Deep Water Temperature Research Articles

Southern jets of the antarctic circumpolar current in the Eastern Pacific Antarctic

The advent of the era of satellite observations of the ocean surface has resulted in a considerable complication of views on the structure of currents in the World Ocean. Up to eight jets came to be distinguished in the zone of the Antarctic Circumpolar Current (ACC). To identify these jets, it is conventional to use qualitative criteria relating a jet’s position to the isoline of a characteristic (temperature, for instance) on any near-horizantal surface. In the present work, based on data of sections and climatology of the World Ocean Circulation Experiment (WOCE) program, we examine the temperature patterns of the subsurface waters of the Southern Ocean, which are commonly used for recognition of fronts. The focus is on the southern jets of the ACC in the Eastern Pacific Antarctic. There are two groups of criteria for these jets, which imply that position of the latter is determined from a certain isotherm on the surface of the minimum (maximum) potential temperature of the Winter water (Upper Circumpolar Deep Water). However, the results of our analysis show that, in fact, the WOCE climatology data allow one to formulate temperature criteria only for the second of the above groups and only for individual sectors of the Southern Ocean-specifically, for the study area. These criteria serve as the basis for determining localization of the southern jets of the ACC in the WOCE sections in this ocean’s region. We also show that the temperature increased by about 0.1°C from the mid-1990s to the mid-2000s in the layer of maximum temperature of the Upper Circumpolar Deep Water in the zone of southern jets of the ACC.

On the Linkage between Antarctic Surface Water Stratification and Global Deep-Water Temperature

Abstract The suggestion is advanced that the remarkably low static stability of Antarctic surface waters may arise from a feedback loop involving global deep-water temperatures. If deep-water temperatures are too warm, this promotes Antarctic convection, thereby strengthening the inflow of Antarctic Bottom Water into the ocean interior and cooling the deep ocean. If deep waters are too cold, this promotes Antarctic stratification allowing the deep ocean to warm because of the input of North Atlantic Deep Water. A steady-state deep-water temperature is achieved such that the Antarctic surface can barely undergo convection. A two-box model is used to illustrate this feedback loop in its simplest expression and to develop basic concepts, such as the bounds on the operation of this loop. The model illustrates the possible dominating influence of Antarctic upwelling rate and Antarctic freshwater balance on global deep-water temperatures.

Deep water temperature, carbonate ion, and ice volume changes across the Eocene‐Oligocene climate transition

Paired benthic foraminiferal stable isotope and Mg/Ca data are used to estimate bottom water temperature (BWT) and ice volume changes associated with the Eocene‐Oligocene Transition (EOT), the largest global climate event of the past 50 Myr. We utilized ODP Sites 1090 and 1265 in the South Atlantic to assess seawater δ18O (δw), Antarctic ice volume, and sea level changes across the EOT (∼33.8–33.54 Ma). We also use benthic δ13C data to reconstruct the sources of the deep water masses in this region during the EOT. Our data, together with previously published records, indicate that a pulse of Northern Component Water influenced the South Atlantic immediately prior to and following the EOT. Benthic δ18O records show a 0.5‰ increase at ∼33.8 Ma (EOT‐1) that represents a ∼2°C cooling and a small (∼10 m) eustatic fall that is followed by a 1.0‰ increase associated with Oi‐1. The expected cooling of deep waters at Oi‐1 (∼33.54 Ma) is not apparent in our Mg/Ca records. We suggest the cooling is masked by coeval changes in the carbonate saturation state (Δ[CO32−]) which affect the Mg/Ca data. To account for this, the BWT, ice volume, and δw estimates are corrected for a change in the Δ[CO32−] of deep waters on the basis of recently published work. Corrected BWT at Sites 1090 and 1265 show a ∼1.5°C cooling coincident with Oi‐1 and an average δw increase of ∼0.75‰. The increase in ice volume during Oi‐1 resulted in a ∼70 m drop in global sea level and the development of an Antarctic ice sheet that was near modern size or slightly larger.

Temperature calibration of Mg/Ca ratios in the intermediate water benthic foraminifer Hyalinea balthica

Core top samples from Indonesian and northeast Atlantic depth transects were used to calibrate Mg/Ca and δ18O in tests of the calcitic benthic foraminifer Hyalinea balthica to bottom water temperature between 4°C and 13°C. This shallow infaunal species is primarily abundant in neritic to upper bathyal sediments (<600 m). Both linear and exponential calibrations suggest a temperature sensitivity of ∼12% per °C that is ∼4 times higher than observed in other species of deep‐sea benthic foraminifera. Culture experiments support the core top calibration. We find no discernible effect of salinity and saturation on Mg/Ca. Comparison between the measured benthic foraminiferal δ18O and predicted equilibrium values suggests that on average H. balthica δ18O is 0.64‰ ± 0.13‰ lower than predicted from the equilibrium composition. To test the reliability of using paired H. balthica Mg/Ca and δ18O measurements for reconstructing seawater δ18Osw and salinity, we apply this calibration to another depth transect from Cape Ghir off NW Africa, which was not included in the calibration. Based on error analysis of the calibration data and this validation test, we show that the uncertainty of reconstructing bottom water temperature and salinity from paired Mg/Ca and δ18O measurements of H. balthica is better than ±0.7°C and ±0.69 practical salinity scale, respectively. The small uncertainties allow for the reconstruction of seawater density to better than 0.3σθ units, which is precise enough for the identification of specific water masses and reconstruction of changes in their properties. We propose that the relatively high Mg content and temperature sensitivity of H. balthica might be due to minor, biologically mediated contribution of high‐Mg calcite to the primarily low Mg calcite test, which is influenced by the ambient temperature. This hypothesis, if correct, suggests that benthic species with relatively high Mg/Ca may be better suited for deepwater temperature reconstructions than species that have thus far been more commonly used.

Benthic foraminiferal oxygen isotope offsets over the last glacial-interglacial cycle

The oxygen isotope (?18O) offset between contemporaneous benthic foraminiferal species is often assumed constant with time and geographic location. We present an inventory of benthic foraminiferal species ?18O offsets from the major ocean basins covering the last glacial-interglacial cycle, showing that of the twenty down-core records investigated, twelve show significant temporal changes in ?18O offsets that do not resemble stochastic variability. Some of the temporal changes may be related to kinetic fractionation effects causing deglacial/interglacial enrichment or glacial depletion in mainly infaunal species, but additional research is needed to confirm this. In addition to stratigraphic implications the finding of temporally varying offsets between co-existing benthic foraminiferal species could have implications for sea-level, deep water temperature, and regional deep water ?18O estimates.

Shifting ocean carbonate chemistry during the Eocene-Oligocene climate transition: Implications for deep-ocean Mg/Ca paleothermometry

To date, no conclusive evidence has been identified for intermediate or deep water cooling associated with the > 1 parts per thousand benthic delta O-18 increase at the Eocene-Oligocene transition (EOT) when large permanent ice sheets first appeared on Antarctica. Interpretation of this isotopic shift as purely ice volume change necessitates bipolar glaciation in the early Oligocene approaching that of the Last Glacial Maximum. To test this hypothesis, it is necessary to have knowledge about deep water temperature, which previous studies have attempted to reconstruct using benthic foraminiferal Mg/Ca ratios. However, it appears likely that contemporaneous changes in ocean carbonate chemistry compromised the Mg/Ca temperature sensitivity of benthic foraminifera at deep sites. New geochemical proxy records from a relatively shallow core, ODP Site 1263 (estimated paleodepth of 2100 m on the Walvis Ridge), reveal that carbonate chemistry change across the EOT was not limited to deep sites but extended well above the lysocline, critically limiting our ability to obtain reliable estimates of deep-ocean cooling during that time. Benthic Li/Ca measurements, used as a proxy for [CO32-], suggest that [CO32-] increased by similar to 29 mu mol/kg at Site 1263 across the EOT and likely impacted benthic foraminiferal Mg/Ca. A [CO32-]-benthic Mg/Ca relationship is most apparent during the early EOT when the overall increase in [CO32-] is interrupted by an apparent dissolution event. Planktonic d18O and Mg/Ca records suggest no change in thermocline temperature and a delta O-18(seawater) increase of up to 0.6 parts per thousand at this site across the EOT, consistent with previous estimates and supporting the absence of extensive bipolar glaciation in the early Oligocene.

Orbital and suborbital environmental changes in the southern Bering Sea during the last 50 kyr

High-resolution geochemical, paleontological and lithological records of two sediment cores in the southern Bering Sea manifest regional environmental changes over the last 50 kyr on orbital and millennial time scales. High ice rafted debris (IRD) content and percentages of radiolarian species Cycladophora davisiana (Ehrenberg) during Marine Isotope Stages (MISs) 3 and 2 indicate active intermediate water ventilation driven by intensive winter sea ice formation in the southern Bering Sea. Although the total abundance of siliceous microfossils in glacial sediments is relatively low, glacial productivity is higher than in the Late Holocene. On the millennial time scale, decreases in the abundance of calcareous and siliceous microfossils and in C. davisiana % at studied core may imply enhancement of sea ice influence synchronous with Heinrich events H 5 to 2. Changes in the δ 18O of fossil benthic and planktonic foraminifera during H 5–3 are inferred to be related to variability in ice sheet volume similar to the pattern from Antarctica accompanied by glacioeustatic sea-level fluctuations up to 20–30 m in amplitude. The maximum benthic and planktonic δ 18O values in the studied cores occur during the LGM when sea level was at the lowest stand and sea bottom water temperature was around − 0.4 °C. Strong environmental changes during the Heinrich event 1 and B/A warming in the southern Bering Sea provide evidence of deglacial injection of very old water and the subsequent increase in productivity due to surface and intermediate water mixing. From the LGM to the mid-Holocene the δ 18O benth foram changes corresponded to changes in the global deep-water δ 18O and a rise in the deep-water temperature to + 1.0 °C at 8.5–6.5 kyr BP. The subsequent environmental changes in late Holocene helped establishment of near modern-day hydrological and environmental conditions, featuring strong surface water stratification and weakened deep-water ventilation.

Pliocene three-dimensional global ocean temperature reconstruction

Abstract. The thermal structure of the mid-Piacenzian ocean is obtained by combining the Pliocene Research, Interpretation and Synoptic Mapping Project (PRISM3) multiproxy sea-surface temperature (SST) reconstruction with bottom water temperature estimates from 27 locations produced using Mg/Ca paleothermometry based upon the ostracod genus Krithe. Deep water temperature estimates are skewed toward the Atlantic Basin (63% of the locations) and represent depths from 1000 m to 4500 m. This reconstruction, meant to serve as a validation data set as well as an initialization for coupled numerical climate models, assumes a Pliocene water mass framework similar to that which exists today, with several important modifications. The area of formation of present day North Atlantic Deep Water (NADW) was expanded and extended further north toward the Arctic Ocean during the mid-Piacenzian relative to today. This, combined with a deeper Greenland-Scotland Ridge, allowed a greater volume of warmer NADW to enter the Atlantic Ocean. In the Southern Ocean, the Polar Front Zone was expanded relative to present day, but shifted closer to the Antarctic continent. This, combined with at least seasonal reduction in sea ice extent, resulted in decreased Antarctic Bottom Water (AABW) production (relative to present day) as well as possible changes in the depth of intermediate waters. The reconstructed mid-Piacenzian three-dimensional ocean was warmer overall than today, and the hypothesized aerial extent of water masses appears to fit the limited stable isotopic data available for this time period.

Weak oceanic heat transport as a cause of the instability of glacial climates

The stability of the thermohaline circulation of modern and glacial climates is compared with the help of a two dimensional ocean—atmosphere—sea ice coupled model. It turns out to be more unstable as less freshwater forcing is required to induce a polar halocline catastrophy in glacial climates. The large insulation of the ocean by the extensive sea ice cover changes the temperature boundary condition and the deepwater formation regions moves much further South. The nature of the instability is of oceanic origin, identical to that found in ocean models under mixed boundary conditions. With similar strengths of the oceanic circulation and rates of deep water formation for warm and cold climates, the loss of stability of the cold climate is due to the weak thermal stratification caused by the cooling of surface waters, the deep water temperatures being regulated by the temperature of freezing. Weaker stratification with similar overturning leads to a weakening of the meridional oceanic heat transport which is the major negative feedback stabilizing the oceanic circulation. Within the unstable regime periodic millennial oscillations occur spontaneously. The climate oscillates between a strong convective thermally driven oceanic state and a weak one driven by large salinity gradients. Both states are unstable. The atmosphere of low thermal inertia is carried along by the oceanic overturning while the variation of sea ice is out of phase with the oceanic heat content. During the abrupt warming events that punctuate the course of a millennial oscillation, sea ice variations are shown respectively to damp (amplify) the amplitude of the oceanic (atmospheric) response. This sensitivity of the oceanic circulation to a reduced concentration of greenhouse gases and to freshwater forcing adds support to the hypothesis that the millennial oscillations of the last glacial period, the so called Dansgaard—Oeschger events, may be internal instabilities of the climate system.

Hydrology, hydrochemistry and geothermal potential of El Chichón volcano-hydrothermal system, Mexico

Fluid and heat discharge rates of thermal springs of El Chichón volcano were measured using the chloride inventory method. Four of the five known groups of hot springs discharge near-neutral Na–Ca–Cl–SO 4 waters with a similar composition (Cl ∼ 1500–2000 mg kg −1 and Cl/SO 4 ∼ 3) and temperatures in the 50–74 °C range. The other group discharges acidic (pH 2.2–2.7) Na–Cl water of high salinity (>15 g/L). All five groups are located on the volcano slopes, 2–3 km in a straight line from the bottom of the volcano crater. They are in the upper parts of canyons where thermal waters mix with surface meteoric waters and form thermal streams. All these streams flow into the Río Magdalena, which is the only drainage of all thermal waters coming from the volcano. The total Cl and SO 4 discharges measured in the Río Magdalena downstream from its junction with all the thermal streams are very close to the sum of the transported Cl and SO 4 by each of these streams, indicating that the infiltration through the river bed is low. The net discharge rate of hydrothermal Cl measured for all thermal springs is about 468 g s −1, which corresponds to 234 kg s −1 of hot water with Cl = 2000 mg kg −1. Together with earlier calculations of the hydrothermal steam output from the volcano crater, the total natural heat output from El Chichón is estimated to be about 160 MWt. Such a high and concentrated discharge of thermal waters from a hydrothermal system is not common and may indicate the high geothermal potential of the system. For the deep water temperatures in the 200–250 °C range (based on geothermometry), and a mass flow rate of 234 kg s −1, the total heat being discharged by the upflowing hot waters may be 175–210 MWt.

Addition of round gobies to the prey community of Lake Ontario and potential implications to thiamine status and reproductive success of Lake Trout

The addition of round goby to the Lake Ontario prey fish community can, because it appears to lack thiaminase, ameliorate the effects of a diet high in thiaminase-rich alewives associated with a thiamine deficiency in Lake Trout. However, the effects of round goby predation may negate such effects. We conducted studies to assess the proportion, by weight, of round gobies in the diet of contemporary Lake Ontario Lake Trout and predicted its effect on egg thiamine concentration, and early mortality syndrome (EMS) and growth retardation, two indicators of thiamine deficiency. We compared these parameters to that for the historic prey community, as well as possible future diet scenarios with progressively greater proportions of round goby (e.g. 50, 75 and 100%). To assess the combined and separate effects of the thiamine deficiency we used a modeling approach to determine the effect of EMS (70%) typical of Lake Ontario Lake Trout, growth retardation, density of Lake Trout egg (e.g. 100, 500, 1000, and 5000 eggs m−2) and round goby (e.g. 1, 9, 18, 35, 75, 150 gobies m−2), three separate durations of round goby residence on Lake Trout spawning habitat (e.g. 30, 60 and 213 days), and at either a shallow water or deepwater temperature regime. Eight years after first invading Lake Ontario, the proportion of round gobies in Lake Trout diets remains low, although the highest observed (25%) would result in significant amelioration of the thiamine deficiency from past conditions. Modeling indicated that the negative effects associated with round goby predation on eggs and fry could easily exceed any positive effects resulting from amelioration of the thiamine deficiency by a diet containing round goby. The effects of goby predation were found to be dependent on density of both Lake Trout eggs and round gobies, and while predation effects were minimally affected by temperature regime, they were highly dependent on the period of round goby residence on Lake Trout spawning habitat.

Deep water temperature variation of Lake Baikal during 1972–2007

An analysis is made of the results of water temperature measurements in Baikal for the period 1972–2007. An anomalous warming in that period was accompanied by a gradual rise in temperature of the upper 300-meter layer, but it had no effect on the state of the waters in the deep zone. Its temperature fluctuations during 1972–1992 were due mainly to changes in dynamical effects of the atmosphere on the water layer which caused interannual variations in activity of the deep-water convection.

Link of ocean deep water thermohaline anomalies with atmospheric state anomalies in the Northern Atlantic

Anomalies of thermohaline characteristics of the ocean deep waters formed in the subpolar North Atlantic are shown to be controlled by the natural oscillations of the atmospheric state in the region, i.e., the North Atlantic Oscillation (NAO). A general mechanism behind the NAO effect on the deep water temperature and salinity on a decadal time scale is proposed. The main factors determining the close link of the deep water thermohaline anomalies and the NAO are the zonal extension of the subpolar gyre and the wintertime deep convection intensity in the Labrador Sea.

A bi-polar signal recorded in the western tropical Pacific: Northern and Southern Hemisphere climate records from the Pacific warm pool during the last Ice Age

Western tropical Pacific sea surface temperatures and Pacific Deep Water temperatures during Marine Isotope Stage 3 have been reconstructed from the δ18O and Mg/Ca of planktonic and benthic foraminifera from Marion Dufresne core MD98-2181. This 36m marine core was collected at 6.3°N from a water depth of 2114m. With sediment accumulation rates of up to 80cm/ky, it provides a decadally resolved history of ocean variability during the Last Glacial period. Surface temperatures and salinities at this site varied in close association with millennial-scale atmospheric temperature swings at high northern latitudes as reflected in the GISP2 ice core. At times of colder atmospheric temperatures over Greenland, the western Pacific was more saline and summer season SSTs were ∼2°C colder. These millennial-scale changes within the tropics are attributed to a southward displacement of the summer season ITCZ in response to steeper meridional temperature gradients within the Pacific. The benthic δ18O record from MD98-2181 documents upper Pacific Deep Water temperature and salinity variability. Benthic δ18O variations of 0.3–0.5‰ during MIS 3 indicate deep waters within the Pacific were varying by ∼1–1.5°C, with the possibility that some of the variability was due to changing salinity and minor glacial–eustatic changes. The observed deep-water variability correlates to changes in Antarctic surface temperatures and thus reflects changes in Southern Ocean temperatures at the site of Pacific Deep Water formation. The combined planktonic and benthic records from MD98-2181 thus provide a northern and southern hemispheric climate record of anti-phased variability during MIS 3 as has been inferred previously from ice core records. Furthermore, the deep sea temperature excursions appear to have led millennial variations in atmospheric CO2 as recorded in the EDML ice core by ∼1kyr.

Modern climate changes and deep water temperature of Lake Baikal

This paper presents the results on measurements of water temperature in Lake Baikal of 1972–2007. The abnormal warming during this period was accompanied by gradual increase of the upper 300 m layer temperature, but did not affect the water state of the deep zone. Temperature fluctuations in 1972–1992 mainly depended on dynamic influence of atmosphere on the water column causing inter-annual changes in the activity of deep convection.

On the effect of the North Atlantic Oscillation on temperature and salinity of the subpolar North Atlantic intermediate and deep waters

Abstract Sarafanov, A. 2009. On the effect of the North Atlantic Oscillation on temperature and salinity of the subpolar North Atlantic intermediate and deep waters. – ICES Journal of Marine Science, 66: 1448–1454. The close relationship between the observed water mass properties and the winter North Atlantic Oscillation (NAO) index (1950–2000s; r2 ≈ 0.65) implies that changes in the NAO-related atmospheric forcing may account for up to two-thirds of thermohaline changes at the intermediate and deep levels in the subpolar North Atlantic on a decadal time-scale. Persistent NAO decline (amplification) results in increase (decrease) in temperature and salinity in the intermediate–deep water column. A general mechanism explaining the close link between the NAO and coherent decadal changes in the intermediate and deep-water temperature and salinity in the region is inferred from the observed changes in the regional circulation and water mass properties. Two factors dominate this link: (i) intensity of convection in the Labrador Sea controlling injection of relatively cold freshwater into the intermediate layer, and (ii) zonal extension of the Subpolar Gyre that regulates the relative contribution of cold fresh subpolar water and warm saline subtropical water to the deep-water formation.

On Ultimate Optical (10000 Channels) Transmission in Submarine Cables under Different Depth Conditions (Rigorous Analysis)

Ultimate optical transmission of 10000 channels huge submarine cables has been investigated under different depth conditions. Two amplification techniques are considered (the engagement of Raman and Erbium-doped fiber amplifiers). The double impact of both temperature and pressure is investigated through the defined depth penalty. Three transmission times division multiplexing techniques are studied namely soliton, nonlinear and maximum time division multiplexing. Also, two multiplexing methods are considered in the design of ultra-wide wavelength division multiplexing (UW-WDM) (10,000 optical channels) and ultra-wide space division multiplexing UW-SDM (400 fiber links). Based on experimental data, both the deep ocean water temperature and pressure are tailored as functions of the water depth. The product of the transmitted bit rate and the repeater spacing is processed over wide ranges of the affecting parameters, where both the repeater spacing and the transmitted soliton bit rate are in positive correlations with the total number of links.

Glacial–interglacial variability in deep sea ostracod assemblage composition at IODP Site U1314 in the subpolar North Atlantic

We present a detailed study of glacial/interglacial deep sea benthic ostracod assemblage variability at IODP Site U1314 (subpolar North Atlantic) in relation to the history of ice-rafting events and changes in deep ocean circulation over the past 170 ky. Our records of ostracod diversity, abundance and dissolution and sediment properties (IRD and CaCO 3) show an excellent correspondence to high amplitude orbital and millennial variability observed in the climate records (δ 13C and δ 18O) from neighboring deep water sites, suggesting that the benthic meiofauna fluctuates synchronously with the prevailing oceanographic conditions (surface ocean conditions, deep ocean circulation and water temperature and food flux). Krithe (dominant), Argilloecia and Cytheropteron are the most abundant and diverse genera in association with Rockallia enigmatica. Three ostracod assemblages are recognized. The genera Pennyella, Argilloecia, Pelecocythere, Ambocythere, Pseudobosquetina, Bradleya and Nannocythere are associated with interglacials and interstadials, and possibly reflect increased flux of food to the sediments and more vigorous NADW formation. A transitional assemblage composed of species of Cytheropteron, Xestoleberis and Eucythere is restricted to climatic transitions and indicate moderate environmental conditions and seasonal productivity. A glacial/stadial assemblage is characterized by a temporal predominance of either intermediate-depth and shallow water Arctic/subarctic species (belonging to Cytheropteron, Polycope, Pedicythere, Swainocythere, Cluthia, Heterocyprideis, Elofsonella and Finmarchinella) or abyssal North Atlantic ostracods ( Bythocythere, Dutoitella, Bathycythere and Bythocypris). The influx of high latitude taxa can be partially explained by ice-rafting, but may also represent a shift of the location of intermediate and deep water convection to the area south of Iceland. Therefore the combination of species characteristic of different watermasses during glacials may reflect shifts in the influence of high nutrient southern source water (e.g. AABW) vs. low nutrient GNAIW during glacials.

Evidence of resource partitioning between humpback and minke whales around the western Antarctic Peninsula

For closely related sympatric species to coexist, they must differ to some degree in their ecological requirements or niches (e.g., diets) to avoid interspecific competition. Baleen whales in the Antarctic feed primarily on krill, and the large sympatric prewhaling community suggests resource partitioning among these species or a nonlimiting prey resource. In order to examine ecological differences between sympatric humpback and minke whales around the Western Antarctic Peninsula, we made measurements of the physical environment, observations of whale distribution, and concurrent acoustic measurements of krill aggregations. Mantel's tests and classification and regression tree models indicate both similarities and differences in the spatial associations between humpback and minke whales, environmental features, and prey. The data suggest (1) similarities (proximity to shore) and differences (prey abundance versus deep water temperatures) in horizontal spatial distribution patterns, (2) unambiguous vertical resource partitioning with minke whales associating with deeper krill aggregations across a range of spatial scales, and (3) that interference competition between these two species is unlikely. These results add to the paucity of ecological knowledge relating baleen whales and their prey in the Antarctic and should be considered in conservation and management efforts for Southern Ocean cetaceans and ecosystems.

Late Miocene “washhouse” climate in Europe

Abstract We present two eight-million year long proxy records of precipitation for Southwest and Central Europe, covering the middle to late Miocene (5.3–13 Ma) at a temporal resolution of about 60 kyr and 150 kyr, respectively. The estimates of precipitation are based on the ecophysiological structure of herpetological assemblages (amphibians and reptiles). From 13.0 Ma until about 9 Ma, both records show a similar trend, evolving from a long dry period (13–11 Ma) into a “washhouse climate” (10.2–9.8 Ma), characterized by global warm conditions and several times more precipitation than present. The transition from washhouse to a dryer climate between 9.7 and 9.5 Ma and the concomitant cooling episode appear to have triggered a severe biotic event known as the Vallesian crisis, which included the extinction of hominoids in Western Europe. A second washhouse period (9.0–8.5 Ma), coeval with a global warm episode, was unprecedentedly intense in Southwest Europe, but less pronounced in Central Europe. From 8 Ma onward, a divergence in the two precipitation records is observed, with Southwest Europe staying wetter and Central Europe becoming dryer than present. Both precipitation records are combined into a common run-off curve as a measure of the relative intensity of the hydrological cycle for moderate latitudes of continental Europe. The run-off curve shows a remarkable positive correlation with Atlantic deep-water temperatures from Ceara Rise by Lear et al. (2003), which are significantly higher (up to + 3 °C) during the two washhouse periods and show no other positive excursion of comparable magnitude. We discuss potential links and the role of the coeval temporary restriction of the Central American Seaway on ocean and atmosphere circulation.