DOCSLIB.ORG

Tropical Glacier Meltwater Contribution to Stream Discharge: a Case Study

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Tropical Glacier Meltwater Contribution to Stream Discharge: a Case Study Journal of Glaciology , Vol. 49, No.165, 2003 Tropical glacier meltwatercontribution tostreamdischarge: acase studyin theCordillera Blanca, Peru Bryan G. MARK,1* Geoffrey O. SELTZER2 1MaxPlanck Institute for Biogeochemistry,D-07745 Jena,Germany E-mail: [email protected] 2Department of Earth Sciences,Syracuse University,Syracuse,NewYork 13244,U.S.A. ABSTRACT.Discharge measurements, climate observationsandhydro chemical samples gatheredmonthly ( 1998/99)inthe Yanamareyand U ruashrajuglacier-fed catch- ments ofthe CordilleraBlanca, Peru, permit ananalysis of the glaciermeltwater contribu- tionto stream-flow .Theseglacier catchments feedthe R õÂoSanta,which discharges into the PacificOcean. Based on a water-balancecomputation, glacier melt contributes anesti- mated 35%of the averagedischarge from the catchments. Forcomparison, a volumetric end-member mixingmodel of oxygen isotopes shows glacier melt contributes 30^45%to the totalannual discharge .Basedon stream geochemistry,dischargefrom the Yanamarey glaciercatchment provides30% of the annualvolume discharged from the Querococha watershed,which is 510%glacierized.By analogy ,the largerR õÂoSantawatershed, also 510%glacierized,receives atleast 12%ofits annualdischarge from melting glacier ice. Tributarywatersheds tothe R õÂoSantawith larger fractions of glaciercover have less vari- ablerunoff and enhanced discharge, demonstrating that the glacierseffectively buffer stream dischargeseasonally .With continuedglacier melting, stream-flow willlikely becomemore variable,and there willbe less dry-seasonrunoff. 1.INTRODUCTION tationcauses tropicalglaciers to accumulate primarily in the wet season,when melting is alsogreatest. Inthe Cordillera Theworld ’stropicalglaciers have been retreating overthe Blanca,70^90% of annual precipitation falls between late20th century ,raisingconcerns about regional water sup- October andMarch (Kaser andGeorges, 1997).Ablation plies inalpine tropical regions (Hastenrath andKruss, 1992; rates inthe wet seasonare 33% greater than in the dryseason Francouand others, 1995b;Ribstein andothers, 1995;Kaser, (Kaser andothers, 1990;Kaser ,1995).Seasonalincreases in 1999).Theconsequence of sustained glacier retreat is the loss of meltingduring the wet seasonare caused by changes in the glaciermeltwater thatprovidesa significantcon tributionto verticalhumidity gradient over the glaciersurface, which stream discharge,which is used fordrinking water ,hydro- alters the latent-heat fluxand provides more energyto melt electric power(HE P)generationand irrigation. If these ice (Wagnonand others, 1999).However,this highermelt rate glaciersdisappear ,there couldbe water -supplycrises (Barry maynot exceed the greateramount of precipitation received andSeimon, 2000 ).Forexam ple,a studyof glacier mass duringthe wetseason that contributes tostream discharge. balancehas shown tha t50%of the meanannual water dis- Consequently,arelativelygreater proportion of glaciermelt chargefrom GlaciarY anamareyof the CordilleraBlanca, Peru, maycontribute to stream dischargein the dryseason than in comes fromnet glaciermass loss dueto retreat (Hastenrath the wet season. andAmes, 1995).Undercurrent rates ofrecession, Glaciar Thispaper presents the results ofwork to evaluate the Yanamareywill disappear completely in half a century.Simi- hydrologicalimpact of glacier meltwater inthe Cordillera larly,GlaciarChacaltaya, Bolivia, could disappear within Blancaat the scales ofboth small glacialcatchments andthe 10years,causing an estimated 30%loss ofstream discharge largerregional watershed of the R õÂoSanta.Individual pro- (Francouand others, 2000).However,it remains questionable glaciallakes are manageable settings formeasuring the ifthe results ofthese limited studies applyto discharge in dynamicsof the annualglacier-hydrological regime, whereas 2 largervalleys, such asthe R õÂoSanta,which drains 5000 km analysesof historicalrunoff data for larger glacierized tribu- alongthe western slopes ofthe CordilleraBlanca (Fig .1). tarystreams ofthe R õÂoSantaaddress the impactof glacier Anothermajor concern is that the proportionof glacier melt towater supply at the regionalscale . melt contributingto stream dischargemay vary seasonally inhigh-elevation tropical regions. Strongly seasonal precipi- 2. SETTING Thetropical mountains of the CordilleraBlanca extend 120km between 8. 5³and 1 0³S alonga northwest^southeast * Present address: Department ofGeography and T opo- strike, dividingstream runoffbetween the Pacificand Atlantic graphicScience, U niversityof Glasgow ,GlasgowG 128QQ, Oceans (Fig.1).Thelargest percentage of glacierizedarea in Scotland. the CordilleraBlanca discharges to the PacificOcean via the 271 Downloaded from https://www.cambridge.org/core. 13 Oct 2020 at 17:07:17, subject to the Cambridge Core terms of use. Journal of Glaciology Fig.1.Contour map of the Cordillera Blanca showing glacierized areas,the R õÂoSanta,the Glaciares Uruashraju andYanamarey catchments (withenlargements) ,and stream gauge sites (solid circles) listed in Table 1.The larger Olleros and Querococha watersheds below the glacier catchments are outlined in dotted lines.Abox with dashed outline shows the area covered by Figure 3. RõÂoSanta.Of the rivers drainingto the Pacificcoast of Peru, coastalcity of T rujillo.The HEP plantat Huallanca ( 1800m the RõÂoSantahas the secondlargest discharge volume, but a.s.l.)delimits the upperR õÂoSantawatershed to an area of maintainsthe most regularflow ,featuringthe least vari- 4901km2 that isreferred toas the Callejonde Huaylas and is abilityin monthly runoff over the year.TheR õÂo Santa des- the focusof these studies. cends from4300 m over300 km, draining a watershedof Theglacierized area contributing to R õÂoSantadischarge 12200 km2.Fourhydroelectric plants along the lowercanyon variesamong the tributarywatersheds alongthe Callejonde of the RõÂoSantasupply power to mines andvillages along its Huaylas,although the CordilleraBlanca has undergone an banksand to the portcity Chimbote with its largesteel mill overallreduction in glacier volume throughout the 20th andanchovy fishery industries. Other channelsdivert water century.TheGlacier Inventoryof Perulists the totalarea of fromthe riverto irrigate large sugar plantations around the glaciersin the CordilleraBlanca as 723km 2,basedon aerial Table1.Discharge data (fromEgenor SA)and glacierized area for R õÂoSantatributary watersheds in the Callejon de Huaylas, west of the Cordillera Blanca Station Stream Period of Watershed Glacierized Glacierized Mean annual Specific Meanmonthly Max.monthly Max./mean record area1 area (1962)1 area (1997)2 discharge discharge specificdischarge specificdischarge discharge km2 % % m3 s^1 mm a^1 mm mm Paron Paron 1953^95 49 55 52 1.89 1220 99 140 1.41 LlanganucoLlanganuco 1 953^9785 41 36 2.99 1110 91 136 1.49 Huillca Collota1 953^8355 32 29 2.75 1580 130 204 1.57 ChancosMarcara 1 953^9722 1 25 22 8.80 1260 101 173 1.72 Cedros Cedros1 953^831 14 22 18 3.54 980 81 116 1.44 Colcas Colcas 1953^85 237 19 18 6.18 820 64 116 1.82 QuillcayQuillcay 1 953^83243 18 17 7.41 960 79 143 1.80 PachacotoPachacoto 1 953^831 94 12 8 4.40 720 59 130 2.19 Olleros Olleros1 970^971 75 11 10 4.77 860 71 132 1.84 LaBalsa Santa 1954^974768 9 8 88.40 580 47 108 2.28 QuitarascaQuitaracsa 1 953^97383 8 7 10.97 900 73 140 1.91 QuerocochaQuerococha 1 956^9662 6 3 1.70 870 71 151 2.12 1Areastaken from 1:1 00000scale maps based on 1962aerial photography . 2Areastaken from 1 997Landsat imagery . 272 Downloaded from https://www.cambridge.org/core. 13 Oct 2020 at 17:07:17, subject to the Cambridge Core terms of use. Mark and Seltzer:Tropical glacial meltwatercontribution tostream discharge 5300m a.s.l.,7 5%ofwhich is coveredby glacier ice. Runoff fromthe catchment flowsto lake Querococha, and monthly dischargerecords fromthe lakeeffluent are available for the period1 956^96.The U ruashrajucatchment covers3 .4km 2 overa slightlylarger elevation range from 4600 to 5 700m, and65% of the areais coveredby glacier ice. Runoffleaving this catchment joinsa stream that flowspast agaugeat Olleros, andmonthly discharge records areavailable for the period1 970^97.Thelarger O lleros andQuerococha water- sheds containingthe Uruashrajuand Yanamareycatchments, respectively,areoutlined in Figure 1 . Themouth of eachglacier catchment isthe outlet froma small proglaciallake that hasformed in the bedrockin front ofeachglacier during recent glacierrecession. Theglacier catchments havevery little vegetation(mosses andgrasses) andpoor soil development over the looselyconsolidated alluviumand till. Thebedrock in the regionconsists of metamorphosedsedimentary rocks(quartzite andhorn- fels),drapingoff the central granodioriticbatholith that forms the coreof the CordilleraBlanca (Wilson andothers, 1967).Glacialmeltwater enteringthe lakesis transmitted directlyto the outlet streams withouta significantlag due tolake storage. The abbreviations Y ANandUR Uwillbe used henceforthto identify the Yanamareyand Uruashraju glaciercatchments, respectively,andalso label discharge sites atthe outlet streams fromthe proglaciallakes (Fig .1). 3.D ATAANDMETHODS 3.1.Annual hydrology of theglacier catchments YAN andUR Uwerevisited monthly from May 1 998to August1999to collect observations of temperature andpreci- Fig.2.(a)M ean monthly precipitation shown as percentage pitation,and to measure stream discharge.W eather stations of the annual total for stations in the Callejon de Huaylas installednear the glaciertermini inthe 1980scontain totaliz- plotted over the hydrological
Load more

Recommended publications
  • Impacts of Glacial Meltwater on Geochemistry and Discharge of Alpine Proglacial Streams in the Wind River Range, Wyoming, USA
    Brigham Young University BYU ScholarsArchive Theses and Dissertations 2019-07-01 Impacts of Glacial Meltwater on Geochemistry and Discharge of Alpine Proglacial Streams in the Wind River Range, Wyoming, USA Natalie Shepherd Barkdull Brigham Young University Follow this and additional works at: https://scholarsarchive.byu.edu/etd BYU ScholarsArchive Citation Barkdull, Natalie Shepherd, "Impacts of Glacial Meltwater on Geochemistry and Discharge of Alpine Proglacial Streams in the Wind River Range, Wyoming, USA" (2019). Theses and Dissertations. 8590. https://scholarsarchive.byu.edu/etd/8590 This Thesis is brought to you for free and open access by BYU ScholarsArchive. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. Impacts of Glacial Meltwater on Geochemistry and Discharge of Alpine Proglacial Streams in the Wind River Range, Wyoming, USA Natalie Shepherd Barkdull A thesis submitted to the faculty of Brigham Young University in partial fulfillment of the requirements for the degree of Master of Science Gregory T. Carling, Chair Barry R. Bickmore Stephen T. Nelson Department of Geological Sciences Brigham Young University Copyright © 2019 Natalie Shepherd Barkdull All Rights Reserved ABSTRACT Impacts of Glacial Meltwater on Geochemistry and Discharge of Alpine Proglacial Streams in the Wind River Range, Wyoming, USA Natalie Shepherd Barkdull Department of Geological Sciences, BYU Master of Science Shrinking alpine glaciers alter the geochemistry of sensitive mountain streams by exposing reactive freshly-weathered bedrock and releasing decades of atmospherically-deposited trace elements from glacier ice. Changes in the timing and quantity of glacial melt also affect discharge and temperature of alpine streams.
    [Show full text]
  • The Generation of Mega Glacial Meltwater Floods and Their Geologic
    urren : C t R gy e o s l e o r a r LaViolette, Hydrol Current Res 2017, 8:1 d c y h H Hydrology DOI: 10.4172/2157-7587.1000269 Current Research ISSN: 2157-7587 Research Article Open Access The Generation of Mega Glacial Meltwater Floods and Their Geologic Impact Paul A LaViolette* The Starburst Foundation, 1176 Hedgewood Lane, Niskayuna, New York 12309, United States Abstract A mechanism is presented explaining how mega meltwater avalanches could be generated on the surface of a continental ice sheet. It is shown that during periods of excessive climatic warmth when the continental ice sheet surface was melting at an accelerated rate, self-amplifying, translating waves of glacial meltwater emerge as a distinct mechanism of meltwater transport. It is shown that such glacier waves would have been capable of attaining kinetic energies per kilometer of wave front equivalent to 12 million tons of TNT, to have achieved heights of 100 to 300 meters, and forward velocities as great as 900 km/hr. Glacier waves would not have been restricted to a particular locale, but could have been produced wherever continental ice sheets were present. Catastrophic floods produced by waves of such size and kinetic energy would be able to account for the character of the permafrost deposits found in Alaska and Siberia, flood features and numerous drumlin field formations seen in North America, and many of the lignite deposits found in Europe, Siberia, and North America. They also could account for how continental debris was transported thousands of kilometers into the mid North Atlantic to form Heinrich layers.
    [Show full text]
  • Freshwater Resources
    3 Freshwater Resources Coordinating Lead Authors: Blanca E. Jiménez Cisneros (Mexico), Taikan Oki (Japan) Lead Authors: Nigel W. Arnell (UK), Gerardo Benito (Spain), J. Graham Cogley (Canada), Petra Döll (Germany), Tong Jiang (China), Shadrack S. Mwakalila (Tanzania) Contributing Authors: Thomas Fischer (Germany), Dieter Gerten (Germany), Regine Hock (Canada), Shinjiro Kanae (Japan), Xixi Lu (Singapore), Luis José Mata (Venezuela), Claudia Pahl-Wostl (Germany), Kenneth M. Strzepek (USA), Buda Su (China), B. van den Hurk (Netherlands) Review Editor: Zbigniew Kundzewicz (Poland) Volunteer Chapter Scientist: Asako Nishijima (Japan) This chapter should be cited as: Jiménez Cisneros , B.E., T. Oki, N.W. Arnell, G. Benito, J.G. Cogley, P. Döll, T. Jiang, and S.S. Mwakalila, 2014: Freshwater resources. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Field, C.B., V.R. Barros, D.J. Dokken, K.J. Mach, M.D. Mastrandrea, T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. Levy, S. MacCracken, P.R. Mastrandrea, and L.L. White (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 229-269. 229 Table of Contents Executive Summary ............................................................................................................................................................ 232 3.1. Introduction ...........................................................................................................................................................
    [Show full text]
  • Himalayan Glaciers
    Himalayan Glaciers Climate Change, Water Resources, and Water Security Scientific evidence shows that most glaciers in South Asia’s Hindu Kush Himalayan region are retreating, but the consequences for the region’s water supply are unclear, this report finds. The Hindu Kush Himalayan region is the location of several of Asia’s great river systems, which provide water for drinking, irrigation, and other uses for about 1.5 billion people. Recent studies show that at lower elevations, glacial retreat is unlikely to cause significant changes in water availability over the next several decades, but other factors, including groundwater depletion and increasing human water use, could have a greater impact. Higher elevation areas could experience altered water flow in some river basins if current rates of glacial retreat continue, but shifts in the location, intensity, and variability of rain and snow due to climate change will likely have a greater impact on regional water supplies. he Himalayan region, which Tcovers eight countries across Asia, is home to some of the world’s largest and most spectacular glaciers. The melt- water generated from these glaciers each summer supplements the rivers and streams of the region, including several of Asia’s great river systems such as the Indus, Ganges, and Brahmaputra. Rising tempera- tures due to climate change are causing glaciers worldwide to Figure 1. Extending over 2000 kilometers across the Asian continent and including all shrink in volume and or part of Afghanistan, Bangladesh, Bhutan, China, India, Nepal, and Pakistan, the mass, a phenomenon Hindu Kush Himalayan region is the source for many of Asia’s major river systems, known as glacial including the Indus, Ganges, and Brahmaputra.
    [Show full text]
  • The Potential of Hudson Valley Glacial Floods to Drive Abrupt Climate Change
    ARTICLE https://doi.org/10.1038/s43247-021-00228-1 OPEN The potential of Hudson Valley glacial floods to drive abrupt climate change ✉ Simon Pendleton 1 , Alan Condron 1 & Jeffrey Donnelly1 The periodic input of meltwater into the ocean from a retreating Laurentide Ice Sheet is often hypothesized to have weakened the Atlantic meridional overturning circulation (AMOC) and triggered several cold periods during the last deglaciation (21,000 to 8,000 years before present). Here, we use a numerical model to investigate whether the Intra-Allerød Cold Period was triggered by the drainage of Glacial Lake Iroquois, ~13,300 years ago. Performing a large suite of experiments with various combinations of single and successive, short fl fi fi 1234567890():,; (1 month) and long (1 year) duration ood events, we were unable to nd any signi cant weakening of the AMOC. This result suggests that although the Hudson Valley floods occurred close to the beginning of the Intra-Allerød Cold Period, they were unlikely the sole cause. Our results have implications for re-evaluating the relationship of meltwater flood events (past and future) to periods of climatic cooling, particularly with regards to flood input location, volume, frequency, and duration. ✉ 1 Woods Hole Oceanographic Institution, Woods Hole, MA, USA. email: [email protected] COMMUNICATIONS EARTH & ENVIRONMENT | (2021) 2:152 | https://doi.org/10.1038/s43247-021-00228-1 | www.nature.com/commsenv 1 ARTICLE COMMUNICATIONS EARTH & ENVIRONMENT | https://doi.org/10.1038/s43247-021-00228-1 n the late 1980s periodic meltwater inputs from a retreating supports a second larger flood (~2500 km3) then drained the ILaurentide Ice Sheet (LIS) were hypothesized to have hindered successor to Lake Iroquois, Lake Frontenac, along with the glacial North Atlantic deep water (NADW) formation, leading to a lake in the Champlain Valley (Lake Fort Ann) down the Hudson weakened Atlantic meridional overturning circulation (AMOC), River9–12 (Fig.
    [Show full text]
  • Origin of the First Global Meltwater Pulse Following the Last Glacial Maximum
    PALEOCEANOGRAPHY, VOL. 11, NO. 5, PAGES 563-577, OCTOBER 1996 Origin of the first global meltwater pulse following the last glacial maximum PeterU. Clark,l Richard B. Alley, 2Lloyd D. Keigwin,3Joseph M. Licciardi,• SigfusJ.Johnsen, 4'•and Huaxiao Wang 6 Abstract. Well-datedsea level recordsshow that the glacioeustaticrise followingthe lastglacial maximumwas characterizedby two or possiblythree brief intervalsof rapid sealevel rise separat- ing periodswith muchlower rates. Thesevery highrates of sealevel rise indicate periods of ex- ceptionallyrapid deglaciation of remainingice sheets.The LaurentideIce Sheetis commonlytar- getedas the sourceof the first, andlargest, of the meltwaterpulses (mwp-IA between-14,200 (12,200•4C years B.P.) and 13,700 years ago (11,700 •4C years B.P.)). In alloceanic records of deglaciationof the formernorthern hemisphere ice sheetsthat we review, only thosefrom the Gulfof Mexico and the Bermuda Rise show evidence oflow ;5•80 values at the time of mwp-IA, identifyingthe southernLaurentide Ice Sheetas a potentialsource for mwp-IA. We questionthis sourcefor mwp-IA, however,because (1) ice sheetmodels suggest that this sectorof the ice sheet contributedonly a fraction(<10%) of the sealevel needed for mwp-IA, (2) meltingthis sector of the ice sheetat the necessaryrate to explainmwp-IA is physicallyimplausible, and (3) ocean modelspredict a muchstronger thermohaline response to theinferred freshwater pulse out of the MississippiRiver into theNorth Atlanticthan is recorded.This leavesthe AntarcticIce Sheetas the only
    [Show full text]
  • City of Homer Stormwater and Meltwater
    Stormwater aaandand Meltwater Management aaandand Mitigation A Handbook for Homer, Alaska .. 2 Homer Stormwater and Meltwater Management and Mitigation A Handbook for Homer, Alaska 2007 City of Homer, Alaska Allegra Bukojemsky, RLA David Scheer, MArch This handbook was created by Allegra Bukojemsky and David Scheer, of DnA Design. The authors may be contracted for future modifications or edits. In no way is the use of the authors’ names condoned for the authorship of future texts without consent All figures and images are by the authors unless otherwise noted. Stormwater Manual i ii Homer Table of Contents Introduction page 1 Chapter 1: Stormwater - An overview page 3 Key Term Definitions Hydrologic cycle Watershed The Hydrograph Development Streams and Lakes Water quality Wetlands and Riparian Areas Plants & Soils Shore and Bluff Infrastructure and Maintenance Regulations – public influence over public effects Stormwater specifics in Homer Chapter 2: Site planning for stormwater management page 12 Site Design – Retain important site function Preserve wetlands and riparian areas Use established vegetation & soils Site Design – Strategies for an effective Site Plan Limit impervious surface area Limit connections between impervious surface Slow runoff and dissipate energy Design a sensitive grading plan Maintain connections beyond your property Site design – Cold climate considerations Freezing – winter conditions Snow Storage and Spring Melt considerations Site Design – Other considerations Siting of constructed stormwater management systems
    [Show full text]
  • A Catastrophic Meltwater Flood Event and the Formation of the Hudson Shelf Valley ⁎ E
    Palaeogeography, Palaeoclimatology, Palaeoecology 246 (2007) 120–136 www.elsevier.com/locate/palaeo A catastrophic meltwater flood event and the formation of the Hudson Shelf Valley ⁎ E. Robert Thieler a, , Bradford Butman a, William C. Schwab a, Mead A. Allison b, Neal W. Driscoll c, Jeffrey P. Donnelly d, Elazar Uchupi d a U.S. Geological Survey, 384 Woods Hole Rd., Woods Hole, MA 02543, USA b Department of Earth and Environmental Sciences, Tulane University, New Orleans, LA 70118, USA c Scripps Institution of Oceanography, La Jolla, CA 92093, USA d Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA Received 26 August 2004; accepted 17 October 2006 Abstract The Hudson Shelf Valley (HSV) is the largest physiographic feature on the U.S. mid-Atlantic continental shelf. The 150-km long valley is the submerged extension of the ancestral Hudson River Valley that connects to the Hudson Canyon. Unlike other incised valleys on the mid-Atlantic shelf, it has not been infilled with sediment during the Holocene. Analyses of multibeam bathymetry, acoustic backscatter intensity, and high-resolution seismic reflection profiles reveal morphologic and stratigraphic evidence for a catastrophic meltwater flood event that formed the modern HSV. The valley and its distal deposits record a discrete flood event that carved 15-m high banks, formed a 120-km2 field of 3- to 6-m high bedforms, and deposited a subaqueous delta on the outer shelf. The HSV is inferred to have been carved initially by precipitation and meltwater runoff during the advance of the Laurentide Ice Sheet, and later by the drainage of early proglacial lakes through stable spillways.
    [Show full text]
  • African Humid Period'' and the Record of Marine Upwelling from Excess Th
    PALEOCEANOGRAPHY, VOL. 21, PA4203, doi:10.1029/2005PA001200, 2006 Click Here for Full Article The ‘‘African humid period’’ and the record of marine upwelling from excess 230Th in Ocean Drilling Program Hole 658C Jess Adkins,1 Peter deMenocal,2 and Gidon Eshel3 Received 26 August 2005; revised 4 February 2006; accepted 13 June 2006; published 20 October 2006. 230 [1] Using a high-resolution Th normalized record of sediment flux, we document the deglacial and Holocene history of North African aridity and coastal upwelling at Ocean Drilling Program Hole 658C. At both the end of the Younger Dryas and after the 8.2 ka event, there are significant drops in terrigenous accumulation at our site, indicating an increase in the monsoon moisture flux over Africa at this time. At 5.5 ka, there is an abrupt end to the ‘‘African humid period’’ and a return to stronger upwelling conditions. For carbonate and opal fluxes the 230Th normalization completely changes the shape of each record based on percentage variations alone. This site is a clear example of how variations in one sediment component can obscure changes in the others, and it demonstrates the need for radionuclide measurements more generally in paleoceanography. By taking our new records and a large amount of previous data from this site we conclude that increases in African moisture are tightly coupled to decreases in coastal upwelling intensity. Citation: Adkins, J., P. deMenocal, and G. Eshel (2006), The ‘‘African humid period’’ and the record of marine upwelling from excess 230Th in Ocean Drilling Program Hole 658C, Paleoceanography, 21, PA4203, doi:10.1029/2005PA001200.
    [Show full text]
  • Heterogeneous CO2 and CH4 Content of Glacial Meltwater from the Greenland Ice Sheet and Implications for Subglacial Carbon Processes
    The Cryosphere, 15, 1627–1644, 2021 https://doi.org/10.5194/tc-15-1627-2021 © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Heterogeneous CO2 and CH4 content of glacial meltwater from the Greenland Ice Sheet and implications for subglacial carbon processes Andrea J. Pain1,a, Jonathan B. Martin1, Ellen E. Martin1, Åsa K. Rennermalm2, and Shaily Rahman1,b 1Department of Geological Sciences, University of Florida, Gainesville, FL 32611, USA 2Department of Geography, Rutgers, The State University of New Jersey, Piscataway NJ 08854, USA anow at: University of Maryland Center for Environmental Science, Horn Point Lab, Cambridge, MD 21613, USA bnow at: Department of Marine Science, University of Southern Mississippi, Stennis Space Center, MS 39529, USA Correspondence: Andrea J. Pain ([email protected]) Received: 18 June 2020 – Discussion started: 3 July 2020 Revised: 22 February 2021 – Accepted: 24 February 2021 – Published: 1 April 2021 Abstract. Accelerated melting of the Greenland Ice Sheet Sheet. Future work should constrain the extent and controls has increased freshwater delivery to the Arctic Ocean and of heterogeneity to improve our understanding of the impact amplified the need to understand the impact of Greenland of Greenland Ice Sheet melt on Arctic greenhouse gas bud- Ice Sheet meltwater on Arctic greenhouse gas budgets. We gets, as well as the role of continental ice sheets in green- evaluate subglacial discharge from the Greenland Ice Sheet house gas variations over glacial–interglacial timescales. for carbon dioxide (CO2) and methane (CH4) concentrations and δ13C values and use geochemical models to evaluate sub- glacial CH4 and CO2 sources and sinks.
    [Show full text]
  • Meltwater Hydrology and Hydrochemistry in Snow- and Ice-Covered Mountain Catchments
    Nordic Hydrology, 12, 1981, 319-334 No part may be reproduced hy any proccss without complctc reference Meltwater Hydrology and Hydrochemistry in Snow- and Ice-Covered Mountain Catchments David N. Collins and Gordon J. Young Department of Geography, University of Manchester and National Hydrology Res.lnst., Environment Canada Electrical conductivity, a surrogate measure of total dissolved solids content, and discharge of meltwaters draining from two adjacent contrasting water- sheds in the Rocky Mountains, Canada, were recorded continuously from mid-May - August 1979, throughout the ablation season, in order to investi- gate the influence of snow- and ice-melt on alpine hydrochemistry. Solute concentration varied inversely diurnally with discharge in both nival and gla- cial meltwaters. Solute content and discharge of the snowmelt-fed Amiskwi River declined with decreasing availability of snowcover through July, fol- lowed by increased solute content during low flows in August. In the glacially- fed Peyto Creek, conductivity decreased with increasing flow during spring snow-melt, but during ice-melt domination of flow from mid-July oscillated daily through a limited range. Snow- and ice-melt are shown to have contrast- ing roles in determining distinctive patterns of diurnal and seasonal temporal variations of discharge and hydrochemistry in mountain basins. Continuous monitoring of water quality is essential in characterising the hydrochemistry of alpine environments. Introduction Both the quantity and quality of runoff from high mountain basins are regulated by the accumulation and melting of seasonal snowcover and melting of permanent glacier ice. Studies of the formation of mountain runoff are of considerable importance, since flows in the headwaters of many great continental rivers origi- nate in the alpine zone, and such sources are extensively utilised by engineering developments for irrigation and hydro-electric power, especially in the western Downloaded from http://iwaponline.com/hr/article-pdf/12/4-5/319/2315/319.pdf by guest on 24 September 2021 D.
    [Show full text]
  • Glaciers and Hydrology on the Glacier Meltwater Contribution to River Runoff
    Glaciers and Hydrology On the glacier meltwater contribution to river runoff Sergiy Vorogushyn Section 5.4: Hydrology GFZ German Research Centre for Geosciences Potsdam CATCOS Summer School Bishkek, 2015 Hydrological cycle and the basic equation in Hydrology Q = P – E – ΔS ΔS: Storage change (glacier, snow, soil moisture, groundwater) P: Precipitation E: Evapotranspiration Q: Runoff 2 Storages and Fluxes Ice & snow Storage Atmosphere Soil Inland surface Fluxes water bodies Groundwater OceanOcean 3 Introduction • „For the whole Tien Shan, the glacial runoff is 15-20% of total volume of river runoff“ (Aizen et al., 1995, Water Resources Bulletin) • „…but there is little doubt that melting glaciers provide a key source of water for the region [Himalya-Hindu Kush] in the summer month: as much as 70% of the summer flow in the Ganges and 50-60% of the flow in other major rivers (references)“ (Barnett et al., 2005, Nature) Introduction • „For the whole Tien Shan, the glacial runoff is 15-20% of total volume of river runoff“ (Aizen et al., 1995, Water Resources Bulletin) no sense! make • „…but there is little doubt that melting glaciers! provide a key source statements careful of water forSuch the region [Himalya very-Hindu Kush] in the summer month: as much as 70% of theBe summer flow in the Ganges and 50-60% of the flow in other major rivers (references)“ (Barnett et al., 2005, Nature) Definition of glacier melt runoff Source Glacier Glacier Glacier meltwater meltwater + meltwater + Snow melt Snow melt + Rainfall on Fraction glacier Stat vs.
    [Show full text]