Research Briefing in 2023

Analysis of sea temperatures using a four-dimensional spatio-temporal framework has revealed a great number of marine heatwaves occurring globally below the sea surface. These extreme events, which threaten the ecologically important epipelagic zone, have occurred increasingly frequently during the past three decades owing to ocean warming.

Deep-sea acidity data combined with ice-core carbon dioxide records reveal that an interplay between the two polar regions modulates ocean ventilation through various modes. These modes explain past variations in deep-sea carbon storage and atmospheric carbon dioxide on millennial timescales.

H₂, which is formed by the oxidation of iron in rocks, was likely a critical source of energy for early life. Analysis of natural rock samples from 3.5–2.7 billion-year-old komatiites, combined with geochemical data from a global database, quantifies the amount of H₂ likely to have been produced in Earth’s ancient oceans.

Megafloods are rare and hence difficult to predict. However, using a collation of historical flood observations across Europe, it is now shown that recent megafloods could have been anticipated — local surprises are in fact not surprising at the continental scale.

Swath radar maps of the subglacial landscape reveal how Antarctica’s geologic history has influenced the evolution of the ice sheet. The findings indicate the role of past interior ice streams in shaping ice-sheet growth and flow from Hercules Dome.

From a stalagmite that grew 14,000–8,500 years ago, isotopic data provide a detailed history of groundwater infiltration associated with a strengthening North American monsoon, as the climate transitioned from a cool dry late-glacial period into a warmer and wetter Early Holocene.

Accurate estimates of the land carbon sink are vital for informing climate projections and net-zero policies. Application of a strict filtering method to microwave satellite data enabled the evaluation of global vegetation biomass carbon dynamics for 2010–2019. The results highlight the role of demography in driving forest carbon gains and losses.

There are two competing hypotheses for the origin of oceanic plateaus: plume versus plate. Thermodynamic modelling of magmatism at Shatsky Rise, in the Pacific Ocean, now suggests that neither mechanism is adequate on its own and in fact plume–ridge interaction is required to explain the formation of this ocean plateau.

Phosphorus from intensive agriculture contributes to increased algal blooms, threatening ecosystems and drinking water sources. We found increasing dissolved phosphorus concentrations in more than 170 Great Lakes Basin streams, despite stable or decreasing total phosphorus levels. Higher latitudes experienced greater relative increases, potentially due to warmer winters and altered flow pathways.

Glacier ice contains high-pressure air bubbles, which burst into seawater as ice melts at tidewater glacier termini. Laboratory measurements found that these bubbles double the rate of ice melt. Theoretically, this effect could be even larger in a real glacier. However, bursting bubbles are currently neglected in models projecting sea level rise.

Analysis of mineral inclusions in magmas that crystallized before and after the Great Oxidation Event reveals marked changes in the oxidation state of sulfur — owing to the recycling into the mantle of sediments that had been geochemically altered at the surface by atmospheric events.

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.