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Sediment has accumulated in Isfjorden, a deep fjord in Spitsbergen, at a rate of 1.7 km3/k.y. during the past 13 k.y. Between 200 ka and 13 ka the fjord was free of ice for 120 k.y. Assuming a similar sediment delivery rate during this ice-free time, 200 km3 of sediment would have accumulated in the fjord. An alternative calculation based on erosion rates suggests that 400 km3 could have been delivered to Isfjorden during this 120 k.y.Seismic studies have identified a 330 km3 package of sediment on the continental shelf and slope west of Isfjorden. This sediment is believed to have accumulated between 200 ka and 13 ka. Herein we argue that this is sediment that was originally deposited in the fjord, and that it was transferred to the shelf by glaciers in the 70 ka during which the fjord was occupied by ice. Calculations using a steady-state numerical model suggest that the sediment could have been moved in a deforming layer of subglacial till and in subglacial melt streams at rates of 7.6 × 106 m3 a−1 and 0.3 × 106 m3 a−1, respectively, resulting in a total flux of 7.9 × 106 m3 a−1. It is unlikely that much sediment was moved in a basal layer of dirty ice, as intense basal melting would have inhibited sediment entrainment.Of the time that glaciers occupied the fjord, 60% would have been required to evacuate the accumulated sediment. During the remaining time, the ice could have been deepening the fjord. 相似文献
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In the geological record, hummocky dead-ice moraines represent the final product of the melt-out of dead-ice. Processes and rates of dead-ice melting in ice-cored moraines and at debris-covered glaciers are commonly believed to be governed by climate and debris-cover properties. Here, backwasting rates from 14 dead-ice areas are assessed in relation to mean annual air temperature, mean summer air temperature, mean annual precipitation, mean summer precipitation, and annual sum of positive degree days. The highest correlation was found between backwasting rate and mean annual air temperature. However, the correlation between melt rates and climate parameters is low, stressing that processes and topography play a major role in governing the rates of backwasting. The rates of backwasting from modern glacial environments should serve as input to de-icing models for ancient dead-ice areas in order to assess the mode and duration of deposition.A challenge for future explorations of dead-ice environments is to obtain long-term records of field-based monitoring of melt progression. Furthermore, many modern satellite-borne sensors have high potentials for recordings of multi-temporal Digital Elevation Models (DEMs) for detection and quantification of changes in dead-ice environments. In recent years, high-accuracy DEMs from airborne laser scanning altimetry (LiDAR) are emerging as an additional data source. However, time series of high-resolution aerial photographs remain essential for both visual inspection and high-resolution stereographic DEM production. 相似文献
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Boon JP van Zanden JJ Lewis WE Zegers BN Goksøyr A Arukwe A 《Marine environmental research》2002,54(3-5):719-724
The short-term effects of the commercial PBDE flame retardant mixtures Penta-BDE and cta-BDE on the expression of cytochrome P450 1A (CYP1A), vitellogenin (Vtg) and zona radiata proteins (Zrp) were investigated in juvenile salmon (Salmo salar). For this purpose, groups of fish were dosed twice (oral intake at days I and 4) with 10 and 50 mg/kg body weight of both commercial mixtures. The fishes were sacrificed at day 7 (n = 5 for each group) and 14 (n = 6 for each group), and blood, liver, fillet, and brain were collected. Blanks and positive controls were also part of the experiment. The expressions of Vtg, Zrp, and CYPIA were measured with several techniques (EROD, ELISA, Western, Northern and Slot Blot). The values in the groups of fish treated with Penta-BDE or Octa-BDE did not significantly differ from the reference group for any of the parameters tested. In contrast, the positive control groups treated with estradiol-17beta for Vtg and Zrp expression, and beta-naphthoflavone for CYP1A expression did show a significant response, indicating the potential sensitivity of the fishes for the parameters measured. Since the results of the chemical analyses showed concentrations of a number of PBDE congeners in liver, fillet, and brain that were about three orders of magnitude above those of fish from the North Sea, it is concluded that the short-term toxicity of both commercial PBDE mixtures for these endpoints was low. 相似文献
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Jonsson H Sandnes KV Schiedek D Schneider R Grøsvik BE Goksøyr A 《Marine environmental research》2004,58(2-5):655-658
In an attempt to learn more about the cytochrome P450 (CYP) system of mussels, we used protein databases and alignment software to extract highly conserved CYP sequences. From these alignments synthetic peptides were produced and used for rabbit immunisation, which yielded polyclonal antibodies against the CYP families 2 and 4. The antibodies were evaluated with Western Blot and ELISA assays, using digestive gland microsomal samples from the mussel Mytilus edulis. Western Blots revealed immunoreactions for both antibodies. The anti-CYP2 sequence rendered one major immunopositive protein of approximately 49 kDa size, and weak signals for proteins of approximately 41 and 56 kDa size. The anti-CYP4 sequence rendered two major bands of approximately 56 and 59 kDa size, and also a weak immunoreaction with a protein of approximately 43 kDa size. ELISA rendered only weak signals even with a 1:50 dilution of IgG-purified serum. A 10-day exposure to Aroclor 1254 did not appear to affect any of the immunopositive proteins, while total PCBs in soft bodies increased from 14-40 ng/g DW in controls to 373-638 ng/g DW in exposed mussels. 相似文献
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Lars Chresten Lund-Hansen Morten Pejrup Jens Valeur Anders Jensen 《Estuarine, Coastal and Shelf Science》1994,38(6)
Gross sedimentation rates (GSR) have been measured using sediment traps placed at nine different levels above the bed (0·3, 0·5, 0·8, 1·0, 2·0, 4·0, 6·0, 8·0 and 10·0 m). The sediment traps were deployed for 1·25 years and recovered 28 times during the study period. Low average GSR values of 5·5 g m-2 day-1 were obtained at 10·0 m, and high average GSR values of 114·8 g m-2 day-1 were obtained at 0·3 m. An expression for the eddy diffusion coefficient of suspended particulate matter (Ks), based on the measured GSR is given. The expression has been used for modelling of Ks at the different trap levels above the bed. High values (≈42 cm2 s-1) of Ks were obtained at the upper traps, whereas low values (≈2 cm2 s-1) were obtained near the bed. Comparison between level of turbulent energy in terms of shear stress at the boundaries of the water column, i.e. from the wind and the bed flow, showed that wind energy exceeded that of the bed flow by a factor 16. At 5·0 m Ks was positively correlated (r=0·66) to the eddy diffusion coefficient of momentum (Km) derived from the wind energy transfer to the water, giving an average β of 0·5 for Ks =βKm. The density difference between surface and bottom waters has been designated a parameter of stratification, and is discussed in relation to variations of Ks and Km . 相似文献
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