Geophysical Institute

Abstract This study reveals a significant increase in the intensity of interannual variability (IIV) of snowfall frequency during autumn in the mid–high latitudes of Eurasia after 2000. During 2000–2021, the combination of warm and humid air from the Mediterranean with dry and cold air from the Arctic is conducive to increased snowfall frequency over Central Siberian Plateau. Anomalous positive temperatures due to increased specific humidity inhibit the occurrence of snowfall over central Asia. Further research demonstrates that the increased IIV of sea ice growth in the Barents–Kara Seas during autumn plays a crucial role in strengthening the snowfall frequency IIV. The rapid increase in autumn sea ice growth leads to more pronounced negative anomaly of Arctic temperature through the local thermal positive feedback, which enlarges the temperature gradient between the Arctic and the mid–high latitudes of Eurasia, thereby causing anomalous westerlies over Central Siberian Plateau and central Asia. Additionally, the rapid increase in sea ice growth may stimulate southward-propagating Rossby waves, contributing to anomalous cyclone/anticyclone over Central Siberian Plateau/central Asia. The anomalous westerlies and cyclone/anticyclone circulation will jointly impact the pathways of water vapor transport and thus modulate the IIV of snowfall frequency over Eurasia. Through numerical experiments with increased sea ice growth of different intensities and AMIP-like experiments, it can be demonstrated that the increased IIV of sea ice growth can affect the location of westerlies and stimulate the southward-propagating Rossby waves, thereby promoting an increase in the IIV of snowfall frequency in the mid–high latitudes of Eurasia. Significance Statement The intensity of interannual variability in autumn snowfall frequency in mid–high latitudes of Eurasia has increased significantly after 2000, which is associated with the rapid increase of sea ice in the Barents–Kara Seas in autumn. The rapid increase in sea ice leads to an increase in the meridional temperature gradient in the Arctic and mid–high latitudes of Eurasia, affecting the location of the westerly, and stimulates southward-propagating Rossby waves, resulting in the potential height anomalies. The sea ice growth anomalies affect water vapor transport through both thermal and dynamical pathways, leading to an increase in the interannual variability of snowfall frequency in Eurasia. Understanding this mechanism exerts a positive influence on snowfall prediction.

Abstract During Arctic summer, meltwater inputs and a fragmented ice cover impede quantifying the role of boundary stress for turbulent mixing in the ice–ocean boundary layer. Here, we show that less than two-thirds of the turbulent kinetic energy (TKE) generated from mean flow shear under drifting sea ice is dissipated, and the remainder can be attributed to balancing stabilizing buoyancy fluxes. We deployed a high-resolution acoustic Doppler current profiler under an ice floe to estimate Reynolds stress, shear production, and dissipation rate of TKE. At 0.75 m below the interface, dissipation rates from 1.5 × 10−9 to 4.2 × 10−7 m2 s−3 and shear production from 6.9 × 10−10 to 7.7 × 10−7 m2 s−3 were measured (5%–95% percentiles), with shear production exceeding dissipation on average. The turbulent stress was largest during an event with ∼9.2-h-period oscillations in the upper ocean, consistent with tidally forced lee waves generated near steep topography. An overall estimate of the quadratic skin drag coefficient representative of the ice floe is . We further identified three qualitative regimes of atmosphere–ice–ocean coupling in our observations: a high-frequency range [>4 cycles per day (cpd)] in which the ice acts like a rigid lid atop the ocean, an intermediate range, and a low-frequency range (<0.8 cpd), where wind-driven ice drift determines the under-ice current. As the latter only contained half of the variance of the ice-relative flow, we emphasize that resolving subdaily time scales is crucial in observing and modeling atmosphere–ice–ocean coupling.

ABSTRACTFjords provide valuable research opportunities for marine scientists. They are excellent natural infrastructure for climate impact studies associated with hypoxic episodes and consequences for mesopelagic and deep‐sea ecosystems involving oceanographic circulation processes and basin water renewals. Repeated sampling from the same populations is possible, making fjords excellent systems for developing time series of data for climate impact studies. We provide an overview of the 14 years of data from Norwegian West Coast fjords, focusing on Masfjorden, and report major findings from Oslofjorden in Eastern Norway, exhibiting recurrent hypoxia in the basin waters. We document that the oxygen levels in Masfjorden decreased rapidly by over 60% at 450 m depth in < 8 years, which is much faster than the average rate of deoxygenation in the global ocean. We also discuss the increase in the deep‐sea and low‐light‐adapted coronate jellyfish Periphylla periphylla in view of altered optical conditions of the basin water potentially related to deoxygenation. We argue that fjords like Masfjorden and Oslofjorden are not only macrocosms for ecological processes but also are likely an accelerated version of deep oceans with respect to climate impacts.

Abstract In the equatorial Indian Ocean, the largest subseasonal temperature variations in the upper ocean are observed below the mixed layer. Subsurface processes can influence mixed layer temperature and consequently air‐sea coupling. However, the physical processes driving temperature variability at these depths are not well quantified. During the boreal winter, the Madden–Julian Oscillation (MJO) partly drives upper ocean heat content (OHC) variations. Therefore, to understand processes driving subseasonal OHC variability in the equatorial Indian Ocean, we use an observationally constrained, physically consistent ocean state estimate from the Estimating the Circulation and Climate of the Ocean (ECCO) Consortium. Using a heat budget analysis, we show that the main driver of subseasonal OHC variability in the ECCO ocean state estimate is horizontal advection. Along the equator, OHC variations are driven by zonal advection while the role of meridional advection becomes more important away from the equator. During the active phase of the MJO, net air‐sea heat fluxes damp OHC variability along the equator, while away from the equator net air‐sea heat fluxes partly drive OHC variability. Equatorial OHC variations are found to be associated with processes driven by Kelvin and Rossby waves consistent with previous studies. By quantifying the physical processes, we highlight the important role of ocean dynamics in contributing to the observed variations of subseasonal OHC in the equatorial Indian Ocean.

The oceanic storage of anthropogenic CO (C) that humans have emitted into the atmosphere has been pivotal for counteracting climate change. Yet multi-decadal trends in the ocean interior storage of C have not been assessed at global scale. Here, we determine storage changes of C by applying the eMLR(C*) regression method to ocean interior observations collected between 1989 and 2020. We find that the global ocean storage of C grew by 29 ± 3 Pg C dec and 27 ± 3 Pg C dec (±1σ) from 1994 to 2004 and 2004 to 2014, respectively. Although the two growth rates are not significantly different, they imply a reduction of the oceanic uptake fraction of the anthropogenic emissions from 36 ± 4 % to 27 ± 3 % from the first to the second decade. We attribute this reduction to a decrease of the ocean buffer capacity and changes in ocean circulation. In the Atlantic Ocean, the maximum storage rate shifted from the Northern to the Southern Hemisphere, plausibly caused by a weaker formation rate of North Atlantic Deep Waters and an intensified ventilation of mode and intermediate waters in the Southern Hemisphere. Between 1994 and 2004, the oceanic C accumulation exceeded the net air-sea flux by 8 ± 4 Pg C dec, suggesting a loss of natural carbon from the ocean during this decade. Our results reveal a substantial sensitivity of the ocean carbon sink to climate variability and change.

The dynamics and evolution of Venus’ mantle are of first-order relevance for the origin and modification of the tectonic and volcanic structures we observe on Venus today. Solid-state convection in the mantle induces stresses into the lithosphere and crust that drive deformation leading to tectonic signatures. Thermal coupling of the mantle with the atmosphere and the core leads to a distinct structure with substantial lateral heterogeneity, thermally and compositionally. These processes ultimately shape Venus’ tectonic regime and provide the framework to interpret surface observations made on Venus, such as gravity and topography. Tectonic and convective processes are continuously changing through geological time, largely driven by the long-term thermal and compositional evolution of Venus’ mantle. To date, no consensus has been reached on the geodynamic regime Venus’ mantle is presently in, mostly because observational data remains fragmentary. In contrast to Earth, Venus’ mantle does not support the existence of continuous plate tectonics on its surface. However, the planet’s surface signature substantially deviates from those of tectonically largely inactive bodies, such as Mars, Mercury, or the Moon. This work reviews the current state of knowledge of Venus’ mantle dynamics and evolution through time, focussing on a dynamic system perspective. Available observations to constrain the deep interior are evaluated and their insufficiency to pin down Venus’ evolutionary path is emphasised. Future missions will likely revive the discussion of these open issues and boost our current understanding by filling current data gaps; some promising avenues are discussed in this chapter.

Introduction. Emissions from industrial enterprises, open pit mining, vehicles, etc. can change the electrical properties of the surface layer of the atmosphere and have undesirable environmental consequences for the environment and technical facilities. Studies of the electrical state of the atmosphere in clear weather were carried out in the area of the Mukulan quarry in the North Caucasus. In the course of the study, increased values of the electric field strength were observed, apparently due to the process of electrization of aerosol particles of different sizes, formed in the process of mechanical destruction and crushing of rock particles.Materials and research methods. Measurements of the electric field strength of the atmosphere, which is one of the important parameters of atmospheric electricity, were carried out using a rotary type fluxmeter at an altitude of 2542 m. At the same time, special attention was paid to the reliability of the results obtained during these measurements. A technique was used for conducting atmospheric-electrical measurements, which excludes errors introduced by various factors, such as the method of placing the measuring equipment, the heterogeneity of the terrain, the weather conditions of the observation point, which was located in the layer of air mass exchange and turbulent diffusion.Results of the study and their discussion. An analysis of the results obtained on days with undisturbed clear weather showed that the only factor influencing the unitary course of the field strength at such a height remains the open pit mining, where on such days there is constant intense dust formation and the associated electrization of aerosol particles of different sizes. If the processes of electrification proceed intensively and for a long time, then an excess space charge accumulates in the surface layer of the atmosphere, which contributes to the formation of increased values of the electric field near the earth’s surface. The average value of the electric field strength was 600-700 V/m, which exceeds by an order of magnitude the results of measurements carried out at such heights by other researchers in undisturbed weather conditions. Local changes in the field strength were also noted when approaching the measuring site, a visually observed cloud of dust, which manifested itself in synchronous changes in the field strength, at which its value decreases and sometimes reaches negative values and recovers after some time to its average values. Local changes in the field are caused by the action of a negative space charge concentrated in a dust cloud consisting of large particles, the average size of which was estimated from the settling rate of aerosol particles and amounted to about 30 μm. It was found that there is a direct relationship between the field strength and the concentration of aerosol particles formed during the mechanical destruction of rocks, as a result of which the particles are electrified.Conclusions. Studies of the electrical state carried out in the area of the Mukulan quarry showed that in good weather conditions, electrization is observed in the surface layer of the atmosphere. Aerosol particles acquire a charge in the process of mechanical destruction of rock particles and disruption of contact between them. At the same time, selective charging and capture of light air ions, depending on their size, and macroseparation in the field of gravitational forces occur, on the one hand, the rapid settling of large particles charged negatively on the earth’s surface, and on the other hand, small particles that can be in suspension for days in the atmosphere, charged with a positive sign, which leads to a decrease in air conductivity and, accordingly, an increase in the field strength in the quarry area.