The discovery of ice erosion at 1-km water depth in the central Arctic Ocean
During the "Arctic Ocean 96" expedition, with the Swedish ice breaker Oden, high-resolution chirp sonar data and sediment cores were collected from the crest of the Lomonosov Ridge, a 1500 km long and 50–70 km wide submarine mountain chain that crosses the Arctic Ocean. The data showed evidence for substantial erosion on the crest of ridge down to ca 1-km present water depth. Ice grounding and/or currents were suggested as the most likely causes of this erosion. These discoveries called for more investigations and during the summer of 1999, the US Navy nuclear submarine, USS Hawkbill, collected acoustic data from the eroded areas under the auspices of the SCICEX program using sidescan swath bathymetric sonar and chirp sonar. These data showed glacial fluting and scouring of seafloor and large-scale glacial erosion of the ridge crest down to 1-km present water depth. Sediment core data made it possible to date the major erosional phase and, thus, the ice grounding on the Lomonosov Ridge to ca 150 000 years ago (Marine Isotope Stage 6).
Polyak, L., Edwards, M. H., Coakley, B. J. and Jakobsson, M., 2001, Ice shelves in the Pleistocene Artic Ocean inferred from glaciogenic deep-sea bedforms, Nature, v. 410, p. 453–457.
Jakobsson, M., 1999, First high-resolution chirp sonar profiles from the central Arctic Ocean reveal erosion of Lomonosov Ridge sediments, Marine Geology, v. 154, p. 111–123.
Chronology of Arctic Ocean sediments
Establishing accurate age-depth relationships for sediment cores retrieved from the central Arctic Ocean have been associated with great difficulties and uncertainties. Sedimentation rates have been suggested to range from mm/1000 years (typical for deep-sea red clay facies) to several cm/1000 years (average modern deep-sea sediments). Together with colleagues from Stockholm University and the University of Bergen I presented a new approach to constrain the Pleistocene chronology of Arctic Ocean sediments (Jakobsson et al., 2000). We found that variations in manganese concentration and sediment color with depth provided a proxy for glacial-interglacial variability that could be correlated to low latitude oxygen isotope glacial-interglacial cyclicity, and thereby permitting the construction of an age model. Our constructed age model showed sedimentation rates of cm-scale/1000 years. To test this time scale further we applied Optically Stimulated Luminescence (OSL) dating on a core raised from the Lomonosov Ridge in the central Arctic Ocean. Prof Andrew Murray at the Nordic Laboratory for Luminescence Dating in Denmark performed this dating. The results support our interpretation that the sedimentation rate in the central Arctic Ocean is of the order of cm-scale/1000 years rather than mm-scale/1000 years.
Jakobsson, M., Backman, J., Murray, A., and Løvlie, R., in press, Optically Stimulated Luminescence Dating Supports Central Arctic Ocean cm-scale Sedimentation Rates, Geochemistry Geophysics Geosystems.
Jakobsson, M., Løvlie, R., Al-Hanbali, H., Arnold, E., Backman, J., and Mörth, M., 2000, Manganese and color cycles in Arctic Ocean sediments constrain Pleistocene chronology, Geology, v. 28, p. 23–26.
The International Bathymetric Chart of the Arctic Ocean (IBCAO)
The International Bathymetric Chart of the Arctic Ocean (IBCAO) is a cooperative effort between the International Arctic Scientific Committee (IASC), the International Hydrographic Commission (IHO), and the Intergovernmental Oceanographic Commission (IOC). Together with Norman Cherkis, a senior cartographer from NRL, I compiled the first outcome within this project; a beta version of a digital grid comprising the bathymetry and topography of the entire Arctic region. The IBCAO model is available for public download from a web page hosted by the National Geophysical Data Center. The visitors of the IBCAO web site reached 100,000 during year 2002 and as much as 46 GB of data (grid model, contours and maps) have been downloaded. It is safe to say that the IBCAO bathymetry model is used by thousands of peoples. The uses include that the bathymetry grid serve as a base in several oceanographic models, as demos in commercial software, and for decision-making in the international political arena.
Related Publications and Datasets
Jakobsson, M., Cherkis, N., Woodward, J., Coakley, B., and Macnab, R., 2000, A new grid of Arctic bathymetry: A significant resource for scientists and mapmakers, EOS Transactions, American Geophysical Union, v. 81, no. 9, p. 89, 93, 96.
Macnab, R. and Jakobsson, M., 2000, Something old, something new: compiling historic and contemporary data to construct regional bathymetric maps, with the Arctic Ocean as a case study, International Hydrographic Review, v. 1, no. 1, p. 2–16.
In the new edition of the General Bathymetric Chart of the Oceans (GEBCO) Digital Atlas, bathymetric contours and grid models for the Arctic Ocean will be included from the IBCAO model. This will be available through the GEBCO web site.
In the global 2-minute (latitude-longitude) resolution elevation database ETOPO2, the Arctic Ocean above 64°N is included from the IBCAO model. A CD-ROM with this data is available through the National Geophysical Data Center (NGDC).
Paleolakes in Northern Russia
Through the QUEEN project (Quaternary Environment of the Eurasian North) I am involved in research regarding huge proglacial lakes that were dammed in northern Russia 90,000 years ago. The damming occurred as a consequence of the early Weichselian Ice Sheet that advanced onto the Northern Russian mainland from the north and blocked the paths of the north-flowing rivers to the Arctic Ocean. I have modeled volumes and areas of these ice dammed lakes by using modern topography, elevations of the former lake surfaces and the geographic position of the damming ice margin. The northern Russian ice dammed lakes were comparable in size to the largest stage (Upper Campbell beach level) of the North American ice dammed Lake Agassiz that formed 9,900–9,500 years ago. These results are published in Journal of Quaternary Science (Mangerud et al, 2001). This project is continued together with Prof. Gary Clarke who models a possible outburst of freshwater into the Arctic Ocean from these lakes. My part in this is hypsometric calculations of the lakes and the investigation of possible drainage paths by GIS modeling.
Hypsometry, volume and physiography of the Arctic Ocean and its constituent seas
Researchers have long been interested in the earth's hypsometry – the distribution of surface area at various elevations of land and depths of ocean. This study was focused on the hypsometry and volume of the Arctic Ocean and its constituent seas. Calculations were based mainly on the IBCAO grid model and the volume and area of each of the Arctic Ocean seas were calculated within constructed polygons defining the seas by inserting a plane and calculating the volume and area below the plane. This plane was lowered in increments of 10 m from 0 m to a depth of 500 m and in increments of 50 m from 550 m down to the deepest depth within the enclosed polygon (see animation). The used methods and scientific results are described in Jakobsson (2002, Geochemistry Geophysics Geosystems). This article was selected as 'Editor's Choice" in the 2002 June issue of Science. Following the hypsometry study I continued with developing a semi-numeric approach of using the IBCAO grid model to define the first order physiographic provinces of the Arctic Ocean. The first step in this classification is an evaluation of seafloor gradients contained in a slope model that was derived from the IBCAO grid. The evaluation of this slope model, which emphasizes certain seafloor process-related features that are reflected in the bathymetric information, is subsequently used along with the bathymetry to classify the first order physiographic provinces. The areas of the provinces so classified are individually calculated, and their morphologies are subsequently discussed in the context of the geologic evolution of the Arctic Ocean Basin as described in the published literature.
Jakobsson, M., 2002, Hypsometry and volume of the Arctic Ocean and its constituent's seas, Geochemistry Geophysics Geosystems, v. 3, no. 2.
On the Effect of Random Errors in Gridded Bathymetric Compilations
The wide use of the IBCAO bathymetry model has called for error estimations of the compiled gridded bathymetry. However, the problem of estimating the quality of gridded bathymetry when the input data consists of multiple datasets of varying origin and, thus, varying quality, is far from trivial. Together with colleagues at the Center for Coastal and Ocean Mapping I have approached the problem of quality assessment of gridded bathymetry via a direct-simulation Monte Carlo method. The final products of our error modeling are a collection of grids containing standard deviation estimates of the depth values in the original bathymetry grid. Our experiments clearly show areas of high certainty associated with the more accurate data in the dataset, and regions which are less reliable, typically associated with contour-based data. We are now able to conclude that uncertainty prediction regarding the random error component in final gridded products is possible to determine using our Monte Carlo approach. We are currently applying the Monte Carlo error modeling approach on historical hydrographic data sets from the Great and Little Bay Estuary, New Hampshire. The purpose for this study is to compare data with different associated errors due to that they were acquired during various times using different techniques. This study is further described at CCOM/JHC home page