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1.
Mark G. Hadfield 《Deep Sea Research Part II: Topical Studies in Oceanography》2011,58(6):764-775
The SAGE iron addition experiment was conducted from R.V. Tangaroa east of South Island, New Zealand, in late March-early April 2004. A desktop survey of climatological data was completed before the experiment, providing information to inform site selection and experiment design. The desktop survey is presented here in updated and enhanced form in order to explain the site selection and describe the conditions expected at the site during the experiment in comparison with those actually encountered.The experiment site was in Subantarctic waters between the Subtropical and Subantarctic Fronts. These waters are characterised by high surface macronutrient concentration, low iron concentration and low chlorophyll. The preferred site based on the desktop survey was in the vicinity of 173.5°E, 47.5°S, in Southern Bounty Trough. The actual release location was chosen immediately before the release and was 112 km to the northwest of this at 172°32′E, 46°44′S. The surface water here has typically come from the southwest (over the northern Campbell Plateau) or the southeast (through Pukaki Gap) and the mean current is directed towards ENE at ∼0.1 m s−1. The release location is well removed from regions of high eddy kinetic energy to the east (where the Subantarctic Front reaches its northern limit) and the west (where fine-scale instabilities develop on the Southland Front, which flows along the continental shelf). Typical conditions at the release site at the end of March are: surface temperature 12 °C; mixed layer depth 40 m; surface chlorophyll concentration ∼0.3 mg m−3; surface photosynthetically active radiation (PAR) 23 E m−2 d−1; surface nutrient concentrations 8-10 mmol m−3 (nitrate), 0.5-0.8 mmol m−3 (phosphate), 1-2 mmol m−3 (silicate) and 0.1-0.5 nM (iron); 99th percentile wind speed 19-21 m s−1. At this time of year, surface PAR is well below its summer maximum, the mixed layer is beginning its seasonal deepening and the silicate concentration is at its seasonal minimum. These factors may have limited the phytoplankton response to iron addition and were compounded in March-April 2004 by strong winds early in the experiment (substantially exceeding the 99th percentile in speed), lower than the average SST, larger than the average mixed layer depth, silicate concentration at the bottom end of the expected range and initially low PAR. 相似文献
2.
Vertical Ozone Profile over Tibet Using Sage I and II Data 总被引：8，自引：0，他引：8
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3.
为了解中国上空SAGE反演的平流层气溶胶数据质量,将合肥地区地基激光雷达观测10年(1996年—2005年)的气溶胶数据与SAGE资料进行比较。通过较为系统全面的比较分析,得到如下结果:(1)10—30 km内SAGE与Li DAR分析的气溶胶变化趋势较为一致,出现峰值和低值的位置也较为接近;(2)SAGE结果普遍比Li DAR测量的偏小,对应的平流层气溶胶AOD差异显著,定量表现为:激光雷达获取的平流层气溶胶AOD基本约为0.004,SAGE反演的平流层气溶胶AOD基本约为0.002,只有前者的一半;(3)两者分析的20—35 km气溶胶季节分布差异较小,再次表明平流层气溶胶比较稳定。 相似文献
4.
J. Kuparinen J. HallM. Ellwood K. SafiJ. Peloquin D. Katz 《Deep Sea Research Part II: Topical Studies in Oceanography》2011,58(6):800-807
We studied the microbial food web in the upper 100 m of the water column in iron-limited sub-Antarctic HNLC waters south-east of New Zealand in the SAGE experiment in 2004, with focus on bacterioplankton. Samples were collected daily from inside and outside the iron enriched patch. Short term enrichment experiments were conducted on board in 4 L polycarbonate bottles with water outside the iron enriched patch to study single and combined effects of micronutrient additions on microbial food web. Low bacterial growth was recorded in the study area with community turnover times of 50 h or more during the study period. Measurements of bacterial standing stocks and production rates in the study show minor responses to the large scale iron enrichment, with increase in rates and stocks after the first enrichment and at the end of the study period after the third iron enrichment when solar radiation increased and wind mixing decreased. The average daily bacterial production rates were 31.5 and 33.7 mgCm−2 d−1 for the OUT and IN stations, respectively; thus overall there was not a significant difference between the control and the iron-enriched patch. In the bottle experiments bacterial thymidine incorporation showed responses to single iron and silicic acid enrichments and a major growth response to the combined iron and sucrose enrichments. Phytoplankton chlorophyll-a showed clear stimulation by single additions of iron and silicic acid and silicic acid enhanced the iron impact. Cobalt additions had no effect on bacteria growth and a negative effect on phytoplankton growth. Low bacterial in situ growth rates and the enrichment experiments suggest that bacteria are co-limited by iron and carbon, and that bacterial iron uptake is dependent on carbon supply by the food web. With the high iron quota (??mol Fe mol C−1) bacteria may scavenge considerable amounts of the excess iron, and thus influence the relative importance of the microbial food web as a carbon sink. 相似文献
5.
Jill Peloquin Julie HallKarl Safi Walker O. Smith Jr.Simon Wright Rick van den Enden 《Deep Sea Research Part II: Topical Studies in Oceanography》2011,58(6):808-823
Areas of high nutrients and low chlorophyll a comprise nearly a third of the world’s oceans, including the equatorial Pacific, the Southern Ocean and the Sub-Arctic Pacific. The SOLAS Sea-Air Gas Exchange (SAGE) experiment was conducted in late summer, 2004, off the east coast of the South Island of New Zealand. The objective was to assess the response of phytoplankton in waters with low iron and silicic acid concentrations to iron enrichment. We monitored the quantum yield of photochemistry (Fv/Fm) with pulse amplitude modulated fluorometry, chlorophyll a, primary productivity, and taxonomic composition. Measurements of Fv/Fm indicated that the phytoplankton within the amended patch were relieved from iron stress (Fv/Fm approached 0.65). Although there was no significant difference between IN and OUT stations at points during the experiment, the eventual enhancement in chlorophyll a and primary productivity was twofold by the end of the 15-day patch occupation. However, no change in particulate carbon or nitrogen pools was detected. Enhancement in primary productivity and chlorophyll a were approximately equal for all phytoplankton size classes, resulting in a stable phytoplankton size distribution. Initial seed stocks of diatoms were extremely low, <1% of the assemblage based on HPLC pigment analysis, and did not respond to iron enrichment. The most dominant groups before and after iron enrichment were type 8 haptophytes and prasinophytes that were associated with ∼75% of chlorophyll a. Twofold enhancement of biomass estimated by flow cytometry was detected only in eukaryotic picoplankton, likely prasinophytes, type 8 haptophytes and/or pelagophytes. These results suggest that factors other than iron, such as silicic acid, light or physical disturbance limited the phytoplankton assemblage during the SAGE experiment. Furthermore, these results suggest that additional iron supply to the Sub-Antarctic under similar seasonal conditions and seed stock will most likely favor phytoplankton <2 ??m. This implies that any iron-mediated gain of fixed carbon will most likely be remineralized in shallow water rather than sink and be sequestered in the deep ocean. 相似文献
6.
《制图学和地理信息科学》2013,40(3):195-204
This paper examines the development of analytical cartography and the contributions Waldo Tobler has made to it, starting well before his definition of the subject in 1976. Analytical cartography's roots in World War II and the Cold War are examined, and the influences and precedents for the academic course that Tobler described are discussed. The systems of knowledge production developed for analytical cartography in its social context are summarized and are found to show a powerful dependence on a working relationship between academia, industry, government, and the intelligence mapping community. Current research trends in analytical cartography, including the organization of research, its institutions, and its priorities, are discussed, and it is proposed that declassifying the "missing pool" of analytical cartographic research literature could be of great benefit in the future. The four-way academic/industrial/government/intelligence partnership is seen as an opportune direction forward for analytical cartography. The next generational shift in the center of the discipline may occur in networks that even Waldo Tobler did not anticipate. 相似文献
7.
8.
Craig Stevens Brian Ward Cliff LawMatt Walkington 《Deep Sea Research Part II: Topical Studies in Oceanography》2011,58(6):776-785
Vessel-based observations of the oceanic surface layer during the 14-day 2004 SAGE ocean fertilization experiment were conducted using ADCP, CTD and temperature microstructure in a frame of reference moving with a patch of injected SF6 tracer. During the experiment the mixed layer depth zmld ranged between 50 and 80 m, with several re-stratifying events that brought zmld up to less than 40 m. These re-stratifying events were not directly attributable to local surface-down development of stratification and were more likely associated with horizontal variation in density structure. Comparison between the CTD and a one-dimensional model confirmed that the SAGE experiment was governed by 3-d processes. A new method for estimating zmld was developed that incorporates a component that is proportional to density gradient. This highlighted the need for well-conditioned near-surface data which are not always available from vessel-based survey CTD profiles. A centred-displacement scale, Lc, equivalent to the Thorpe lengthscale, reached a maximum of 20 m, with the eddy-centroid located at around 40 m depth. Temperature gradient microstructure-derived estimates of the vertical turbulent eddy diffusivity of scalar (temperature) material yielded bin-averaged values around 10−3 m2 s−1 in the pycnocline rising to over 10−2 m2 s−1 higher in the surface layer. This suggests transport rates of nitrate and silicate at the base of the surface layer generate mixed layer increases of the order of 38 and 13 mmol/m2/day, respectively, during SAGE. However, the variability in measured vertical transport processes highlights the importance of transient events like wind mixing and horizontal intrusions. 相似文献
9.
Jill Peloquin Julie HallKarl Safi Michael Ellwood Cliff S. LawKaren Thompson Jorma KuparinenMichael Harvey Stuart Pickmere 《Deep Sea Research Part II: Topical Studies in Oceanography》2011,58(6):824-838
The SOLAS Air-Sea Gas Exchange (SAGE) experiment was conducted in Sub-Antarctic waters off the east coast of the South Island of New Zealand in the late summer of 2004. This mesoscale iron enrichment experiment was unique in that chlorophyll a (chl a) and primary productivity were only 2× OUT stations values toward the end of the experiment and this enhancement was due to increased activity of non-diatomaceous species. In addition, this enhancement in activity appeared to occur without a significant build up of particulate organic carbon. Picoeukaryotes (<2 ??m) were the only members of the phytoplankton assemblage that showed a statistically significant increase, a doubling in biomass. To better understand the controls of phytoplankton growth and biomass, we present results from a series of on-deck perturbation experiments conducted during SAGE. Results suggest that the pico-dominated phytoplankton assemblage was only weakly inhibited by iron. Diatoms with high growth rates comprised a small (<1%) fraction of the phytoplankton assemblage, were likely iron limited, and potentially further limited by silicic acid and therefore did not significantly contribute to bloom dynamics. On deck experiments and comparison of SAGE with other iron addition experiments suggested that neither light availability nor deep mixed layers limited phytoplankton growth. Although no substantial increase in grazing rate or specific phytoplankton growth rate was detected, microzooplankton biomass doubled over SAGE as a result of an increase in cell size. The importance of microzooplankton grazing was highlighted by the fact that they were capable of consuming 15-49% of the total phytoplankton production per day. Removal was highest on eukaryotic picophytoplankton production with a mean value of 72% (29-143%). Patch dilution played an important role during SAGE; the mean patch net algal growth:dilution rate, 1.13 (0.4-2.2) was the lowest reported for a mesoscale iron enrichment experiment. Phytoplankton biomass, estimated by chlorophyll a, only accumulated when phytoplankton growth exceeded grazing and when net algal growth exceeded dilution rate. The SAGE results highlight the function of the smallest phytoplankton size fraction described by the ecumenical Iron Hypothesis. Thus, adding iron to HNLC-low silicic acid regions during certain times of the year may simply transfer more carbon through the microbial food web. A primary implication of this study is that any iron-mediated gain in fixed carbon with this set of environmental conditions has a high probability of being recycled in surface waters. 相似文献
10.
Peter J. Minnett Murray Smith 《Deep Sea Research Part II: Topical Studies in Oceanography》2011,58(6):861-868
Spectroradiometric measurements of the ocean skin temperature and thermometric measurements of the bulk temperature at a depth of about 5 cm taken from the R/V Tangaroa during SAGE (SOLAS/SAGE: surface-ocean lower-atmosphere studies air-sea gas exchange experiment) off New Zealand are analyzed to reveal the wind speed dependence of the temperature difference across the thermal skin layer (??T). The wind speeds used here are corrected for flow distortion by the ship. Unlike most previously published measurements of ??T, these data include those taken during the day, prior analyses being usually restricted to night-time measurements to avoid contamination of the data by diurnal heating. The results show the same dependence of ??T on wind speed at night-time measurements, with an asymptotic behavior at a value of −0.13 K at high winds. These data show larger ??T at low wind speeds than previous studies, and there is an indication that this may reveal a dependence on sea surface temperature. 相似文献