Transcontinental Moving and Storage: the Orinoco and Amazon Rivers Transfer the Andes to the Atlantic

Meade, Robert H.

doi:10.1002/9780470723722.ch4

Cited by 54 publications

(48 citation statements)

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“…In this case, the moisture supply is stronger in June-July-August (JJA). It is worth noting that the Magdalena and Orinoco river basins are also the principal moisture sinks in northern South America (Meade, 2007;Poveda et al, 2001). Despite this, they provide a summertime contribution to Central American rainfall.…”

Section: Methodsmentioning

confidence: 99%

“…A large deep convective core is located over the Panama Bight (Zuluaga and Houze Jr., 2015), with an extended area of stratiform precipitation that becomes relevant for overall rainfall. The effect of mid-latitude interactions is known to be mostly related to the occurrence of rainfall during the dry period on the Pacific slope between November and February (Zárate, 2013;Sáenz and Durán-Quesada, 2015;Moron et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Role of moisture transport for Central American precipitation

2017

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Abstract.A climatology of moisture sources linked with Central American precipitation was computed based upon Lagrangian trajectories for the analysis period 1980-2013. The response of the annual cycle of precipitation in terms of moisture supply from the sources was analysed. Regional precipitation patterns are mostly driven by moisture transport from the Caribbean Sea (CS). Moisture supply from the eastern tropical Pacific (ETPac) and northern South America (NSA) exhibits a strong seasonal pattern but weaker compared to CS. The regional distribution of rainfall is largely influenced by a local signal associated with surface fluxes during the first part of the rainy season, whereas large-scale dynamics forces rainfall during the second part of the rainy season. The Caribbean Low Level Jet (CLLJ) and the Chocó Jet (CJ) are the main conveyors of regional moisture, being key to define the seasonality of large-scale forced rainfall. Therefore, interannual variability of rainfall is highly dependent of the regional LLJs to the atmospheric variability modes. The El Niño-Southern Oscillation (ENSO) was found to be the dominant mode affecting moisture supply for Central American precipitation via the modulation of regional phenomena. Evaporative sources show opposite anomaly patterns during warm and cold ENSO phases, as a result of the strengthening and weakening, respectively, of the CLLJ during the summer months. Trends in both moisture supply and precipitation over the last three decades were computed, results suggest that precipitation trends are not homogeneous for Central America. Trends in moisture supply from the sources identified show a marked north-south seesaw, with an increasing supply from the CS Sea to northern Central America. Long-term trends in moisture supply are larger for the transition months (March and October). This might have important implications given that any changes in the conditions seen during the transition to the rainy season may induce stronger precipitation trends.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Role of moisture transport for Central American precipitation

2017

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“…The spatial presumption of hydraulic connectivity from original source to ultimate sink is probably valid for the flow of water (upper panel of Figure 2), in which one may reasonably expect a given molecule or parcel of water to leave the headwaters and arrive at the sea within a single runoff season. However, the presumption does not apply so well to sediment, which moves downriver in episodic or periodic pulses (Meade, 1985(Meade, , 2007Moody and Meade, 2008). While most of the finest colloidal particles may well behave like water molecules and be transported long distances during a runoff season, the annual trajectory of a sand grain may be only from one point bar to the next point bar downstream.…”

Section: Missouri-mississippi River Sediment-delivery Systemmentioning

confidence: 99%

“…Kesel et al (1992, p. 712) present a useful graph showing that the activities most likely to have induced changes in sediment discharge during the post-1950 years represented by the Tarbert Landing record are, in addition to the closure of the dams on Missouri River, meander cutoffs and the construction of river-training structures on the Missouri and Lower Mississippi rivers (Figure 8). These rivertraining structures serve to trap and store sediment and the revetments prevent river-bank erosion, which, in the preengineered Mississippi and in other nonengineered rivers, has proven to be a major source of suspended sediment (Dunne et al, 1998;Hudson and Kesel, 2000;Meade, 2007). Even where bank-erosion sources of sediment are counterbalanced by deposition elsewhere (point bars, e.g.)…”

Section: Effects Of Other Causesmentioning

confidence: 99%

Causes for the decline of suspended‐sediment discharge in the Mississippi River system, 1940–2007

Meade

Moody

2009

Hydrological Processes

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385

251

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Abstract:Before 1900, the Missouri-Mississippi River system transported an estimated 400 million metric tons per year of sediment from the interior of the United States to coastal Louisiana. During the last two decades (1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006), this transport has averaged 145 million metric tons per year. The cause for this substantial decrease in sediment has been attributed to the trapping characteristics of dams constructed on the muddy part of the Missouri River during the 1950s. However, reexamination of more than 60 years of water-and sediment-discharge data indicates that the dams alone are not the sole cause. These dams trap about 100-150 million metric tons per year, which represent about half the decrease in sediment discharge near the mouth of the Mississippi. Changes in relations between water discharge and suspended-sediment concentration suggest that the Missouri-Mississippi has been transformed from a transport-limited to a supply-limited system. Thus, other engineering activities such as meander cutoffs, river-training structures, and bank revetments as well as soil erosion controls have trapped sediment, eliminated sediment sources, or protected sediment that was once available for transport episodically throughout the year. Removing major engineering structures such as dams probably would not restore sediment discharges to pre-1900 state, mainly because of the numerous smaller engineering structures and other soil-retention works throughout the Missouri-Mississippi system. Published in

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“…The model assumes steady state between sediment flux from bank erosion and bar deposition, a simplification termed quasisteady state, which is valid for most fluvial conditions (Lauer and Parker, 2008). This assumption may not be valid for short periods, but on timescales encompassed by channel belt formation from sediment accumulation and aggradation (~ 10 4 y), the vertical accretion of floodplains is counterbalanced by the lateral erosion of the exposed bank (Wolman and Leopold, 1957;Trimble, 1995;Bridge, 2003;Meade, 2007). Therefore, Q be equals Q bd .…”

Section: Model Setupmentioning

confidence: 99%

Cosmogenic nuclide budgeting of floodplain sediment transfer

Wittmann

Blanckenburg

2009

Geomorphology

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Cosmogenic nuclides produced in quartz may either decay or accumulate while sediment is moved through a river basin. A change in nuclide concentration resulting from storage in a floodplain is potentially important in large drainage basins in which sediment is prone to repeated burial and remobilization as a river migrates through its floodplain. We have modeled depth-and time-dependent cosmogenic nuclide concentration changes for 10 Be, The cosmogenic nuclide composition of old deposits in currently inactive floodplains that have been isolated for periods of millions of years from the river that once deposited them are predicted to either increase or decrease in C, nuclide concentrations modeled for the in situ-produced variety of this nuclide are, however, sensitive to floodplain storage on residence times of < 20 ky. 10 Be and 26 Al concentration, depending on the depositional depth. These conditions can be evaluated using the 26 Al/ 10 We illustrate these models with examples from the Amazon basin. As predicted, modern bedload collected from an Amazon tributary, the Bolivian Beni River, shows no systematic change in nuclide concentration as sediment is moved through 500 km of floodplain by river meandering. In contrast, in the central Amazon floodplain currently untouched by the modern river system, low Be ratio that readily discloses the depth and duration of storage.26 Al/ 10 The important result of this analysis is that in all likely cases of active floodplains, cosmogenic Be ratios account for minimum burial depths of 5 to 10 m for a duration of > 5 My. 10 Be and 26 Al concentrations remain virtually unchanged over the interval sediment usually spends in the basin. Thus, spatially-averaged denudation rates of the sediment-producing area can be inferred throughout the entire basin, provided that nuclide production rates are scaled for the altitudes of the sediment-producing area only, because floodplain storage does not modify nuclide concentrations introduced from the sediment source area.

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Transcontinental Moving and Storage: the Orinoco and Amazon Rivers Transfer the Andes to the Atlantic

Cited by 54 publications

References 50 publications

Role of moisture transport for Central American precipitation

Role of moisture transport for Central American precipitation

Causes for the decline of suspended‐sediment discharge in the Mississippi River system, 1940–2007

Cosmogenic nuclide budgeting of floodplain sediment transfer

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