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The Mediterranean Sea releases approximately 1 Sv of water into the North Atlantic through the Gibraltar Straits, forming the saline Mediterranean Outflow Water (MOW). Its impact on large‐scale flow and specifically its northbound Lagrangian pathways are widely debated, yet a comprehensive overview of MOW pathways over recent decades is lacking. We calculate and analyze synthetic Lagrangian trajectories in 1980–2020 reanalysis velocity data. Sixteen percent of the MOW follow a direct northbound path to the sub‐polar gyre, reaching a 1,000 m depth crossing window at the southern tip of Rockall Ridge in about 10 years. Surprisingly, time‐dependent chaotic advection, not steady currents, drives over half of the northbound transport. Our results suggest a potential 15–20 years predictability in the direct northbound transport. Additionally, monthly variability appears more significant than inter‐annual variability in Lagrangian mixing and spreading the MOW. Plain Language Summary The Mediterranean Sea and the North Atlantic Ocean sustain a constant exchange of water through the shallow, narrow Straits of Gibraltar. Due to intense evaporation, the Mediterranean water is saltier and denser than its Atlantic counterpart and flows out of the Mediterranean Sea into the middepth North Atlantic Ocean to create the Mediterranean Outflow Water (MOW). This salty input reaches 1,000 m depth and spreads and mixes into the North Atlantic Ocean, and is thought to have a non‐negligible impact on its flow regime, specifically through its northbound transport and direct contribution to the salinity of the northern water of the North Atlantic. However, a comprehensive survey of the various pathways taken by the MOW is lacking. In this work, we track the 3D pathways of virtual trajectories starting at the Gibraltar Straits at various depths for 20 years. We find that 16% of the particles take a direct northbound path. Surprisingly, over half of this transport is not due to steady currents that lead the MOW to the north. Rather, it is a result of time‐dependent chaotic advection, a phenomenon that allows pathways in a time‐dependent flow to circumvent stationary barriers of transport. Key Points Synthetic Lagrangian trajectories initialized at the Gibraltar Straits, based on SODA3.4.2 reanalysis velocity data from 1980 to 2020, are used to study the pathways, Lagrangian mixing, and spreading of the Mediterranean Outflow Water (MOW) 16% of the MOW particles take a direct northbound route Over half of the direct northbound transport results from time‐dependent chaotic advection and not from a steady northbound current

Mediterranean Outflow Water (MOW) critically influences the Atlantic Meridional Overturning Circulation, yet its northward transport dynamics along the Iberian Margin remain unclear. Using terrigenous grain‐size sortable silt and benthic foraminiferal carbon isotopes from two depth‐strategic sites (U1389: 644 m vs. U1588: 1,339 m), we constrain MOW's northward depth fluctuations over the last 250 kyr. Results show that MOW progressively deepened from ∼100 to 60 ka, then stabilized—synchronized with the prevalence of millennial‐scale climate variability. During interglacials, MOW directly influenced U1588, while deepened below this site during glacials. Flow speed gradients between Sites U1389 and U1588 show pronounced precession cycles. At precession maxima—Northern Hemisphere summer insolation minima—when flow intensified, MOW underwent enhanced mixing and dilution during northward transport. This results from increased density contrasts between MOW and ambient waters, indicating deeper MOW penetration. We demonstrate precessional forcing on both the strength and depth of MOW's northward propagation.

The study of hydrologic partition has great significance in exploring the water cycle mechanism of Badain Jaran Desert (BJD) lakes in northwest China. This study analyzes the characteristics of δD and δ18O isotopes of 160 groups of water bodies in the BJD area, an isotopic buildup model is constructed to classify the hydrologic partition of the lakes by estimating the ratio between lake evaporation (E) and discharge (I), and the maintenance mechanism of the lake group indicated by E/I is discussed. The results show that the lake group primarily relies on groundwater recharge and direct recharge of a small amount of local rainwater and the local rainwater is not the main source of groundwater recharge. The mean E/I values of δD and δ18O calculated for 30 lakes in the BJD ranged from 0.74 to 1.33 (mean 1.05), indicating that the lake group largely maintained total recharge and evaporation at the same level; however, lake group have a tendency for terminal lakes to evolve into desiccating lakes. The primary reasons for the constant E/I of approximately 1 and the stability of lake group are: (1) stable groundwater recharge ensures the stability of total recharge and (2) small interannual changes in temperature, relative humidity, and the salinity effect ensure the stability of the annual evaporation of salt lakes. E/I of Badandong Lake to estimate the amount of water discharged by its seasonal drainage channels in winter and spring is approximately 10,649.16 m3/a. The outflow water discharges salt, which is the main reason the lake maintains a brackish water state. This study provides a reference for future research on the water cycle mechanism of lakes in arid regions.

The Mediterranean-Atlantic water mass exchange provides the ideal setting for deciphering the role of gateway evolution in ocean circulation. However, the dynamics of Mediterranean Outflow Water (MOW) during the closure of the Late Miocene Mediterranean-Atlantic gateways are poorly understood. Here, we define the sedimentary evolution of Neogene basins from the Gulf of Cádiz to the West Iberian margin to investigate MOW circulation during the latest Miocene. Seismic interpretation highlights a middle to upper Messinian seismic unit of transparent facies, whose base predates the onset of the Messinian salinity crisis (MSC). Its facies and distribution imply a predominantly hemipelagic environment along the Atlantic margins, suggesting an absence or intermittence of MOW preceding evaporite precipitation in the Mediterranean, simultaneous to progressive gateway restriction. The removal of MOW from the Mediterranean-Atlantic water mass exchange reorganized the Atlantic water masses and is correlated to a severe weakening of the Atlantic Meridional Overturning Circulation (AMOC) and a period of further cooling in the North Atlantic during the latest Miocene.

The WRF-lake, as a one-dimensional (1D) lake model popularly used for coupling with the Weather Research and Forecasting (WRF) system and modeling lake–atmosphere interactions, does not consider the heat exchange caused by inflow–outflow, which is an important characteristic of large reservoirs and can affect the energy budget and reservoir–atmosphere interactions. We evaluated the WRF-lake model by applying it at a large dimictic reservoir, Miyun Reservoir, in northern China. The results show that the WRF-lake model, though ignoring inflow–outflow, yields good surface water temperature simulation through reasonable parameterization. The Minlake model, as a better physically based model in reservoirs, was used to test the effect of inflow–outflow, including heat carried by inflow–outflow water exchange and water level change on the 1D model's performance. The effect of heat carried by inflow–outflow is mainly in summer, negatively correlated with hydraulic residence time and positively correlated with temperature difference between inflow and outflow. For a reservoir with hydraulic residence time of 3 years and temperature difference between inflow and outflow about 108C in summer, the heat carried by inflow–outflow is far less than the heat exchange through the surface (<2%) and therefore has little influence on total energy balance. The effect of water level change is mainly on latent heat and sensible heat in unit area, rather than outgoing longwave radiation. Though influencing the temperature in deep layers, the water level change does not have a significant impact on the surface temperature.

The distribution of dissolved aluminium (dAl) in the water column of the North Atlantic and Labrador Sea was studied along GEOTRACES section GA01 to unravel the sources and sinks of this element. Surface water dAl concentrations were low (median of 2.5 nM) due to low aerosol deposition and removal by biogenic particles (i.e. phytoplankton cells). However, surface water dAl concentrations were enhanced on the Iberian and Greenland shelves (up to 30.9 nM) due to continental inputs (rivers, glacial flour, and ice melt). Dissolved Al in surface waters scaled negatively with chlorophyll a and biogenic silica (opal) concentrations. The abundance of diatoms exerted a significant (p<0.01) control on the surface particulate Al (pAl) to dAl ratios by decreasing dAl levels and increasing pAl levels. Dissolved Al concentrations generally increased with depth and correlated strongly with silicic acid (R2>0.76) west of the Iberian Basin, suggesting net release of dAl at depth during remineralization of sinking opal-containing particles. Enrichment of dAl at near-bottom depths was observed due to the resuspension of sediments. The highest dAl concentrations (up to 38.7 nM) were observed in Mediterranean Outflow Waters, which act as a major source of dAl to mid-depth waters of the eastern North Atlantic. This study clearly shows that the vertical and lateral distributions of dAl in the North Atlantic differ when compared to other regions of the Atlantic and global oceans. Responsible for these large inter- and intra-basin differences are the large spatial variabilities in the main Al source, atmospheric deposition, and the main Al sink, particle scavenging by biogenic particles.

A mass balance of dissolved silica (DSi) based on daily measurements at the inflow and outflow of the Three Gorges Reservoir (TGR) in 2007 and a more precise budget, with inflow, outflow, primary production, biogenic silica (BSi) settlement, dissolution of BSi in the water column and flux of DSi at the sediment–water interface in the dry season (April) of 2007 were developed. We address the following question: How much does the Three Gorges Dam (TGD) affect silica transport in the TGR of the Changjiang River (Yangtze River)? The DSi varied from 71.1 to 141 μmol/l with an average of 108 μmol/l, and it ranged between 68.1 and 136 μmol/l, with an average of 107 μmol/l in inflow and outflow, respectively, in the TGR in 2007. The linear relationship of DSi between inflow and outflow water is significant (r = 0.87, n = 362, p < 0.01). Along the main stream of the TGR, the DSi concentration decreases with an average concentration of 84.0 μmol/l in the dry season. However, the stratification of DSi was not obvious in the main channel of the TGR in the dry season. The BSi is within the range of 0.04–5.00 μmol/l, with an average concentration of 2.1 μmol/l in the main channel of the TGR, while it is much higher in Xiangxi Bay (1.30–47.7 μmol/l, 13.1 μmol/l) than in the main stream of the TGR and the other bays. After the third filling of the TGR, approximately 3.8% of the DSi was retained by the TGR based on a 12-month monitoring scheme in 2007, which would slightly reduce nutrient fluxes of the Changjiang River to the East China Sea (2%). DSi was lost during January to June and November, whereas the additions of DSi were found during the other months in 2007. The budget results also indicate that there is a slight retention of DSi. The retention of DSi in the reservoir is approximately 2.9%, while BSi is approximately 44%. Compared with the total silica load, the retention of DSi and BSi in the reservoir is only 5.0% in the dry season. With its present storage capacity, the reservoir does not play an important role as a silica sink in the channel of the TGR. The DSi load is significantly related to discharge both in inflow and outflow waters (p < 0.01). DSi retention, to some extent, is the runoff change due to impoundment.

The Mediterranean overflow water is one of the most important intermediate-depth water masses in the North Atlantic. To investigate its properties a pre-industrial simulation with the earth system model EC-Earth is used. The multidecadal variability of the outflow is analysed by examining the modelled volume and salt transports through the Strait of Gibraltar as well as different atmospheric patterns (such as the wind pattern and the net freshwater fluxes). The salinity evolution in the main core of the outflow in the mid-Atlantic is also taken into account. The leading empirical orthogonal functions for the modelled salinity 900 m coincided with the modelled distribution of outflow water. The associated principal component showed a multidecadal variability of the salinity field. The variability of the net salt transport through the Strait of Gibraltar showed a similar behaviour where the Atlantic-Mediterranean system manifested two clear states. One of these is when the Mediterranean imports salt from the Atlantic and the other is where salt export to the Atlantic predominates. This result indicates that the Mediterranean Sea acts as a storage of salt alternating between the two states. The negative phase of the North Atlantic oscillation appears to play a role driving the variability of the salt transport and its impact on the overturning circulation in the North Atlantic.

The authors examine small-scale spatiotemporal variability of the layer nearly 2000-m depth, which is the “bottom” of the present Argo observation system, using all of available Argo float data. The 10-day change, Δ T 10 , is defined as the difference of temperature between two successive observations with an interval of nearly 10 days for each individual float at an isobaric surface. |Δ T 10 | is large along the western boundary currents at 1000 dbar, and becomes less remarkable with depth. At 1950 dbar, mean |Δ T 10 | is noticeable in the northeastern Atlantic Ocean (NEAO), the Argentine basin, and the northwestern Indian Ocean. In the Southern Ocean, large |Δ T 10 | is localized in some areas located over the ridges or leeward of the plateau. Basically, Δ T 10 at isobaric surfaces is accounted for by the heave component, but the spiciness component is dominant or comparable to the other in the NEAO and the Argentine basin. Δ T 10 decreases with depth monotonically most of the world, suggesting that wind energy input is attenuated with depth. In some areas in the Southern Ocean, however, the vertical profile of |Δ T 10 | implies enhanced bottom-induced turbulence. |Δ T 10 | peaks at 1300 dbar in the NEAO, corresponding to the spread of the Mediterranean Outflow Water. |Δ T 10 | is smaller in the Pacific Ocean compared with the other oceans, but is enhanced along the equator, the Kuroshio and its Extension, the Kuril, Aleutian, Hawaii, and Mariana Islands, and the Emperor Seamount Chain.

Seamounts constitute an obstacle to the ocean circulation, modifying it. As a result, a variety of hydrodynamical processes and phenomena may take place over seamounts, among others, flow intensification, current deflection, upwelling, Taylor caps, and internal waves. These oceanographic effects may turn seamounts into very productive ecosystems with high species diversity, and in some cases, are densely populated by benthic organisms, such corals, gorgonians, and sponges. In this study, we describe the oceanographic conditions over seamounts and other underwater features in the path of the Mediterranean Outflow Water (MOW), where populations of benthic suspensions feeders have been observed. Using CTD, LADPC and biochemical measurements carried out in the Ormonde and Formigas seamounts and the Gazul mud volcano (Northeast Atlantic), we show that Taylor caps were not observed in any of the sampled features. However, we point out that the relatively high values of the Brunt–Väisälä frequency in the MOW halocline, in conjunction with the slope of the seamount flanks, set up conditions for the breakout of internal waves and amplification of the currents. This may enhance the vertical mixing, resuspending the organic material deposited on the seafloor and, therefore, increasing the food availability for the communities dominated by benthic suspension feeders. Thus, we hypothesize that internal waves could be improving the conditions for benthic suspension feeders to grow on the slope of seamounts.