Arctic permafrost coasts are sensitive to changing climate. The lengthening open water season and the increasing open water area are likely to induce greater erosion and threaten community and industry infrastructure as well as dramatically change nutrient pathways in the near-shore zone. The shallow, mediterranean Arctic Ocean is likely to be strongly affected by changes in currently poorly observed arctic coastal dynamics. We present a geomorphological classification scheme for the arctic coast, with 101,447 km of coastline in 1,315 segments. The average rate of erosion for the arctic coast is 0.5 m year −1 with high local and regional variability. Highest rates are observed in the Laptev, East Siberian, and Beaufort Seas. Strong spatial variability in associated database bluff height, ground carbon and ice content, and coastline movement highlights the need to estimate the relative importance of shifting coastal fluxes to the Arctic Ocean at multiple spatial scales.

This study investigates the rate of erosion during the 1951Á2006 period on the Bykovsky Peninsula, located north-east of the harbour town of Tiksi, north Siberia. Its coastline, which is characterized by the presence of ice-rich sediment (Ice Complex) and the vicinity of the Lena River Delta, retreated at a mean rate of 0.59 m/yr between 1951 and 2006. Total erosion ranged from 434 m of erosion to 92 m of accretion during these 56 years and exhibited large variability (s 0 45.4). Ninety-seven percent of the rates observed were less than 2 m/yr and 81.6% were less than 1 m/yr. No significant trend in erosion could be recorded despite the study of five temporal subperiods within 1951Á 2006. Erosion modes and rates actually appear to be strongly dependant on the nature of the backshore material, erosion being stronger along low-lying coastal stretches affected by past or current thermokarst activity. The juxtaposition of wind records monitored at the town of Tiksi and erosion records yielded no significant relationship despite strong record amplitude for both data sets. We explain this poor relationship by the only rough incorporation of sea-ice cover in our storm extraction algorithm, the use of land-based wind records vs. offshore winds, the proximity of the peninsula to the Lena River Delta freshwater and sediment plume and the local topographical constraints on wave development.

No abstract

Abstract. The distribution and abundance of Sphagnum spores in North America and Eurasia are mapped for the past 21 ka. The present-day distribution of abundant Sphagnum spores corresponds closely to areas with peatland development, with maximum Sphagnum abundance between 630 and 1300 mm annual precipitation and between -2 ø and 6øC mean annual air temperature. During the Wisconsin glaciation, there were apparently not large areas of peatland in North America, except in Alaska. High Sphagnum spore percentages were found in eastern North America during deglaciation. Major peatland development occurred in boreal North America after 9 ka and there was a southward movement of high Sphagnum spore abundance after 5 ka in the western Great Lakes region. Major peatland development began after 9 ka in Europe and Asia. On the basis of maps of the area supporting peatlands, carbon accumulation in peatlands is estimated to be low prior to 11 ka, increased slightly between 11 and 5 ka, and greatly increased during the past 5 ka. However, the general restriction of Sphagnum to these sites is only partly determined by the environment, with Sphagnum playing a considerable role in creating these conditions [Andrus, 1986]. The success of Sphagnum is due to its ability to create a 297

There is debate concerning the spatial extent and magnitude of the recently identified 1500 yr climate oscillation. Existing evidence is largely restricted to the North Atlantic and adjacent landmasses. The spatial extent, magnitude, and effects of these climate variations within the terrestrial environment during the Holocene have not been established. We show that millennial-scale climate variability caused changes in vegetation communities across all of North America with a periodicity of 1650 ؎ 500 yr during the past 14 000 calendar years (cal yr). Times of major transitions identified in pollen records occurred at 600, 1650, 2850, 4030, 6700, 8100, 10 190, 12 900, and 13 800 cal yr B.P., consistent with ice and marine records. We suggest that North Atlantic millennial-scale climate variability is associated with rearrangements of the atmospheric circulation with far-reaching influences on the climate.

To address the hypothesis that impaired ATP synthesis rates caused by changes in the creatine kinase system is an important mechanism underlying cardiac failure, we measured total creatine kinase activity, isoenzyme composition and creatine content in two animal models of hypertrophy with cardiac dysfunction, the spontaneously hypertensive rat in the transition to failure and the creatine-depleted hyperthyroid rat heart challenged by hypoxia. During the transition from stable compensated hypertrophy to failure characterized by decreased functional capacity, we found that total creatine kinase activity and particularly mitochondrial creatine kinase activity decreased. The decrease in functional capacity, the further increase in heart size and the derangements in the creatine kinase system did not occur if these animals were treated for 6 months with the antihypertensive agents, guanethidine or hydralazine. These results suggest that changes in the creatine kinase system occur coordinately with the transition to failure. To assess whether the changes in the creatine system may be causally linked to decreased functional capacity, we used 31P NMR spectroscopy of isolated perfused hearts to define the high energy phosphate content and cardiac performance of creatine-depleted (approximately 50%) hypertrophied hearts challenged by hypoxia. These hearts displayed greater susceptibility to hypoxic injury with regard to both systolic and diastolic function during and following hypoxia. We also measured total creatine kinase activity in right ventricular biopsy specimens from patients with various forms of cardiomyopathy and low ejection fractions, and found a positive correlation between total creatine kinase activity and ejection fraction. Taken together, these results support the hypothesis that decreasing the energy reserve for ATP synthesis renders the heart more susceptible to systolic and diastolic failure.

The North Pacific and Bering Sea regions represent loci of cyclogenesis and storm track activity. In this paper climatological properties of extratropical storms in the North Pacific/Bering Sea are presented based upon aggregate statistics of individual storm tracks calculated by means of a feature-tracking algorithm run using NCEP-NCAR reanalysis data from 1948/49 to 2008, provided by the NOAA/Earth System Research Laboratory and the Cooperative Institute for Research in Environmental Sciences, Climate Diagnostics Center. Storm identification is based on the 850-hPa relative vorticity field (z) instead of the often-used mean sea level pressure; z is a prognostic field, a good indicator of synoptic-scale dynamics, and is directly related to the wind speed. Emphasis extends beyond winter to provide detailed consideration of all seasons.Results show that the interseasonal variability is not as large during the spring and autumn seasons. Most of the storm variables-genesis, intensity, track density-exhibited a maxima pattern that was oriented along a zonal axis. From season to season this axis underwent a north-south shift and, in some cases, a rotation to the northeast. This was determined to be a result of zonal heating variations and midtropospheric moisture patterns. Barotropic processes have an influence in shaping the downstream end of storm tracks and, together with the blocking influence of the coastal orography of northwest North America, result in high lysis concentrations, effectively making the Gulf of Alaska the ''graveyard'' of Pacific storms. Summer storms tended to be longest in duration. Temporal trends tended to be weak over the study area. SST did not emerge as a major cyclogenesis control in the Gulf of Alaska.

No abstract