Surface Height Difference Research Articles

Improved surface quality components enabled by dual-laser additive/subtractive hybrid manufacturing process: Thermal behavior and ablation mechanisms

A high roughness of the laser powder bed fusion (LPBF) process has been one of the most concerned issues in the integrated fabrication of complicated metal parts. In this research, a dual (continuous and ultrafast) laser additive-subtractive hybrid manufacturing (LASHM) process is introduced to improve the surface quality of the LPBF-processed components. Effects of the laser subtractive times and the feed rates on the side surface morphology of the LASHM-processed AISI 316L components were studied. Meanwhile, the VOF transient physical model of LPBF and double temperature physical model of LASHM were established to investigate the individual thermal behaviors and the material melting-ablation mechanisms. For the LPBF process, the operating temperature of the molten pool bottom was firstly stable in 300 K (< 25 ms), then increased to 630 K (25 ms-35 ms) and finally exponentially increased to 3000 K (>35 ms), implying the delayed thermal effect. Meanwhile, the operating temperature of the top region was linearly increased to 2050 K. While for the ultrafast laser subtractive process, the operating temperature of the top region was remained at ∼ 300 K with the temperature rapid increase to 2900 K below 104 ps in the bottom region, leading to the direct material ablation and maintaining the LPBF-processed microstructure. At the laser subtractive times equal to four with the sequence feed rates of 10 μm, 10 μm, 8 μm and 6 μm, the surface roughness Sa and the maximum surface height difference Sz were considerably reduced from 10.774 μm and 73.387 μm to 1.933 μm and 18.151 μm.

Study of thermal stress deformation in hybrid 3D printing and milling process of PEEK material

Hybrid manufacturing can enable rapid production of personalized artificial bones that are made of Polyether-ether-ketone (PEEK) by integrating 3D printing and milling. A main challenge, however, is the thermal stress deformation that arises from the fused deposition process, leading to warping and shrinkage. As a result, the fabrication accuracy is significantly diminished. This work aims to address this challenge by investigating the thermal stress deformation behavior of PEEK in hybrid manufacturing. The main contributions of this work, therefore, include the development of a model for this thermal deformation behavior, and the identification of key parameters such as cross-section length ( Ls), printed layer thickness ( Lh), and current workpiece height ( He). Further, experiments are conducted based on response surface methodology (RSM) to explore the relationships between temperature variation rate (Δ T), end surface height difference (Δ S), and length shrinkage rate (Δ L) with critical hybrid processing parameters. Optimal parameter combinations are then identified. Our experiments demonstrate that the proposed methods effectively reduce the effects of warping and shrinkage.

Exploring Siamese network to estimate sea state bias of synthetic aperture radar altimeter

Sea state bias (SSB) is a crucial error of satellite radar altimetry over the ocean surface. For operational nonparametric SSB (NPSSB) models, such as two-dimensional (2D) or three-dimensional (3D) NPSSB, the solution process becomes increasingly complex and the construction of their regression functions pose challenges as the dimensionality of relevant variables increases. And most current SSB correction models for altimeters still follow those of traditional nadir radar altimeters, which limits their applicability to Synthetic Aperture Radar altimeters. Therefore, to improve this situation, this study has explored the influence of multi-dimensional SSB models on Synthetic Aperture Radar altimeters. This paper proposes a deep learning-based SSB estimation model called SNSSB, which employs a Siamese network framework, takes various multi-dimensional variables related to sea state as inputs, and uses the difference in sea surface height (SSH) at self-crossover points as the label. Experiments were conducted using Sentinel-6 self-crossover data from 2021 to 2023, and the model is evaluated using three main metrics: the variance of the SSH difference, the explained variance, and the SSH difference variance index (SVDI). The experimental results demonstrate that the proposed SNSSB model can further improve the accuracy of SSB estimation. On a global scale, compared to the traditional NPSSB, the multi-dimensional SNSSB not only decreases the variance of the SSH difference by over 11%, but also improves the explained variance by 5-10 cm2 in mid- and low-latitude regions. And the regional SNSSB also performs well, reducing the variance of the SSH difference by over 10% compared to the NPSSB. Additionally, the SNSSB model improves the computational efficiency by approximately 100 times. The favorable results highlight the potential of the multi-dimensional SNSSB in constructing SSB models, particularly the five-dimensional (5D) SNSSB, representing a breakthrough in overcoming the limitations of traditional NPSSB for constructing high-dimensional models. This study provides a novel approach to exploring the multiple influencing factors of SSB.

The microhardness, morphology and tribological property of TC4 subjected to machine hammer peening

Ti alloy has become an indispensable material in harsh working environments due to its excellent wear resistance, corrosion resistance and impact resistance. These environments place stringent requirements on the fatigue life, friction and wear, and surface strength of materials. Therefore, this study aims to deeply explore the surface mechanical properties of Ti-6Al-4V (TC4) alloy after machine hammer peening (MHP) treatment. By conducting experiments on TC4 alloys treated with different hammering energies, the changes in surface hardness, morphology, roughness, tensile properties, and friction properties were analyzed, and the strengthening mechanism of MHP was discussed. Experimental results show that MHP treatment can effectively improve the surface properties of TC4. With the increase of hammer energy, due to the double-sided hammering of the plate, the microhardness first increases, then decreases, and then rises again. The tensile strength and yield strength of the sample increase slightly, but the elongation at break decreases. The surface roughness of the sample increases first and then decreases. Similarly, after MHP treatment, the wear resistance of the samples increased, the friction coefficient decreased, and the wear amount and surface height difference showed a trend of first increasing and then decreasing. The wear mechanism mainly included adhesive wear, abrasive wear and fatigue wear.

Beneficial role of manganese dioxide for reducing surface resistivity to increase surface flashover voltage of vacuum insulating ceramics

Electric vacuum insulated devices generate surface flashover and breakdown under instantaneous high voltage. Flashover voltage can be increased through coating without changing the structure of the ceramic device. Herein, multiphase coatings with different manganese dioxide contents are prepared on α-Al2O3 insulating ceramic surface by screen printing and solid-state sintering methods to yield an average film thickness of about 12.38 μm with good bonding strength. X-ray diffraction shows that the crystal phases of the coating are (Al0.9Cr0.1)2O3 and MnAl2O4. Scanning electron micrographs and atomic force microscopy reveal that greater surface height difference and deeper surface depth are more conducive to increasing the surface roughness and the formation of "pores", and decreasing the surface potential decay rate. When MnO2 content is 0.0069 mol, the deep trap center energy level on the material surface reaches its maximum, increasing from 1.506 eV to 1.550 eV, and the surface resistivity of ceramics decreases from 1016 Ω to 1013 Ω. The formation of deep trap centers on the surface makes it difficult for surface charges to detach, which reduces the charge mobility and surface potential decay rate, and leads to decrease in surface resistivity and increase in surface flashover voltage.

Improving the formability and quality of CMT additively manufactured aluminum thin-wall parts via laser stabilization effect

In the recent past, the deposition efficiency has been one of the most concerned problems in aluminum additive manufacturing. In this research, a comparative study on the formation quality, microstructures and mechanical properties of aluminum alloy thin-wall structures between the oscillating laser-arc hybrid additive manufacturing (O-LHAM) and wire-arc additive manufacturing (WAAM) at high deposition speed was performed. The formation quality of the additively manufactured thin-wall parts under O-LHAM was significantly improved compared with WAAM. The molten pool overflow was significantly eliminated due to the higher support force on the molten pool, thus the surface roughness Sa and the maximum surface height difference Sz of O-LHAM thin walls were reduced by 13% and 22%, respectively. Compared with thin wall manufactured via WAAM, the microstructure of O-LHAM mainly consisted of coarse columnar grains and showed anisotropic characteristics due to the increased heat accumulation. Moreover, owing to the higher porosity in the interlayer combination regions of WAAM sample, the elongation of thin walls manufactured via O-LHAM was higher than WAAM in both horizontal and vertical directions, reaching 36.8% and 32.5%, respectively. This work will provide more guidance on thin-wall additive manufacturing with high deposition efficiency.

Wind‐Induced Quasi‐Seasonal and Quasi‐Monthly Variations of Near‐Bottom Temperature on the Chukchi Slope of the Southwestern Canada Basin

AbstractThe time series of near‐bottom temperatures collected from September 2018 until August 2020 from an array of three current‐ and pressure‐recording inverted echo sounders showed quasi‐seasonal and quasi‐monthly (∼28 days) variations at a depth of ∼1,300 m near the Chukchi slope in the western Arctic Ocean. They revealed an increase of ∼0.1°C during the winter‐spring period compared with the summer‐fall period. These variations were observed in the data‐assimilated Hybrid Coordinate Ocean Model (HYCOM) outputs near the observation site (correlation coefficient &gt;0.7). They confirmed that variations in near‐bottom temperature are related to changes in the intensity of the Atlantic Water (AW) boundary current, concurrent with the deepening of the lower AW layer by approximately 50 m. The difference in sea surface height (SSH) between the Canada Basin and the Chukchi Shelf increased because of the negative wind stress curl (WSC) and retarded the AW boundary current according to the geostrophic effect. When the near‐bottom temperature increased during the winter‐spring period, the SSH in the Chukchi Shelf was lower than that in the summer‐fall period because of the less negative WSC. Quasi‐monthly variations were related to SSH on the Chukchi Shelf owing to the negative WSC. HYCOM outputs from 1994 to 2015 showed that the AW boundary current weakened more recently than in the past due to the increased melting of sea ice. The results imply that a longer sea‐ice‐free season in the Arctic amplifies changes in the AW boundary current and deep ocean temperature owing to increased atmospheric forcing.

448 Deformable Medial Modeling to Generate Novel Shape Features of the Placenta Using Automated versus Manual Segmentations

OBJECTIVES/GOALS: In this study, we implemented deformable medial modeling as a morphometric approach in first trimester placentas to characterize morphometric differences between fully automated and manual segmentations. METHODS/STUDY POPULATION: Twenty placentas from singleton pregnancies between 11-14 weeks’ gestation were manually and automatically segmented from 3D ultrasound volumes. Automated segmentations were produced by a trained convolutional neural network pipeline. Dice overlap scores and volumes were computed between manual and automated segmentations. Deformable medial modeling was applied to both manual and automated segmentations to produce the following metrics: maternal and chorionic surface areas (SA), thickness, circumference, and diameter along the generated medial surface. Placental non-planarity was also determined as the greatest medial surface height difference. A paired t-test and simple linear regression was performed between manual and automated segmentations for each shape metric. RESULTS/ANTICIPATED RESULTS: Mean placental volume measurements between manual and automated segmentations were similar, with a percent difference of 3.28% and a mean Dice overlap score of 0.85 ± 0.07. There were strong, statistically significant (p &lt;0.01) linear correlations with chorionic and maternal SA, SA difference, thickness, circumference, medial surface diameter, and medial surface height difference. No significant differences were noted with chorionic SA, thickness, circumference, maximum medial surface diameter, or medial surface height difference. However, statistically significant differences (p &lt;0.01-0.03) were noted in maternal SA, SA difference, and mean medial surface diameter. Despite these differences, mean percent difference for all morphometric parameters was less than or equal to 10%. DISCUSSION/SIGNIFICANCE: A deformable medial model evaluate unique global and regional shape placental features with highly correlated values between manual versus automated placental segmentations. However, clinical studies are needed to determine if minor differences would impact the clinical utility of these features as potential indicators of placental function.

Analisis Stabilitas Lereng dengan Metode Bishop pada Proyek Geotechnical Investigation Jalur Transportasi Pelabuhan Batubara Marangkayu Kabupaten Kutai Kartanegara

A slope is a surface that has a slope and forms a certain angle to the horizontal plane and is not protected. The slope and angle formed cause the slopes to have differences in surface height. Differences in slope surface height result in forces acting to push, and also forces in the soil acting to resist or resist, so that the position of the soil remains stable. The stability of a slope is expressed in the slope safety factor which is obtained or obtained by comparing the holding force and the pushing force. Based on topographic data of ground investigation drilling points on the Marangkayu Coal Port transportation route, Kutai Kartanegara Regency, it is known that there are several drilling points with soil conditions in the form of slopes or hills, so it is predicted that they could cause the potential for landslides because these points will become transportation routes for loading and unloading materials. coal. The aim of this research is to determine the slope safety figures, and to obtain a safe slope with the original slope conditions. The method used to analyze slope stability in this research uses Geostudio Slope Bishop method software. The results of the analysis of the original slope conditions at the OLC-FBH-03 and OLC-FBH-06 test points showed that the slope safety value was obtained with the result being that the slope condition was safe from landslides (FK&gt;1.25). With this, it can be concluded that the Marangkayu Coal Harbor transportation route, Kutai Kartanegara Regency is safe from landslides.Keywords: Bishop Method, Geostudio Slope, Slope Stability, Slope Safety Value

Effect of carbon dioxide on lamellar arrangement in poly(lactic acid) ring band spherulites

AbstractIn this research, the formation of ring band spherulite of poly(lactic acid) (PLA) under carbon dioxide (CO2) was in‐situ studied and the internal lamellar arrangement of ring band spherulite formed under CO2 was revealed for the first time. The spherulites by PLA crystallized under air and different CO2 pressures have been studied, and the surface and internal lamellar arrangement of the ring band spherulites have also been analyzed in detail. It was found that PLA would form ring band spherulite under air and 6 MPa CO2, while the internal structures of the two types of ring band spherulites were different. The surface height difference of ring band spherulites formed under air was small, at 278.9 nm, and the twisting angle of the lamellae was also small. However, the difference in the surface height of the ring band spherulite formed under 6 MPa CO2 was big, reaching 778.3 nm. Through analysis on the internal lamellar arrangement of the ring band spherulite, it was found that the valley for the ring band spherulites formed under 6 MPa CO2 was composed of flat‐on lamellae, the ridge was composed of edge‐on lamellae and the sudden twist occurred between the flat‐on lamellae and edge‐on lamellae.

ENSO Modulates Mean Currents and Mesoscale Eddies in the Caribbean Sea

AbstractAlthough El Niño‐Southern Oscillation (ENSO) and its global impacts through teleconnection have been known for decades, if and how the mean currents and mesoscale eddies in the Caribbean Sea are linked to ENSO remains an open question. Here, by analyzing satellite observations and an ocean reanalysis product, we found a close connection between mean currents, eddies in the Caribbean Sea and ENSO on interannual timescales. Strong El Niño events result in enhanced north‐south sea surface height differences and consequently stronger mean currents in the Caribbean Sea, and the opposite happens during La Niña events. The eddy kinetic energy responds to ENSO via eddy‐mean flow interaction, primarily through baroclinic instability, which releases the available potential energy stored in the mean currents to mesoscale eddies. Our results suggest some predictability of the mean currents and eddies in the Caribbean Sea, particularly during strong El Niño and La Niña events.

A nano-radian precision absolute local slope measurement method for X-ray reflectors.

Ultra-precise reflectors in the advanced light source facilities urgently call for local slope error measurements with nano-radian precision. However, the existing methods currently utilized in the long trace profiler systems struggle to meet the requirements. In this paper, we present a weak-value amplification enhanced absolute local slope measurement scheme, in which the surface height difference between two adjacent points can be measured directly with precision on the pico-meter level. As a result, the absolute local slope measurement reaches a record precision level of 9.7 nrad (RMS) with a small lateral separation of 0.5 mm. Comparing to the existing methods, our scheme is more disturbance-resistant, more compact and cost-effective. The local curvature measuring capability is also validated with two synchronously parallel local slope measurement paths, between which the separation is set as 2mm. A local curvature measurement is obtained with precision of 3.4 × 10-6m-1 (RMS) and its corresponding slope variation is 6.8 nrad. Our method exhibits important application prospects in the field of ultra-precise surface fabrication inspection.

Elimination of defects in laser metal deposited TiCp/Ti6Al4V composite by synchronous ultrasonic impact treatment

TiCp/Ti6Al4V composites produced by laser metal deposition (LMD) are usually characterized by internal defects and resultant deteriorated mechanical properties. In the present work, a synchronous ultrasonic impact treatment (UIT) was introduced during LMD of TiCp/Ti6Al4V composites. The effect of synchronous UIT on the defects was investigated. The defects in the LMDed composites are sub-spherical pores distributed in the interlayer region. With the assistance of UIT, the maximum surface height difference reduces from 200.2 ± 0.5 μm to 25 ± 0.5 μm and the internal porosity decreases from 1.95% to 0.09%, which is attributed to inhibiting the nucleation of defects and increasing molten pool flow. This work may provide a solution to effectively reduce the defects in additively manufactured parts.

Drastic Fluctuation in Water Exchange Between the Yellow Sea and Bohai Sea Caused by Typhoon Lekima in August 2019: A Numerical Study

AbstractConnecting the Bohai Sea (BS) and Yellow Sea (YS), the Bohai Strait is vital in controlling physical‐biogeochemical conditions in the East Asian marginal seas. In August 2019, Typhoon Lekima moved northward inland into eastern China and caused drastic water exchange through the Bohai Strait. The specific variation and underlying dynamics involved were investigated with observations and high‐resolution numerical simulations. Volume transport featured an intense inflow followed by an intense outflow, with a fluctuation magnitude of 1.88 Sv, which was much greater than the seasonal‐interannual variations. The corresponding current patterns presented three phases: strait‐wide inflow, strait‐wide outflow, and outflow in the south and inflow in the north. The strait‐wide inflow was driven by strong east‐northeasterly winds through local Ekman dynamics. The strait‐wide outflow resulted from the dynamic adjustment of ocean currents accompanying the rapid weakening of easterly winds. The third current pattern was part of a large‐scale cyclonic circulation in the BS and North YS and was governed by different factors in the southern and northern straits. Further comparisons indicated that transport caused by winter storms and other typhoons in the year had opposite phase variations to that caused by Lekima. The underlying dynamics mainly involved local Ekman dynamics and/or remote wind forcing via the propagation of coastal trapped waves but could differ greatly from events. Finally, we found that to a large extent, geostrophic transport derived from the sea surface height difference across the Bohai Strait could be used as actual transport during synoptic weather events.

SARAL’s Full Mission Reprocessing: Improvement with the GDR-F Standard

Seven years (2013–2019) of the French/Indian mission SARAL altimetry data have been successfully reprocessed within the SALP contract supported by CNES to produce a new data set of GDR (Geophysical Data Record) using an updated, modern set of algorithms and models. The main objective of this article is to assess the quality of the reprocessed dataset and estimate the system’s performance using GDR-F products. To achieve this goal, the new dataset has been validated against the previous one (identified as GDR-T) using mono-mission metrics and comparisons to reference altimetry missions such as Jason-2 and Jason-3. The new data set shows a clear improvement in data quality. The product validation shows a reduction of the standard deviation of crossovers’ Sea Surface Height differences from 5.5 cm (GDR-T) to 5.2 cm (GDR-F). This paper presents the main processing changes and shows some of the results from the validation and quality-assurance processes. The major improvement of the GDR-F data set with respect to the previous one is due to the use of state-of-the-art orbit standards (POE-F) and geophysical corrections, including new tidal models, a new wet troposphere retrieval algorithm, and a new algorithm for sea state estimation. The intent of this paper is to highlight the overall benefit of this new dataset.

Relative importance of ENSO and IOD on interannual variability of Indonesian Throughflow transport

IntroductionThe Indonesian Throughflow (ITF) connects the Pacific Ocean and the Indian Ocean. It plays an important role in the global ocean circulation system. The interannual variability of ITF transport is largely modulated by climate modes, such as Central-Pacific (CP) and Eastern-Pacific (EP) El Niño and Indian Ocean Dipole (IOD). However, the relative importance of these climate modes importing on the ITF is not well clarified.MethodsDominant roles of the climate modes on ITF in specific periods are quantified by combining a machine learning algorithm of the random forest (RF) model with a variety of reanalysis datasets.ResultsThe results reveal that during the period from 1993 to 2019, the average ITF transport derived from high-resolution reanalysis datasets is -14.97 Sv with an intensification trend of -0.06 Sv year-1, which mainly occurred in the upper layer. Four periods, which are 1993–2000, 2002–2008, 2009–2012 and 2013–2019, are identified as Niño 3.4, Dipole Mode Index (DMI), no significant dominant index, and DMI dominated, respectively.DiscussionThe corresponding sea surface height differences between the Northwest Tropical Pacific Ocean (NWP) and Southeast Indian Ocean (SEI) in these three periods when exist dominant index are -0.50 cm, 0.99 cm and -3.22 cm, respectively, which are responsible for the dominance of the climate modes. The study provides a new insight to quantify the response of ITF transport to climate drivers.

Brightness Temperature and Wet Tropospheric Correction of HY-2C Calibration Microwave Radiometer Using Model-Derived Wet Troposphere Path Delay from ECMWF

The Calibration Microwave Radiometer (CMR) is a three-band radiometer deployed on the HY-2C satellite in a near-Earth orbit, and since it launched, there are few studies presented on the performance of CMR to date. Therefore, this paper focuses on providing an assessment of HY-2C CMR brightness temperature and wet troposphere correction (WTC). CMR works at 18.7 GHz, 23.8 GHz and 37 GHz in a nadir-viewing direction, aligned with the HY-2C radar altimeter. The wet troposphere path delay of the radar altimeter signal caused by water vapour and cloud liquid water content can be monitored and corrected by CMR. In this paper, guided by the concept of antenna pattern correction algorithm and a purely statistical method, we directly establish the function between the CMR antenna temperature and the model-derived WTC calculated by the European Centre from Medium-Range Weather Forecasting (ECMWF) Reanalysis data, which can obtain the brightness temperature and the WTC of CMR simultaneously. Firstly, the algorithm principle of CMR to establish the function between the antenna temperature and the model-derived WTC is introduced, and then the brightness temperature of CMR is evaluated using reference brightness temperatures of the Advanced Microwave Radiometer 2 (AMR-2) on Jason-3 satellite at crossover points. Furthermore, the performance of the CMR WTC is validated in three ways: (1) directly comparing with the colocated WTC measured by Jason-3 AMR-2, (2) directly comparing with model-derived WTC from ECMWF, which allows a rapid check at a global scale, (3) comparing the standard deviation of the Sea Surface Height (SSH) difference at crossover points using different WTC retrieval methods. The linear fit with Jason-3 brightness temperature and WTC in all non-precipitation conditions demonstrated a good agreement with Jason-3. In addition, the WTC of CMR has an obvious decrease in the standard deviation of the SSH difference compared with model-derived WTC, indicating the CMR can significantly improve the accuracy of the HY-2C SSH measurements. All the assessments indicate that the CMR performances are satisfying the expectations and fulfilling the mission requirements.

Effects of SMILE with different residual stromal thicknesses on corneal biomechanical properties of rabbits in vivo

Femtosecond laser small incision lenticule extraction (SMILE) with different residual stromal thicknesses (RST) is set to investigate its effect on corneal biomechanical properties of rabbits in vivo. In this study, 24 healthy adult Japanese rabbits were randomly divided into group A and B. The RST of group A was set 30% of the corneal central thickness (CCT), and the RST of group B was 50% of the CCT. The thickness of the corneal cap in both groups was set one third of CCT. Corneal visualization Scheimpflug technology (Corvis ST) and Pentacam three-dimensional anterior segment analyzer were used to determine corneal biomechanical and morphological parameters before surgery, and 1 week, 1 month and 3 months after surgery. Pearson correlation analysis was used to analyze factors affecting corneal biomechanical parameters after SMILE. The results showed that the corneal stiffness of group A was significantly higher than that of group B at 1 week and 1 month after surgery, and most biomechanical parameters returned to preoperative levels at 3 months postoperatively. The results of correlation analysis showed that postoperative CCT and RST were the main factors affecting corneal biomechanical parameters after SMILE. There was no significant difference in corneal posterior surface height (PE) between 3 months after surgery and before surgery in both two groups. It indicates that although the ability to resist deformation of cornea decreases in SMILE with thicker corneal cap and less RST, there is no tendency to keratoconus, which may be related to the preservation of more anterior stromal layer.

Projected future changes in the contribution of Indo-Pacific sea surface height variability to the Indonesian throughflow

The Indonesian throughflow (ITF) transports a significant amount of warm freshwater from the Pacific to the Indian Ocean, making it critical to the global climate system. This study examines decadal ITF variations using ocean reanalysis data as well as climate model simulations from the Coupled Model Inter-comparison Project Phase 5 (CMIP5). While the observed annual cycle of ITF transport is known to be correlated with the annual cycle of sea surface height (SSH) difference between the Pacific and Indian Oceans, ocean reanalysis data (1959–2015) show that the Pacific Ocean SSH variability controls more than 85% of ITF variation on decadal timescales. In contrast, the Indian Ocean SSH variability contributes less than 15%. While those observed contributions are mostly reproduced in the CMIP5 historical simulations, an analysis of future climate projections shows a 25–30% increase in the Indian Ocean SSH variability to decadal ITF variations and a corresponding decrease in the Pacific contribution. These projected changes in the Indian Ocean SSH variability are associated with a 23% increase in the amplitudes of negative zonal wind stress anomalies over the equatorial Indian Ocean, along with a 12º eastward shift in the center of action in these anomalies. This combined effect of the increased amplitude and eastward shift in the zonal wind stress increases the SSHA variance over the Indian Ocean, increasing its contribution to the ITF variation. The decadal ITF changes discussed in this study will be crucial in understanding the future global climate variability, strongly coupled to Indo-Pacific interactions.

The Role of the Irminger Current in the Irminger Sea Northward Transport Variability

AbstractThe Irminger Current (IC) on the western flank of the Reykjanes Ridge is an important contributor to the northward transport in the Atlantic Meridional Overturning Circulation. Here, we combine 28 years of Copernicus Marine Environment Monitoring Service (CMEMS) ocean reanalysis data with 6 years of mooring data to investigate variability in volume transport of the IC. We found a mean volume transport for the IC of 11.6 Sv between 1993 and 2020 revealing the dominance of the IC in the total Irminger Sea northward volume transport (20.3 Sv). We found a significant decrease (−3.7 Sv) in volume transport of the IC until 2011 followed by a steeper (but shorter, leading to +2.7 Sv) increase until 2020. These changes across the Irminger Sea section are dominated by the IC, which in turn are driven by changes in the density gradient across the Irminger Sea related to convection. On decadal and interannual time scales the IC volume transport is well correlated with the decrease in the sea surface height difference over the basin. In 2019, a temporary intensification of the western IC core led to an exceptionally strong volume transport of the IC with 20 Sv. This was caused by density changes within the IC boundaries due to the presence of mesoscale eddies. Thus, IC transport variability is a superposition of basin‐wide to local processes that influence the velocity field on different time scales.