A Modified Field Infiltrometer Test for Clay Liners

Regulatory agencies are looking more frequently to in situ field hydraulic conductivity tests for the assessment of a liner\u27s compliance to a specified hydraulic conductivity. Most field tests have evaluated hydraulic conductivity by measuring the infiltration rate of the liner. The infiltration rate can be used to arrive at a hydraulic conductivity value if the hydraulic boundary conditions of the test can be identified or if the head loss at different depths can be measured. A test fill of a clay liner was evaluated for its saturated vertical hydraulic conductivity. This paper discusses the use of eight tensiometers to measure soil suction at four depths beneath a double ring infiltrometer. The hydraulic conductivity results using the tensiometer data displayed good consistency and agreed well with laboratory test results

Sustained high-level expression of human factor IX (hFIX) after liver-targeted delivery of recombinant adeno-associated virus encoding the hFIX gene in rhesus macaques

The feasibility, safety, and efficacy of liver-directed gene transfer was evaluated in 5 male macaques (aged 2.5 to 6.5 years) by using a recombinant adeno-associated viral (rAAV) vector (rAAV-2 CAGG-hFIX) that had previously mediated persistent therapeutic expression of human factor IX (hFIX; 6%-10% of physiologic levels) in murine models. A dose of 4 × 1012 vector genomes (vgs)/kg of body weight was administered through the hepatic artery or portal vein. Persistence of the rAAV vgs as circular monomers and dimers and high-molecular-weight concatamers was documented in liver tissue by Southern blot analysis for periods of up to 1 year. Vector particles were present in plasma, urine, or saliva for several days after infusion (as shown by polymerase chain reaction analysis), and the vgs were detected in spleen tissue at low copy numbers. An enzyme-linked immunosorption assay capable of detecting between 1% and 25% of normal levels of hFIX in rhesus plasma was developed by using hyperimmune serum from a rhesus monkey that had received an adenoviral vector encoding hFIX. Two macaques having 3 and 40 rAAV genome equivalents/cell, respectively, in liver tissue had 4% and 8% of normal physiologic plasma levels of hFIX, respectively. A level of hFIX that was 3% of normal levels was transiently detected in one other macaque, which had a genome copy number of 25 before abrogation by a neutralizing antibody (inhibitor) to hFIX. This nonhuman-primate model will be useful in further evaluation and development of rAAV vectors for gene therapy of hemophilia B. © 2002 by The American Society of Hematology

Alternative Methods of Estimating Forage Height in Pastures can be Cross Calibrated

Describes how to cross calibrate alternative measurements of pasture forage mass

Reconciling tracer and float observations of the export pathways of Labrador Sea Water

For more than fifty years, it has been generally accepted by oceanographers that the Deep Western Boundary Current (DWBC) is the principal conduit of recently-convected Labrador Sea Water (LSW) exported from the high-latitude North Atlantic to the equator. Supporting this supposition is observational evidence that the waters of the DWBC have consistently greater equatorward velocities, higher concentrations of passive tracers, and younger ages compared to ocean interior waters. However, recent observations and simulations of floats launched in the DWBC in the Labrador Sea show that most water parcels are quickly ejected from the DWBC and follow instead interior pathways to the subtropics. Here, we show that tracer observations from the last three decades are compatible with the existence of both DWBC and basin-interior export pathways. From analyses of observational data and model output, we find that equatorward transport in the basin interior is consistent with the large-scale vorticity balance at mid-depth. Furthermore, from the modeling analysis we show that despite higher, localized concentrations of tracer and particles in the DWBC, only 5% of particles released in the Labrador Sea are transported from the subpolar to subtropical gyre via a continuous DWBC pathway. Thus, the interior pathway is a significant contributor to LSW export. Highlights: - Lagrangian observations of Labrador Sea Water match Eulerian observations - There is deep equatorward flow in the basin interior - This interior pathway is significant compared to the pathway along the boundar

The present and future system for measuring the Atlantic meridional overturning circulation and heat transport

of the global combined atmosphere-ocean heat flux and so is important for the mean climate of the Atlantic sector of the Northern Hemisphere. This meridional heat flux is accomplished by both the Atlantic Meridional Overturning Circulation (AMOC) and by basin-wide horizontal gyre circulations. In the North Atlantic subtropical latitudes the AMOC dominates the meridional heat flux, while in subpolar latitudes and in the subtropical South Atlantic the gyre circulations are also important. Climate models suggest the AMOC will slow over the coming decades as the earth warms, causing widespread cooling in the Northern hemisphere and additional sea-level rise. Monitoring systems for selected components of the AMOC have been in place in some areas for decades, nevertheless the present observational network provides only a partial view of the AMOC, and does not unambiguously resolve the full variability of the circulation. Additional observations, building on existing measurements, are required to more completely quantify the Atlantic meridional heat transport. A basin-wide monitoring array along 26.5°N has been continuously measuring the strength and vertical structure of the AMOC and meridional heat transport since March 31, 2004. The array has demonstrated its ability to observe the AMOC variability at that latitude and also a variety of surprising variability that will require substantially longer time series to understand fully. Here we propose monitoring the Atlantic meridional heat transport throughout the Atlantic at selected critical latitudes that have already been identified as regions of interest for the study of deep water formation and the strength of the subpolar gyre, transport variability of the Deep Western Boundary Current (DWBC) as well as the upper limb of the AMOC, and inter-ocean and intrabasin exchanges with the ultimate goal of determining regional and global controls for the AMOC in the North and South Atlantic Oceans. These new arrays will continuously measure the full depth, basin-wide or choke-point circulation and heat transport at a number of latitudes, to establish the dynamics and variability at each latitude and then their meridional connectivity. Modeling studies indicate that adaptations of the 26.5°N type of array may provide successful AMOC monitoring at other latitudes. However, further analysis and the development of new technologies will be needed to optimize cost effective systems for providing long term monitoring and data recovery at climate time scales. These arrays will provide benchmark observations of the AMOC that are fundamental for assimilation, initialization, and the verification of coupled hindcast/forecast climate models

Upper ocean manifestations of a reducing meridional overturning circulation

Most climate models predict a slowing down of the Atlantic Meridional Overturning Circulation during the 21st century. Using a 100year climate change integration of a high resolution coupled climate model, we show that a 5.3Sv reduction in the deep southward transport in the subtropical North Atlantic is balanced solely by a weakening of the northward surface western boundary current, and not by an increase in the southward transport integrated across the interior ocean away from the western boundary. This is consistent with Sverdrup balance holding to a good approximation outside of the western boundary region on decadal time scales, and may help to spatially constrain past and future change in the overturning circulation. The subtropical gyre weakens by 3.4Sv over the same period due to a weakened wind stress curl. These changes combine to give a net 8.7Sv reduction in upper western boundary transport. © 2012. American Geophysical Union. All Rights Reserved

Role of air–sea fluxes and ocean surface density in the production of deep waters in the eastern subpolar gyre of the North Atlantic

Wintertime convection in the North Atlantic Ocean is a key component of the global climate as it produces dense waters at high latitudes that flow equatorward as part of the Atlantic Meridional Overturning Circulation (AMOC). Recent work has highlighted the dominant role of the Irminger and Iceland basins in the production of North Atlantic Deep Water. Dense water formation in these basins is mainly explained by buoyancy forcing that transforms surface waters to the deep waters of the AMOC lower limb. Air–sea fluxes and the ocean surface density field are both key determinants of the buoyancy-driven transformation. We analyze these contributions to the transformation in order to better understand the connection between atmospheric forcing and the densification of surface water. More precisely, we study the impact of air–sea fluxes and the ocean surface density field on the transformation of subpolar mode water (SPMW) in the Iceland Basin, a water mass that “pre-conditions” dense water formation downstream. Analyses using 40 years of observations (1980–2019) reveal that the variance in SPMW transformation is mainly influenced by the variance in density at the ocean surface. This surface density is set by a combination of advection, wind-driven upwelling and surface fluxes. Our study shows that the latter explains ∼ 30 % of the variance in outcrop area as expressed by the surface area between the outcropped SPMW isopycnals. The key role of the surface density in SPMW transformation partly explains the unusually large SPMW transformation in winter 2014–2015 over the Iceland Basin

Atlantic deep water formation occurs primarily in the Iceland Basin and Irminger Sea by local buoyancy forcing

The Atlantic Meridional Overturning Circulation (AMOC), a key mechanism in the climate system, delivers warm and salty waters from the subtropical gyre to the subpolar gyre and Nordic Seas, where they are transformed into denser waters flowing southward in the lower AMOC limb. The prevailing hypothesis is that dense waters formed in the Labrador and Nordic Seas are the sources for the AMOC lower limb. However, recent observations reveal that convection in the Labrador Sea contributes minimally to the total overturning of the subpolar gyre. In this study, we show that the AMOC is instead primarily composed of waters formed in the Nordic Seas and Irminger and Iceland basins. A first direct estimate of heat and freshwater fluxes over these basins demonstrates that buoyancy forcing during the winter months can almost wholly account for the dense waters of the subpolar North Atlantic that are exported as part of the AMOC

Relocation risky for bumblebee colonies

Climate change impacts on bumblebees converge across continentsFil: Lozier, Jeffrey. University of Alabama; Estados UnidosFil: Cameron, Sydney. University of Illinois; Estados UnidosFil: Duennes, Michelle. University of Illinois; Estados UnidosFil: Strange, James. State University of Utah; Estados UnidosFil: Williams, Paul. Natural History Museum; Reino UnidoFil: Goulson, David. University of Sussex; Reino UnidoFil: Brown, Mark. University of London; Reino UnidoFil: Morales, Carolina Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Jepsen, Sarina. Xerces Society; Estados Unido

Propagation and transformation of upper North Atlantic deep water from the subpolar gyre to 26.5°N

Because new observations have revealed that the Labrador Sea is not the primary source for waters in the lower limb of the Atlantic Meridional Overturning Circulation (AMOC) during the Overturning in the Subpolar North Atlantic Programme (OSNAP) period, it seems timely to re‐examine the traditional interpretation of pathways and property variability for the AMOC lower limb from the subpolar gyre to 26.5°N. In order to better understand these connections, Lagrangian experiments were conducted within an eddy‐rich ocean model to track upper North Atlantic Deep Water (uNADW), defined by density, between the OSNAP line and 26.5°N as well as within the Labrador Sea. The experiments reveal that 77% of uNADW at 26.5°N is directly advected from the OSNAP West section along the boundary current and interior pathways west of the Mid‐Atlantic Ridge. More precisely, the Labrador Sea is a main gateway for uNADW sourced from the Irminger Sea, while particles connecting OSNAP East to 26.5°N are exclusively advected from the Iceland Basin and Rockall Trough along the eastern flank of the Mid‐Atlantic Ridge. Although the pathways between OSNAP West and 26.5°N are only associated with a net formation of 1.1 Sv into the uNADW layer, they show large density changes within the layer. Similarly, as the particles transit through the Labrador Sea, they undergo substantial freshening and cooling that contributes to further densification within the uNADW layer