Propagation of Thermohaline Anomalies and their predictive potential along the Atlantic water pathway

We assess to what extent seven state-of-the-art dynamical prediction systems can retrospectively predict winter sea surface temperature (SST) in the subpolar North Atlantic and the Nordic Seas in the period 1970-2005. We focus on the region where warm water flows poleward, i.e., the Atlantic water pathway to the Arctic, and on interannual-to-decadal time scales. Observational studies demonstrate predictability several years in advance in this region, but we find that SST skill is low with significant skill only at lead time 1-2 years. To better understand why the prediction systems have predictive skill or lack thereof, we assess the skill of the systems to reproduce a spatio-temporal SST pattern based on observations. The physical mechanism underlying this pattern is a propagation of oceanic anomalies from low to high latitudes along the major currents; the North Atlantic Current and the Norwegian Atlantic Current. We find that the prediction systems have difficulties in reproducing this pattern. To identify whether the misrepresentation is due to incorrect model physics, we assess the respective uninitialized historical simulations. These simulations also tend to misrepresent the spatio-temporal SST pattern, indicating that the physical mechanism is not properly simulated. However, the representation of the pattern is slightly degraded in the predictions compared to historical runs, which could be a result of initialization shocks and forecast drift effects. Ways to enhance predictions, could be through improved initialization, and better simulation of poleward circulation of anomalies. This might require model resolutions in which flow over complex bathymetry and physics of mesoscale ocean eddies and their interactions with the atmosphere are resolved.

Propagation of Thermohaline Anomalies and their predictive potential in the Northern North Atlantic

<p>In this study we assess to what extent seven different dynamical prediction systems can retrospectively predict the winter sea surface temperature (SST) in the subpolar North Atlantic and the Nordic Seas in the time period 1970-2005. We focus in particular on the region where warm water flows poleward, i.e., the Atlantic water pathway, and on interannual-to-decadal time scales. To better understand why dynamical prediction systems have predictive skill or lack thereof, we confront them with a mechanism identified from observations – propagation of oceanic anomalies from low to high latitudes – on different forecast lead times. This observed mechanism shows that warm and cold anomalies propagate along the Atlantic water pathway within a certain time frame. A key result from this study is that most models have difficulty representing this mechanism, resulting in an overall poor prediction skill after 1-2 years lead times (after applying a band-pass filter to focus on interannual-to-decadal time scales). There is a link, although not very strong, between predictive skill and the representation of the SST propagation. Observational studies demonstrate predictability several years in advance in this region, thus suggesting a great potential for improvement of dynamical climate predictions by resolving the causes for the misrepresentation of the oceanic link. Inter model differences in simulating surface velocities along the Atlantic water pathway suggest that realistic velocities are important to better circulate anomalies poleward, and hence, increase predictive skill on interannual-to-decadal time scales in the oceanic gateway to the Arctic.</p>

Takeda G-protein Receptor (TGR)-5 Evolves Classical Activestate Conformational Signatures in Complex with Chromolaena Odorata-derived Flavonoid-5,7-dihydroxy-6-4-dimethoxyflavanone

Background: Takeda G-protein receptor 5 (TGR5) via glucagon-like peptide release and insulin signaling underlies antidiabetic roles of TGR5 agonists. Chromolaena Odorata- derived flavonoid-5,7-dihydroxy-6-4-dimethoxyflavanone (COF) has been identified as (TGR5) agonist. The structural basis for their interaction has not been studied. Objective: This study aimed at providing both structural and dynamic insights into COF/TGR5 interaction. Methods: Classical GPCR activation signatures (TMIII-TMVI ionic lock, toggle switches, internal water pathway) using classical MD simulation have been used. Results: Y893.29, N933.33 and E1695.43 are key residues found to be involved in ligand binding; the continuous internal water pathway connects hydrophilic groups of the ligand to the TMIII-TMVI interface in COF-bound state, TMIII-TMVI ionic locks ruptures in COF-TGR5 complex but not antagonist-bound state, and ruptured ionic lock is associated with the evolution of active-state “VPVAM” (analogous to “NPxxY”) conformation. Dihedral angles (c2) calculated along the trajectory strongly suggest W2376.48 as a ligand-dependent toggle switch. Conclusion: TGR5 evolves active state conformation from a starting intermediate state conformation when bound to COF, which further supports its underlying anti-diabetic activities.

Channelization of water pathway and encapsulation of DS in the SL of the TFC FO membrane as a novel approach for controlling dilutive internal concentration polarization

In this study, we explored the use of hydrophobic and hydrophilic water-stable MOFs as well as their mixture for the fabrication of high-performance MMM-based TFC FO membranes for controlling ICP.