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Abstracts / Quaternary International 279-280 (2012) 233–345 257
and flat to slightly concave bottom. Pools (100 to 350 m long and depthsbetween 32 and 47 m) with symmetrical cross section and asymmetricallongitudinal profile were also detected, indicating the position of sub-fluvial cataracts. Conditions of macroturbulent and fine sediment-impov-erished flood would have facilitated the preservation of erosive featuresand their enhancement during the Quaternary.
RAPID CASPIAN SEA LEVEL OSCILLATIONS IN THE HOLOCENE:SYNCHRONICITY WITH GLOBAL CLIMATE CHANGE
Salomon Kroonenberg. TUDelft, NetherlandsE-mail address: [email protected]
The Caspian Sea, a closed basin with a sea-level regime of its own, experi-ences sea-level oscillations in tidal, seasonal, decadal, centennial/millenialandglacial/interglacial time scales, eachwith different forcingmechanisms.The interference of these time scales hampers forecasts solely on the base ofthe instrumental record since 1834. Moreover, so far it has not been clearwhether sea-level change in the Caspian follows the pace of global climatechange, or behaves independently or even chaotically.We improved therefore the data base of the past in the framework of IGCP481 Dating Caspian Sea Level Change. We studied coastal processes duringthe last three-metres sea-level cycle between1929 and 1995 in order tofindthe best sites for dating Holocene sea-level cycles. Holocene highstandswere AMS-dated in Dagestan on in situ mollusks from lagoonal depositsoverridden by highstand barriers, now perched above the present -27 msea-level. Transgressive phases were dated in the ramp delta of the Volgariver in Russia, which, as has been shown during the 20th century sea-levelcycle, progrades along the ramp during regressions, but aggrades verticallyduring transgressions. Lowstands were dated in corings through uncon-formities discovered during seismic surveys offshore the Kura delta inAzerbaijan.Dating and palynological, malacological, and organic and inorganicgeochemical data suggest a LateGlacial +50mhighstand,with deposition ofreddish-brown clays similar to coeval deposits in the Black Sea; a deepregression to at least -92m at the Pleistocene-Holocene transition;a prominent highstand at -22 m correlating with the w2600 BP climatedeterioration at the start of the Subatlantic; a -48m lowstand in the WarmMediaeval Period and a -25mLittle Ice Agehighstand. Precipitation changesin the Volga basin coinciding with major Holocene climatic cycles are themain forcing mechanisms that explain rapid Caspian Sea level change
A GLOBAL DATASET OF HUMAN POPULATION AND INTENSIFICATIONOVER THE HOLOCENE
Kristen Krumhardt. École Polytechnique Fédérale de Lausanne (EPFL),SwitzerlandE-mail address: [email protected]
The population of humans on Earth changed significantly in space and timeover the Holocene. Especially since the beginning of agriculture, humanstransformed their environment worldwide. An important quantity forunderstanding Holocene environmental change is the number and spatialdistribution of people on Earth. Here, we constructed a new database of“potential natural” global human population over the Holocene based ona demographic-resource model that is constrained by census data, expertestimates, and archaeological data. To model population, we used theGlobal Land Use and technological Evolution Simulator (GLUES), whichsimulates the potential size and density of human populations based onenvironment, technology, and societal structure. The final databasecontains estimates of population for 209 country-sized regions and can bedistributed onto a grid based on land suitability for agriculture. In certainareas of theworld, e.g., Europe or China, quality estimates of population thatexist for the early historical period enabled us to constrain the GLUESestimated population well, while in other areas where uncertainty in thehistorical data is very high, e.g., pre-contact Americas and south Asia, wegive the simulated data higher preference. By distributing populationwithin each region according to land suitability for agriculture, we canquantify land use intensity. Applying Boserupian land use theory, weassume that populations and area under land use expand until suitable landis scarce at which point populations are forced to intensify. We conclude
that China and Southwest Asia were among the first areas in the world tointensify land use in response to population pressure. Whether land usewas extensive or intensive throughout history has important implicationsfor global carbon cycling (e.g., carbon loss due to deforestation or erosion)and contains lessons about what constitutes environmental sustainability.
MILLENNIAL-SCALE VARIATIONS IN EAST ASIAN SUMMER MONSOONDURING THE LAST GLACIAL PERIOD BASED ON MG/CA AND OXYGENISOTOPE OF GLOBIGERINOIDES RUBER FROM THE NORTHERN EASTCHINA SEA
Yoshimi Kubota. University of Tokyo, JapanE-mail address: [email protected]
Millennial-scale variations in the East Asian summer monsoon [EASM] areassociated with the Dansgaard-Oeschger [D-O] cycles and Heinrich eventsin the high-latitude North Atlantic during the last glacial period. Today,interannual variability of summer sea surface salinity [SSS] in the northernEast China Sea [ECS] is influenced strongly by discharge of the YangtzeRiver. Thus variation in d18O of seawater [d18Osw] in the northern ECS,a function of SSS, reflects variation in the summer rainfall over the YangtzeRiver catchment. We reconstructed Mg/Ca-based sea surface temperature[SST] and d18Osw of planktic foraminifera, Globigerinoides ruber, in coreKR07-12-01 recovered from the northern ECS to investigate variations inthe summer rainfall in south China during the last glacial period. Prelim-inary age model of KR07-12-01 was constructed based on correlation ofcolor variation patterns with well-age-controlled core MD 982195 ob-tained from the near-by site and ash layer of Aira-Tanzawa (29 ka), andrevealed that the core reached 42 ka. Lower SST events are observed at 39-40, w33, w29 ka in the northern ECS, which seems to coincide with D-Ostadials #9, #6, and #5, respectively, suggesting teleconnection betweenhigh-latitude North Atlantic and EASM regions. Heavier shift of d18Osw wasobserved atw39 andw30 ka in the northern ECS, which seems to coincidewith Heinrich events #4 and #3 respectively and maxima of stalagmites'd18O in south China. On the other hand, the reconstructed d18Osw in thenorthern ECS has not changed significantly at Younger Dryas event. This isin contrast with stalagmites’ d18O records from east China, which showsignificant changes in association with Younger Dryas, suggesting that themillennial-scale variations in the EASM depend on the planetary boundaryconditions of climate and are larger in amplitude during the last glacialperiod than during the last deglacial period.
CONSTRAINS ON SEA SURFACE TEMPERATURE RECONSTRUCTIONS OFTHE LAST GLACIAL MAXIMUM OCEAN AND THEIR COMPARISON WITHCLIMATE MODEL HINDCASTS
Michal Kucera. Department of Geosciences, University of Tubingen, GermanyE-mail address: [email protected]
The sea surface temperature (SST) of the Last Glacial Maximum (LGM)oceans continues to serve as the prime target for data-model comparison.The early recognition of this target led to the availability of large amountsof data and facilitated the development of spatially continuous andunambiguously resolved LGM SST patterns. The latest LGM SST synthesispresented by the MARGO (Multiproxy Approach for the Reconstruction ofthe Glacial Ocean surface) group marks a step away from this practice. Themotivation for this paradigm shift stems from an analysis of the sources ofuncertainty in individual spatially discrete reconstructions. Such analysisbecame possible because of the development of new geochemical paleo-thermometers and higher spatial sampling in several regions. Previously,uncertainties associated with individual reconstructions have been basedon estimates of calibration errors. Yet, the increasing availability of SSTreconstructions by multiple proxies in the same regions indicates that theprime challenge in the interpretation of LGM SST reconstructions and theirmeaningful comparison with climate model hindcasts lies in the correctseasonal and vertical attribution of SST reconstructed by different methodsin different oceanic settings. The secondmajor challenge is the existence ofsignificant regional structure in the pattern of LGM SST anomalies, whichnecessarily leads to large uncertainties when SST reconstructions areextrapolated into unsampled regions. At 5�x5� resolution, the MARGOdataset only covers 20% of the global ocean, with only 30% of the grid cells
