scholarly journals Madagascar corals reveal Pacific multidecadal modulation of rainfall since 1708

2012 ◽  
Vol 8 (2) ◽  
pp. 787-817
Author(s):  
C. A. Grove ◽  
J. Zinke ◽  
F. Peeters ◽  
W. Park ◽  
T. Scheufen ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Southern Africa ◽  
Water Resource Management ◽  
Decadal Variability ◽  
Southern Oscillation ◽  
Rainfall Variability ◽  
Western Indian Ocean ◽  
The Pacific ◽  
Eastern Australia ◽  
Instrumental Records

Abstract. The Pacific Ocean modulates Australian and North American rainfall variability on multidecadal timescales, in concert with the Pacific Decadal Oscillation (PDO). It has been suggested that Pacific decadal variability may also influence Indian Ocean surface temperature and rainfall in a far-field response, similar to the El Niño Southern Oscillation (ENSO) on interannual timescales. However, instrumental records of rainfall are too short and too sparse to confidently assess such multidecadal climatic teleconnections. Here, we present four climate archives spanning the past 300 yr from giant Madagascar corals. We decouple 20th century human deforestation effects from rainfall induced soil erosion using spectral luminescence scanning and geochemistry. The corals provide the first evidence for Pacific decadal modulation of rainfall over the Western Indian Ocean. We find that positive PDO phases are associated with increased Indian Ocean temperatures and rainfall in Eastern Madagascar, while precipitation in Southern Africa and Eastern Australia declines. Consequently, the negative PDO phase that started in 1998 should lead to reduced rainfall over Eastern Madagascar and increased precipitation in Southern Africa and Eastern Australia. We conclude that the PDO has important implications for future multidecadal variability of African rainfall, where water resource management is increasingly important under the warming climate.

scholarly journals Madagascar corals reveal a multidecadal signature of rainfall and river runoff since 1708

2013 ◽  
Vol 9 (2) ◽  
pp. 641-656 ◽  
Author(s):  
C. A. Grove ◽  
J. Zinke ◽  
F. Peeters ◽  
W. Park ◽  
T. Scheufen ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Southern Africa ◽  
River Runoff ◽  
Decadal Variability ◽  
Rainfall Variability ◽  
Western Indian Ocean ◽  
Phase Changes ◽  
Monsoon Circulation ◽  
Eastern Australia ◽  
Instrumental Records

Abstract. Pacific Ocean sea surface temperatures (SST) influence rainfall variability on multidecadal and interdecadal timescales in concert with the Pacific Decadal Oscillation (PDO) and Interdecadal Pacific Oscillation (IPO). Rainfall variations in locations such as Australia and North America are therefore linked to phase changes in the PDO. Furthermore, studies have suggested teleconnections exist between the western Indian Ocean and Pacific Decadal Variability (PDV), similar to those observed on interannual timescales related to the El Niño Southern Oscillation (ENSO). However, as instrumental records of rainfall are too short and sparse to confidently assess multidecadal climatic teleconnections, here we present four coral climate archives from Madagascar spanning up to the past 300 yr (1708–2008) to assess such decadal variability. Using spectral luminescence scanning to reconstruct past changes in river runoff, we identify significant multidecadal and interdecadal frequencies in the coral records, which before 1900 are coherent with Asian-based PDO reconstructions. This multidecadal relationship with the Asian-based PDO reconstructions points to an unidentified teleconnection mechanism that affects Madagascar rainfall/runoff, most likely triggered by multidecadal changes in North Pacific SST, influencing the Asian Monsoon circulation. In the 20th century we decouple human deforestation effects from rainfall-induced soil erosion by pairing luminescence with coral geochemistry. Positive PDO phases are associated with increased Indian Ocean temperatures and runoff/rainfall in eastern Madagascar, while precipitation in southern Africa and eastern Australia declines. Consequently, the negative PDO phase that started in 1998 may contribute to reduced rainfall over eastern Madagascar and increased precipitation in southern Africa and eastern Australia. We conclude that multidecadal rainfall variability in Madagascar and the western Indian Ocean needs to be taken into account when considering water resource management under a future warming climate.

scholarly journals Understanding Recent Eastern Horn of Africa Rainfall Variability and Change

2014 ◽  
Vol 27 (23) ◽  
pp. 8630-8645 ◽  
Author(s):  
Brant Liebmann ◽  
Martin P. Hoerling ◽  
Chris Funk ◽  
Ileana Bladé ◽  
Randall M. Dole ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Southern Oscillation ◽  
Rainfall Variability ◽  
Statistical Significance ◽  
Western Indian Ocean ◽  
Eastern Africa ◽  
Wet Season ◽  
Central Pacific ◽  
Equatorial Africa ◽  
Sst Forcing

Abstract Observations and sea surface temperature (SST)-forced ECHAM5 simulations are examined to study the seasonal cycle of eastern Africa rainfall and its SST sensitivity during 1979–2012, focusing on interannual variability and trends. The eastern Horn is drier than the rest of equatorial Africa, with two distinct wet seasons, and whereas the October–December wet season has become wetter, the March–May season has become drier. The climatological rainfall in simulations driven by observed SSTs captures this bimodal regime. The simulated trends also qualitatively reproduce the opposite-sign changes in the two rainy seasons, suggesting that SST forcing has played an important role in the observed changes. The consistency between the sign of 1979–2012 trends and interannual SST–precipitation correlations is exploited to identify the most likely locations of SST forcing of precipitation trends in the model, and conceivably also in nature. Results indicate that the observed March–May drying since 1979 is due to sensitivity to an increased zonal gradient in SST between Indonesia and the central Pacific. In contrast, the October–December precipitation increase is mostly due to western Indian Ocean warming. The recent upward trend in the October–December wet season is rather weak, however, and its statistical significance is compromised by strong year-to-year fluctuations. October–December eastern Horn rain variability is strongly associated with El Niño–Southern Oscillation and Indian Ocean dipole phenomena on interannual scales, in both model and observations. The interannual October–December correlation between the ensemble-average and observed Horn rainfall 0.87. By comparison, interannual March–May Horn precipitation is only weakly constrained by SST anomalies.

scholarly journals Rainfall variability in southeast and west-central Africa during the Little Ice Age: do documentary and proxy records agree?

2021 ◽  
Vol 168 (1-2) ◽  
Author(s):  
Matthew J. Hannaford ◽  
Kristen K. Beck
Keyword(s):  
Southern Africa ◽  
Little Ice Age ◽  
Southern Oscillation ◽  
Rainfall Variability ◽  
Central Africa ◽  
Ice Age ◽  
West Central ◽  
Early Colonial ◽  
Instrumental Records

AbstractUnderstanding of long-term climatic change prior to instrumental records necessitates reconstructions from documentary and palaeoclimate archives. In southern Africa, documentary-derived chronologies of nineteenth century rainfall variability and palaeoclimate records have permitted new insights into rainfall variability over past centuries. Rarely considered, however, is the climatic information within early colonial documentary records that emerge from the late fifteenth century onwards. This paper examines evidence for (multi-)seasonal dry and wet events within these earlier written records (c. 1550–1830 CE) from southeast Africa (Mozambique) and west-central Africa (Angola) in conjunction with palaeoclimate records from multiple proxies. Specifically, it aims to understand whether these sources agree in their signals of rainfall variability over a 280-year period covering the ‘main phase’ Little Ice Age (LIA) in southern Africa. The two source types generally, but do not always, show agreement within the two regions. This appears to reflect both the nature of rainfall variability and the context behind documentary recording. Both source types indicate that southeast and west-central Africa were distinct regions of rainfall variability over seasonal and longer timescales during the LIA, with southeast Africa being generally drier and west-central Africa generally wetter. However, the documentary records reveal considerable variability within these mean state climatic conditions, with multi-year droughts a recurrent feature in both regions. An analysis of long-term rainfall links with the El Niño–Southern Oscillation (ENSO) in southeast Africa suggests a complex and possibly non-stationary relationship. Overall, early colonial records provide valuable information for constraining hydroclimate variability where palaeoclimate records remain sparse.

scholarly journals On the Remote Drivers of Rainfall Variability in Australia

2009 ◽  
Vol 137 (10) ◽  
pp. 3233-3253 ◽  
Author(s):  
James S. Risbey ◽  
Michael J. Pook ◽  
Peter C. McIntosh ◽  
Matthew C. Wheeler ◽  
Harry H. Hendon
Keyword(s):  
Large Scale ◽  
Decadal Variability ◽  
Southern Oscillation ◽  
Rainfall Variability ◽  
Southern Annular Mode ◽  
Wet Season ◽  
The North ◽  
Eastern Australia ◽  
Different Seasons ◽  
The Individual

Abstract This work identifies and documents a suite of large-scale drivers of rainfall variability in the Australian region. The key driver in terms of broad influence and impact on rainfall is the El Niño–Southern Oscillation (ENSO). ENSO is related to rainfall over much of the continent at different times, particularly in the north and east, with the regions of influence shifting with the seasons. The Indian Ocean dipole (IOD) is particularly important in the June–October period, which spans much of the wet season in the southwest and southeast where IOD has an influence. ENSO interacts with the IOD in this period such that their separate regions of influence cover the entire continent. Atmospheric blocking also becomes most important during this period and has an influence on rainfall across the southern half of the continent. The Madden–Julian oscillation can influence rainfall in different parts of the continent in different seasons, but its impact is strongest on the monsoonal rains in the north. The influence of the southern annular mode is mostly confined to the southwest and southeast of the continent. The patterns of rainfall relationship to each of the drivers exhibit substantial decadal variability, though the characteristic regions described above do not change markedly. The relationships between large-scale drivers and rainfall are robust to the selection of typical indices used to represent the drivers. In most regions the individual drivers account for less than 20% of monthly rainfall variability, though the drivers relate to a predictable component of this variability. The amount of rainfall variance explained by individual drivers is highest in eastern Australia and in spring, where it approaches 50% in association with ENSO and blocking.

Cryptic lineages of little free-tailed bats,Chaerephon pumilus(Chiroptera: Molossidae) from southern Africa and the western Indian Ocean islands

2009 ◽  
Vol 44 (1) ◽  
pp. 55-70
Author(s):  
Peter John Taylor ◽  
Jennifer Lamb ◽  
Devendran Reddy ◽  
Theshnie Naidoo ◽  
Fanja Ratrimomanarivo ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Southern Africa ◽  
Western Indian Ocean ◽  
Ocean Islands

Elemental proxy evidence for late Quaternary palaeoenvironmental change in southern African sedimentary records: interpretation and applications

2021 ◽  
Author(s):  
M.S. Humphries
Keyword(s):  
Environmental Change ◽  
Southern Africa ◽  
Southern Oscillation ◽  
Late Quaternary ◽  
Rainfall Variability ◽  
Analytical Techniques ◽  
Summer Rainfall ◽  
Geochemical Data ◽  
Complex Nature ◽  
Cape Coast

Abstract Sediments are the most important source of Late Quaternary palaeoclimate information in southern Africa, but have been little studied from a geochemical perspective. However, recent advances in analytical techniques that allow rapid and near-continuous elemental records to be obtained from sedimentary sequences has resulted in the increasing use of elemental indicators for reconstructing climate. This paper explores the diverse information that can be acquired from the inorganic component of sediments and reviews some of the progress that has been made over the last two decades in interpreting the climatic history of southern Africa using elemental records. Despite the general scarcity of elemental records, excellent examples from the region exist, which provide some of the longest and most highly resolved sequences of environmental change currently available. Records from Tswaing crater and marine deposits on the southern KwaZulu-Natal coastline have provided rare glimpses into hydroclimate variability over the last 200 000 years, suggesting that summer rainfall in the region responded predominantly to insolation forcing on glacial-interglacial timescales. Over shorter timescales, lakes and wetlands found in the Wilderness embayment on the southern Cape coast and along the Maputaland coast in north-eastern South Africa have yielded highly-resolved elemental records of Holocene environmental change, providing insight into the changing interactions between tropical (e.g., El Niño-Southern Oscillation) and temperate (e.g., mid-latitude westerlies) climate systems affecting rainfall variability in the region. The examples discussed demonstrate the multiple environmental processes that can be inferred from elemental proxies and the unique insight this can provide in advancing our understanding of past climate change on different timescales. The interpretation of geochemical data can be complicated by the complex nature of sedimentary environments, various proxy assumptions and analytical challenges, and the reliability of sediment-based climate reconstructions is substantially enhanced through multi-proxy approaches.

scholarly journals Climatology of the Mascarene High and Its Influence on Weather and Climate over Southern Africa

Climate ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 86 ◽  
Author(s):  
Nkosinathi G. Xulu ◽  
Hector Chikoore ◽  
Mary-Jane M. Bopape ◽  
Nthaduleni S. Nethengwe
Keyword(s):  
Indian Ocean ◽  
Southern Africa ◽  
Lower Troposphere ◽  
Western Indian Ocean ◽  
Vital Role ◽  
Tropical Cyclone Genesis ◽  
Trade Winds ◽  
Mascarene High ◽  
Weather And Climate ◽  
Cyclone Genesis

Globally, subtropical circulation in the lower troposphere is characterized by anticyclones over the oceans. Subtropical anticyclones locate over subtropical belts, modulating weather and climate patterns in those regions. The Mascarene High is an anticyclone located over the Southern Indian Ocean and has a vital role in weather and climate variability over Southern Africa. The warm Western Indian Ocean is a major source of moisture for the subcontinent also permitting tropical cyclone genesis. In this study, we review the dynamics of the Mascarene High, its interactions with the ocean, and its impact on weather and climate over Southern Africa. We also review studies on the evolution of subtropical anticyclones in a future warmer climate. The links between SST modes over the Indian Ocean and the strengthening and weakening of the Mascarene High have been demonstrated. One important aspect is atmospheric blocking due to the Mascarene High, which leads to anomalous rainfall and temperature events over the subcontinent. Blocking leads to landfall of tropical cyclones and slow propagation of cut-off lows resulting in severe weather and flooding over the subcontinent. Understanding how expansion of the Mascarene High due to warming will alter trade winds and storm tracks and change the mean climate of Southern Africa is crucial.

scholarly journals Decadal Variability of the Indian and Pacific Walker Cells since the 1960s: Do They Covary on Decadal Time Scales?

2017 ◽  
Vol 30 (21) ◽  
pp. 8447-8468 ◽  
Author(s):  
Weiqing Han ◽  
Gerald A. Meehl ◽  
Aixue Hu ◽  
Jian Zheng ◽  
Jessica Kenigson ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Decadal Variability ◽  
Tropical Indian Ocean ◽  
Warm Pool ◽  
Past Century ◽  
The Pacific ◽  
Decadal Variations ◽  
Long Term Trends ◽  
The Indian Ocean ◽  
The 1960S

Previous studies have investigated the centennial and multidecadal trends of the Pacific and Indian Ocean Walker cells (WCs) during the past century, but have obtained no consensus owing to data uncertainties and weak signals of the long-term trends. This paper focuses on decadal variability (periods of one to few decades) by first documenting the variability of the WCs and warm-pool convection, and their covariability since the 1960s, using in situ and satellite observations and reanalysis products. The causes for the variability and covariability are then explored using a Bayesian dynamic linear model, which can extract nonstationary effects of climate modes. The warm-pool convection exhibits apparent decadal variability, generally covarying with the Indian and Pacific Ocean WCs during winter (November–April) with enhanced convection corresponding to intensified WCs, and the Indian–Pacific WCs covary. During summer (May–October), the warm-pool convection still highly covaries with the Pacific WC but does not covary with the Indian Ocean WC, and the Indian–Pacific WCs are uncorrelated. The wintertime coherent variability results from the vital influence of ENSO decadal variation, which reduces warm-pool convection and weakens the WCs during El Niño–like conditions. During summer, while ENSO decadal variability still dominates the Pacific WC, decadal variations of ENSO, the Indian Ocean dipole, Indian summer monsoon convection, and tropical Indian Ocean SST have comparable effects on the Indian Ocean WC overall, with monsoon convection having the largest effect since the 1990s. The complex causes for the Indian Ocean WC during summer result in its poor covariability with the Pacific WC and warm-pool convection.

scholarly journals Cereal Production Trends under Climate Change: Impacts and Adaptation Strategies in Southern Africa

Agriculture ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 30 ◽  
Author(s):  
Luxon Nhamo ◽  
Greenwell Mathcaya ◽  
Tafadzwanashe Mabhaudhi ◽  
Sibusiso Nhlengethwa ◽  
Charles Nhemachena ◽  
...  
Keyword(s):  
Food Security ◽  
Southern Africa ◽  
Crop Production ◽  
Southern Oscillation ◽  
Rainfall Variability ◽  
International Aid ◽  
Adaptation Strategies ◽  
Irrigated Agriculture ◽  
Cereal Production ◽  
The Impact

The increasing frequency and intensity of droughts and floods, coupled with increasing temperatures and declining rainfall totals, are exacerbating existing vulnerabilities in southern Africa. Agriculture is the most affected sector as 95% of cultivated area is rainfed. This review addressed trends in moisture stress and the impacts on crop production, highlighting adaptation possible strategies to ensure food security in southern Africa. Notable changes in rainfall patterns and deficiencies in soil moisture are estimated and discussed, as well as the impact of rainfall variability on crop production and proposed adaptation strategies in agriculture. Climate moisture index (CMI) was used to assess aridity levels. Southern Africa is described as a climate hotspot due to increasing aridity, low adaptive capacity, underdevelopment and marginalisation. Although crop yields have been increasing due to increases in irrigated area and use of improved seed varieties, they have not been able to meet the food requirements of a growing population, compromising regional food security targets. Most countries in the region depend on international aid to supplement yield deficits. The recurrence of droughts caused by the El Niño Southern Oscillation (ENSO) continue devastating the region, affecting livelihoods, economies and the environment. An example is the 2015/16 ENSO drought that caused the region to call for international aid to feed about 40 million people. In spite of the water scarcity challenges, cereal production continues to increase steadily due to increased investment in irrigated agriculture and improved crop varieties. Given the current and future vulnerability of the agriculture sector in southern Africa, proactive adaptation interventions are important to help farming communities develop resilient systems to adapt to the changes and variability in climate and other stressors.

A new deep-water goatfish of the genus Upeneus (Mullidae) from northern Australia and the Philippines, with a taxonomic account of U. subvittatus and remarks on U. mascareinsis

Zootaxa ◽  
2012 ◽  
Vol 3550 (1) ◽  
pp. 61 ◽  
Author(s):  
FRANZ UIBLEIN ◽  
MARK MCGROUTHER
Keyword(s):  
New Species ◽  
Indian Ocean ◽  
Deep Water ◽  
Western Indian Ocean ◽  
First Record ◽  
The Philippines ◽  
Northern Australia ◽  
Meristic Characters ◽  
The Pacific ◽  
Interspecific Comparisons

Upeneus stenopsis n. sp. is described based on four specimens collected off northern Australia and Quezon Island,Philippines, at depths between 165 to 275 m and compared with four closely related species: the deep-water dwellingUpeneus davidaromi (Red Sea) and U. mascareinsis (Western Indian Ocean) and the shallow Indo-West Pacific species,U. subvittatus and U. vittatus. The new species can be distinguished from all other Upeneus species by a narrow caudalpeduncle and a combination of morphometric and meristic characters. This is the first record of a deep-water goatfish ofthe genus Upeneus from the Pacific. A juvenile Upeneus collected off Quezon at 127–142 m depth was also assigned tothe new species and compared to four similar-sized (69–79 mm SL) specimens of U. mascareinsis. A diagnosis is providedfor U. subvittatus, along with evidence of its occurrence in the Eastern Indian Ocean and interspecific comparisons. Thecontinued need to screen scientific fish collections for the occurrence of undescribed species that have successfully colonized and adapted to the depth zone surrounding the ocean margin is outlined.

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