Swath sonar bathymetry during SONNE cruise SO202 (INOPEX) with links to multibeam raw data files

Multibeam data were measured during R/V SONNE cruise SO202 (INOPEX) along track lines of 6938 NM total length in the North Pacific and Bering Sea during transits and stationary work. Starting from Hokkaido (Japan) data were achieved east of the Kuril-Kamchatka Trench and south of the Aleutian Trench. The track crosses the Bowers Ridge, the continental margin of Alaska and the Umnak Plateau in the Bering Sea. Further data were gained in the North Pacific in the area of the Patton Seamounts, Gibson Seamount, Hess Rise and Shatsky Rise. The multibeam sonar system Simrad EM 120 from Kongsberg was operated using 191 beams and an aperture angle of 90° to 140° due to particular conditions. The refraction correction was achieved utilizing 6 CTD profiles measured during the cruise and one from cruise SO201. The quality of data might be reduced during bad weather periods. The dataset contains raw data that are not processed and thus may contain errors and blunders in depth and position.

(Table 1) Seasonal sea ice concentration and the observed changes from 1972 to 2007 for the Southern Beaufort Sea

A reliable data set of Arctic sea ice concentration based on satellite observations exists since 1972. Over this time period of 36 years western arctic temperatures have increased; the temperature rise varies significantly from one season to another and over multi-year time scales. In contrast to most of Alaska, however, on the North Slope the warming continued after 1976, when a circulation change occurred, as expressed in the PDO index. The mean temperature increase for Barrow over the 36-year period was 2.9°C, a very substantial change. Wind speeds increased by 18% over this time period, however, the increase were non-linear and showed a peak in the early 1990s. The sea ice extent of the Arctic Ocean has decreased strongly in recent years, and in September 2007 a new record in the amount of open water was recorded in the Western Arctic. We observed for the Southern Beaufort Sea a fairly steady increase in the mean annual amount of open water from 14% in 1972 to 39% in 2007, as deduced from the best linear fit. In late summer the decrease is much larger, and September has, on average, the least ice concentration (22%), followed by August (35%) and October (54%). The correlation coefficient between mean annual values of temperature and sea ice concentration was 0.84. On a monthly basis, the best correlation coefficient was found in October with 0.88. However, the relationship between winter temperatures and the sea ice break-up in summer was weak. While the temperature correlated well with the CO2 concentration (r=0.86), the correlation coefficient between CO2 and sea ice was lower (r=-0.68). After comparing the ice concentration with 17 circulation indices, the best relation was found with the Pacific Circulation Index (r=-0.59).

(Table 1) Trace element and isotopic data for ODP Hole 145-887D basalts

Age-progressive, linear seamount chains in the northeast Pacific appear to have formed as the Pacific plate passed over a set of stationary hotspots; however, some anomalously young ages and the lack of an "enriched" isotopic signature in basalts from the seamounts do not fit the standard hotspot model. For example, published ages (28-30 Ma) for basalts dredged from the Patton-Murray seamount platform in the Gulf of Alaska are 2-4 m.y. younger than the time when the platform was above the Cobb hotspot. However, the lowermost basalt recovered by ocean drilling on Patton-Murray yielded a 40Ar-39Ar age of 33 Ma. This age exactly coincides with the time when the seamount platform was above the Cobb hotspot, consistent with a stationary, long-lived mantle plume. A 27 Ma alkalic basalt flow recovered 8 m above the 33 Ma basalt is similar in age and composition to the previously dredged basalts, and may be the alkalic capping phase typical of many hotspot volcanoes. A 17 Ma tholeiitic basalt sill recovered 5 m above the 27 Ma basalt was emplaced long after the seamount platform moved away from the hotspot, and may be associated with a period of intraplate extension. Anomalously young phases of volcanism on this and other hotspot seamounts suggest that they can be volcanically rejuvenated by nonhotspot causes, but this rejuvenation does not rule out the hotspot model as an explanation for the initial creation of the seamount platform. The lack of an "enriched" isotopic signature in any of these basalts shows that enriched compositions are not necessary characteristics of plume-related basalts. The isotopic compositions of the lower basalts are slightly more depleted than the 0-9 Ma products of the Cobb hotspot, despite the fact that the hotspot was closer to a spreading ridge at 0-9 Ma. It appears that this hotspot, like several others, has become more enriched with time.