A diagnostic study of the Arctic Ocean winter density-driven circulation in 1973–79

Diagnostic computations of density-driven circulation for seven winters from 1973 through 1979 were carried out. The only forcing was provided by observed temperature and salinity data collected during onsite Russian winter surveys in 1973–79. Computed circulations from 1973 through 1978 were close to the mean circulation obtained earlier by averaging observed 1973–79 temperature and salinity (Polyakov & Timokhov 1994). The computed 1979 density-driven circulation flowed counter-clockwise to the north of the Laptev Sea. This circulation pattern was caused by an anomalous salinity distribution associated with changes in the atmospheric circulation regime in 1979. Prevailing offshore winds blew fresh water from the Laptev and East Siberian shelves toward Fram Strait. Fresh water was exchanged for saltier intermediate water that upwelled to the surface along the slope. The observed surface salinity anomalies at the continental slope of the Laptev Sea in 1979 increased by several salinity units. One may speculate that the same process may have caused the observed salinification of the Eurasian Basin in the 1990s.     

A song of volumes,surfaces and fluxes: The case study of the Central Mallorca Depression (Balearic Promontory) during the Messinian Salinity Crisis

The Central Mallorca Depression (CMD) located in the Balearic Promontory (Western Mediterranean) contains a well-preserved evaporitic sequence belonging to the Messinian Salinity Crisis (MSC) salt giant, densely covered by high- and low-resolution seismic reflection data. It has been proposed recently that the MSC evaporitic sequence in the CMD could be a non-deformed analogue of the key MSC area represented by the Caltanissetta Basin in Sicily. This presumed similarity makes the CMD an interesting system to better understand the MSC events. Physics-based box models of the water mixing between sub-basins, built on conservation of mass of water and salt, help constrain the hydrological conditions under which evaporites formed during the MSC. Those models have been widely used in the literature of the MSC in the past two decades. They have been mostly applied to the Mediterranean Sea as a whole focusing on the Mediterranean–Atlantic connection, or focusing on the influence of the Sicily Sill connecting the Western and Eastern Mediterranean Sea. In this study, we apply a downscaled version of such modelling technique to the CMD. First, we quantify the present-day volumes of the MSC units. We then use a reconstructed pre-MSC paleo-bathymetry to model salinity changes as a function of flux exchanges between the CMD and the Mediterranean. We show that a persistent connection between the CMD and the Mediterranean brine near gypsum saturation can explain volume of Primary Lower Gypsum under a sea level similar to the present. For the halite, on the contrary, we show that the observed halite volume cannot be deposited from a connected CMD-Mediterranean scenario, suggesting a drawdown of at least 850 m (sill depth) is necessary. Comparison between the deep basin halite volume and that of the CMD shows that it is possible to obtain the observed halite volume in both basins from a disconnected Mediterranean basin undergoing drawdown, although determining the average salinity of the Western Mediterranean basin at the onset of drawdown requires further investigation.     

Long-term variability in Arctic sea surface temperatures

In this study, we used 30 years of an operational sea surface temperature (SST) product, the NOAA Optimum Interpolation (OI) SST Version 2 dataset, to examine variations in Arctic SSTs during the period December 1981–October 2011. We computed annual SST anomalies and interannual trends in SST variations for the period 1982–2010; during this period, marginal (though statistically significant) increases in SSTs were observed in oceanic regions poleward of 60°N. A warming trend is evident over most of the Arctic region, the Beaufort Sea, the Chuckchi Sea, Hudson Bay, the Labrador Sea, the Iceland Sea, the Norwegian Sea, Bering Strait, etc.; Labrador Sea experienced higher temperature anomalies than those observed in other regions. However, cooling trends were observed in the central Arctic, some parts of Baffin Bay, the Kara Sea (south of Novaya Zemlya), the Laptev Sea, the Siberian Sea, and Fram Strait. The central Arctic region experienced a cooling trend only during 1992–2001; warming trends were observed during 1982–1991 and 2002–2010. We also examined a 30-yr (1982–2011) record of summer season (June–July–August) SST variations and a 29-yr (1982–2010) record of September SST variations, the results of which are discussed.     

Diatom stratigraphy in five offshore sediment cores from the northwestern Baltic proper implying large scale circulation changes during the last 8500 years

Five Holocene sediment cores from the northwestern Baltic proper were analysed for lithology, siliceous microfossil assemblages and geochemical parameters. The data indicate that surface water salinity and redox conditions below the halocline have changed drastically at least four times since the Baltic Sea changed from a fresh water lake (the Ancylus Lake) to a semi-enclosed brackish water sea (the Litorina Sea) c. 8500 yrs BP. These variations appear to be mainly effects of changes in water depth at the thresholds of inlet areas. Based on these changes, and earlier studies of the shoreline displacement in the inlet areas, we propose a tentative model for changes of large scale water circulation in the Baltic Sea during the last c. 8500 yrs.At the transition from fresh to brackish water 8500 ¹⁴C yrs BP, upwelling of nutrient rich bottom water started to occur, causing a slight increase in primary production. Diatom assemblages in sediments indicate a slow rise in surface water salinity during this period.At 7000-6500 ¹⁴C yrs BP, surface water salinity and primary production simultaneously increased, as anoxic bottom conditions were established at depth below the halocline. We suggest that high primary production was caused by increased input of oceanic water, leading to increased upwelling of nutrient rich bottom water. At the anoxic bottoms laminated sediments formed until 5000-4500 ¹⁴C yrs BP. This period (c. 7000-4500 ¹⁴C BP) was contemporaneous with the post-glacial transgression maximum in Öresund, and we suggest it represents the most saline phase of the Baltic Sea post-glacial history.Due to a regression in Öresund starting 4500 ¹⁴C yrs BP, upwelling decreased and the halocline was lowered, resulting in decreased primary productivity and hence oxic deep water conditions. The diatom assemblages of the sediments indicate a lowering of salinity at the beginning of this period.We suggest that the second period of anoxic bottom conditions c. 2000-1500 ¹⁴C yrs BP was caused by a change of dominating inflows from the Öresund to the Belt Sea. This resulted in decreased salinity of the inflowing water which did not penetrate to the deepest parts of the basin as frequently as before. The diatom record indicates both a second lowering of salinity and a change in the large scale water circulation at the beginning of this period.     

Sediment transport to the Laptev Sea–hydrology and geochemistry of the Lena River

This study focuses on the fluvial sediment input to the Laptev Sea and concentrates on the hydrology of the Lena basin and the geochemistry of the suspended particulate material. The paper presents data on annual water discharge, sediment transport and seasonal variations of sediment transport. The data are based on daily measurements of hydrometeorological stations and additional analyses of the SPM concentrations carried out during expeditions from 1975 to 1981. Samples of the SPM collected during an expedition in 1994 were analysed for major, trace, and rare earth elements by ICP-OES and ICP-MS. Approximately 700 km³ freshwater and 27 times 10⁶ tons of sediment per year are supplied to the Laptev Sea by Siberian rivers, mainly by the Lena River. Due to the climatic situation of the drainage area, almost the entire material is transported between June and September. However, only a minor part of the sediments transported by the Lena River enters the Laptev Sea shelf through the main channels of the delta, while the rest is dispersed within the network of the Lena Delta. Because the Lena River drains a large basin of 2.5 times 10⁶ km², the chemical composition of the SPM shows a very uniform composition. In contrast, smaller rivers with more restricted catchment areas exhibit significant differences.     

Holocene diatom stratigraphy in the Archipelago Sea,northern Baltic Sea

Two sediment cores from the Archipelago Sea in the northern Baltic Sea were examined for their siliceous microfossils in order to study the Holocene palaeoenvironmental history of the area. The diatom record was divided into local diatom assemblage zones (LDAZ). An age model was constructed using independent palaeomagnetic and AMS-¹⁴C methods. The early history of the Archipelago Sea was freshwater. Initial brackish-water influence is observed at 7,950 ± 80 cal. BP (LDAZ4), but fully brackish conditions were established at 7,700 ± 80 cal. BP (LDAZ5). Diatom assemblages indicate increasing salinity, warming climate, and possible increasing trophic state during the transition from lacustrine to brackish-water conditions. The decreasing abundance of Pseudosolenia calcar-avis (Schultze) Sundström and the increasing abundance of the ice-cover indicator species Pauliella taeniata (Grunow) Round and Basson indicate reduced salinity and climatic cooling after ～5,000 cal. BP. LDAZ boundaries do not always correlate with changes in the sediment appearance, which underlines the importance of defining biostratigraphic boundaries independently to the sediment visual character, in contrast with the conventional practice for classifying the Baltic Sea sediments.     

Natural and anthropogenic aquatic environmental changes reconstructed by paleolimnological analyses in Lake Kitaura,central Japan

In order to assess the recent anthropogenic environmental changes in Lake Kitaura, central Japan, changes during the past few centuries were reconstructed from results of radiometric and tephrochlonological age determination, magnetic susceptibility measurements, total organic carbon analyses, total nitrogen analyses and fossil diatom analyses on a sediment core from the lake. A total of six major and sub-zones are recognized according to the diatom fossil assemblages, and we discuss aquatic environmental change in Lake Kitaura mainly based on these diatom assemblage change. Zone Ia and Zone Ib (older than AD 1707) are marine to brackish. In Zone IIa (AD␣1707–AD 1836), most of the brackish diatoms disappeared, and were replaced by freshwater species indicating a decrease in salinity. We interpret the salinity decrease in Zone I–IIa as a sea-level fall during the Little Ice Age. The salinity of the lake decreased to near freshwater conditions in Zone IIb (AD 1836–AD 1970), which could arise from alteration in River Tone or development of a sandspit in the mouth of River Tone in addition to sea-level change. In Zone IIIa (AD 1970–AD 1987), the diatom assemblage indicates a freshwater environment, and sedimentation rates increase rapidly. These changes reflect sedimentary environment change and an ecosystem transition due to the construction of the tide gate. In Zone IIIb (AD 1987–AD 2002), the diatom flux (valves cm⁻² y⁻¹) increased and species composition changed. The changes in Zone IIIb show a good agreement with limnological monitoring data gathered from the lake. These paleolimnological data suggest that the recent human-induced changes of the aquatic environment of the lake after the 1970s exceed rates during the period concerned in this study.     

Seasonal and long-term sea level variability in the marginal seas of the Arctic Ocean

One of the parameters useful for monitoring large-scale climate variability in the Arctic Ocean is sea level. It integrates virtually all static and dynamic processes in the hydrosphere and atmosphere of the Arctic. Previously unavailable mean monthly sea level data at 44 coastal and island stations in the Kara, Laptev, East Siberian and Chukchi seas covering years from 1950 to 1990 were used to analyse seasonal and inter-annual variability. Sea level has a significant annual cycle with an average seasonal amplitude (from peak to peak) in the coastal zone of the Arctic seas on the order of 20 - 30 cm. The analysis of inter-annual and inter-decadal changes has shown that at nearly all stations in the Kara, Laptev, East Siberian and Chukchi seas from the beginning of the 1950s through the end of 1980s there is a positive trend in sea level variability. The main contribution to the sea level rise was in the 1980s; on average for the coastal zone of Siberian shelf the sea level in the 1980s was 5-6 cm higher than in the previous decades. A reasonable agreement between observed decadal mean sea level values and the results of diagnostic model simulations suggests that this rise in the Arctic seas is connected with the reorganization of large-scale circulation of the Arctic Ocean, rather than the regional lowering of the coasts, as has been suggested previously.     

Influence of Mediterranean sea-level changes on the Dacic Basin (Eastern Paratethys) during the late Neogene: the Mediterranean Lago Mare facies deciphered

A recently published scenario viewing the Messinian salinity crisis as two evaporitic steps rather than one has led to a search for new indices of the crisis in the Eastern Paratethys. Fluvial processes characterized the southwestern Dacic Basin (Southern Romania, i.e. the Carpathian foredeep) whereas brackish sediments were continuously deposited in its northern part. This is consistent with previously evidenced responses of the Black Sea to the Messinian salinity crisis. High sea‐level exchanges between the Mediterranean Sea and Eastern Paratethys are considered to have occurred just before and just after desiccation of the Mediterranean. This accounts for two successive Mediterranean nannoplankton‐dinocyst influxes into the Eastern Paratethys that, respectively, belong to zones NN 11 and NN 12. Meanwhile, two separate events that gave rise to Lago Mare facies (with Paratethyan Congeria, ostracods and/or dinoflagellate cysts) arose in the Mediterranean Basin in response to these high sea‐level exchanges and located 5.52 and 5.33 Ma (isotopic stages TG 11 and TG 5, respectively), i.e. just before and just after the almost complete desiccation of the Mediterranean). These Lago Mare facies formed independently of lakes with ostracods of the Cyprideis group that developed in the central basins during the final stages of desiccation. The gateway faciliting these water exchanges is not completely identified. A proto‐Bosphorus strait seems unlikely. A plausible alternative route extends from the northern part of the Thessaloniki region up to the Dacic Basin and through Macedonia and the Sofia Basin. The expression ‘Lago Mare’ is chronostratigraphically ambiguous and should be discontinued for this purpose, although it might remain useful as a palaeoenvironmental term.     

北极海冰快速减少期间加拿大海盆上层海洋夏季淡水含量变化

北极海冰近年来快速减少,北冰洋淡水含量也出现了急剧变化。加拿大海盆作为北冰洋淡水的主要存储区域,研究其淡水含量变化对于认识北冰洋淡水收支有重要意义。本文根据2003年、2008年中国北极考察以及2004年至2007年的加拿大考察数据进行计算,发现除2006年以外,夏季加拿大海盆淡水含量在此期间每年增加1m以上厚度。增加主要发生在冬季白令海水以上的上层海水中,而在此之下,淡水含量维持在3m左右,没有显著年际差异。在2006年,加拿大海盆西部上层淡水含量略微减少,但东部和北部海域淡水含量仍略有增加。与2003年相比,2008年加拿大海盆中心海区淡水含量增加量最高可达7m。分析表明,近年来的海冰减退对加拿大海盆上层淡水含量的增加起着重要作用,北极涛动(AO)正负相位变化也是控制其淡水含量变化的一个重要因素。而降水、径流以及白令海峡入流水的变化对加拿大海盆淡水含量变化影响较小。     

Effects of freeze–thaw cycles on soil N_2O concentration and flux in the permafrost regions of the Qinghai–Tibetan Plateau

Nitrous oxide(N_2 O) is one of the most important greenhouse gases in the atmosphere; freeze–thaw cycles(FTCs) might strongly influence the emission of soil N_2 O on the Qinghai–Tibetan Plateau(QTP). However, there is a lack of in situ research on the characteristics of soil N_2 O concentration and flux in response to variations in soil properties caused by FTCs.Here, we report the effect of FTC-induced changes in soil properties on the soil N_2 O concentration and flux in the permafrost region of the higher reaches of the Shule River Basin on the northeastern margin of the QTP. We measured chemical properties of the topsoil, activities of soil microorganisms, and air temperature(AT), as well as soil N_2 O concentration and flux, over an annual cycle from July 31, 2011, to July 30, 2012. The results showed that soil N_2 O concentration was significantly affected by soil temperature(ST), soil moisture(SM), soil salinity(SS), soil polyphenol oxidase(SPO), soil alkaline phosphatase(SAP), and soil culturable actinomycetes(SCA), ranked as SMSSSTSPOSAPSCA, whereas ST significantly increased soil N_2 O flux, compared with SS. Overall, our study indicated that the soil N_2 O concentration and flux in permafrost zone FTCs were strongly affected by soil properties, especially soil moisture, soil salinity, and soil temperature.     

Simulation of currents, ice melting, and vertical mixing in the Barents Sea using a 3-D baroclinic model

A baroclinic. 3-D model is described. It is adapted to the Barents Sea and includes thermodynamics and atmospheric input. The freezing and melting of ice is allowed for in the model. The main task of the study is to look at the development of the ice cover, the vertical mixing, and the vertical and horizontal density gradients.
Despite simple approximations in the air temperature input, realistic ice-cover is produced in the model area during simulation of a "freezing period" (winter). This intermediate result is briefly discussed and also forms the start of a "melting period" simulation (spring/summer). Atmospheric input data (wind, air pressure, and heat flux) from the spring and summer 1983 is used, and details about vertical mixing, temperature, and salinity are discussed. The simulation results demonstrate the temporal variation of the thermocline depth, the variation of the ice cover, and the horizontal changes of density. The conclusion is that despite often simplified input, the model seems to produce a physical picture characteristic of the Barents Sea.     

Interannual variability of dense shelf water salinities in the north-western Barents Sea

The maximum dense shelf water salinity formed during winter in the Svalbard Bank area of the north-western Barents Sea is reconstructed for the period 1952–2000 by analysing the transformation of summer remnants. The variability of 34.7 - 35.4, waters being at the freezing point, is mainly generated by interannual variations in the near surface salinity. On interannual time scales the latter is strongly linked to the sea ice import. In contrast, no correlation of the salinity of the Atlantic Water (AW) throughflow to the Arctic Ocean with the ice import is found. Salinities of both the dense shelf water site in the north-west Barents Sea and the north-eastward AW throughflow show a long term decrease, which can partly be explained by a less saline inflow of AW from the Norwegian Sea. The unusually low dense water salinities in the north-west Barents Sea during the 1990s appear to have a different origin, consistent with a response to oceanic heat advection and decreasing sea ice extent.     

伊朗高原和北非感热异常对夏季塔里木盆地降水的影响

基于1971—2019年日本气象厅提供的JRA-55地表感热、大气环流再分析数据和国家气象信息中心提供的我国陆面逐月格点降水数据,研究了夏季伊朗高原和北非感热异常对同期塔里木盆地降水的可能影响。结果表明：（1） 夏季伊朗高原感热和北非感热均与塔里木盆地夏季降水密切联系,将2个区域加热共同考虑,其与塔里木盆地降水的关系要比仅考虑单一区域加热更为紧密。（2） 当伊朗高原感热整体偏强,且北非感热呈北弱南强异常分布时,对应中亚副热带西风急流相对偏南,中亚和蒙古高原上空分别为异常气旋和反气旋控制,塔里木盆地上空南风加强;热带印度洋水汽在阿拉伯海与中亚的异常环流配合下北上进入塔里木盆地;以上条件共同导致了同期塔里木盆地降水的增多,反之亦然。（3） 北非和伊朗高原加热均可单独影响塔里木盆地夏季降水,其中伊朗高原感热对大尺度环流和水汽输送的影响均显著,因此其与降水的关系也更加密切。北非感热加热的影响主要体现在大尺度环流方面,对水汽输送的影响和伊朗高原存在差异,主要体现在印度半岛上空的异常反气旋位置偏南,导致阿拉伯海水汽无法进入塔里木盆地。     

Environmental change in Northern Egyptian Delta lakes during the late Holocene,based on diatom analysis

Quantitative and qualitative diatom analyses from the north Nile Delta lakes sediments of Egypt were used to evaluate the paleoenvironmental development of the lakes and climatic changes during the late Holocene. We analyzed 565 samples taken from 19 cores from Manzala, Burullus and Edku lakes. A total of 263 diatom species and varieties were identified. Multivariate statistical analyses distinguished 17 ecological groups that reflect changes in water salinity, lake-level and trophic state of the lakes, which in turn are mainly related to climatic changes and anthropogenic impacts. Manzala and Burullus lakes experienced a series of alternation between fresh, brackish and marine episodes, which were associated with wet and dry climates. Edku Lake cores, however, contained only three ecological groups that are characteristic of brackish water conditions. The general depositional regime in the lakes indicated five environmental phases: (a) a deep freshwater phase when the Nile flood water reach the lakes during humid warm climate; (b) a shallow freshwater phase with some macrophytes during a dry climate; (c) a shallow brackish water phase when Nile floodwater ceased during a dry climate and the lakes shifted to brackish conditions; (d) a mixed environmental phase when the seawater mixed with freshwater from drains and canals (water salinity fluctuated widely from freshwater to estuarine and full marine conditions); (e) a fully marine phase when seawater entered the lakes at all stages of the tide.     

The thermal field in a basin after a sudden passive pure shear lithospheric extension and sublithospheric mechanical erosion:the case of the Tuscan Basin (Italy)

A simple new model for sudden lithospheric thinning that considers the crust to be stretched and the lower layer of the lithosphere to be partially stretched and partially mechanically eroded is proposed. This model allows calculation of the thermal field of the lithosphere during the initial warming phase and the surface uplift.
Application of this model to the Tuscan Basin explains the high regional heat flux density values (>100 mW m⁻² ), the tectonic subsidence (about 1 km) and the average uplift (>400 m) observed in this region well.     

Observations of Ebria tripartita (Schumann) Lemmermann in Baltic sediments

Sediment finds of Ebria tripartita (Schumann) Lemmermann in the Baltic Sea are reported and light and electron micrographs of the remains of the taxon are presented. Stratigraphic ebriid analysis performed on two sediment cores (one from the deep Gotland Basin and the other from the shallow Töölö bay, central Helsinki) provided clear indications of frequency changes of E. tripartita. These changes are apparently related to the variations in trophic status and salinity, yet competition and degree of preservation may also have contributed to the distributions. Due to identification problems, the species may actually be more common in the sediment material of the Baltic Sea than has hitherto been recognized. E. tripartita may have a significant potential as an indicator species in paleolimnological research as more information is gathered about its present-day ecological requirements.     

北极拉普捷夫海海冰多年变化研究

拉普捷夫海是北冰洋的边缘海和冰源地,对北冰洋的海冰变化有重要影响。通过分析AMSR-E海冰密集度数据以及NECP-DOE的风场、温度场数据,结果表明拉普捷夫海海冰在2002—2011年经历了如下过程：重冰年(2002—2004)—过渡性质年份(2005—2006) —轻冰年(2007、2009—2011),即冰情由重向轻转变。研究结果也表明拉普捷夫海的冰情轻重与融冰期长短有较好的相关性,融冰期持续时间越短,冰情越重。4个参数,包括海冰距平指数、最小海冰覆盖率、积温、风驱动指数描述了拉普捷夫海的海冰多年变化过程。海冰距平指数是时间（3—11月）平均下的海冰覆盖率距平值,定量给出了各年冰情的轻重;最小海冰覆盖率是夏季海冰的极限情况,变化范围在0.45%—48.73%,发生时间为8月底至10月上旬。积温是上一个冬季气温积累对当年冰情的影响,结果表明积温是影响当年冰情轻重的主要因素。2008年的上一个冬季经历了异常低温,造成当年的异常重冰年。风驱动指数给出了风场对海冰覆盖率变化的短期影响,与同时期其他年份相比,2006年4月、2007年9月均出现了异常强北风,一定程度上造成了2006年融冰开始时间延后、2007年夏季最小海冰覆盖率的明显偏大。     

环北极沉积盆地结构与构造演化特征——来自环北极地质长剖面的证据

通过对北极地区不同盆地结构的系统研究与对比分析,绘制了环北极沉积盆地群长剖面,剖面全长约13 000 km,涉及季曼-伯朝拉盆地等15个盆地和微陆。由于整个剖面尺度巨大,在若干缺乏详细资料的地区采用将邻近地区的其他剖面平移到本剖面中,或由其两侧的剖面地层和构造形式推测。剖面涉及的盆地多属叠合性质,涵盖克拉通盆地、裂谷盆地、前陆盆地、被动大陆边缘盆地等多种盆地类型;各区域沉积厚度差异显著,最厚的东巴伦支海等盆地沉积了自古生界至新生界的地层,沉积厚度可达近15 km ,而沉积最薄处的拉普捷夫海等盆地则只发育了从中生界上白垩统至新生界的沉积,厚度不超过4 km。以北大西洋—北冰洋洋中脊为界,北极地区分属欧亚板块和北美板块,很多盆地为大陆的一部分或大陆向北冰洋的延伸部分（大陆架）。各盆地的发育主要受波罗的板块、西伯利亚板块与劳伦古陆显生宙以来的构造演化控制;加里东运动、埃尔斯米尔运动、海西运动（乌拉尔运动）及大西洋洋脊自南向北的扩张对环北极盆地均有显著影响,具体表现为造成盆地类型的改变、改变盆地沉降速率等。     

Morphology and origin of major Cenozoic sequence boundaries in the eastern North Sea Basin: top Eocene,near‐top Oligocene and the mid‐Miocene unconformity

Unconformities in sedimentary successions (i.e. sequence boundaries) form in response to the interplay between a variety of factors such as eustasy, climate, tectonics and basin physiography. Unravelling the origin of sequence boundaries is thus one of the most pertinent questions in the analysis of sedimentary basins. We address this question by focusing on three of the most marked physical discontinuities (sequence boundaries) in the Cenozoic North Sea Basin: top Eocene, near‐top Oligocene and the mid‐Miocene unconformity. The Eocene/Oligocene transition is characterized by an abrupt increase in sediment supply from southern Norway and by minor erosion of the basin floor. The near‐top Oligocene and the mid‐Miocene unconformity are characterized by major changes in sediment input directions and by widespread erosion along their clinoform breakpoints. The mid‐Miocene shift in input direction was followed by a marked increase in sediment supply to the southern and central North Sea Basin. Correlation with global δ¹⁸O records suggests that top Eocene correlates with a major long‐term δ¹⁸O increase (inferred climatic cooling and eustatic fall). Near‐top Oligocene does not correlate with any major δ¹⁸O events, while the mid‐Miocene unconformity correlates with a gradual decrease followed by a major long‐term increase in δ¹⁸O values The abrupt increases in sediment supply in post‐Eocene and post‐middle Miocene time correlate with similar changes worldwide and with major δ¹⁸O increases, suggesting a global control (i.e. climate and eustasy) of the post‐Eocene sedimentation in the North Sea Basin. Erosional features observed at near‐top Oligocene and at the mid‐Miocene unconformity are parallel to the clinoform breakpoints and resemble scarps formed by mass wasting. Incised valleys have not been observed, indicating that sea level never fell significantly below the clinoform breakpoint during the Oligocene to middle Miocene.