ocean circulation and mixing. The opening of the North Atlantic, beginning some 190 million years ago, led to the formation of passive continental margins whose subsequent history of organic- rich sedimentation has resulted in their being today major regions of oil and gas exploitation. Understanding seafloor structures is a prerequisite for understanding ocean circulation. Seafloor structures also play an important role in questions of biodiversity, hazards and resources, and are central to many ocean management considerations.