T cells infiltrating inflammatory sites are usually of the activated/memory type. The precise mechanism for the positioning of these cells within tissues is unclear. Adhesion molecules certainly play a role; however, the intricate control of cell migration appears to be mediated by numerous chemokines and their receptors. Particularly important chemokines for activated/memory T cells are the CXCR3 ligands IP-10 and Mig and the CCR5 ligands RANTES, macrophage inflammatory protein-1alpha, and macrophage inflammatory protein-1beta. We raised anti-CXCR3 mAbs and were able to detect high levels of CXCR3 expression on activated T cells. Surprisingly, a proportion of circulating blood T cells, B cells, and natural killer cells also expressed CXCR3. CCR5 showed a similar expression pattern as CXCR3, but was expressed on fewer circulating T cells. Blood T cells expressing CXCR3 (and CCR5) were mostly CD45RO+, and generally expressed high levels of beta1 integrins. This phenotype resembled that of T cells infiltrating inflammatory lesions. Immunostaining of T cells in rheumatoid arthritis synovial fluid confirmed that virtually all such T cells expressed CXCR3 and approximately 80% expressed CCR5, representing high enrichment over levels of CXCR3+ and CCR5+ T cells in blood, 35 and 15%, respectively. Analysis by immunohistochemistry of various inflamed tissues gave comparable findings in that virtually all T cells within the lesions expressed CXCR3, particularly in perivascular regions, whereas far fewer T cells within normal lymph nodes expressed CXCR3 or CCR5. These results demonstrate that the chemokine receptor CXCR3 and CCR5 are markers for T cells associated with certain inflammatory reactions, particularly TH-1 type reactions. Moreover, CXCR3 and CCR5 appear to identify subsets of T cells in blood with a predilection for homing to these sites.

No abstract

The Atlantic Meridional Overturning Circulation (AMOC) is an important component of ocean thermohaline circulation. Melting of Greenland's ice sheet is freshening the North Atlantic; however, whether the augmented freshwater flux is disrupting the AMOC is unclear. Dense Labrador Sea Water (LSW), formed by winter cooling of saline North Atlantic water and subsequent convection, is a key component of the deep southward return flow of the AMOC. Although LSW formation recently decreased, it also reached historically high values in the mid-1990s, making the connection to the freshwater flux unclear. Here we derive a new estimate of the recent freshwater flux from Greenland using updated GRACE satellite data, present new flux estimates for heat and salt from the North Atlantic into the Labrador Sea and explain recent variations in LSW formation. We suggest that changes in LSW can be directly linked to recent freshening, and suggest a possible link to AMOC weakening.

Abstract. An ocean general circulation model is used to simulate the thermohaline circulation in the Mediterranean sea during the last glacial maximum and the Holocene, when the sapropel $• was deposited.

We examine the historical variability of Irminger Water (IW) along 3 sections across the West Greenland Current over 1950–2005. Significant variability in the salinity, size and position of the IW core are seen over time. Some of the saltiest and warmest IW ever recorded have been seen since 1995 (comparable to previous maximums in the 1960s). During these periods, the volume of IW is also larger, leading to larger transports into the Labrador Sea. For the period 1984–2005 transports at Cape Farewell are 3.8 ± 0.9 Sv, 7.5 ± 2.2 × 1013 J and 8.5 ± 1.8 mSv of salt referenced to 35.0. LSW formation is also correlated to IW transport at Cape Farewell with a lag of one year (0.51).

The Atlantic meridional overturning circulation (AMOC) represents the zonally integrated stream function of meridional volume transport in the Atlantic Basin. The AMOC plays an important role in transporting heat meridionally in the climate system. Observations suggest a heat transport by the AMOC of 1.3 PW at 26°N-a latitude which is close to where the Atlantic northward heat transport is thought to reach its maximum. This shapes the climate of the North Atlantic region as we know it today. In recent years there has been significant progress both in our ability to observe the AMOC in nature and to simulate it in numerical models. Most previous modeling investigations of the AMOC and its impact on climate have relied on models with horizontal resolution that does not resolve ocean mesoscale eddies and the dynamics of the Gulf Stream/North Atlantic Current system. As a result of recent increases in computing power, models are now being run that are able to represent mesoscale ocean dynamics and the circulation features that rely on them. The aim of this review is to describe new insights into the AMOC provided by high-resolution models. Furthermore, we will describe how high-resolution model simulations can help resolve outstanding challenges in our understanding of the AMOC. Key Points:• Observations and high-resolution models have changed view on the AMOC pathways • High-resolution models suggest the presence of previously unknown high-frequency AMOC variability • High-resolution models allow to estimate the intrinsic/chaotic component of the AMOCCorrespondence to:

For decades oceanographers have understood the Atlantic meridional overturning circulation (AMOC) to be primarily driven by changes in the production of deep-water formation in the subpolar and subarctic North Atlantic. Indeed, current Intergovernmental Panel on Climate Change (IPCC) projections of an AMOC slowdown in the twenty-first century based on climate models are attributed to the inhibition of deep convection in the North Atlantic. However, observational evidence for this linkage has been elusive: there has been no clear demonstration of AMOC variability in response to changes in deep-water formation. The motivation for understanding this linkage is compelling, since the overturning circulation has been shown to sequester heat and anthropogenic carbon in the deep ocean. Furthermore, AMOC variability is expected to impact this sequestration as well as have consequences for regional and global climates through its effect on the poleward transport of warm water. Motivated by the need for a mechanistic understanding of the AMOC, an international community has assembled an observing system, Overturning in the Subpolar North Atlantic Program (OSNAP), to provide a continuous record of the transbasin fluxes of heat, mass, and freshwater, and to link that record to convective activity and water mass transformation at high latitudes. OSNAP, in conjunction with the Rapid Climate Change–Meridional Overturning Circulation and Heatflux Array (RAPID–MOCHA) at 26°N and other observational elements, will provide a comprehensive measure of the three-dimensional AMOC and an understanding of what drives its variability. The OSNAP observing system was fully deployed in the summer of 2014, and the first OSNAP data products are expected in the fall of 2017.

Accelerating since the early 1990s, the Greenland Ice Sheet mass loss exerts a significant impact on thermohaline processes in the sub‐Arctic seas. Surplus freshwater discharge from Greenland since the 1990s, comparable in volume to the amount of freshwater present during the Great Salinity Anomaly events, could spread and accumulate in the sub‐Arctic seas, influencing convective processes there. However, hydrographic observations in the Labrador Sea and the Nordic Seas, where the Greenland freshening signal might be expected to propagate, do not show a persistent freshening in the upper ocean during last two decades. This raises the question of where the surplus Greenland freshwater has propagated. In order to investigate the fate, pathways, and propagation rate of Greenland meltwater in the sub‐Arctic seas, several numerical experiments using a passive tracer to track the spreading of Greenland freshwater have been conducted as a part of the Forum for Arctic Ocean Modeling and Observational Synthesis effort. The models show that Greenland freshwater propagates and accumulates in the sub‐Arctic seas, although the models disagree on the amount of tracer propagation into the convective regions. Results highlight the differences in simulated physical mechanisms at play in different models and underscore the continued importance of intercomparison studies. It is estimated that surplus Greenland freshwater flux should have caused a salinity decrease by 0.06–0.08 in the sub‐Arctic seas in contradiction with the recently observed salinification (by 0.15–0.2) in the region. It is surmised that the increasing salinity of Atlantic Water has obscured the freshening signal.