Reviews & Analysis

There is a large discrepancy between estimates of oceanic plastic input and the amount of plastic measured floating at the ocean surface. Model results show that this can be explained by large objects being underestimated in previous mass budget analyses, combined with lower input estimates.

Analysis of the microfossil content of sediment cores from areas where thick Arctic sea ice persists today reveals that a subpolar species associated with Atlantic water expanded deep into the Arctic Ocean during the Last Interglacial. This finding implies that summers in the Arctic were likely sea-ice-free during this period.

Two contrasting sinuosity patterns were identified in lowland rivers on Earth and Mars. The channel sinuosity either substantially increases or remains constant towards the coast. These bimodal patterns reflect the age of the channels and their lateral migration rates, which are associated with sediment supply and discharge variability.

The post-garnet transition has been found to have a curved phase boundary, with negative slopes in cold regions and positive slopes in hot regions of the Earth’s mantle. This varying slope could be a reason for the puzzling dynamics of subducting slabs and upwelling plumes observed seismically in the upper part of the lower mantle.

Icequake observations were combined with an analytical friction model to measure friction and slip at the bed of an Antarctic ice stream. Friction and slip are found to be highly variable in space and time, controlled by higher-than-expected normal stresses at the ice–bed interface.

Rock organic carbon from glacial runoff, once assumed to be non-bioavailable, is identified as a substrate used by marine sedimentary microbes. This challenges the traditional view that rock organic carbon bypasses the active carbon cycle and indicates an additional source of fossil greenhouse-gas emissions on geological, or possibly even shorter, timescales.

Lightning can produce bioavailable nitrogen oxides, but it is unknown whether this was a substantial nutrient source for Earth’s earliest biosphere. Comparison of nitrogen isotope measurements from spark discharge experiments to those from the rock record suggests that lightning was likely not the main source of bioavailable nitrogen for the biosphere throughout most of Earth’s history.

Field studies reveal that carbon sequestration, nutrient cycling, organic matter decomposition and soil-borne plant pathogen control are greater in soils beneath mosses than in unvegetated soils. Based on these studies, modelling shows the likely extent of soil moss cover and underlines its value to the planet.

Analogue experiments show that powerful eruption columns deliver material to the sea surface and seabed in periodic annular sedimentation waves. Depending on the water depth, the impact and spread of these waves at the sea surface and seabed can excite tsunamis, drive radial pyroclastic density currents, and build concentric terraces.

Subaqueous glacier mass losses are not accounted for by traditional geodetic mass balance calculations. Estimates based on proglacial lake volume changes revealed that the mass loss of glaciers terminating into lakes in the greater Himalaya during 2000−2020 was previously underestimated by approximately 6.5%, with the largest underestimation in the central Himalaya.

Numerical simulations show that convection in the mantle shapes the long-term structure of Earth’s magnetic field. The mantle influences the magnetic field by imposing a pattern of cooling that controls the dynamics of fluid flow at the top of the outer core.

Satellite observations show that 24.1% of tropical moist forests are degraded. In addition to the warming effects of the release of carbon from biomass, satellite data suggest that degradation could also increase the land surface temperatures of the affected regions. This biophysical feedback could hinder forest restoration initiatives.

A remotely-operated underwater vehicle was used to map the ice, ocean, and seafloor conditions near the point where the floating Ross Ice Shelf meets the seafloor, also known as the grounding line. The study identified refreezing crevasses and geomorphological signatures of past grounding line retreat.

Satellite observations reveal that glaciers on the west coast of the Antarctic Peninsula flow 12% faster on average in summer than in winter. These increased flow speeds are attributed to a combination of seasonal atmospheric and oceanographic forcing mechanisms.

Seismic observations reveal that the Earth’s inner core oscillates with a period of approximately seven decades. The multidecadal periodicity coincides with that of several other geophysical observations, particularly the variations in the length of day and the Earth’s magnetic field, suggesting dynamic interactions between the major layers of the Earth.

The environmental sensors aboard the Perseverance rover on Mars are gathering meteorological data at Jezero crater. These data capture an active atmospheric surface layer that responds to multiple dynamical phenomena, ranging in spatial and temporal scales from metres to thousands of kilometres and from seconds to a Martian year, respectively.

Anthropogenic nitrogen deposition is known to affect forest soil respiration, but it remains unclear how soil respiration responds to nitrogen deposition over time. Monitoring of CO₂ emissions over 9–13 years of nitrogen-addition treatments in three tropical forests in southern China reveals a three-phase pattern of soil respiration.

Satellite measurements show that dust emission is enhanced following large wildfires, producing considerable dust loadings for days to weeks over normally dust-free regions. These sequential fire and dust extremes will likely become more frequent and severe under global warming, having increased societal and ecological impacts.

Large channels of meltwater snake beneath the ice in the Weddell Sea region of Antarctica. This water affects the speed of ice flow above and the melt rate of the ice when it reaches the ocean, having a direct role in the response of Antarctica to climate change.

Melting of the edges of the Greenland ice sheet by the ocean since 1979 is — counterintuitively — controlled almost as much by air temperature as by ocean temperature.