Sea-level science has seen many recent developments in observations and modelling of the different contributions and the total mean sea-level change. In this overview, we discuss (1) the evolution of the Intergovernmental Panel on Climate Change (IPCC) projections, (2) how the projections compare to observations and (3) the outlook for further improving projections. We start by discussing how the model projections of 21st century sea-level change have changed from the IPCC AR5 report (2013) to SROCC (2019) and AR6 (2021), highlighting similarities and differences in the methodologies and comparing the global mean and regional projections. This shows that there is good agreement in the median values, but also highlights some differences. In addition, we discuss how the different reports included high-end projections. We then show how the AR5 projections (from 2007 onwards) compare against the observations and find that they are highly consistent with each other. Finally, we discuss how to further improve sea-level projections using high-resolution ocean modelling and recent vertical land motion estimates.

The relict beach deposit of the Cala Mosca marine terrace is considered an important section of Marine Isotopic Stage (MIS) 5e (ca. 125 ka) sea-level highstands. Analysis of the stratigraphy and sediments of the deposit indicates the presence of a composite marine terrace comprising two superimposed marine units, luminescence dated to the MIS 5e (137 ± 7, 134 ± 7 ka) and MIS 5c (92 ± 6 ka) substages. The stratigraphic superimposition of the two highstands, both placed ~5 m above present sea level, agrees with other areas along the Sardinia coasts. The evident superimposition of two sea-level highstands and development of the composite terrace cannot be accounted solely by high-frequency sea-level oscillation that occurred within MIS 5 for the Mediterranean Sea. This suggests controversial, but significant, regional versus local tectonic activity occurred during the Late Pleistocene.

We reconstructed the late Holocene relative sea-level (RSL) evolution of the ancient harbour of Naples, one of the largest coastal conurbations in the Mediterranean. We carried out multiproxy investigations, coupling archaeological evidence with biological indicators. Our data robustly constrain 2000 yr of non-monotonic changes in sea level, chiefly controlled by the complex volcano-tectonic processes that characterize the area. Between ~200 BC and AD ~0, a subsidence rate of more than ~1.5 mm/yr enhanced the postglacial RSL rise, while negligible or moderate land uplift < ~0.5 mm/yr triggered a RSL stabilization during the Roman period (first five centuries AD). This stabilization was followed by a post-Roman enhancement of the sea-level rise when ground motion was negative, attested by a subsidence rate of ~0.5 to ~1 mm/yr. Our analysis seems to indicate very minor impacts of this nonmonotonic RSL evolution on the activities of the ancient harbour of Naples, which peaked from the third century BC to the second century AD. After this period, the progressive silting of the harbour basin made it impossible to safely navigate within the basin, leading to the progressive decline of the harbour.

The continental shelf strata provide information regarding sea-level fluctuation and climate changes in the Quaternary period. A 5831.47-km-long high-resolution seismic profile and borehole core (YS01) were acquired to reconstruct the evolutionary history of the strata in South Yellow Sea (SYS) during the late Pleistocene. The strata recorded three transgression events (HI, HII, and HIII) and three stages of paleochannel development (LI, LII, and LIII). Based on the distribution, thickness, and volume of the strata formed in the three transgressions, we concluded that the scale of the three transgressions during the late Pleistocene was HIII, HI, and HII, in descending order. In addition, our data show that the Yellow River extended to the Yellow Sea Trough during the last glacial maximum. The influence of the tectonic framework on sedimentation in the SYS was completely concealed by sea-level changes and sediment supply in the late Pleistocene (~Marine Isotope Stage 5). Since then, the accommodation space, a crucial prerequisite for sedimentation, has been controlled solely by sea-level changes in the SYS. Furthermore, two “source to sink” models of the neritic shelf in the marine and terrestrial environments were established, including high sea-level and shelf-exposure models.

Over 100 whole-rock amino acid racemization (AAR) ratios from outcrops around Rottnest Island (32.0° S Latitude near Perth) indicate distinct pulses of eolian deposition during the late Quaternary. Whole-rock d-alloisoleucine/l-isoleucine (A/I) ratios from bioclastic carbonate deposits fall into three distinct modal classes or “aminozones.” The oldest, Aminozone E, averages 0.33 ± 0.04 (n = 21). Red palaeosol and thick calcrete generally cap the Aminozone E deposits. A younger Aminozone C averages 0.22 ± 0.03 (n = 63); comprising two submodes at 0.26 ± 0.01 (n = 14) and 0.21 ± 0.02 (n = 49). Multiple dune sets of this interval are interrupted by relatively weak, brown to tan “protosols.” A dense, dark brown rendzina palaeosol caps the Aminozone C succession. Ratios from Holocene dune and marine deposits (“Aminozone A”) center on 0.11 ± 0.02 (n = 15), comprising submodes of 0.13 ± 0.01 (9) and 0.09 ± 0.01 (6). Calibration of A/I averages from Aminozones E and A are provided by U/Th and 14C radiometric ages of 125,000 yr (marine oxygen isotope stage (MIS) 5e and 2000–6000 14C yr B.P. (MIS 1), respectively. The whole-rock A/I results support periodic deposition initiated during MIS 5e, continuing through MIS 5c, and then peaking at the end of MIS 5a, about 70,000–80,000 yr ago. Oceanographic evidence indicates the area was subjected to much colder conditions during MIS 2–4 (10,000 to 70,000 yr ago), greatly slowing the epimerization rate. Eolianite deposition resumed in the mid Holocene (∼6000 yr ago) up to the present. The A/I epimerization pathway constructed from Rottnest Island shows remarkable similarity to that of Bermuda in the North Atlantic (32° N Latitude). These findings suggest that, like Bermuda, the eolian activity on Rottnest occurred primarily during or shortly after interglacial highstands when the shoreline was near the present datum, rather than during glacial lowstands when the coastline was positioned 10–20 km to the west.

Reevaluation of geological and archaeological evidence from western Mount Carmel constrains its maximal tectonic uplift since the Middle Pleistocene. Tabun Cave, presently 45 m above sea level (asl), revealed human occupation from about 600 ka to 90 ka before present. The 25 m thick archaeological strata at Tabun are composed of laminated fine sand, silt and clays. Moreover, no marine deposits were found in Tabun or nearby caves. Since sea level in the last 600 ka reached a maximal of 5 to 10 m asl, Tabun Cave could not have been uplifted since then by more than 35 to 40 m, that is a maximal average rate of 58 to 67 mm/ka.

The Early to Late Triassic development of a carbonate ramp system in the subtropical belt of the NW Tethys was controlled by the interplay of several global and regional factors: geotectonic setting (slow continuous subsidence on a passive continental margin), antecedent topography (low-gradient relief inherited from preceding depositional regime), climate and oceanography (warm and dry climatic conditions, storm influence), relative sea-level changes (Olenekian to Anisian eustatic rise, middle Anisian to early Carnian sea-level fall), lack of frame-builders (favouring the maintenance of ramp morphology), and carbonate production (abundant formation of lime mud, non-skeletal grains and marine cements, development of diverse biota controlled by biological evolution and environmental conditions). Elevated palaeorelief affected the ramp initialization on a local scale, while autogenic processes largely controlled the formation of peritidal cyclicity during the early stage of ramp retrogradation. Probably fault-driven differential subsidence caused a local distal steepening of the ramp profile in middle–late Anisian time. The generally favourable conditions promoted long-term maintenance of homoclinal ramp morphology and accumulation of carbonate sediments having great maximum thickness (~500 m). Shutdown of the carbonate factory and demise of the ramp system in the early Carnian resulted from relative sea-level fall and subsequent emergence. After a period of subaerial exposure with minor karstification, the deposition of continental quartz arenites suggests the possible effect of the Carnian Pluvial Episode.

In this contribution, a case is made for the significance of sedimentation and sea-level change for groundwater management of coastal areas. In groundwater practice these geological processes are rarely considered. The role of sediment loading in causing anomalous fluid pressures and flow fields in relatively shallow aquifer systems is discussed and illustrated via both case studies and generic modelling studies. The role of sea-level changes in controlling current salinity distributions is discussed likewise. Central in the discussion is the concept of memory of groundwater systems, which provides the basic reason why processes that were operative in the geological past are still of relevance today. It is argued and shown that awareness and knowledge of the influence of sediment loading and sea level change on current hydrological conditions can lead to improved characterization of the distribution of hydraulic parameters and of the distribution of water quality in coastal areas. This improved characterization, in turn, serves to enhance the validity of impact assessment studies for the long-term development and management of those areas.

A condensed succession at Annopol is of key importance for the mid-Cretaceous palaeontology and palaeobiogeography in Poland. Here, the planktonic and benthic foraminifera from the Albian and Cenomanian intervals are studied. The local foraminiferal record is strongly influenced by burrowers. On the one hand, piping down of the foraminiferal tests through burrows disturbed the original succession, for example by introduction of the Cenomanian foraminifera into the Albian phosphorite horizon. On the other hand, the foraminifera in the burrow fills near the base of the Cenomanian provide the sole piece of evidence of a lower upper Cenomanian unit lost from the record by erosion. Changes in foraminiferal assemblages allow for the interpretation of the succession in terms of bathymetry and biological productivity. The highest rate of primary production is deduced for the Albian phosphorite horizon. Integration of foraminiferal and ammonite biostratigraphy with sedimentology allows for the comparison of a pattern of sea-level oscillations recorded at Annopol with the relevant portion of the classic graph of sea-level changes for the British Isles. It turns out that all important elements of the British curve, that is, transgressive peaks and regressive troughs or lows, left their distinctive, albeit highly residual, record in the Annopol succession. This study demonstrates that even extremely condensed marine deposits, such as those at Annopol, may provide a foraminiferal record of better quality, order and resolution than conventionally anticipated.

The most prominent of the two major global δ13C excursions in the Ordovician, the Hirnantian δ13C excursion (HICE), which is previously recorded from the uppermost Ordovician in a few sections in Nevada, Quebec, Arctic Canada, Baltoscandia, Scotland and China, is documented for the first time from the North American Midcontinent. Samples through the Girardeau Limestone and Leemon Formation in Missouri and Illinois show elevated δ13C values of +4‰ to +5‰. Although not determined precisely, the beginning of the HICE is likely to be in the upper part of the Orchard Creek Shale, and it ends in the upper Leemon Formation. Being extraordinarily useful chronostratigraphically, the presence of the HICE makes it possible to provide a firm dating of the study interval, whose age has long been controversial. Comparison between the study sections and coeval HICE sequences in North America and Europe show striking similarities, especially in sea-level history, indicating that major local lowstands reflect eustatic sea-level changes. A comparison with Hirnantian diamictite successions in North and South Africa and Argentina suggests that these lowstands correspond to two major Gondwanan glacial episodes.

The outcrops of the Sierra de Albarracín (NE Spain) allow a precise reconstruction of the shallow sedimentary domains of a late Kimmeridgian carbonate ramp, developed in western marginal areas of the Iberian Basin. The sedimentary record shows a hierarchical sequence stratigraphic organization, which implies sea-level changes of different frequencies. The studied succession is arranged in a long-term transgressive–regressive sequence, which is likely to reflect local variation in the subsidence rates. This sequence includes four higher-order sequences A to D, which have variable thickness (from 3 to 21 m). The similar sedimentary evolution observed in distant localities suggests the existence of high-frequency sea-level fluctuations controlling the sequence development. The average amplitude of these cycles would range from 5 to 10 m. The precise estimation of their duration (some few hundreds of kyr) and their possible assignment to any of the long-term orbital cycles (the 100 or the 400 kyr eccentricity cycles) is uncertain. Sequences A and B, formed during the long-term transgressive interval, are relatively thin (from 3 to 9 m) give-up sequences that were never subaerially exposed. These sequences are locally formed by five shallowing-upward elementary sequences. Sequences C and D are catch-down sequences with evidence of emersion of subtidal facies. Sequence C, formed during the stage of maximum gain of long-term accommodation, is the thickest sequence (from 13 to 21 m) and includes coral–microbial reefs (pinnacles up to 16 m in height). The increased production rates were able to fill part of the accommodation created during the early stage of high-frequency sea-level rise and the shallow platform was eventually exposed to subaereal erosion and meteoric cementation.

In the eastern Mendip Hills, on the northern margin of the Wessex Basin, SW England, the Carboniferous Limestone is cut by numerous fissures that are filled with Mesozoic sediments (sedimentary dykes, neptunian dykes). The fissures contain a record of Triassic–Lower Jurassic sediments that are only sparingly preserved in their normal stratigraphical position between the Carboniferous Limestone and the unconformably overlying Upper Inferior Oolite of Bajocian age. Detailed analysis of cross-cutting relationships, facies analysis, biostratigraphy, lithostratigraphy and strontium-isotope ages of relevant Mesozoic sediments has allowed the construction of an Upper Triassic–Lower Jurassic fissure-fill stratigraphy for the eastern Mendip area. Most fissures were clearly formed by rapid influx of unlithified sediment from the land surface or sea floor. Some smaller cavities, or larger cavities with restricted access to the unconformity, were apparently filled by sediment that trickled down into the fissure system. The vast majority of the Mendip fissures are interpreted as having formed as a response of the Carboniferous Limestone, north of major basin-bounding faults, to pulses of tectonic extension during Ladinian–Norian/Rhaetian, late Hettangian–early Sinemurian, late Sinemurian–early Pliensbachian, mid-Pliensbachian, late Pliensbachian and Bajocian times. Triassic–earliest Jurassic fissures have a broad spread of strike from E–W to NW–SE to N–S, accommodating extension in a roughly NE–SW direction. Younger Jurassic fissures show well-defined E–W and N–S trends with the former becoming dominant through time. Total extension of ∼4.7% N–S and ∼0.6% E–W was produced by the formation of Triassic–Jurassic fissures within the Carboniferous Limestone. Such patterns of extension are thought likely to be characteristic of the subsurface geology in much of southern England and Wales. Major implications of this study are that: (1) the presence of seismically unresolvable sediment-filled fissures in supposedly rigid fault blocks can lead to a significant underestimate of regional extension based on the restoration of motion on normal faults on seismic-reflection profiles, and (2) the isolation of pulses of tectonic activity with a temporal resolution of 105–106 years may provide a means of identifying a tectonic signal in relative sea-level curves derived from the Jurassic sedimentary record.