Increase In Water Fraction Research Articles

Fluorescence Lifetime Measurement For Studying Evaporation Of Bi-Component Droplet

Sprays are essential in engineering applications like evaporators and combustion chambers. Predicting the evaporation of multi-component liquid droplets is complex due to changing composition and properties. Measuring droplet composition is challenging, with limited non-intrusive methods available. Raman spectroscopy faces hurdles like weak signals and interference. Intensity based Laser-Induced Fluorescence (LIF) requires optical models to interpret data due to varying droplet size and position. Fluorescent dyes in liquid mixtures are sensitive to temperature, complicating measurements. Fluorescence lifetime measurements offer a promising alternative, being an absolute quantity less affected by reabsorption. This study develops a novel method using fluorescence lifetime to analyze droplet composition, leveraging Time-Correlated Single Photon Counting (TCSPC) for precise measurements. Factors such as dye concentration, solvent polarity, and temperature sensitivity are investigated. Calibration curves for ethanol-water mixtures correlate fluorescence lifetime with volume fraction. Experimental setups use TCSPC and femtosecond lasers for dye excitation. Results show that fluorescence lifetime decreases linearly with solvent polarity and is influenced by temperature and dye concentration. High dye concentrations cause self-quenching, altering temperature sensitivity. The method was applied to study the evaporation of ethanol-water droplets under acoustic levitation. Findings indicate that evaporation rates slow as the water fraction increases, with initial measurements showing higher water content due to partial evaporation. This research introduces a novel technique for droplet compositional analysis using fluorescence lifetime, providing insights into optimizing measurement accuracy and advancing understanding in engineering and related fields.

Methyl‐ and Methoxy‐substituted 2‐(Pyridin‐2‐yl)‐4‐(4‐aminophenyl)quinazolines: Synthesis and Photophysical Properties

AbstractA series of novel 2‐(2‐pyridyl)quinazoline luminophores containing a donor aryl fragment at position 4 and methyl or methoxy groups at benzene ring has been synthesized by efficient three‐step route. The linear optical properties have been studied by UV/Vis absorption and photoluminescence spectra in two solvents. We revealed that introduction of additional methyl group or the replacement of methyl substituents with methoxy ones lead to sequentially shift of absorption and emission maximum to blue region. 9H‐Carbazol‐9‐yl‐containing derivative is characterized by hypsochromically shifted absorption band compared to its NEt2 and NPh2 counterparts. Unlike 9H‐carbazol‐9‐yl‐derivative, Et2N‐ and Ph2N‐bearing quinazolines demonstrate considerable decrease in quantum yield values when going from toluene to MeCN. Solvatochromic properties have been explored, the pronounced bathochromic shift was observed in fluorescence spectra with the increase of solvents polarity. Moreover, the compounds show significant shift of emission band with the increase of water fraction in DMSO/H2O mixture. Two‐photon optical properties have been also studied, the two‐photon absorption cross‐sections in MeCN and toluene reached 120 GM and 210 GM, respectively. The presence of additional methyl group has little impact on δTPA value, while introduction of methoxy substituents dramatically decreases TPA cross sections. Additionally, a quantum‐chemical calculations of synthesized compounds were performed to support the experimental data.

Manipulating the ESPT process and photophysical properties of HQCT by water-based hydrogen bond bridge

The 8-hydroxyquinoline-2-carboxaldehyde thiosemicarbazone (HQCT) is sensitive to water molecules in dimethyl sulfoxide according to the experimental phenomenon description, with a sensory performance that is dependent on the water-based hydrogen bond bridge as mediator. Here the excited state intramolecular (ESAPT) and intermolecular (ESEPT) proton transfer mechanism involved by water solvent and the optical properties associated with them are clarified in details. Along the minimum energy pathways in the scanned potential energy surfaces (PESs), we find that the ESEPT reaction induced by water molecule is a synergistic double-proton transfer process. And the results indicate that trace water molecules can promote the reaction effectively. In addition, we also investigate the photophysical properties involved with the excited state proton transfer (ESPT) reaction with the increase of water fraction in the solvent. The results show that the fluorescent oscillator strength (f) and radiative rates (kr) decrease with the increase of water fraction, which are consistent with the experimental phenomenon. We attribute the phenomenon of fluorescence quenching to the increasing transition dipole moment (μ) which accelerates the intramolecular charge transfer (ICT) process. Our work not only explain the water-detection mechanism in the organic solvent before water-sensitive reactions essentially, but also provide a theoretical basis for the synthesis of new Schiff base fluorescent chromophores for the water detection in organic solvents.

Phenothiazine-derived fluorescent chemosensor: A versatile platform enabling swift cyanide ion detection and its multifaceted utility in paper strips, environmental water, food samples and living cells

A phenothiazine-linked pyridine acetonitrile with a cyanoethylene bond PZ-PY has been synthesized by Knoevenagel condensation reaction and characterized by spectroscopic and analytical techniques. The structure of PZ-PY was confirmed through single-crystal X-ray diffraction studies; revealing its monoclinic crystal system with a P21/c space group. The absorption maximum and emission spectrum of the PZ-PY receptor were observed at 431 and 608 nm respectively. Cyanide anion is one of the most prevalent chemicals in the environment, its toxic nature poses a constant threat to human daily life. The PZ-PY receptor’s recognition of cyanide ions is associated with remarkable photophysical properties. The binding stoichiometry of PZ-PY-CN- was confirmed by Job’s plot, B-H studies, 1H NMR titration, TD-DFT, and ESI-mass spectroscopy. The relatively low limit of detection was determined to be 8.79 × 10 -8 M in a linear range between 0 and 120 µL. PZ-PY receptor exhibits an aggregation-caused quenching (ACQ) nature with the increase in water fraction; it is stable between pH 2 to 11. Moreover, the practical applicability of PZ-PY was investigated through the test strip, solid-state, bioimaging (A547 cell line), detection of cyanide in diverse water samples (tap water, distilled water, and lake water), and food samples (sprouted potatoes, bitter almonds, and cassava).

Fabrication of double emulsion gel using monoacylglycerol and whey protein concentrate: The effects of primary emulsion gel fraction and particle size

The fabrication of novel double emulgels (DEGs; O/W/O) was examined upon gelling all three phases as oleogel-in-hydrogel-in-oleogel using monoacylglycerol (MAG) and whey protein concentrate (WPC) as gelling agents. Various water proportions from 6.8% to 27.2% (w/w) were incorporated using High-intensity ultrasound (HIU). The HIU effectively stabilised the DEGs for >20 days owing to reducing the particle size of the inner oil phase (from 56.1 μm to 6.5 μm) and causing WPC gelling, immobilising the water phase. The increase in water fraction altered the particle size, whilst the DEG30 sample with 20.4% (w/w) water content reinforced the hardness value (0.48 N) and gel strength. The DEG30 was further treated with various levels of HIU to obtain different particle sizes (104 μm, 67 μm, 88 μm, and 49 μm). The reduction in particle size impacted the final DEGs' rheological behaviour, texture, and Tgel-sol transition temperatures.

NUMERICAL STUDY OF WATER ADDITION ON THE COMBUSTION CHARACTERISTICS IN AN HCCI ETHANOL ENGINE

Low-temperature combustion modes have attracted global attention in recent years, especially the homogeneous charge compression ignition (HCCI) mode. The HCCI combustion produces high-speed combustion, achieving relatively high thermal efficiencies while emitting low NOX and soot. However, due to the lack of direct control to start the combustion, one of the main challenges in this type of engine is to ensure that auto-ignition occurs close to the top dead center for a wide operation range. There are a few combustion phase control techniques to solve this limitation, and one of them is water injection. In this regard, this paper explores the influence of water concentration in an ethanol HCCI engine as a form of combustion phasing control. The work was conducted numerically using a zero-dimensional single-zone model with a chemical kinetic mechanism containing 56 species and 383 reactions. The numerical model results were well agreed with the reported experimental data. The water fraction ranged from 0 to 18% by mass at 3% intervals. The results demonstrate that water injection is an efficient strategy to control the combustion phasing by adjusting the charge reactivity. The increase in water fraction reduced in-cylinder pressure and heat release rates. Furthermore, the combustion phase was advanced, the combustion duration was extended, and thermal efficiency was about 44.3% with the increase in water concentration.

Study on water fraction of oil–gas–water three-phase flow based on electrical methods

Oil–gas–water multiphase flows are widely used in petrochemical, biochemical, food chemical, mineral engineering and energy engineering. In this paper, the double-ring conductivity probe and the double-helical capacitance probe were extended to the water fraction measurement of oil–gas–water multiphase flow in the vertical pipe. The test pipe section of the multiphase flow of oil–gas–water in the vertical riser was designed. In the experiment, the self-designed double-ring conductivity probe and the corresponding signal processing circuit were used to measure the water fraction in the oil–gas–water three-phase flow. In this paper, the dynamic calibration of oil–gas–water three-phase flow was carried out under the working condition of high water fraction. Under uniform bubbly flow, with the increase of water fraction, the measurement error of the double-ring conductivity probe decreased, which can be controlled within 8% under working conditions with a water fraction of more than 90%. The results of water fraction were performed for different flow patterns in oil–gas–water multiphase flow. Under the bubbly flow pattern, the error reaches the maximum and the error is only related to the water fraction when the water fraction is about 85%. Under the slug flow pattern, the two measurement results of the double-ring conductivity probe and the double-helix capacitance probe were compared. It is found that the double-ring conductivity probe can clearly and accurately reflect the change of the flow pattern in the pipe.

Amphiphilic fluorescent nanospheres for quantitative sensing of trinitrophenol in water system

2,4,6-Trinitrophenol (TNP) is an important chemical and widely applied in industry. However, on account of its high toxicity, flammability and explosive nature, just trace amounts of TNP may cause potential threats to ecosystem and human security, so it is significant to establish a rapid and reliable method for the detection of TNP. Herein, a novel amphiphilic fluorescent probe TPE-CD was successfully designed and synthesized by the functionalization of hydrophilic β-cyclodextrin with a hydrophobic Aggregation Induced Emission (AIE) fluorophore. Moreover, spherical nanoparticles formed in H2O/CH3OH solution with the increase of water fraction (fw). Fluorescence titration of TNP indicated that TPE-CD exhibited excellent sensitivity to TNP with LOD = 0.31 μmol L−1 and Ksv = 3.06 × 104 L mol−1. The introduced β-cyclodextrin remarkably enhanced the ability of TPE-CD rather than its precursor TPE-COOH to capture TNP molecules through forming spherical nanoparticles, improving the fluorescence quenching efficiency. Density Functional Theory (DFT) calculations and experimental results confirmed that the response mechanism of TPE-CD to TNP involved Photoinduced Electron Transfer (PET) and Fluorescence Resonance Energy Transfer (FRET) with PET being predominant. Furthermore, the probe showed excellent selectivity and anti-interference to aqueous TNP samples. Moreover, the test strips prepared by soaking in TPE-CD solution also exhibited good sensitivity to TNP, providing a convenient, rapid and reliable method for the detection of TNP.

Experimental study on the ultrasonic echo characteristics of oil–water emulsion

In order to investigate the ultrasonic echo characteristics, a series of oil–water emulsion samples are prepared. The water fraction of the samples is in the range of 0–100%, the stirring speed is set to be 500, 1000, 1500, and 2000r/min, respectively. The ultrasonic measurement was operated in pulse-echo mode. The ultrasonic velocity and attenuation of the samples are measured and analyzed. The results have shown that with the increase of water fraction, the sound velocity tends to increase. The attenuation coefficient is very sensitive to the distribution of the emulsion droplets. Maximum attenuation loss occurred around the phase inversion point, where multiple emulsion is formed. The study has shown a potential to apply the attenuation coefficient for the characterization of emulsion phase inversion.

A polymerizable Aggregation Induced Emission (AIE)-active dye with remarkable pH fluorescence switching based on benzothiazole and its application in biological imaging

In recent years, Aggregation Induced Emission (AIE)-active fluorescent materials have been attracting considerable attention because they play an important role in clinical medicine, photoelectricity, environmental science, biological imaging, and sensors. In this contribution, a novel tetraphenylethylene (TPE) derivative of 2-(4-(1,2,2-triphenylvinyl)benzene) benzothiazole methacrylate (TPBMA) monomer was synthesized by a Suzuki coupling and an acylation reaction using TPE and benzothiazole as structural units, whose maximum emission wavelength respectively appeared at 506 nm in neutral medium and 579 nm in acidic medium with excellent pH sensitivity, and it could change repeatedly at 500 nm and 579 nm under HCl/NH3 fuming, indicating the reversible fluorescence conversion property. As compared with the TPB dye, the emission wavelength of TPBMA spectra has an obvious red-shift, which is consistent with the transition energy level difference (△E) of highest occupied molecular orbital (HOMO) and lowest unoccupied orbital (LUMO) situation by quantum chemistry calculation. Subsequently, the copolymers PEG-TB were successfully prepared by RAFT polymerization of TPBMA and poly (ethylene glycol) monomethacrylate (PEGMA), and their molecular weight (Mw) was about 2.12 × 104 with a narrow polydispersity index (PDI). From the 1H NMR analysis, the actual fraction of TPBMA in the PEG-TB copolymers increased to 22.6% from 17.4% when the feed ratio of TBMTA changed to 25.0% from 20.0%. The obtained PEG-TB could self-assemble into fluorescent organic nanoparticles (FONs) with 100–150 nm diameter in aqueous solution, and their fluorescence intensity increased gradually with the increase of water fraction in the THF solution, indicating the obvious AIE behavior. Moreover, the as-prepared PEG-TB FONs exhibited the prospective potential in the field of biological imaging due to their low cytotoxicity, excellent biocompatibility and easy cells absorption.

Selective Expression of a Carbazole-Phenothiazine Derivative Leads to Dual-mode AIEE, TADF and Distinctive Mechanochromism.

In this article, we report a newly designed D-A-D' derivative (CNCzPTZ), which displays selective expression of chromophores. This enables CNCzPTZ with solvatochromism, rare dual-mode AIEE properties, solid-state dual-emissions with phosphorescence and distinctive mechanochromism.CNCzPTZ exhibits dual-mode AIEE properties, since the emission band abruptly shifts from 550 nm to 500 nm as the water fraction increases. In the crystalline state, CNCzPTZ demonstrated dual emission bands of 478 nm and 538 nm.CNCzPTZ shows distinctive mechanochromic property in the solid state due to the planarization.

Effect of Water on the Chain Reaction Characteristics of Gas Explosion.

In order to explore the influence of water on the chain reaction characteristics of gas explosion, the 20 L explosion ball experiment and the homogeneous constant volume combustion reactor of CHEMKIN 17.0 simulations were carried out. The gas explosion response under four different water contents was tested and simulated. The effects of water on the pressure, free radicals, and reactants of gas explosion were compared and analyzed. The research results show that the inhibition of water on gas explosion was enhanced with the increase of water fraction in the initial mixture; the temperature, pressure, catastrophic gases such as CO, and concentration of activation centers in the reaction system can be reduced by water; the intensity of gas explosion can be reduced by inhibiting the formation of H, O, and OH free radicals, the main reactants of gas explosion and gas explosion energy.

Effects of substituents on the optical properties of AIEE-active 9, 10-dithiopheneanthrylene derivatives and their applications in cell imaging

A series of asymmetric 9, 10-dithiopheneanthrylene derivatives (DTAs) with various substituent groups and large Stokes shifts (>80 nm) have been synthesized and characterized. All of them displayed aggregation-induced emission enhancement (AIEE) behaviors expect for DTA-M, which fluorescence was gradually enhanced in low water fraction (50%), but dramatically quenched with the increase of water fraction to 90% due to the twisted intramolecular charge transfer (TICT) effect. The size of particles in aggregates were studied by using a scanning electron microscope, indicating the formation of morphological diversity nanoparticles due to the various substituents on 2-position of lateral thiophene ring. Furthermore, all of them exhibited reversible mechanofluorochromic and vapochromic luminescence behaviors, especially compound DTA-M, which showed high color contrast mechanofluorochromism between yellow and red color. In addition to the AIEE and mechanofluorochromic properties, HeLa cells fluorescence imaging experiments proved that these DTAs are capable to achieving bioimaging.

Substituted 2-(2-hydroxyphenyl)–3H-quinazolin-4-ones and their difluoroboron complexes: Synthesis and photophysical properties

2-(2-Hydroxyphenyl)–3H-quinazolin-4-ones with diverse substituents at phenol ring and their six-membered difluoroboron complexes have been synthesized via few-stage approach. The photophysical properties of target compounds have been investigated in two solvents as well as in the solid state. The nature of substituents and substitution point in the phenol moiety of ligands and resulting BF2-complexes on the photophysical properties of dyes have been explored. The complex bearing two t-Bu groups proved to be the most emissive in solid state, whereas its 5-methoxy and 4-diethylamino counterparts possess strong emission in toluene solution. The dyes exhibited large Stokes shifts which was attributed to excited state intramolecular proton transfer (ESIPT). Additionally, fluorescence of quinazolinones in the mixture of THF/water was studied. All ligands demonstrated emission enhancement with increase of water fraction which was due to aggregation induced emission.

Aggregation-Induced Electrochemiluminescence of Tetraphenylbenzosilole Derivatives in an Aqueous Phase System for Ultrasensitive Detection of Hexavalent Chromium.

Herein, aggregation-induced electrochemiluminescence (AIECL) of tetraphenylbenzosilole derivatives in an aqueous phase system with the participation of a co-reactant was systematically investigated for the first time. All organics that we studied exhibit excellent stability and dramatically enhanced electrochemiluminescence (ECL) and photoluminescence (PL) emission when the water fraction increases. The influence of substituents in the structure of tetraphenylbenzosilole derivatives on AIECL performance was proved by fluorescence, cyclic voltammetry, and related theoretical calculation. Among them, 2,3-bis(4-cyanophenyl)-1,1-diphenyl-benzosilole (TPBS-C) with strong electron-withdrawing cyano groups exhibits the best ECL behavior with the highest ECL efficiency (184.36%). The strongest ECL emission of TPBS-C not only stems from the aggregated molecules that restrict the intramolecular motion of peripheral phenyl groups, which inhibits the nonradiative transition, but also comes from the fact that TPBS-C has the lowest reduction potential, and twice the reduction process of TPBS-C occurs to produce more anion radicals (TPBS-C·-). Significantly, the ECL sensor based on TPBS-C nanoaggregates exhibits excellent detection performance for toxic Cr(VI) with a wide linear range from 10-12 to 10-4 M and an extremely low detection limit of 0.83 pM. This work developed an efficient luminophore with unique AIECL properties and realized the ultrasensitive detection of Cr(VI) in the aqueous phase system.

Quantitative characterization of the blockage effect from dispersed phase on wax molecular diffusion in water-in-oil emulsion

Molecular diffusion is the main mechanism of wax deposition, whereas the dispersed water droplets influence the wax diffusivity in water-in-oil (w/o) emulsion by restricting the diffusion path. In the present work, geometric analysis method was used to analyze the blockage effect from dispersed phase on the restricted diffusion path of wax molecules in w/o emulsion, and a correlation was proposed relating the blockage effect with water fraction, dispersed degree and nonuniformity of dispersed phase in real emulsions. Firstly, regarding water droplets as spherical particles with uniform size and arrangement pattern, the average tortuosity of different wax diffusion paths was deduced in two-dimensional (2D) and three-dimensional (3D) ideal conditions. The results showed that the blockage degree was enhanced with the increase in water fraction. Moreover, the droplet size distribution of different w/o emulsions was investigated by microscopic observation and a set of microstructure characterization parameters were summarized in statistics. A 3D microstructure model of real emulsion was established to derive the tortuosity, taking the effect of droplet size distribution into consideration. The blockage effect was enhanced by the increase in the dispersity and polydispersity of water droplets, but this influence was not significant and water fraction was still the main influencing factor. On this basis, a correlation of blockage coefficient with water fraction, number-averaged diameter and polydispersity was proposed and validated using the 1H/19F-NMR test results in literature with the average relative error being 3.17%. This will provide a support to the revealing of wax diffusion mechanism in w/o emulsions and the wax deposition prediction of multiphase flow pipelines.

Synthesis and photophysical properties of donor-acceptor flavone-based derivatives with good aggregation-induced emission characteristics

Four novel compounds (1–4) were synthesized using 2-phenyl-4H-1-benzopyran-4-one (flavone) moiety as an acceptor and phenoxazine, phenothiazine, 9,9-dimethyl-9,10-dihydroacridine, diphenylamine as donors. Their photophysical properties were studied with spectroscopic and theoretical methods. The results show that 1 and 2 exhibit good aggregation-induced emission (AIE) properties in tetrahydrofuran (THF)/water mixtures, whose maximum photoluminescence (PL) intensities are 156- and 187-fold higher than those in pure THF solutions, and can reach 256- and 506-fold higher than those in the mixtures at water fractions of 50%, respectively. 3 displays similar PL property except for obvious emission in pure THF solution. However, PL intensity of 4 decreases with an increase in water fraction, and then is enhanced with further increase in water fraction. Moreover, 4 shows high quantum yields both in toluene solution (0.61) and in solid state (0.83). It exhibits a positive solvatochromism. In addition, 2 possesses mechanofluorochromic transition from sky blue to yellow after grinding. It can also be applied in live-cell imaging.

Ultrasonication assisted formation and stability of water-in-oil nanoemulsions: Optimization and ternary diagram analysis

An energy efficient and scalable method designed to form stable and transparent water-in-oil (W/O) nanoemulsion can be attained by optimization of process parameters and study of ternary diagram. Application of high energy in addition to the low energy at the optimized conditions have been targeted to make the process energy efficient, since later part is applied to droplets formed at less energy. In the present work, formation of combined energy mixed surfactant nanoemulsion was achieved by combined approach of isothermal low energy followed by ultrasonication that could be used as a fuel in compression ignition engine free from NOx and particulate matter emissions. A mixture of two functional groups (ether and ester) non-ionic surfactants was used at optimized ratio of 0.71/0.29 (Span 80/TX-100; w/w). Optimization of ultrasonicated parameters resulted in 25% amplitude, 0.5 pulse mode factor and 8.5 min of sonication time. A ternary diagram study was performed to recognize the compositions accountable for the formation of transparent, translucent and opaque emulsions in the bounded range of water fraction 0.02 to 0.11 and surfactant fraction 0.10 to 0.20. Surfactant-to-water (β) ratio found applicable for the production of nano-sized droplets in the range of 2 ≤ β ≤ 3. A minimum droplet size of 25 ± 1 nm was attained in the present study. An increase in surfactant fraction decreased average droplet size, whereas, increase in water fraction increased average droplet size. Reduction in droplet size was prominently found in the range of energy density from 15.23 J.ml−1 to 40 J.ml−1 thereafter, it decelerated up to 160 J.ml−1. Prediction of average droplet size modeled with energy density fitted well and could be used for scaling up and tuning the droplet size. Resultant nanoemulsion samples displayed kinetic stability whereas long term stability (45 days) assessed using Ostwald ripening model showed stability in the order of β = 2.0 > β = 2.5 > β = 3.0 > β = 4.0.

Synthesis, characterization and aggregation-induced emission of alternating copolymers containing cyclophanes and tetraphenylethenes

The alternating copolymers containing tetraphenylethenes bonded to pseudo-para or pseudo-meta [2.2]paracyclophanes were synthesized by palladium catalyzed Suzuki-Miyaura cross-coupling reaction. Relatively high molecular weights of polymers were obtained by the reaction of their corresponding comonomers using Pd(OAc)2 as a catalyst with S-Phos as a ligand and K3PO4 as a base under a high base to monomer ratio. The maximum emission intensity of polymer in THF increases gradually as the addition of water fraction increases. The polymers exhibited aggregation-induced emission in aggregated state. In particular, the photoluminescence quantum yield of those tetraphenylethenes bonded to pseudo-meta [2.2]paracyclophanes is up to 0.334 when the water fraction reaches to 90%. The polymers used in the detection of 2,6-dinitrotoluene are more sensitive than that of small molecule containing the same conjugated segment of the polymers. They are promising candidates for potential uses in the optoelectronic applications.

Relative Contributions of Atmospheric Energy Transport and Sea Ice Loss to the Recent Warm Arctic Winter

Abstract The relative contributions of atmospheric energy transport (via heat and moisture advection) and sea ice decline to recent Arctic warming were investigated using high-resolution reanalysis data up to 2017. During the Arctic winter, a variation of downward longwave radiation (DLR) is fundamental in modulating Arctic surface temperature. In the warm Arctic winter, DLR and precipitable water (PW) are increasing over the entire Arctic; however, the major drivers for such increases differ regionally. In areas such as the northern Greenland Sea, increasing DLR and PW are caused mainly by convergence of atmospheric energy transport from lower latitudes. In regions of maximum sea ice retreat (e.g., northern Barents–Kara Seas), continued sea ice melting from previous seasons drive the DLR and PW increases, consistent with the positive ice–insulation feedback. Distinct local feedbacks between open water and ice-retreat regions were further compared. In open water regions, a reduced ocean–atmosphere temperature gradient caused by atmospheric warming suppresses surface turbulent heat flux (THF) release from the ocean to the atmosphere; thus, surface warming cannot accelerate. Conversely, in ice-retreat regions, sea ice reduction allows the relatively warm ocean to interact with the colder atmosphere via surface THF release. This increases temperature and humidity in the lower troposphere consistent with the positive ice–insulation feedback. The implication of this study is that Arctic warming will slow as the open water fraction increases. Therefore, given sustained greenhouse warming, the roles of atmospheric heat and moisture transport from lower latitudes are likely to become increasingly critical in the future Arctic climate.