Tropical East African climate change and its relation to global climate: A record from Lake Tanganyika, Tropical East Africa, over the past 90+ kyr

Burnett, Allison P.; Soreghan, Michael J.; Scholz, Christopher A.; Brown, E. T.

doi:10.1016/j.palaeo.2010.02.011

Cited by 122 publications

(85 citation statements)

References 50 publications

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“…Therefore, we suggest that the observed H1 dry conditions in the uplands are part of a north-south dipole rainfall anomaly over eastern Africa and the Indian Ocean, which corroborates the seesaw hypothesis supported by further climate model studies (Claussen et al, 2003) and which is consistent with a southward shift of the ITCZ annual mean position in response to Northern Hemisphere cooling . The ITCZ shift is part of a reorganization of the annual mean Hadley circulation driven by Northern Hemisphere climatic fluctuations (Broccoli et al, 2006;Kang et al, 2009;Chiang and Friedman, 2012; al., 2013) and is supported by several studies in the Indian Ocean (Johnson et al, 2002;Brown et al, 2007;Castañeda et al, 2007;Schefuß et al, 2011;. We suggest that the reorganization of the Hadley circulation and the associated southward ITCZ shift resulted in an anomalous descent of air over the Rufiji region in the annual mean (and hence less rainfall) and an anomalous ascent (and hence more rainfall) to the south.…”

Section: Paleoclimate and Controlling Mechanisms In The Uplands Durinsupporting

confidence: 79%

“…The direct comparison of our record with terrestrial studies shows that the signal of decreased precipitation coincides with lowered lake levels of Sacred Lake in Kenya (Street-Perrot et al, 1997); Lake Challa, Tanzania (Verschuren et al, 2009); Lake Rukwa, Tanzania (Vincens et al, 2005); and Lake Tanganyika (Burnett et al, 2011). Dry H1 conditions are also suggested by isotope records of the Tanganyika basin (Tierney et al, 2008) and Lake Malawi (Johnson et al, 2002;Brown et al, 2007;Castañeda et al, 2007). The expansion of forest and humid woodlands (Fig.…”

Section: Paleoclimate and Controlling Mechanisms In The Uplands Durinmentioning

confidence: 54%

“…The African tropics, a region of major importance for the global hydrologic cycle, have experienced large-scale changes in hydroclimate and rainfall over the last deglaciation and the Holocene (e.g., Street-Perrot and Perrot, 1990;Lézine et al, 1995;Gasse, 2000;Gasse et al, 2008;Johnson et al, 2002;Vincens et al, 2005;Castañeda et al, 2007;Tierney et al, 2008;Schefuß et al, 2011;Stager et al, 2011;Bouimetarhan et al, , 2012Bouimetarhan et al, , 2013Ivory et al, 2012). While millennial-scale hydroclimatic variations in northwest Africa are commonly linked to atmospheric processes involving latitudinal migrations of the intertropical convergence zone (ITCZ) related to North Atlantic climate anomalies (Dahl et al, 2005;Stouffer et al, 2006;Tjallingii et al, 2008;Mulitza et al, 2008;Itambi et al, 2009, Penaud et al, 2010Bouimetarhan et al, 2012;Kageyama et al, 2013), the mechanisms responsible for tropical southeastern African climate fluctuations remain a matter of debate.…”

Section: Introductionmentioning

confidence: 99%

“…While millennial-scale hydroclimatic variations in northwest Africa are commonly linked to atmospheric processes involving latitudinal migrations of the intertropical convergence zone (ITCZ) related to North Atlantic climate anomalies (Dahl et al, 2005;Stouffer et al, 2006;Tjallingii et al, 2008;Mulitza et al, 2008;Itambi et al, 2009, Penaud et al, 2010Bouimetarhan et al, 2012;Kageyama et al, 2013), the mechanisms responsible for tropical southeastern African climate fluctuations remain a matter of debate. While it has been suggested that Indian Ocean sea surface temperatures (SST) influence eastern African rainfall variability on longer timescales (Tierney et al, 2008Tierney and deMenocal, 2013;Stager et al, 2011), other studies suggest that eastern African rainfall variations were atmospherically linked to North Atlantic climate fluctuations through a southward shift of the ITCZ (Johnson et al, 2002;Broccoli et al, 2006;Brown et al, 2007;Castañeda et al, 2007;Schefuß et al, 2011;Chiang and Friedman, 2012;.…”

Section: Introductionmentioning

confidence: 99%

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Northern Hemisphere control of deglacial vegetation changes in the Rufiji uplands (Tanzania)

et al. 2015

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Abstract. In tropical eastern Africa, vegetation distribution is largely controlled by regional hydrology, which has varied over the past 20 000 years. Therefore, accurate reconstructions of past vegetation and hydrological changes are crucial for a better understanding of climate variability in the tropical southeastern African region. We present high-resolution pollen records from a marine sediment core recovered offshore of the Rufiji River delta. Our data document significant shifts in pollen assemblages during the last deglaciation, identifying, through changes in both upland and lowland vegetation, specific responses of plant communities to atmospheric (precipitation) and coastal (coastal dynamics and sea-level changes) alterations. Specifically, arid conditions reflected by a maximum pollen representation of dry and open vegetation occurred during the Northern Hemisphere cold Heinrich event 1 (H1), suggesting that the expansion of drier upland vegetation was synchronous with cold Northern Hemisphere conditions. This arid period is followed by an interval in which forest and humid woodlands expanded, indicating a hydrologic shift towards more humid conditions. Droughts during H1 and the shift to humid conditions around 14.8 kyr BP in the uplands are consistent with latitudinal shifts of the intertropical convergence zone (ITCZ) driven by high-latitude Northern Hemisphere climatic fluctuations. Additionally, our results show that the lowland vegetation, consisting of well-developed salt marshes and mangroves in a successional pattern typical for vegetation occurring in intertidal habitats, has responded mainly to local coastal dynamics related to marine inundation frequencies and soil salinity in the Rufiji Delta as well as to the local moisture availability. Lowland vegetation shows a substantial expansion of mangrove trees after ∼ 14.8 kyr BP, suggesting an increased moisture availability and river runoff in the coastal area. The results of this study highlight the decoupled climatic and environmental processes to which the vegetation in the uplands and the Rufiji Delta has responded during the last deglaciation.

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Section: Paleoclimate and Controlling Mechanisms In The Uplands Durinsupporting

confidence: 79%

Section: Paleoclimate and Controlling Mechanisms In The Uplands Durinmentioning

confidence: 54%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Northern Hemisphere control of deglacial vegetation changes in the Rufiji uplands (Tanzania)

et al. 2015

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“…Here T exp is the experimental time, whereas T e exp is the experimental equilibrium time, i.e., the time at which the landscape achieves steady state which is approximately 8 h in our experiment (see time axis in Figure 2). Thus, to a gross approximation, our experiment represents an equilibrium state and the perturbation of increased precipitation (which lasted for 30 min translated to 3000 years in our experiment) is interpreted as a climatic trend, i.e., a shift to an increased mean annual precipitation regime of a type observed in many parts of the world over millennial time scales [e.g., Baker et al, 2001;Burnett et al, 2011]. Note that uplift rates $ 1 cm/yr have been observed in natural landscapes [see for example, Lav e and Avouac, 2000; Lague and Davy, 2003].…”

Section: Scaling and Realism Of The Experimentsmentioning

confidence: 99%

Landscape reorganization under changing climatic forcing: Results from an experimental landscape

Singh

Reinhardt

Foufoula‐Georgiou

2015

Water Resources Research

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Understanding how landscapes respond to climate dynamics in terms of macroscale (average topographic features) and microscale (landform reorganization) is of interest both for deciphering past climates from today's landscapes and for predicting future landscapes in view of recent climatic trends. Although several studies have addressed macro-scale response, only a few have focused on quantifying smaller-scale basin reorganization. To that goal, a series of controlled laboratory experiments were conducted where a self-organized complete drainage network emerged under constant precipitation and uplift dynamics. Once steady state was achieved, the landscape was subjected to a fivefold increase in precipitation (transient state). Throughout the evolution, high-resolution spatiotemporal topographic data in the form of digital elevation models were collected. The steady state landscape was shown to possess three distinct geomorphic regimes (unchannelized hillslopes, debris-dominated channels, and fluvially dominated channels). During transient state, landscape reorganization was observed to be driven by hillslopes via accelerated erosion, ridge lowering, channel widening, and reduction of basin relief as opposed to channel base-level reduction. Quantitative metrics on which these conclusions were based included slope-area curve, correlation analysis of spatial and temporal elevation increments, and wavelet spectral analysis of the evolving landscapes. Our results highlight that landscape reorganization in response to increased precipitation seems to follow ''an arrow of scale'': major elevation change initiates at the hillslope scale driving erosional regime change at intermediate scales and further cascading to geomorphic changes at the channel scale as time evolves.

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Choosing optimal exposure times for XRF core‐scanning: Suggestions based on the analysis of geological reference materials

Huang

Löwemark

Chang

et al. 2016

Geochem Geophys Geosyst

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X‐ray fluorescence (XRF) core‐scanning is a fast and nondestructive technique to assess elemental variations of unprocessed sediments. However, although the exposure time of XRF‐scanning directly affects the scanning counts and total measurement time, only a few studies have considered the influence of exposure time during the scan. How to select an optimal exposure time to achieve reliable results and reduce the total measurement time is an important issue. To address this question, six geological reference materials from the Geological Survey of Japan (JLK‐1, JMS‐1, JMS‐2, JSD‐1, JSD‐2, and JSD‐3) were scanned by the Itrax‐XRF core scanner using the Mo‐ and the Cr‐tube with different exposure times to allow a comparison of scanning counts with absolute concentrations. The regression lines and correlation coefficients of elements that are generally used in paleoenvironmental studies were examined for the different exposure times and X‐ray tubes. The results show that for those elements with relatively high concentrations or high detectability, the correlation coefficients are higher than 0.90 for all exposure times. In contrast, for the low detectability or low concentration elements, the correlation coefficients are relatively low, and improve little with increased exposure time. Therefore, we suggest that the influence of different exposure times is insignificant for the accuracy of the measurements. Thus, caution must be taken when interpreting the results of elements with low detectability, even when the exposure times are long and scanning counts are reasonably high.

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Tropical East African climate change and its relation to global climate: A record from Lake Tanganyika, Tropical East Africa, over the past 90+ kyr

Cited by 122 publications

References 50 publications

Northern Hemisphere control of deglacial vegetation changes in the Rufiji uplands (Tanzania)

Northern Hemisphere control of deglacial vegetation changes in the Rufiji uplands (Tanzania)

Landscape reorganization under changing climatic forcing: Results from an experimental landscape

Choosing optimal exposure times for XRF core‐scanning: Suggestions based on the analysis of geological reference materials

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