Sinking rates of particles measured from deployments in the Atlantic Ocean based on seasonal data

The flux of materials to the deep sea is dominated by larger, organic-rich particles with sinking rates varying between a few meters and several hundred meters per day. Mineral ballast may regulate the transfer of organic matter and other components by determining the sinking rates, e.g. via particle density. We calculated particle sinking rates from mass flux patterns and alkenone measurements applying the results of sediment trap experiments from the Atlantic Ocean. We have indication for higher particle sinking rates in carbonate-dominated production systems when considering both regional and seasonal data. During a summer coccolithophorid bloom in the Cape Blanc coastal upwelling off Mauritania, particle sinking rates reached almost 570 m per day, most probably due the fast sedimentation of densely packed zooplankton fecal pellets, which transport high amounts of organic carbon associated with coccoliths to the deep ocean despite rather low production. During the recurring winter-spring blooms off NW Africa and in opal-rich production systems of the Southern Ocean, sinking rates of larger particles, most probably diatom aggregates, showed a tendency to lower values. However, there is no straightforward relationship between carbonate content and particle sinking rates. This could be due to the unknown composition of carbonate and/or the influence of particle size and shape on sinking rates. It also remains noticeable that the highest sinking rates occurred in dust-rich ocean regions off NW Africa, but this issue deserves further detailed field and laboratory investigations. We obtained increasing sinking rates with depth. By using a seven-compartment biogeochemical model, it was shown that the deep ocean organic carbon flux at a mesotrophic sediment trap site off Cape Blanc can be captured fairly well using seasonal variable particle sinking rates. Our model provides a total organic carbon flux of 0.29 Tg per year down to 3000 m off the NW African upwelling region between 5 and 35° N. Simple parameterisations of remineralisation and sinking rates in such models, however, limit their capability in reproducing the flux variation in the water column.

Organic matter based proxies from surface sediments along three transects on the Pakistan continental margin

A valid assessment of selective aerobic degradation on organic matter (OM) and its impact on OM-based proxies is vital to produce accurate environmental reconstructions. However, most studies investigating these effects suffer from inherent environmental heterogeneities. In this study, we used surface samples collected along two meter-scale transects and one longer transect in the northeastern Arabian Sea to constrain initial OM heterogeneity, in order to evaluate selective aerobic degradation on temperature, productivity and alteration indices at the sediment-water interface. All of the studied alteration indices, the higher plant alkane index, alcohol preservation index, and diol oxidation index, demonstrated that they are sensitive indicators for changes in the oxygen regime. Several export production indices, a cholesterol-based stanol/stenol index and dinoflagellate lipid- and cyst-based ratios, showed significant (more than 20%) change only over the lateral oxygen gradients. Therefore, these compounds do not exclusively reflect surface water productivity, but are significantly altered after deposition. Two of the proxies, glycerol dibiphytanyl glycerol tetraether-based TEX86 sea surface temperature indices and indices based on phytol, phytane and pristane, did not show any trends related to oxygen. Nevertheless, unrealistic sea surface temperatures were obtained after application of the TEX86, TEX86L, and TEX86H proxies. The phytol-based ratios were likely affected by the sedimentary production of pristane. Our results demonstrate the selective impact of aerobic organic matter degradation on the lipid and palynomorph composition of surface sediments along a short lateral oxygen gradient and suggest that some of the investigated proxies may be useful tracers of changing redox conditions at the sediment-water interface.

Marine ice-rafted debris records and age determinations along the northern Eurasian margin

Ice-rafted debris (IRD) (>2 mm), input in eight sediment cores along the Eurasian continental margin (Arctic Ocean), have been studied over the last two glacial/interglacial cycles. Together with the revised chronologies and new micropaleontological data of two cores from the northern Barents Sea (PS2138) and northeastern Kara Sea (PS2741) spanning Marine Isotope Stages (MIS) 6 to 1, the IRD data give new insights into the glacial history of northern Eurasian ice-sheets over the last 150 ka. The chronologies of the cores are based on stable isotope records, AMS 14C datings, paleomagnetic and biostratigraphic data. Extensive episodes of northern Barents Sea ice-sheet growth, probably to the shelf edge, occurred during the late Weichselian (MIS 2) and the Saalian (MIS 6). Major IRD discharge at the MIS 4/3-transition hints to another severe glaciation, probably onto the outer shelf, during MIS 4. IRD-based instabilities of the marine-based ice margin along the northern Barents Sea between MIS 4 and 2 are similar in timing with North Atlantic Heinrich events and Nordic Seas IRD events, suggesting similar atmospheric cooling over a broad region or linkage of ice-sheet fluctuations through small sea-level events. In the relatively low-precipitation areas of eastern Eurasia, IRD peak values during Termination II and MIS 4/3-transition suggest a Kara Sea ice-sheet advance onto the outer shelf, probably to the shelf edge, during glacial MIS 6 and 4. This suggests that during the initial cooling following the interglacials MIS 5, and possibly MIS 7, the combined effect of sustained inflow of Atlantic water into the Arctic Ocean and penetration of moisture-bearing cyclones into easterly direction supported major ice build-up during Saalian (MIS 6) and Mid-Weichselian (MIS 4) glaciation. IRD peak values in MIS 5 indicate at least two advances of the Severnaya Semlya ice-sheet to the coast line during the Early Weichselian. In contrast, a distinct Kara Sea ice advance during the Late Weichselian (MIS 2) is not documented by the IRD records along the northeastern Kara Sea margin.

Diatom abundance and fatty acid composition of ice algae and of Calanus glacialis in samples obtained in 2008 in the eastern Beaufort Sea

The copepod Calanus glacialis plays a key role in the lipid-based energy flux in Arctic shelf seas. By utilizing both ice algae and phytoplankton, this species is able to extend its growth season considerably in these seasonally ice-covered seas. This study investigated the impacts of the variability in timing and extent of the ice algal bloom on the reproduction and population success of C. glacialis. The vertical distribution, reproduction, amount of storage lipids, stable isotopes, fatty acid and fatty alcohol composition of C. glacialis were assessed during the Circumpolar Flaw Lead System Study. Data were collected in the Amundsen Gulf, south-eastern Beaufort Sea, from January to July 2008 with the core-sampling from March to April. The reduction in sea ice thickness and coverage observed in the Amundsen Gulf in 2007 and 2008 affected the life strategy and reproduction of C. glacialis. Developmental stages CIII and CIV dominated the overwintering population, which resulted in the presence of very few CV and females during spring 2008. Spawning began at the peak of the ice algal bloom that preceded the precocious May ice break-up. Although the main recruitment may have occurred later in the season, low abundance of females combined with a potential mismatch between egg production/development to the first feeding stage and phytoplankton bloom resulted in low recruitment of C. glacialis in the early summer of 2008.

Middle to Late Quaternary sedimentation and rock-magnetic of ODP Site 105-646

We examine rock-magnetic, carbonate, and planktonic foraminiferal fluxes to identify climatically controlled changes of terrigenous and pelagic sedimentation at Ocean Drilling Program (ODP) Site 646 (the Labrador Sea). Terrigenous sediments are brought to the site principally by bottom currents. We use a rock-magnetic parameter sensitive to changes in magnetic mineral grain size, the ratio of anhysteretic susceptibility to low-field magnetic susceptibility (XARM/X), to monitor changes in bottom-current intensity over time, with large values of XARM/X (finer-grained magnetic minerals) indicating weaker bottom currents. A second rock-magnetic parameter, magnetic mineral accumulation rate (KaT) was used to indicate variations in terrigenous flux. Planktonic foraminiferal and carbonate accumulation rates (Pfar and CaC03ar) are used as indicators of pelagic flux. Absolute age assignments are based on correlation between the planktonic foraminiferal oxygen-isotope variations for Site 646 and the SPECMAP master oxygen-isotope curve. Cross-correlation analyses of the parameters that we studied with respect to the SPECMAP curve suggest that from oxygen-isotope stages 21 to 11, sedimentation rate, KaT, X, CaCO3ar, and Pfar were at their maximums, whereas XARM/X was at its minimum during peak interglacials (i.e., 0 k.y. lag time with respect to minimum ice volume). However, all parameters we examined lag behind minimum ice volume from stages 11 to 1, indicating a change in timing of both pelagic and terrigenous fluxes at approximately 400 k.y. BP. The negative correlation coefficient between XARM/X and the SPECMAP curve further suggest that finer-grained magnetic minerals are deposited during glacial periods, which probably reflects weaker bottom currents. The shift observed in the lag times of parameters examined with respect to the SPECMAP record is attributed to a change in significance of orbital parameters. Spectral results exhibit strong power in eccentricity (about 100 k.y.) throughout the record. Kap X, CaCO3flr, and Pfar show significant power in obliquity (about 41 k.y.), whereas XARM/X shows significant power at 73 k.y. from stages 21 to 11. The 73-k.y. period in XARM/X is near the difference tone of obliquity and eccentricity: 1/43-1/102 = 1/69. Kar and XARM/X show power only in eccentricity from stages 11 to 1. X and Pfar show significant power in precession (about 18 and 22 k.y.) whereas CaC03ar has power at 34 k.y, which could be a combination of precession and obliquity. The shift in power of orbital parameters may by attributed to the effect of the about 413-k.y. signal of eccentricity.

(Appendix 1) Coral analysis and isostatic rebound effects from different Holes of IODP Expedition 310

Past sea-level records provide invaluable information about the response of ice sheets to climate forcing. Some such records suggest that the last deglaciation was punctuated by a dramatic period of sea-level rise, of about 20 metres, in less than 500 years. Controversy about the amplitude and timing of this meltwater pulse (MWP-1A) has, however, led to uncertainty about the source of the melt water and its temporal and causal relationships with the abrupt climate changes of the deglaciation. Here we show that MWP-1A started no earlier than 14,650 years ago and ended before 14,310 years ago, making it coeval with the Bølling warming. Our results, based on corals drilled offshore from Tahiti during Integrated Ocean Drilling Project Expedition 310, reveal that the increase in sea level at Tahiti was between 12 and 22 metres, with a most probable value between 14 and 18 metres, establishing a significant meltwater contribution from the Southern Hemisphere. This implies that the rate of eustatic sea-level rise exceeded 40 millimetres per year during MWP-1A.

Sedimentation rates calculated on surface sediment samples from different site of the Atlantic and Pacific Oceans (Table 1)

Radiocarbon ages on CaCO3 from deep-sea cores offer constraints on the nature of the CaCO3 dissolution process. The idea is that the toll taken by dissolution on grains within the core top bioturbation zone should be in proportion to their time of residence in this zone. If so, dissolution would shift the mass distribution in favor of younger grains, thereby reducing the mean radiocarbon age for the grain ensemble. We have searched in vain for evidence supporting the existence of such an age reduction. Instead, we find that for water depths of more than 4 km in the tropical Pacific the radiocarbon age increases with the extent of dissolution. We can find no satisfactory steady state explanation and are forced to conclude that this increase must be the result of chemical erosion. The idea is that during the Holocene the rate of dissolution of CaCO3 has exceeded the rain rate of CaCO3. In this circumstance, bioturbation exhumes CaCO3 from the underlying glacial sediment and mixes it with CaCO3 raining from the sea surface.

Radiolarian-based bransfer function for the estimation of sea surface temperatures in the Southern Ocean (Atlantic Sector)

A new radiolarian-based transfer function for sea surface temperature (SST) estimations has been developed from 23 taxa and taxa groups in 53 surface sediment samples recovered between 35° and 72°S in the Atlantic sector of the Southern Ocean. For the selection of taxa and taxa groups ecological information from water column studies was considered. The transfer function allows the estimation of austral summer SST (December-March) ranging between -1 and 18°C with a standard error of estimate of 1.2°C. SST estimates from selected late Pleistocene squences were sucessfully compared with independend paleotemperature estimates derived from a diatom transfer function. This shows that radiolarians provide an excellent tool for paleotemperature reconstructions in Pleistocene sediments of the Southern Ocean.

(Table 1) Sea surface temperature reconstruction for eastern equatorial Pacific surface sediment samples

Significant uncertainties persist in the reconstruction of past sea surface temperatures in the eastern equatorial Pacific, especially regarding the amplitude of the glacial cooling and the details of the post-glacial warming. Here we present the first regional calibration of alkenone unsaturation in surface sediments versus mean annual sea surface temperatures (maSST). Based on 81 new and 48 previously published data points, it is shown that open ocean samples conform to established global regressions of Uk'37 versus maSST and that there is no systematic bias from seasonality in the production or export of alkenones, or from surface ocean nutrient concentrations or salinity. The flattening of the regression at the highest maSSTs is found to be statistically insignificant. For the near-coastal Peru upwelling zone between 11-15°S and 76-79°W, however, we corroborate earlier observations that Uk'37 SST estimates significantly over-estimate maSSTs at many sites. We posit that this is caused either by uncertainties in the determination of maSSTs in this highly dynamic environment, or by biasing of the alkenone paleothermometer toward El Niño events as postulated by Rein et al. (2005).

Event marketing: an innovative promotional tool and its impact on consumer memory and brand awareness

Event Marketing represents a common promotional strategy that involves direct contact between brands and consumers at special events, namely concerts, festivals, sporting events and fairs. Brands have been investing in sponsorship as a means of associating themselves with particular events, essentially with the goal to enhance brand image and brand awareness. Interestingly, the response of consumers to event marketing has not yet been fully understood. This dissertation fills this gap. More specifically, it intends to determine the extent to which sponsoring brands at events favors brand awareness (recall and recognition) and how it relates to brand attitude. Based on three Portuguese music festivals, two studies were conducted to ascertain event sponsorship’s impact on consumer memory, notably Brand Recall and Brand Recognition, and correlation with attitudes towards the brands such as familiarity and liking. The key findings of these studies show that recognition is much higher for those respondents who attended the festivals, presenting a score of 73,9%, in comparison with recall, presenting a much lower score of 37,5%. Further, and surprisingly, it suggests that the ability to recall and recognize sponsoring brands is not associated to consumer attitudes towards the brands. Instead, it relates to the time consumers dedicated to these particular events, that is, the number of music festivals attended.

A combined analysis of two randomized controlled trials evaluating the effect of Mindfulness-Based Stress Reduction on self-reported emotional experience and physiological symptoms among Veterans with Posttraumatic Stress Disorder

Thesis (Master's)--University of Washington, 2016-06

Adaptive designs in the time to event setting: The potential for benefit and risk

Thesis (Ph.D.)--University of Washington, 2016-06

Bariatric surgery in women of child-bearing age, timing between an operation and birth, and associated perinatal complications

Thesis (Master's)--University of Washington, 2016-06