Download PDF Fall Bridge on Ocean Exploration and its Engineering Challenges September 18, 2018 Volume 48 Issue 3 This issue is dedicated to the engineering methods used to enhance understanding of the world’s oceans. Editor's Note: The Oceans of Planet Earth: Truly the Last Frontier Thursday, September 20, 2018 Author: Antononio Busalacchi Jr. and Cameron Fletcher The oceans have long been an important domain for exploration, resource extraction, shipping, national security, understanding of weather and climate, and more recently the emerging Blue Economy. The opening of Arctic sea lanes against the backdrop of climate change is a matter of national security. Sea level rise has severe ramifications for coastal infrastructure and populations. Moreover, the overall health of the oceans and integrity of the coasts are critical to the millions who live near and depend on them in this country alone. But when compared with the rapid expansion of knowledge of the universe, oceans are a woefully underexplored frontier—certainly if the utter disappearance of aircraft is any indication, there is much to be learned about Earth’s watery depths. This issue is dedicated to the engineering methods used to enhance understanding of the world’s oceans. Maps no longer proclaim “Here be dragons,” but how much is known even today about the deep blue sea? What are the major challenges to ocean observation and surveying? What is the status of ocean monitoring? What technologies are emerging to explore the oceans, to enhance understanding of this realm, and assess ocean interactions with the atmosphere above and laterally with coastal zones? Approximately 70 percent of the Earth is covered by ocean, and this vast expanse, in both surface area and depth, presents myriad engineering challenges, such as a corrosive environment, vast distances, opaqueness to electromagnetic remote sensing (in contrast to the atmosphere), pressures of the deep ocean, vandalism at sea, and biofouling. These in turn create challenges for communications, power, durability, and coverage, among others. At the same time, autonomous and -other emerging technologies for observing the ocean can accelerate exploration, enhance resource management, and improve understanding of the role of the oceans in the coupled climate system. The articles in this issue describe the interdisciplinary field of ocean science and engineering from the past to the decades ahead. In the opening article, Don Walsh traces the history of ocean engineering from the perspective of the United States’ use of the oceans in four categories: ocean science, ocean engineering, economics and public policy, and manmade constraints. A coherent US national ocean policy is essential to coordinate these uses to ensure the country’s interests. Vice Admiral Paul Gaffney then provides a historical perspective on US campaigns to explore, survey, and observe the oceans. He describes previous observational methods and calls for renewed collaborative efforts to make the most of disparate data sources, limited resources, and emerging technologies that can greatly expand reach, coverage, and knowledge without increasing costs. Arthur Baggeroer and colleagues survey ocean observations and observatories. They describe a paradigm shift in oceanography in the early 2000s away from sparse (in both space and time) ship-deployed observations to real-time data relayed from sensors to shore via cables or satellite uplinks. The engineering challenges in maintaining these observatories in the harsh ocean environment are highlighted. Larry Mayer describes challenges and advances in mapping the bathymetry of the world’s oceans, from the lead line to today’s satellite altimetry and multibeam sonar. Notwithstanding the advances, he points out that 82 percent of the ocean floor has never had a direct measurement of depth at a 1 km × 1 km scale. More is known about the topography of the Moon and Mars than about large swaths of the Earth’s seafloor. William Kuperman delves into the details of imaging the ocean through the use of noise. Acoustic arrays detect noise that can reveal information about ocean floor depth and topography, water temperature, and ships and other bodies in the water. Sound propagation in the ocean and signal processing techniques are used to monitor changes in the ocean environment that influence the ocean sound field. In the last article, Lee-Lueng Fu and Dean -Roemmich explain how global sea level rise is measured from spaceborne and in situ sensors. They trace the evolution of early methods that constructed global mean sea level from sparse tide gauges to present-day estimates of sea level rise—3 mm/year—derived from satellite -altimeters, spaceborne gravity missions, and some 3,800 in situ profiling floats operated by a coalition of 27 countries. The resulting global data are able to reveal the relative contributions to sea level rise from the -thermal expansion of seawater and glacial ice melt. We thank the authors for their thoughtful and enthusiastic contributions to this issue. Collectively, the articles depict how, why, and where the oceans have been observed, and how new and emerging technologies are changing knowledge and understanding of the oceans going forward. We are also indebted to the following experts for their assistance in improving this collection of papers by reading and offering thoughtful comments on them: Kenneth Brink, Deborah Glickson, Arnold Gordon, Mardi Hastings, James Miller, and Robert Weller. About the Author:Antonio Busalacchi Jr. (NAE) is president of the University of Corporation for Atmospheric Research (UCAR) and Cameron Fletcher is managing editor of The Bridge.