Sea Ice And Upper Ocean Variability In The Southern Ocean

Sea ice, which covers up to 7% of the planet’s surface, is a major component of the world’s oceans, partly driving ocean circulation and global climate patterns. It provides a habitat for a rich diversity of marine organisms, and is an extremely valuable source of information in studies of global climate change and the evolution of present day life forms. Increasingly sea ice is being used as a proxy for extraterrestrial ice covered systems. Sea Ice provides a comprehensive review of our current available knowledge of polar pack ice, the study of which is severely constrained by the logistic difficulties of working in such harsh and remote regions of the earth. The book’s editors, Drs Thomas and Dieckmann have drawn together an impressive group of international contributing authors, providing a well-edited and integrated volume, which will stand for many years as the standard work on the subject. Contents of the book include details of the growth, microstructure and properties of sea ice, large-scale variations in thickness and characteristics, its primary production, micro-and macrobiology, sea ice as a habitat for birds and mammals, sea ice biogeochemistry, particulate flux, and the distribution and significance of palaeo sea ice. Sea Ice is an essential purchase for oceanographers and marine scientists, environmental scientists, biologists, geochemists and geologists. All those involved in the study of global climate change will find this book to contain a wealth of important information. All libraries in universities and research establishments where these subjects are studied and taught will need multiple copies on their shelves. David Thomas is at the School of Ocean Sciences, University of Wales, Bangor, UK. Gerhard Dieckmann is at the Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany

This dissertation explores key physical mechanisms that control upper ocean and sea ice variability in the Southern Ocean. The first portion of this work presents an observational analysis of wintertime upper ocean stability and pycnocline heat availability in the Antarctic sea ice zone. This analysis reveals that the southern Weddell Sea region, which features a weak upper ocean stratification and relatively strong thermocline, is preconditioned for exceptionally high rates of winter ventilation. In other open-ocean regions, such as the northern Ross Sea, the stronger winter stratification greatly limits the efficiency with which heat may be extracted from the pycnocline. The coupling between winter ice growth and upper ocean ventilation is further explored using an idealized 1D sea ice-ocean model. This model is used to simulate winter ice growth in different regions under identical surface forcing. Consistent with the observational analysis, these simulations show that the unique thermohaline structure of the Weddell Sea, specifically that near Maud Rise, facilitates a strong negative feedback to winter sea ice growth. For this region, the entrainment of heat into the mixed layer can maintain a near-constant ice thickness over much of winter. However, these simulations also reveal that this quasi-equilibrium is attained when the pycnocline is thin and supports a large vertical temperature gradient. Further experimentation demonstrates that the surface stress imparted by a powerful storm may upset this balance and lead to substantial ice melt. In simulations initialized with profiles from more strongly stratified regions, such as near the sea ice edge of the major polar gyres, the entrainment of heat into the mixed layer had weak impact on winter ice growth---even during periods of strong wind forcing. Thus, a key takeaway is that the thermodynamic coupling between winter sea ice growth and ocean ventilation has significant regional variability. This regionality must be considered when evaluating the response of the Antarctic ice-ocean system to future changes in ocean stratification and surface forcing. In the final portion of this dissertation, focus is shifted to variations in Southern Ocean sea surface temperature (SST) and sea ice extent (SIE) on seasonal timescales. This work is motivated by the abrupt reversal of Southern Ocean SST and SIE trends that occurred in 2016 and 2017. The first half of this chapter examines the role of surface winds in the initiation of the anomalous sea ice retreat that occurred in late 2016. This is done via a simple regression analysis that quantifies the linear relationship between seasonal SIC anomalies and near-instantaneous local wind anomalies, using observations and reanalysis. With this empirical relationship, we demonstrate that surface wind anomalies can largely explain the SIC anomalies observed in the winter and spring of 2016. In the Weddell Sea, some of this preconditioning was associated with the winter polynyas that appeared that year. These events are linked to strong upwelling in the Weddell Sea and the passage of powerful winter storms. Lastly, we construct an updated seasonal mixed layer heat budget for the Southern Ocean, which is then used to explain the near-record Southern Ocean SSTs that occurred in the summer of 2016--2017. This analysis reveals that the warming maximum was the combined effect of enhanced air-sea heating, reduced northward Ekman transport, and shallower than normal mixed layer depths. From these results, we conclude that the 2016--2017 Southern Ocean SST and SIE anomalies were primarily caused by a serendipitous sequence of anomalous atmospheric and oceanic conditions. These anomalies coincided with an unusual synchronization of tropical and extratropical modes of climate variability.

The sea ice surrounding Antarctica has increased in extent and concentration from the late 1970s, when satellite-based measurements began, until 2015. Although this increasing trend is modest, it is surprising given the overall warming of the global climate and the region. Indeed, climate models, which incorporate our best understanding of the processes affecting the region, generally simulate a decrease in sea ice. Moreover, sea ice in the Arctic has exhibited pronounced declines over the same period, consistent with global climate model simulations. For these reasons, the behavior of Antarctic sea ice has presented a conundrum for global climate change science. The National Academies of Sciences, Engineering, and Medicine held a workshop in January 2016, to bring together scientists with different sets of expertise and perspectives to further explore potential mechanisms driving the evolution of recent Antarctic sea ice variability and to discuss ways to advance understanding of Antarctic sea ice and its relationship to the broader ocean-climate system. This publication summarizes the presentations and discussions from the workshop.

This is the first book to provide a comprehensive overview of climate change–related investigations carried out by Indian researchers through initiatives in southern high latitude regions. It explains climate variability over the Southern Ocean and Antarctica; air, sea, ice, and atmosphere interactions; and the impact of climate variability on sea ice and the polar atmosphere. The data were gathered at two Indian research bases, Maitri and Bharti, which are ideal sites to study and understand climatic evolution in Antarctic in the past and recent changes. This book helps to understand climatological perspectives and to evaluate some of the most pressing issues in the south polar region. FEATURES Highlights the achievements of India in the contemporary field of Antarctic climatology Presents four decades of research by Indian scientists in Antarctica, which is now shared for the first time with the global community Includes case studies on climatological and environmental conditions of natural archives to shed light on climate scenarios in the Southern Ocean and Antarctic regions Covers various aspects of climate variability and induced air-sea-ice-atmosphere interactions This book is edited by one of the top scientists and researchers of India in the field of paleoclimatology, and the contributors are experts in the Antarctic region.

Elements of Physical Oceanography is a derivative of the Encyclopedia of Ocean Sciences, 2nd Edition and serves as an important reference on current physical oceanography knowledge and expertise in one convenient and accessible source. Its selection of articles—all written by experts in their field—focuses on ocean physics, air-sea transfers, waves, mixing, ice, and the processes of transfer of properties such as heat, salinity, momentum and dissolved gases, within and into the ocean. Elements of Physical Oceanography serves as an ideal reference for topical research. References related articles in physical oceanography to facilitate further research Richly illustrated with figures and tables that aid in understanding key concepts Includes an introductory overview and then explores each topic in detail, making it useful to experts and graduate-level researchers Topical arrangement makes it the perfect desk reference

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 interannual variability of the sea ice in the Southern Ocean and its evolution projected for the end of the 21st century are investigated using observations and different types of models. First of all, none of the known atmospheric modes of variabilit

The oceans exert a vital moderating influence on the Earth's climate system. They provide inertia to the global climate, essentially acting as the pacemaker of climate variability and change, and they provide heat to high latitudes, keeping them habitable. Climate and the Oceans offers a short, self-contained introduction to the subject. This illustrated primer begins by briefly describing the world's climate system and ocean circulation and goes on to explain the important ways that the oceans influence climate. Topics covered include the oceans' effects on the seasons, heat transport between equator and pole, climate variability, and global warming. The book also features a glossary of terms, suggestions for further reading, and easy-to-follow mathematical treatments. Climate and the Oceans is the first place to turn to get the essential facts about this crucial aspect of the Earth's climate system. Ideal for students and nonspecialists alike, this primer offers the most concise and up-to-date overview of the subject available. The best primer on the oceans and climate Succinct and self-contained Accessible to students and nonspecialists Serves as a bridge to more advanced material

The World Ocean Circulation Experiment drove the development of estimates of the decadal scale time evolving general circulation that are dynamically and kinematically consistent. A long timescale, and a goal of estimation rather than prediction, preclude the use of meteorological methods called “data assimilation (DA).” Instead, “state estimation” methods are reviewed here and distinguished from DA. Results from the dynamically consistent family of solutions from the project Estimating the Circulation and Climate of the Ocean based upon least-squares Lagrange multipliers (adjoints) are used to discuss the determination of the dominant elements of the circulation in the period since 1992—which marked the beginning of the satellite altimetric record. Significant changes documented in the Arctic in recent decades now mandate consideration of the coupled ocean-cryospheric state.