Global Ocean Circulation Patterns Research Articles

Primary Drivers of the Recent Changes Observed in Global Ocean Circulation Patterns in Mozambique

Purpose: The aim of the study was to examine the primary drivers of the recent changes observed in global ocean circulation patterns in Mozambique Methodology: This study adopted a desk methodology. A desk study research design is commonly known as secondary data collection. This is basically collecting data from existing resources preferably because of its low cost advantage as compared to a field research. Our current study looked into already published studies and reports as the data was easily accessed through online journals and libraries. Findings: The study revealed that primary drivers of the recent changes observed in global ocean circulation patterns are involving a combination of natural variability and anthropogenic influences. Key factors identified include global warming, alterations in wind patterns, sea surface temperature anomalies, and increased freshwater input from melting ice caps and glaciers. These elements interact in intricate ways to influence the dynamics of ocean currents, which are critical for regulating Earth's climate and supporting marine ecosystems. Unique Contribution to Theory, Practice and Policy: Bronfenbrenner's Ecological Systems Theory & Abraham Maslow's Hierarchy of Needs may be used to anchor future studies on primary drivers of the recent changes observed in global ocean circulation patterns in Mozambique. Increase investment in global ocean monitoring systems, such as Argo floats, satellite missions, and autonomous underwater vehicles, to collect high-resolution data on temperature, salinity, and currents. This data is crucial for validating models and understanding the current state and trends of ocean circulation. Strengthen international cooperation to address global warming, a primary driver of changes in ocean circulation. This includes adhering to and expanding commitments under the Paris Agreement to reduce greenhouse gas emissions.

Rainfall trends and variation in the Maasai Mara ecosystem and their implications for animal population and biodiversity dynamics.

Rainfall exerts a controlling influence on the availability and quality of vegetation and surface water for herbivores in African terrestrial ecosystems. We analyse temporal trends and variation in rainfall in the Maasai Mara ecosystem of East Africa and infer their implications for animal population and biodiversity dynamics. The data originated from 15 rain gauges in the Mara region (1965–2015) and one station in Narok Town (1913–2015), in Kenya’s Narok County. This is the first comprehensive and most detailed analysis of changes in rainfall in the region of its kind. Our results do not support the current predictions of the International Panel of Climate Change (IPCC) of very likely increases of rainfall over parts of Eastern Africa. The dry season rainfall component increased during 1935–2015 but annual rainfall decreased during 1962–2015 in Narok Town. Monthly rainfall was more stable and higher in the Mara than in Narok Town, likely because the Mara lies closer to the high-precipitation areas along the shores of Lake Victoria. Predominantly deterministic and persistent inter-annual cycles and extremely stable seasonal rainfall oscillations characterize rainfall in the Mara and Narok regions. The frequency of severe droughts increased and floods intensified in the Mara but droughts became less frequent and less severe in Narok Town. The timings of extreme droughts and floods coincided with significant periodicity in rainfall oscillations, implicating strong influences of global atmospheric and oceanic circulation patterns on regional rainfall variability. These changing rainfall patterns have implications for animal population dynamics. The increase in dry season rainfall during 1935–2015 possibly counterbalanced the impacts of resource scarcity generated by the declining annual rainfall during 1965–2015 in Narok Town. However, the increasing rainfall extremes in the Mara can be expected to create conditions conducive to outbreaks of infectious animal diseases and reduced vegetation quality for herbivores, particularly when droughts and floods persist over multiple years. The more extreme wet season rainfall may also alter herbivore space use, including migration patterns.

Efficient computation of past global ocean circulation patterns using continuation in paleobathymetry

In the field of paleoceanographic modeling, the different positioning of Earth’s continental configurations is often a major challenge for obtaining equilibrium ocean flow solutions. In this paper, we introduce numerical parameter continuation techniques to compute equilibrium solutions of ocean flows in the geological past, where we change the continental geometry and allow the flow to deform using a homotopy parameter. The methods are illustrated by computing equilibrium three-dimensional global ocean circulation patterns over the last 65 Ma under a highly idealized atmospheric forcing. These results already show interesting major transitions in ocean circulation patterns due to changes in ocean gateways, that may have been relevant for Cenozoic climate transitions. In addition, the techniques are shown to be computationally efficient compared to the established continuation spin-up approach.

Carbon isotope offsets between benthic foraminifer species of the genus Cibicides (Cibicidoides) in the glacial sub‐Antarctic Atlantic

AbstractEpibenthic foraminifer δ13C measurements are valuable for reconstructing past bottom water dissolved inorganic carbon δ13C (δ13CDIC), which are used to infer global ocean circulation patterns. Epibenthic δ13C, however, may also reflect the influence of 13C‐depleted phytodetritus, microhabitat changes, and/or variations in carbonate ion concentrations. Here we compare the δ13C of two benthic foraminifer species, Cibicides kullenbergi and Cibicides wuellerstorfi, and their morphotypes, in three sub‐Antarctic Atlantic sediment cores over several glacial‐interglacial transitions. These species are commonly assumed to be epibenthic, living above or directly below the sediment‐water interface. While this might be consistent with the small δ13C offset that we observe between these species during late Pleistocene interglacial periods (Δδ13C = −0.19 ± 0.31‰, N = 63), it is more difficult to reconcile with the significant δ13C offset that is found between these species during glacial periods (Δδ13C = −0.76 ± 0.44‰, N = 44). We test possible scenarios by analyzing Uvigerina spp. δ13C and benthic foraminifer abundances: (1) C. kullenbergi δ13C is biased to light values either due to microhabitat shifts or phytodetritus effects and (2) C. wuellerstorfi δ13C is biased to heavy values, relative to long‐term average conditions, for instance by recording the sporadic occurrence of less depleted deepwater δ13CDIC. Neither of these scenarios can be ruled out unequivocally. However, our findings emphasize that supposedly epibenthic foraminifer δ13C in the sub‐Antarctic Atlantic may reflect several factors rather than being solely a function of bottom water δ13CDIC. This could have a direct bearing on the interpretation of extremely light South Atlantic δ13C values at the Last Glacial Maximum.

Remoteness from sources of persistent organic pollutants in the multi-media global environment

Quantifying the remoteness from sources of persistent organic pollutants (POPs) can inform the design of monitoring studies and the interpretation of measurement data. Previous work on quantifying remoteness has not explicitly considered partitioning between the gas phase and aerosols, and between the atmosphere and the Earth's surface. The objective of this study is to present a metric of remoteness for POPs transported through the atmosphere calculated with a global multimedia fate model, BETR-Research. We calculated the remoteness of regions covering the entire globe from emission sources distributed according to light emissions, and taking into account the multimedia partitioning properties of chemicals and using averaged global climate data. Remoteness for hypothetical chemicals with distinct partitioning properties (volatile, semi-volatile, hydrophilic, low-volatility) and having two different half-lives in air (60-day and 2-day) are presented. Differences in remoteness distribution among the hypothetical chemicals are most pronounced in scenarios assuming 60-day half-life in air. In scenarios with a 2-day half-life in air, degradation dominates over wet and dry deposition processes as a pathway for atmospheric removal of all chemicals except the low-volatility chemical. The remoteness distribution of the low-volatility chemical is strongly dependent on assumptions about degradability on atmospheric aerosols. Calculations that considered seasonal variability in temperature, hydroxyl radical concentrations in the atmosphere and global atmospheric and oceanic circulation patterns indicate that variability in hydroxyl radical concentrations largely determines the seasonal variability of remoteness. Concentrations of polybrominated diphenyl ethers (PBDEs) measured in tree bark from around the world are more highly correlated with remoteness calculated using our methods than with proximity to human population, and we see considerable potential to apply remoteness calculations for interpretation of monitoring data collected under programs such as the Stockholm Convention Global Monitoring Plan.

Late Palaeozoic global changes affecting high-latitude environments and biotas: An introduction

The Late Palaeozoic Ice Age (LPIA), spanning approximately from ~320 Ma (Serpukhovian, late Mississippian) to 290 Ma (mid-Sakmarian, Early Permian), represents the vegetated Earth’s largest and most long-lasting regime of severe and multiple glaciations, involving processes and patterns probably comparable to those of the Last Ice Age. Accompanying the LPIA occurred a number of broadly synchronous global environmental and biotic changes. These global changes, as briefly reviewed and summarized in this introductory paper, comprised (but are not limited to) the following: massive continental reorganization in the lead up to the final assembly of Pangea resulting in profound changes in global palaeogeography, palaeoceanography and palaeobiogeogarphy; substantially lowered global atmospheric carbon dioxide concentrations ( pCO 2), coupled with an unprecedented increase in atmospheric oxygen concentrations reaching Earth's all-time high in its last 600 million year history; sharp global temperature and sea-level drops (albeit with considerable spatial and temporal variability throughout the ice age); and apparently a prolonged period of global sluggish macro-evolution with both low extinction and origination rates compared to other times. In the aftermath of the LPIA, the world's climate entered into a transitional climate phase through the late Early to Middle Permian before its transformation into a greenhouse state towards the end-Permian. In recent years, considerable amount of data and interpretations have been published concerning the physical evidence in support of the LPIA, its broad timeframe and eustatic and ecosystem responses from the lower latitudes, but relatively less attention has been drawn to the impact of the ice age on late Palaeozoic high-latitude environments and biotas. It is with this mission in mind that we have organized this special issue, with the central focus on late Palaeozoic high latitude regions of both hemispheres, that is, Gondwana and northern Eurasia. Our aim is to gather a set of papers that not only document the physical environmental changes that had occurred in the polar regions of Gondwana and northern Eurasia during the LPIA, but also review on the biotic responses at different taxonomic, ecological and spatial scales to these physical changes in a refined chronological timeframe. This introductory paper is designed to provide a global context for the special issue, with a brief review of key late Palaeozoic global environmental changes (including: changes in global land-sea configurations, atmospheric chemistry, global climate regimes, global ocean circulation patterns and sea levels) and large-scale biotic (biogeographic and evolutionary) responses, followed by a summary of what we see as unresolved scientific issues and various working hypotheses concerning late Palaeozoic global changes and, in particular, the LPIA, as a possible reference to future research.

A 35 ka pollen and isotope record of environmental change along the southern margin of the Kalahari from a stalagmite and animal dung deposits in Wonderwerk Cave, South Africa

A 0.6-m-long horizontal core from a stalagmite in the entrance area of Wonderwerk Cave in South Africa, a National Heritage Site, has provided a 35 ka record of environmental change. A pollen sequence from the stalagmite, and two animal dung deposits, is longer and more detailed for the end of the Pleistocene than previous palynological reports from the southern Kalahari region. This pollen record closely matches information from spring peats at Wonderkrater in Northern Province indicating that speleothem pollen can provide reliable paleovegetation data. The δ 18O and δ 13C records resemble those from Cold Air Cave in Northern Province and parallel variations in Greenland Ice Sheet GISP2 paleotemperature. This indicates that past climate changes in southern Africa were linked to changes in global atmospheric and oceanic circulation patterns possibly triggered by conditions in the North Atlantic region. The Wonderwerk data suggest wetter conditions at ca. 33 ka, from 23 to 17 ka, and from 4 ka to present. Conditions were drier 17–13 ka, when microstromatolitic carbonate was deposited on the flank of the stalagmite, and possibly also during depositional hiatuses from 33 to 23 ka and 13 to 4 ka.

The multifractal structure of satellite sea surface temperature maps can be used to obtain global maps of streamlines

Abstract. Nowadays Earth observation satellites provide information about many relevant variables of the ocean-climate system, such as temperature, moisture, aerosols, etc. However, to retrieve the velocity field, which is the most relevant dynamical variable, is still a technological challenge, specially in the case of oceans. New processing techniques, emerged from the theory of turbulent flows, have come to assist us in this task. In this paper, we show that multifractal techniques applied to new Sea Surface Temperature satellite products opens the way to build maps of ocean currents with unprecedented accuracy. With the application of singularity analysis, we show that global ocean circulation patterns can be retrieved in a daily basis. We compare these results with high-quality altimetry-derived geostrophic velocities, finding a quite good correspondence of the observed patterns both qualitatively and quantitatively; and this is done for the first time on a global basis, even for less active areas. The implications of this findings from the perspective both of theory and of operational applications are discussed.

CRYPTIC DIVERSITY IN PLANKTIC FORAMINIFERA IN THE NORTHWEST PACIFIC OCEAN

Research Article| July 01, 2009 CRYPTIC DIVERSITY IN PLANKTIC FORAMINIFERA IN THE NORTHWEST PACIFIC OCEAN Yurika Ujiié; Yurika Ujiié * 1UMR CNRS 7144 Evolution du Plancton et PaleOceans, Station Biologique, BP 74, 29682 Roscoff, France. *Correspondence author. E-mail: ujiie@sb-roscoff.fr Search for other works by this author on: GSW Google Scholar Jere H. Lipps Jere H. Lipps 2Museum of Paleontology and Department of Integrative Biology, University of California, Berkeley, CA 94720-4780, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Yurika Ujiié * 1UMR CNRS 7144 Evolution du Plancton et PaleOceans, Station Biologique, BP 74, 29682 Roscoff, France. Jere H. Lipps 2Museum of Paleontology and Department of Integrative Biology, University of California, Berkeley, CA 94720-4780, USA *Correspondence author. E-mail: ujiie@sb-roscoff.fr Publisher: Cushman Foundation for Foraminiferal Research Received: 29 Oct 2008 Accepted: 23 Jan 2009 First Online: 03 Mar 2017 Online ISSN: 1943-264X Print ISSN: 0096-1191 © 2009 Journal of Foraminiferal Research Journal of Foraminiferal Research (2009) 39 (3): 145–154. https://doi.org/10.2113/gsjfr.39.3.145 Article history Received: 29 Oct 2008 Accepted: 23 Jan 2009 First Online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Yurika Ujiié, Jere H. Lipps; CRYPTIC DIVERSITY IN PLANKTIC FORAMINIFERA IN THE NORTHWEST PACIFIC OCEAN. Journal of Foraminiferal Research 2009;; 39 (3): 145–154. doi: https://doi.org/10.2113/gsjfr.39.3.145 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyJournal of Foraminiferal Research Search Advanced Search Abstract Recent molecular studies show multiple cases of cryptic diversification in planktic foraminifera; however, the geographic distribution of the cryptic species is poorly known. Herein, we present the first insight into the cryptic diversity of planktic foraminifera from Northwest Pacific samples. We obtained 97 new SSU rDNA sequences representing 13 planktic foraminiferal morphospecies, including the first sequence data for Candeina nitida. Bayesian phylogenetic analysis of 192 sequences (97 new and 95 known sequences) from 21 morphospecies identified 36 genetic types, including three new ones. Thirty of the genetic types have transoceanic distributions that can be explained by global oceanic circulation patterns, particularly around the Cape of Good Hope. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Seismic stratigraphy of the Adare Trough area, Antarctica

The Adare Trough, located 100 km NE of Cape Adare, Antarctica, is the extinct third arm of a Tertiary spreading ridge that separated East from West Antarctica. We use seismic reflection data, tied to DSDP Site 274, to link our seismic stratigraphic interpretation to changes in ocean-bottom currents, Ross Sea ice cover, and regional tectonics through time. Two extended unconformities are observed in the seismic profiles. We suggest that the earliest hiatus (early Oligocene to Mid-Miocene) is related to low sediment supply from the adjacent Ross Shelf, comprised of small, isolated basins. The later hiatus (mid-Miocene to late Miocene) is likely caused by strong bottom currents sourced from the open-marine Ross Sea due to increased Antarctic glaciation induced by mid-Miocene cooling (from Mi-3). Further global cooling during the Pliocene, causing changes in global ocean circulation patterns, correlates with Adare Basin sediments and indicate the continuing but weakened influence of bottom currents. The contourite/turbidite pattern present in the Adare Trough seismic data is consistent with the 3-phase contourite growth system proposed for the Weddell Sea and Antarctic Peninsula. Multibeam bathymetry and seismic reflection profiles show ubiquitous volcanic cones and intrusions throughout the Adare Basin that we interpret to have formed from the Oligocene to the present. Seismic reflection profiles reveal trans-tensional/strike-slip faults that indicate oblique extension dominated Adare Trough tectonics at 32–15 Ma. Observed volcanism patterns and anomalously shallow basement depth in the Adare Trough area are most likely caused by mantle upwelling, an explanation supported by mantle density reconstructions, which show anomalously hot mantle beneath the Adare Trough area forming in the Late Tertiary.

Effect of ocean gateways on the global ocean circulation in the late Oligocene and early Miocene

We investigate the effect of changes in the tectonic boundary conditions on global ocean circulation patterns. Using a fully coupled climate model in an idealized setup, we compare situations corresponding to the late Oligocene, the early Miocene, and present day. The model results show the existence of a flow reversal through the Panama Seaway between the Oligocene and Miocene. This flow reversal is induced by global tectonic changes related to the widening of the Southern Ocean passages and the closing of the Tethys Seaway. It mainly involves the wind‐driven ocean circulation, in agreement with previous model studies. The global thermohaline circulation in the Oligocene and Miocene simulations is significantly different from the present‐day conveyor circulation, as there is deepwater formation in both the North Atlantic and the North Pacific oceans. In particular, in the Oligocene simulation the salinity contrast between the Atlantic and Pacific oceans is reduced because of water mass exchange through the low‐latitude connections between the two oceans.

Reducing Vulnerability of Agriculture and Forestry to Climate Variability and Change: Workshop Summary and Recommendations

The International Workshop on Reducing Vulnerability of Agriculture and Forestry to Climate Variability and Climate Change held in Ljubljana, Solvenia, from 7 to 9 October 2002 addressed a range of important issues relating to climate variability, climate change, agriculture, and forestry including the state of agriculture and forestry and agrometeological information, and potential adaptation strategies for agriculture and forestry to changing climate conditions and other pressures. There is evidence that global warming over the last millennium has already resulted in increased global average annual temperature and changes in rainfall, with the 1990s being likely the warmest decade in the Northern Hemisphere at least. During the past century, changes in temperature patterns have, for example, had a direct impact on the number of frost days and the length of growing seasons with significant implications for agriculture and forestry. Land cover changes, changes in global ocean circulation and sea surface temperature patterns, and changes in the composition of the global atmosphere are leading to changes in rainfall. These changes may be more pronounced in the tropics. For example, crop varieties grown in the Sahel may not be able to withstand the projected warming trends and will certainly be at risk due to projected lower amounts of rainfall as well. Seasonal to interannual climate forecasts will definitely improve in the future with a better understanding of dynamic relationships. However, the main issue at present is how to make better use of the existing information and dispersion of knowledge to the farm level. Direct participation by the farming communities in pilot projects on agrometeorological services will be essential to determine the actual value of forecasts and to better identify the specific user needs. Old (visits, extension radio) and new (internet) communication techniques, when adapted to local applications, may assist in the dissemination of useful information to the farmers and decision makers. Some farming systems with an inherent resilience may adapt more readily to climate pressures, making long-term adjustments to varying and changing conditions. Other systems will need interventions for adaptation that should be more strongly supported by agrometeorological services for agricultural producers. This applies, among others, to systems where pests and diseases play an important role. Scientists have to guide policy makers in fostering an environment in which adaptation strategies can be effected. There is a clear need for integrating preparedness for climate variability and climate change. In developed countries, a trend of higher yields, but with greater annual fluctuations and changes in cropping patterns and crop calendars can be expected with changing climate scenarios. Shifts in projected cropping patterns can be disruptive to rural societies in general. However, developed countries have the technology to adapt more readily to the projected climate changes. In many developing countries, the present conditions of agriculture and forestry are already marginal, due to degradation of natural resources, the use of inappropriate technologies and other stresses. For these reasons, the ability to adapt will be more difficult in the tropics and subtropics and in countries in transition. Food security will remain a problem in many developing countries. Nevertheless, there are many examples of traditional knowledge, indigenous technologies and local innovations that can be used effectively as a foundation for improved farming systems. Before developing adaptation strategies, it is essential to learn from the actual difficulties faced by farmers to cope with risk management at the farm level. Agrometeorologists must play an important role in assisting farmers with the development of feasible strategies to adapt to climate variability and climate change. Agrometeorologists should also advise national policy makers on the urgent need to cope with the vulnerabilities of agriculture and forestry to climate variability and climate change. The workshop recommendations were largely limited to adaptation. Adaptation to the adverse effects of climate variability and climate change is of high priority for nearly all countries, but developing countries are particularly vulnerable. Effective measures to cope with vulnerability and adaptation need to be developed at all levels. Capacity building must be integrated into adaptation measures for sustainable agricultural development strategies. Consequently, nations must develop strategies that effectively focus on specific regional issues to promote sustainable development.

Association of influenza epidemics in France and the USA with global climate variability

Background: The reasons for the seasonality and annual changes in the impact of influenza epidemics remain poorly understood. A strong coherence of influenza epidemics at a hemispheric level may suggest the role of global factors, such as climate, as a driving force of seasonality. The El Niño Southern Oscillation (ENSO) represents the largest signal in inter-annual climate variation, affecting global atmospheric and oceanic circulation patterns. The phenomenon undergoes cycles between warm ENSO conditions (which are extreme during El Niño episodes) and cold ENSO conditions (extreme during La Nina episodes). Materials and methods: We investigated the covariations between ENSO and the impact of influenza as measured by the number of pneumonia and influenza (P&I) excess deaths in France and the USA during the winter epidemics of 1971–1997. Results: On average in France (60.2 (M) million inhabitants in 2003), 2500 P&I excess deaths occurred per season (range 0–9500) during the 1971–1997 period. An average of 6215 excess deaths (range 0–13,600) occurred in the USA (290.3 M inhabitants in 2003). In both countries, the number of P&I excess deaths was significantly higher during the 10 seasons with cold ENSO conditions (mean±S.E.; 3530±654 excess deaths in France; 8290±900 in the USA) than during the 16 seasons with warm ENSO conditions (1856±574; 4919±977) (Wilcoxon rank test for France P=0.05 and for the USA P=0.03). Conclusion: These findings suggest that the impact of influenza epidemics, in terms of excess mortality, is associated with the ENSO conditions. An understanding of the mechanisms responsible for this association could lead to improved early warning and better control of influenza.

A methane fuse for the Cambrian explosion: carbon cycles and true polar wander

The dramatic diversification of animal groups known as the Cambrian Explosion (evolution’s ‘Big Bang’) remains an unsolved puzzle in Earth Science. The Vendian–Cambrian interval is characterized by anomalously high rates of apparent plate motion, interpreted as True Polar Wander (TPW), and by more than a dozen large, high-frequency perturbations in carbon isotopes that dwarf all others observed through the past 65 million years. We suggest that these biological, tectonic, and geochemical events are intimately related in the following fashion. First, tropical continental margins and shelf-slopes which formed during fragmentation of the supercontinent Rodinia accumulated massive quantities of isotopically-light organic carbon during Late Neoproterozoic time, as indicated by strikingly heavy isotope ratios in inorganic carbon during interglacial intervals. Second, an initial phase of Vendian TPW moved these organic-rich deposits to high latitude, where conditions favored trapping biogenic methane in layers of gas hydrate and perhaps permafrost. Continued sedimentation during Late Vendian time added additional hydrate/gas storage volume and stabilized underlying units until the geothermal gradient moved them out of the clathrate stability field, building up deep reservoirs of highly pressurized methane. Finally, a burst of TPW brought these deposits back to the Tropics, where they gradually warmed and were subjected to regional-scale thermohaline eddy variation and related sedimentation regime changes. Responding to the stochastic character of such changes, each reservoir reached a critical failure point independently at times throughout the Cambrian. By analogy with the Late Paleocene Thermal Maximum event, these methane deposits yield transient, greenhouse-induced pulses of global warming when they erupt. Temperature correlates powerfully with biodiversity; the biochemical kinetics of metabolism at higher temperature decrease generation time and maintain relatively rich and dense invertebrate populations. Repeated thermal pulses along with progressive disruption and alteration of global ocean circulation patterns by TPW could cause the increase in diversity that accompanied the radiation of metazoans. We suggest that a methane ‘fuse’ ignited the Cambrian Evolutionary Explosion.

Prediction of global rainfall probabilities using phases of the Southern Oscillation Index

THE El Nino/Southern Oscillation (ENSO) is a quasi-periodic interannual variation in global atmospheric and oceanic circulation patterns, known to be correlated with variations in the global pattern of rainfall1–3. Good predictive models for ENSO, if they existed, would allow accurate prediction of global rainfall variations, thus leading to better management of world agricultural production4,5, as well as improving profits and reducing risks for farmers6,7. But our current ability to predict ENSO variation is limited. Here we describe a probabilistic rainfall 'forecasting' system that does not require ENSO predictive ability, but is instead based on the identification of lag-relationships between values of the Southern Oscillation Index, which provides a quantitative measure of the phase of the ENSO cycle, and future rainfall. The system provides rainfall probability distributions three to six months in advance for regions worldwide, and is simple enough to be incorporated into management systems now.

Stable (δ13C, δ18O) and strontium () isotopes through the Paleocene at Gebel Aweina, eastern Tethyan region

Abstract Stable ( δ 13 C, δ 18 O) and strontium ( 87 Sr 86 Sr ) isotopic records have been established through the Paleocene section at Gebel Aweina, in the Eastern Desert, Egypt. The section has been formed in a shelf-upper bathyal environment and, spans the interval from planktonic foraminiferal Zones P1d to P6a or P6b. Integrated evaluation of isotopic results and scanning electron microscope observations suggest that, strontium and whole-rock δ 13 C records reflect primarily original isotopic trends, whereas δ 18 O and foraminiferal δ 13 C values have been severely affected by diagenesis. The whole-rock δ 13 C record exhibits a continuous increase of 4‰ from the early Paleocene to middle late Paleocene. The increase is followed by a stepwise δ 13 C decrease of the same magnitude through the late late Paleocene and onwards. The gross trends of this δ 13 C record have earlier been registered in many coeval deep-sea sections, but there are also some significant disparities. At Aweina, for example, the Paleocene carbon isotopic changes have a higher amplitude. In the deep sea, the mid-to-late Paleocene δ 13 C increase has been interpreted to reflect high biological productivity and/or changes in the global carbon mass balance. The δ 13 C decrease in the upper part of the Aweina section can be identified as the Paleocene-Eocene transitional long-term (> 10 3 kyr) negative δ 13 C shift, which may reflect a major reorganisation in global oceanic circulation patterns. The well-known latest Paleocene, deep-sea, benthic foraminiferal extinction event has been found in the upper part of the Aweina section, and coincides with a distinct and rapid δ 13 C decrease of 1.5‰ The benthic extinction event and the associated δ 13 C anomaly thus represent important stratigraphic markers also in more shallow environments. The Gebel Aweina δ 13 C record shows considerably lower values compared to the global δ 13 C record during early and early late Paleocene and in the latest Paleocene. In the early late Paleocene (foraminiferal Zones P3a to the base of P4) the Aweina δ 13 C values increase rapidly by 1.5‰, and converge with the global record; thereafter the two records covary up to the benthic extinction event, after which they diverge. The convergence between the records may reflect sea-level rise and more open water-mass exchange between the eastern Tethys and the world ocean. The similarity of pilot δ 13 C records from Greece and Tunisia with the Aweina record support this interpretation. Diagenetic processes, however, cannot be ruled out, and further studies are required to determine the significance of the 13 C depletions in the eastern Tethyan sediments. The 87 Sr 86 Sr ratios through the Paleocene at Gebel Aweina are remarkably invariable close to a value of 0.7077. This is the same trend that has been reported in some earlier detailed studies conducted on well-preserved calcitic material from the Paleocene, indicating original Sr-isotopic signatures at Gebel Aweina. The homogeneity of Sr-isotopic ratios throughout the Paleocene contrasts with the prominent changes observed in the carbon isotope record, indicating a decoupling of the mechanisms regulating the mass fluxes of these elements. The invariable Sr-isotopic ratios suggest stable conditions as regards to relative changes in mass fluxes of riverine and/or hydrothermal Sr during the Paleocene.

An intermediate one‐dimensional thermodynamic sea ice model for investigating ice‐atmosphere interactions

A one‐dimensional thermodynamic model of sea ice is presented that focuses on those features that are most relevant to interactions with the atmosphere, namely the surface albedo and leads. It includes a surface albedo parameterization that interacts strongly with the state of the surface, and explicitly includes meltwater ponds. The lead parameterization contains a minimum lead fraction, absorption of solar radiation in and below the leads, lateral accretion and ablation of the sea ice, and a prescribed sea ice divergence rate. The model performed well in predicting the current climatic sea ice conditions in the central Arctic when compared with observations and other theoretical calculations. Results of parameter sensitivity tests produced large equilibrium ice thicknesses for small values of ice divergence or large values of minimum lead fraction as a result of positive feedback mechanisms involving cooling of water in the leads. The ice thickness was also quite sensitive to the meltwater runoff fraction and moderately sensitive to the other parameters in the melt pond parameterization, a result of the strong dependence of the surface albedo, and hence the net flux, on the surface conditions. To further investigate the physical interactions and internal feedback processes governing the sea ice‐lead system, sensitivity tests were also performed for each of the external forcing variables. The model's equilibrium sea ice thickness was extremely sensitive to changes in the downward longwave and shortwave fluxes and atmospheric temperature and humidity, moderately sensitive to the value of the ocean heat flux, and insensitive to values of wind speed, snowfall, and rainfall in the immediate vicinity of the baseline forcing, although significant changes in thickness occurred for larger variations in wind speed and snowfall. Four important positive feedback loops were identified and described: (1) the surface albedo feedback, (2) the conduction feedback, (3) the lead solar flux feedback, and (4) the lead fraction feedback. The destabilizing effects of these positive feedbacks were mitigated by two strong negative feedbacks: (1) the outgoing longwave flux feedback, and (2) the turbulent flux feedback. Considering the strong influence which sea ice has on global atmospheric and oceanic circulation patterns, it is essential that climate models be able to treat these feedback processes appropriately.

Global ocean circulation patterns based on seasat altimeter data and the GEML2 gravity field

The Seasat altimeter data has been completely adjusted by a crossing arc technique to reduce the crossover discrepancies to approximately ±30 cm in five regional adjustments. This data was then used to create sea surface heights at 1° intersections in the ocean areas with respect to the GRS80 ellipsoid. These heights excluded the direct tidal effects but included the induced permanent deformation.

Preface [to SEASAT II

SEASAT, the first satellite designed to assess the value of microwave sensors for remote sensing of the world's oceans, was launched on June 27, 1978. The satellite operated successfully until October 10, 1978, when a power failure brought transmission to a stop. Despite its short lifetime, SEASAT acquired a wealth of data on sea-surface winds and temperatures, ocean wave heights, internal waves, atmospheric water content, sea ice, topography of the ocean surface, and shape of the marine geoid. Analysis of these data has demonstrated the success of SEASAT in accurately measuring, on a global scale, important oceanographic parameters from space. The SEASAT sensors included a radar altimeter, a scanning multi-channel radiometer, a synthetic aperture radar, a windfield scatterometer, and a visual and infrared radiometer. From these instruments have come the first global maps of the variability of ocean currents, surface wind speed, surface temperature, wave height, and water vapor in the atmosphere. The success of SEASAT has been the major impetus for plans in the United States, Europe, and Japan to launch microwave ocean monitoring satellites in the late 1980s. This is the second of two special issues of the Journal of Geophysical Research dedicated to the SEASAT mission. The first issue (vol. 87, no. C5, April 30, 1982) focused on the processing algorithms used for converting sensor data into geophysically useful information. This issue emphasizes cientific results from the SEASAT sensors. Scientists from numerous government centers and universities from the United States and abroad have performed oceanographic and geodetic studies with SEASAT data. However, much research still remains to be done, particularly in the application of the global scatterometer windfie!ds to weather prediction and the use of altimeter data to refine knowledge of the marine geoid and global ocean circulation patterns. This issue is a demonstration of the increasingly important role that satellites play in oceanography and geodesy. The papers were processed through normal JGR review procedures. We thank the authors, associate editors, and reviewers for their contributions and assistance in preparing this issue.