Oceanography Of The Ross Sea Antarctica

The era of the exploration of the World Ocean is not yet over: some areas still lack an adequate number of observations. The relationships between the physical, chemical and biological processes, which sustain the life on this planet, are not yet fully understood. In short, knowledge of the oceans is still far from satisfactory. This book covers an important period in the study of one of the last investigated areas of the World Ocean: the Ross Sea, Antarctica. During the 1990s, long-term experiments were conducted in this area as part of the Climatic Long-term Interaction for the Mass balance in Antarctica (CLIMA) project of the Italian National Programme for Antarctic Research (PNRA), providing a wealth of oceanographic information. This book is an outcome of the CLIMA field obser vations and international collaborations with the most important programmes in the Ross Sea-Southern Ocean area. It contributes to the st!ldies of the spatial and temporal variability of Ross Sea water masses and circulation and their relation ship with the Southern Ocean circulation. A comprehensive review of historical data is offered, and new data sets are analysed. The studies presented in this book show that much progress has been achieved during the last decade, but large gaps in our understanding of the physical processes in the Ross Sea are still to be filled. However, these studies contribute significantly to the investigation of some specific aspects regarding the circula tion of the main water masses.

Oceanographic survey was performed in the Ross Sea, Antarctica, from 25 January to 8 March 1967 aboard GLACIER and STATEN ISLAND. Oceanographic stations were occupied in the central part of the sea to complement previous work done by NAVOCEANO in the investigation of Circumpolar Water intrusion into the Ross Sea and at the annual ice forecasting station locations. Current meter arrays were moored at two locations for direct current readings, and a special bathymetric survey was conducted along the Victoria Land coast. Preliminary analysis of oceanographic station data indicates that the main intrusion of Circumpolar Water enters the Ross Sea at about 174W longitude and that bottom topography is an influencing factor in deflecting this water southward into the Ross Sea.

This dissertation examines several aspects of the unique physical-biological system that controls biogeochemical cycling in the Ross Sea, the largest continental shelf sea along the Antarctic margin and the most biologically productive region in the Southern Ocean. The core component of the research involves interpretation of data from two oceanographic cruises to the region, one during Summer of 2005--2006 and another in Spring of 2006--2007. Four key research questions are addressed. (1) What physical mechanisms force spatial and temporal variability in mixing depths? (2) How does the dynamic physical environment characteristic of Antarctic continental shelf seas structure distributions of biomass and chemical tracers of production? (3) What key physical and physiological mechanisms control the 13C/12C ratio of organic and inorganic carbon in waters on the Ross Sea continental shelf? and (4) How do physiological variables interact with environmental variability to control phytoplankton taxonomic zonation? Chapter 1 presents an introduction to ocean carbon biogeochemistry and the oceanography of the Southern Ocean and the Ross Sea. Chapter 2 examines the mechanisms effecting early season stratification in the Ross Sea. Lateral advection in the region of upper ocean fronts is shown to be an important mechanism setting early season stratification. Chapter 3 examines several tracer-based methods for estimating upper ocean net community production in the Ross Sea, with explicit recognition of the complexities associated with control volume assumptions and high rates of temporal change. Chapter 4 considers the environmental controls on the distribution of 13C/12C ratios in the Ross Sea. It is shown quantitatively that the two dominant phytoplankton taxa in the Ross Sea have different intrinsic fractionation factors, likely as a result of differing carbon-acquisition physiologies. Air-sea exchange is shown to occur with very noisy fractionation. Finally, Chapter 5 examines the interaction of algal physiology with environmental variability, addressing the key physiological-environmental controls on the taxonomic distribution of phytoplankton in the Ross Sea. While it is difficult to draw concrete conclusions, the most compelling line of evidence suggests that differing photoprotective capacities is the most important physiological characteristic structuring taxonomic distributions. An appendix presents a design for an infrared absorbance-based instrument for the determination of total dissolved inorganic carbon in seawater.

The Antarctic represents the last of the world's still unexplored continents. Since 1985, Italy has sent 10 expeditions to this region, three of those have been exclusively devoted to research on the marine ecology of the Ross Sea region. This volume presents a global picture of this research. It includes contributions on water mass characteristics, particulate organic matter and nutrient utilization, and physiological aspects of primary production. Further topics are zooplankton, krill and top predator interactions in relation to physical and biological parameters, ecological features of coastal fish communities and the spatio-temporal variability of benthic biocenoses.

A large body of recent oceanographic research has shown that the Antarctic Circumpolar Current (ACC), an ocean current that flows from west to east around Antarctica, plays a crucial role in global ocean circulation. The region where the cold waters of the ACC meet and mingle with the warmer waters of the north defines a distinct border - the Antarctic Convergence - which fluctuates with the seasons, but which encompasses a discrete body of water and a unique ecologic region. The Convergence concentrates nutrients, which promotes marine plant life, and which, in turn, allows for a greater abundance of animal life. In 2000, the International Hydrographic Organization delimited the waters within the Convergence as a fifth world ocean - the Southern Ocean - by combining the southern portions of the Atlantic Ocean, Indian Ocean, and Pacific Ocean. The Southern Ocean extends from the coast of Antarctica north to 60 degrees south latitude, which coincides with the Antarctic Treaty Limit and which approximates the extent of the Antarctic Convergence. As such, the Southern Ocean is now the fourth largest of the world's five oceans (after the Pacific Ocean, Atlantic Ocean, and Indian Ocean, but larger than the Arctic Ocean).