A variational proof of a disentanglement theorem for multilinear norm inequalities

In [1] and [2] we developed a duality theory for multilinear norm inequalities. This duality theory is underpinned by a disentanglement theorem, which states that estimates on a weighted geometric mean over (convex) families of functions can be disentangled into quantitatively linked estimates on each family separately. The disentanglement theorem was proved in [1] via minimax theory together with weak*-compactness arguments in the space of finitely additive measures, and an application of the Yosida-Hewitt theory of such measures. In this paper we provide an alternate, rather elementary approach to the disentanglement theorem: we first prove a finite-dimensional case via perturbation and strong compactness, and then, building on that, the general infinite-dimensional case via the finite intersection property and weak compactness.Comment: 15 pages, 1 diagra

Recent changes in the freshwater composition east of Greenland

Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 42 (2015): 2326–2332, doi:10.1002/2014GL062759.Results from three hydrographic surveys across the East Greenland Current between 2011 and 2013 are presented with focus on the freshwater sources. End-member analysis using salinity, δ18O, and nutrient data shows that while meteoric water dominated the freshwater content, a significant amount of Pacific freshwater was present near Denmark Strait with a maximum in August 2013. While in 2011 and 2012 the net sea ice melt was dominated by brine, in 2013 it became close to zero. The amount of Pacific freshwater observed near Denmark Strait in 2013 is as large as the previous maximum in 1998. This, together with the decrease in meteoric water and brine, suggests a larger contribution from the Canadian Basin. We hypothesize that the increase of Pacific freshwater is the result of enhanced flux through Bering Strait and a shorter pathway of Pacific water through the interior Arctic to Fram Strait.The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7 2007–2013) under grant agreement 308299, NACLIM Project, and from the U.S. National Science Foundation under grant OCE-085041.2015-10-0

Evolution and Transformation of the North Icelandic Irminger Current Along the North Iceland Shelf

The North Icelandic Irminger Current (NIIC) flowing northward through Denmark Strait is the main source of salt and heat to the north Iceland shelf. We quantify its along-stream evolution using the first high-resolution hydrographic/velocity survey north of Iceland that spans the entire shelf along with historical hydrographic measurements as well as data from satellites and surface drifters. The NIIC generally follows the shelf break. Portions of the flow recirculate near Denmark Strait and the Kolbeinsey Ridge. The current's volume transport diminishes northeast of Iceland before it merges with the Atlantic Water inflow east of Iceland. The hydrographic properties of the current are modified along its entire pathway, predominantly because of lateral mixing with cold, fresh offshore waters rather than air-sea interaction. Progressing eastward, the NIIC cools and freshens by approximately 0.3°C and 0.02–0.03 g kg−1 per 100 km, respectively, in both summer and winter. Dense-water formation on the shelf is limited, occurring only sporadically in the historical record. The hydrographic properties of this locally formed water match the lighter portion of the North Icelandic Jet (NIJ), which emerges northeast of Iceland and transports dense water toward Denmark Strait. In the region northeast of Iceland, the NIIC is prone to baroclinic instability. Enhanced eddy kinetic energy over the steep slope there suggests a dynamical link between eddies shed by the NIIC and the formation of the NIJ as previously hypothesized. Thus, while the NIIC rarely supplies the NIJ directly, it may be dynamically important for the overturning circulation in the Nordic Seas.publishedVersio

Evolution and transformation of the North Icelandic Irminger Current along the North Iceland Shelf

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Semper, S., Våge, K., Pickart, R., Jónsson, S., & Valdimarsson, H. Evolution and transformation of the North Icelandic Irminger Current along the North Iceland Shelf. Journal of Geophysical Research: Oceans, 127(3), (2022): e2021JC017700, https://doi.org/10.1029/2021jc017700.The North Icelandic Irminger Current (NIIC) flowing northward through Denmark Strait is the main source of salt and heat to the north Iceland shelf. We quantify its along-stream evolution using the first high-resolution hydrographic/velocity survey north of Iceland that spans the entire shelf along with historical hydrographic measurements as well as data from satellites and surface drifters. The NIIC generally follows the shelf break. Portions of the flow recirculate near Denmark Strait and the Kolbeinsey Ridge. The current's volume transport diminishes northeast of Iceland before it merges with the Atlantic Water inflow east of Iceland. The hydrographic properties of the current are modified along its entire pathway, predominantly because of lateral mixing with cold, fresh offshore waters rather than air-sea interaction. Progressing eastward, the NIIC cools and freshens by approximately 0.3°C and 0.02–0.03 g kg−1 per 100 km, respectively, in both summer and winter. Dense-water formation on the shelf is limited, occurring only sporadically in the historical record. The hydrographic properties of this locally formed water match the lighter portion of the North Icelandic Jet (NIJ), which emerges northeast of Iceland and transports dense water toward Denmark Strait. In the region northeast of Iceland, the NIIC is prone to baroclinic instability. Enhanced eddy kinetic energy over the steep slope there suggests a dynamical link between eddies shed by the NIIC and the formation of the NIJ as previously hypothesized. Thus, while the NIIC rarely supplies the NIJ directly, it may be dynamically important for the overturning circulation in the Nordic Seas.This research was supported by the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 101022251 (S. Semper), the Trond Mohn Foundation Grant BFS2016REK01 (S. Semper and K. Våge), and the U.S. National Science Foundation Grants OCE-1558742 and OCE-1259618 (R. S. Pickart)

Vaccination of COPD patients with a pneumococcus type 6B tetanus toxoid conjugate vaccine

To access publisher full text version of this article. Please click on the hyperlink in Additional Links fieldThis paper examines how pneumococcal type 6B polysaccharide conjugated to tetanus toxoid (Pn6B-TT) compares to a 23 valent pneumococcal vaccine (pneumococcal polysaccharide (PPS)-23) with respect to immunogenicity and serum opsonic activity in patients with chronic obstructive pulmonary disease (COPD). Patients with COPD aged 55-75 yrs were vaccinated with Pn6B-TT (n=10) or with PPS-23 (n=9). Healthy young adults (HA) were vaccinated with Pn6B-TT as controls. Total antibodies to serotype 6B polysaccharide were measured by radioimmunoassay and immunoglobulin (Ig)G antibodies by enzyme-linked immunosorbent assay. Opsonic activity was measured by a phagocytosis assay using human neutrophils as effector cells. The patient groups were comparable by age, smoking history, lung function and use of steroids. COPD patients vaccinated with Pn6B-TT or PPS-23 showed an increase in IgG antibodies and a nonsignificant increase in opsonic activity. This was similar to the increase in IgG and opsonic activity seen in HA. There was a significant correlation between antibody levels and opsonic activity in COPD patients vaccinated both with Pn6B-TT and PPS-23. Pneumococcal antibodies have been shown to confer protection from infection. The results of the present study indicate that protective immunity can be expected in elderly chronic obstructive pulmonary disease patients vaccinated with conjugate vaccines

Leucocyte counts and lymphocyte subsets in relation to pregnancy and HIV infection in Malawian women.

Problem We investigated leukocyte and lymphocyte subsets in HIV-infected or HIV-uninfected, pregnant or non-pregnant Malawian women to explore whether HIV infection and pregnancy may act synergistically to impair cellular immunity. Method of study We recruited 54 pregnant and 48 non-pregnant HIV-uninfected women and 24 pregnant and 20 non-pregnant HIV-infected Malawian women. We compared peripheral blood leukocyte and lymphocyte subsets between women in the four groups. Results Parturient HIV-infected and HIV-uninfected women had more neutrophils (each P<.0001), but fewer lymphocytes (P<.0001; P=.0014) than non-pregnant women. Both groups had fewer total T cells (P<.0001; P=.002) and CD8+ T cells (P<.0001; P=.014) than non-pregnant women. HIV-uninfected parturient women had fewer CD4+ and γδ T cells, B and NK cells (each P<.0001) than non-pregnant women. Lymphocyte subset percentages were not affected by pregnancy. Conclusion Malawian women at parturition have an increased total white cell count due to neutrophilia and an HIV-unrelated pan-lymphopenia

Water mass transformation in the Iceland Sea: Contrasting two winters separated by four decades

Dense water masses formed in the Nordic Seas flow across the Greenland–Scotland Ridge and contribute substantially to the lower limb of the Atlantic Meridional Overturning Circulation. Originally considered an important source of dense water, the Iceland Sea gained renewed interest when the North Icelandic Jet — a current transporting dense water from the Iceland Sea into Denmark Strait — was discovered in the early 2000s. Here we use recent hydrographic data to quantify water mass transformation in the Iceland Sea and contrast the present conditions with measurements from hydrographic surveys conducted four decades earlier. We demonstrate that the large-scale hydrographic structure of the central Iceland Sea has changed significantly over this period and that the locally transformed water has become less dense, in concert with a retreating sea-ice edge and diminished ocean-to-atmosphere heat fluxes. This has reduced the available supply of dense water to the North Icelandic Jet, but also permitted densification of the East Greenland Current during its transit through the presently ice-free western Iceland Sea in winter. Together, these changes have significantly altered the contribution from the Iceland Sea to the overturning in the Nordic Seas over the four decade period.publishedVersio

Structure and variability of the North Icelandic Jet from two years of mooring data

Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 124(6), (2019): 3987-4002, doi:10.1029/2019JC015134.Mooring data from September 2011 to July 2013 on the Iceland slope north of Denmark Strait are analyzed to better understand the structure and variability of the North Icelandic Jet (NIJ). Three basic configurations of the flow were identified: (1) a strong separated East Greenland Current (EGC) on the mid‐Iceland slope coincident with a weak NIJ on the upper slope, (2) a merged separated EGC and NIJ, and (3) a strong NIJ located at its climatological mean position, coincident with a weak signature of the separated EGC at the base of the Iceland slope. Our study reveals that the NIJ‐dominant scenario was present during different times of the year for the two successive mooring deployments—appearing mainly from September to February the first year and from January to July the second year. Furthermore, when this scenario was active it varied on short timescales. An energetics analysis demonstrates that the high‐frequency variability is driven by mean‐to‐eddy baroclinic conversion at the shoreward edge of the NIJ, consistent with previous modeling work. The seasonal timing of the NIJ dominant scenario is investigated in relation to the atmospheric forcing upstream of Denmark Strait. The resulting lagged correlations imply that strong turbulent heat fluxes in a localized region on the continental slope of Iceland, south of the Spar Fracture zone, lead to a stronger NIJ dominant state with a two‐month lag. This can be explained dynamically in terms of previous modeling work addressing the circulation response to dense water formation near an island.The authors thank the crew members of the R/V Knorr, RRS James Clark Ross, and R/V Bjarni Sæmundsson for the deployment and recovery of the moorings. D. Torres and F. Bahr processed the second year of mooring data. We thank K. Våge, B. Harden, Z. Song, J. Li, and M. Li for helpful discussions regarding the work. Funding was provided by the National Science Foundation under grants OCE‐1558742 (J. H., R. P., P. L., and M. S.) and OCE‐1534618 (M. S.). The mooring data are available at http://kogur.whoi.edu/php/index.php.2019-12-0

A numerical study of interannual variability in the North Icelandic Irminger Current

Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 123(12), (2018): 8994-9009, doi:10.1029/2018JC013800.The North Icelandic Irminger Current (NIIC) is an important component of the Atlantic Water (AW) inflow to the Nordic Seas. In this study, both observations and a high‐resolution (1/12°) numerical model are used to investigate the seasonal to interannual variability of the NIIC and its forcing mechanisms. The model‐simulated velocity and hydrographic fields compare well with the available observations. The water mass over the entire north Icelandic shelf exhibits strong seasonal variations in both temperature and salinity, and such variations are closely tied to the AW seasonality in the NIIC. In addition to seasonal variability, there is considerable variation on interannual time scales, including a prominent event in 2003 when the AW volume transport increased by about 0.5 Sv. To identify and examine key forcing mechanisms for this event, we analyzed outputs from two additional numerical experiments: using only the seasonal climatology for buoyancy flux (the momentum case) and using only the seasonal climatology for wind stress (the buoyancy case). It is found that changes in the wind stress are predominantly responsible for the interannual variations in the AW volume transport, AW fraction in the NIIC water, and salinity. Temperature changes on the shelf, however, are equally attributable to the buoyancy flux and wind forcing. Correlational analyses indicate that the AW volume transport is most sensitive to the wind stress southwest of Iceland.This work is supported by the U.S. National Science Foundation (NSF) under grants OCE‐1634886 (J. Zhao and J. Yang) and OCE‐1558742 (R. Pickart), and by the Bergen Research Foundation grant BFS2016REK01 (K. Våge and S. Semper). We thank Xiaobiao Xu at Florida State University for providing the initial model configuration. Comments from anonymous reviewers help to improve the manuscript. The altimeter products are produced and distributed by the Copernicus Marine and Environment Monitoring Service (CMEMS, http://www.marine.copernicus.eu). The hydrographic maps along the Hornbanki section are available at http://www.hafro.is/Sjora/.2019-04-1

On the hydrography of Denmark Strait

Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 122 (2017): 306–321, doi:10.1002/2016JC012007.Using 111 shipboard hydrographic sections across Denmark Strait occupied between 1990 and 2012, we characterize the mean conditions at the sill, quantify the water mass constituents, and describe the dominant features of the Denmark Strait Overflow Water (DSOW). The mean vertical sections of temperature, salinity, and density reveal the presence of circulation components found upstream of the sill, in particular the shelfbreak East Greenland Current (EGC) and the separated EGC. These correspond to hydrographic fronts consistent with surface-intensified southward flow. Deeper in the water column the isopycnals slope oppositely, indicative of bottom-intensified flow of DSOW. An end-member analysis indicates that the deepest part of Denmark Strait is dominated by Arctic-Origin Water with only small amounts of Atlantic-Origin Water. On the western side of the strait, the overflow water is a mixture of both constituents, with a contribution from Polar Surface Water. Weakly stratified “boluses” of dense water are present in 41% of the occupations, revealing that this is a common configuration of DSOW. The bolus water is primarily Arctic-Origin Water and constitutes the densest portion of the overflow. The boluses have become warmer and saltier over the 22 year record, which can be explained by changes in end-member properties and their relative contributions to bolus composition.US National Science Foundation (RP and DM) Grant Number: OCE-0959381; ;Norwegian Research Council Grant Number: 231647 (KV)2017-07-2