Sea Floor Mapping and Exploration in a Changing Arctic Sea Ice Environment

SEA FLOOR MAPPING AND EXPLORATION IN A CHANGING ARCTIC SEA ICE ENVIRONMENT

Larry Mayer1

Abstract The earliest charts of the deep Arctic Ocean basins, produced at the beginning of the twentieth century, were based on lead-line soundings collected from ice islands and vessels frozen into the ice, and depicted a single deep basin greater than 3000 m (meters) deep. As technology improved, lead-lines were replaced with single-beam echo-sounders that were deployed from ice islands, aircraft and occasionally submarines. By the end of the twentieth century there were tens of thousands of individual depth soundings in the deep Arctic Ocean basin that revealed a very complex basin divided by numerous submarine ridges and elevations, but given the huge area of the region, the fundamental data base was still very sparse. With the beginning of the twenty-first century renewed interest in mapping the Arctic sea floor has come from the recognition of the role that the bathymetry plays in global climate through controlling ocean circulation and thus the distribution of global heat, as well as the large potential for extended continental shelves in the resource- rich Arctic under Article 76 of the United Nations Convention on the Law of the Sea. Modern multibeam echo-sounders have been deployed on icebreakers for mapping in ice-covered regions but only with the recent changes in the extent and age of the Arctic ice (including the record minimum in the summer of 2007), have conditions allowed the collection of multibeam echo-sounding data over much of the high Arctic. Taking advantage of the diminished ice cover over the past few years, the United States has, thus far, mounted four multibeam sonar mapping expeditions on the USCG icebreaker Healy and a collaborative (with the Canadians), two-ship seismic data acquisition program in the area of the Chukchi Borderlands, Canada Basin and the Alpha-

1 Professor and Director, Center for Coastal and Ocean Mapping, University of New Hampshire, Durham, NH. The author’s PowerPoint presentation can be viewed at http://www.virginia.edu/colp/pdf/Mayer-seafloor-mapping.pdf

Larry Mayer Mendeleev ridge complex. The data collected on these cruises have dramatically changed our understanding of the bathymetry and structure of the Arctic Ocean Basin and will have important ramifications on any potential submissions for an extended continental shelf in the region. In addition many new features have been discovered that will have a profound effect on our understanding of the origin of this part of the Arctic and the geologic processes at work in the region. While the trend in reduced ice has, in general, made access to this region simpler, the Arctic Ocean is by no means ice-free—the ability to maneuver and safely navigate is very dependent on local wind and ice conditions.

Introduction

Humans are compelled to explore. We explore to seek knowledge and understanding, for the thrill of discovery, for wealth and, with the development of nation-states, for the establishment of national sovereignty. A fundamental aspect of exploration is mapping—bringing unknown regions into a geospatial reference frame that provides a two- or three-dimensional context for all future activities. Few places on Earth have attracted more exploration than the vast, ice- and snow- covered regions of the Arctic. Early explorers battled bitter cold and treacherous conditions to slowly piece together maps of the Arctic coast. With the coming of the twentieth century, explorers vied to be the first to travel to the North Pole, but as these early explorers pushed further and further north, they knew nothing of what lay beneath the ice they travelled on. The earliest maps of the Arctic (e.g. Mercator, 1595), based solely on speculation and imagination, depict an island at the North Pole surrounded by four large landmasses. The concept of landmasses or land bridges beneath the Arctic ice continued to the end of the nineteenth century when Fridtjof Nansen collected the first bathymetric measurements in the deep Arctic as he drifted across the Arctic Ocean from 1893 to 1896 in the specially built vessel Fram (Nansen, 1904). Nansen locked the Fram into the ice pack off the New Siberian Islands and while it drifted with the ice pack across the Arctic Ocean (eventually passing through the straits between Greenland and Spitsbergen now known as the Fram Straits) he collected eight deep sea soundings using a “lead-line,” a weight at the end of a long rope or wire lowered to the sea floor to measure the depth. 84