Regional climate signal vs. local noise: a two-dimensional view of water isotopes in Antarctic firn at Kohnen station, Dronning Maud Land
Clim. Past Discuss., 11, 5605-5649, doi:10.5194/cpd-11-5605-2015, 2015
Was the Little Ice Age more or less El Niño-like than the Mediaeval Climate Anomaly? Evidence from hydrological and temperature proxy data
Summary: To understand future ENSO behaviour we must look at the past, but temperature and rainfall proxies (e.g. treerings, sediment cores) appear to show different responses. We tested this by making separate multi-proxy ENSO reconstructions for precipitation and temperature, and found no evidence of a disagreement between ENSO-driven changes in precipitation and temperature. While this supports our physical understanding of ENSO, the lack of good proxy data must be addressed to further explore this.
Clim. Past Discuss., 11, 5549-5604, doi:10.5194/cpd-11-5549-2015, 2015
Climatic and insolation control on the high-resolution total air content in the NGRIP ice core
Clim. Past Discuss., 11, 5509-5548, doi:10.5194/cpd-11-5509-2015, 2015
Sea surface temperature variability in the central-western Mediterranean Sea during the last 2700 years: a multi-proxy and multi-record approach
Summary: We present a high-resolution multi-proxy study about the evolution of sea surface conditions along the last 2700 yr in the north-western Mediterranean Sea based on five sediment records from two different sites north of Minorca. The novelty of the results and the followed approach constructing stack records from the studied proxies to preserve the most robust patterns, provide a special value to the study. This complex period appears to have significant regional changes in the climatic signal.
Clim. Past Discuss., 11, 5439-5508, doi:10.5194/cpd-11-5439-2015, 2015
Impact of Holocene climate variability on lacustrine records and human settlements in South Greenland
Summary: To reconstruct past climate changes and their influence on Human settlements, we have study lacustrine sediments retrieved from two Greenlandic lakes (Lake Qallimiut and Little Kangerluluup), recording at high resolution past environmental changes. 37 flood events are identified in these cores, resulting of ice and snow-melting episodes. They are mainly occurred during cooler and wetter periods and and have been mainly responsible for the Human demise.
Clim. Past Discuss., 11, 5401-5438, doi:10.5194/cpd-11-5401-2015, 2015
Effects of melting ice sheets and orbital forcing on the early Holocene warming in extratropical Northern Hemisphere
Summary: We explore how the forcings contributed to climate change during the early Holocene that marked the final transition to the warm and stable stage. Our results indicate that 1) temperature at the onset of Holocene was lower than in the preindustrial era over the Northern extratropics with the exception in Alaska, and the magnitude of this cooling varies regionally as a response to varying climate forcings and diverse mechanisms; 2) rate of the early Holocene warming also spatially heterogenous.
Clim. Past Discuss., 11, 5345-5399, doi:10.5194/cpd-11-5345-2015, 2015
On the spatial and temporal variability of ENSO precipitation and drought teleconnection in mainland Southeast Asia
Summary: This paper examined the patterns of ENSO-related precipitation anomalies over the mainland Southeast Asia (1980-2013) and the long-term ENSO-hydroclimate connection (1650-2004). It was found that precipitation anomalies evolve in time and space during the ENSO events and they were wide-spread during the boreal spring and that the ENSO has affected the mainland Southeast Asia over 96% of the long-term study period and during half of this time the effect was strong.
Clim. Past Discuss., 11, 5307-5343, doi:10.5194/cpd-11-5307-2015, 2015
Marine sediment records as indicator for the changes in Holocene Saharan landscape: simulating the dust cycle
Summary: We demonstrate for the first time the direct link between dust accumulation in marine sediment cores and Saharan land surface by simulating the mid-Holocene and pre-industrial dust cycle as a function of Saharan land surface cover and atmosphere-ocean conditions using the coupled atmosphere-aerosol model ECHAM6-HAM2.1. Mid-Holocene surface characteristics, including vegetation cover and lake surface area, are derived from proxy data and simulations.
Clim. Past Discuss., 11, 5269-5306, doi:10.5194/cpd-11-5269-2015, 2015
Sporopollen evidence for Late Miocene stepwise aridification on the Northeastern Tibetan Plateau
Summary: The Late Cenozoic basins in the northeastern Tibetan Plateau document both the tectonic uplift process and its associated environmental changes. Here, we investigated a Late Miocene sporopollen record from the Tianshui Basin in the northeastern Tibetan Plateau. The results show that a persistent aridification trend parallels the global cooling of the Late Miocene, while the stepwise vegetation succession is consistent with the major uplift events of the Tibetan Plateau.
Clim. Past Discuss., 11, 5243-5268, doi:10.5194/cpd-11-5243-2015, 2015
The impact of the North American ice sheet on the evolution of the Eurasian ice sheet during the last glacial cycle
Clim. Past Discuss., 11, 5203-5241, doi:10.5194/cpd-11-5203-2015, 2015
Impacts of climate and humans on the vegetation in NW Turkey: palynological insights from Lake Iznik since the Last Glacial
Summary: We analyze the vegetation and climate in NW Turkey during last ca. 31,000 years based on a new pollen dataset from lacustrine sediment cores. The study reveals vegetation responses to long-term and rapid climate changes. Moreover, it documents human activities in the catchment of Lake Iznik and shows a clear anthropogenic impact on the vegetation since the Early Bronze Age.
Clim. Past Discuss., 11, 5157-5201, doi:10.5194/cpd-11-5157-2015, 2015
French summer droughts since 1326 AD: a reconstruction based on tree ring cellulose δ18O
Summary: This article presents a reconstruction of summer droughts in France for the last 680 years, based on oxygen isotope ratios in tree ring cellulose from living trees and building timbers at two sites, Fontainebleau and Angoulême. Both sites show coherent drought patterns during the 19th and 20th century, and are characterized by increasing drought in recent decades. A decoupling between sites points to a more heterogeneous climate in France during earlier centuries.
Clim. Past Discuss., 11, 5113-5155, doi:10.5194/cpd-11-5113-2015, 2015
Optimal site selection for a high resolution ice core record in East Antarctica
Summary: This study details a systematic approach to finding a new high resolution East Antarctic ice core site. The study initially outlines seven criteria that a new site must fulfil, encompassing specific accumulation, ice dynamics and atmospheric circulation aspects. We then use numerous techniques including Antarctic surface mass balance syntheses, ground-truthing of satellite data by airborne radar surveys and reanalysis products to pinpoint promising regions.
Clim. Past Discuss., 11, 5073-5111, doi:10.5194/cpd-11-5073-2015, 2015
Late Cretaceous (Late Campanian–Maastrichtian) sea surface temperature record of the Boreal Chalk Sea
Summary: We present here for the first time a very high-resolution record of sea-surface temperature changes in the Boreal Chalk Sea for the last 8 Million years of the Cretaceous. This record was obtained from 1932 bulk oxygen isotope measurements and their interpretation into temperature trends is validated by similar trends observed from changes in phytoplankton assemblages.
Clim. Past Discuss., 11, 5049-5071, doi:10.5194/cpd-11-5049-2015, 2015
Early westward flow across the Tasman Gateway
Summary: The timing and role in ocean circulation and climate of the opening of Southern Ocean gateways is as yet elusive. Here, we present the first model results specific to the early-to-middle Eocene where, in agreement with the field evidence, southerly shallow opening of the Tasman Gateway indeed causes a westward flow across the Tasman Gateway, in agreement with recent micropaleontological studies.
Clim. Past Discuss., 11, 5021-5048, doi:10.5194/cpd-11-5021-2015, 2015
Fossil plant stomata indicate decreasing atmospheric CO2 prior to the Eocene–Oligocene boundary
Summary: Our manuscript ‘Fossil plant stomata indicate decreasing atmospheric CO2 prior to the Eocene-Oligocene boundary’ reports that ~40% decrease in pCO2 preceded the large shift in marine oxygen isotope records that characterizes the Eocene-Oliogocene climate transition. The results endorse the theory that pCO2 drawdown was the main forcer of the Eocene-Oligocene climate change, and a ‘tipping point’ was reached in the latest Eocene, triggering the plunge of the Earth System into icehouse conditions.
Clim. Past Discuss., 11, 4985-5019, doi:10.5194/cpd-11-4985-2015, 2015
Frequency and intensity of palaeofloods at the interface of Atlantic and Mediterranean climate domains
Summary: The long-term response of the flood activity to both Atlantic and Mediterranean climatic influences was explored by reconstructing the Foréant record. Both influences result in a higher flood frequency during past cold periods. Atlantic influences seem to result in more frequent high-intensity flood events during past warm periods, suggesting an increase in flood intensity under the global warming. However, no high-intensity events occurred during the 20th century.
Clim. Past Discuss., 11, 4943-4984, doi:10.5194/cpd-11-4943-2015, 2015
A generalised approach to reconstructing geographical boundary conditions for palaeoclimate modelling
Summary: One of the major difficulties in modelling palaeoclimate is constricting the boundary conditions, causing significant discrepancies between different studies. Here, a new method is presented to automate much of the process of generating the necessary geographical reconstructions. The latter can be made using various rotational frameworks and topography/bathymetry input, allowing for easy inter-comparisons and the incorporation of the latest insights from geoscientific research.
Clim. Past Discuss., 11, 4917-4942, doi:10.5194/cpd-11-4917-2015, 2015
An astronomical correspondence to the 1470 year cycle of abrupt climate change
Summary: Sun-Moon-Earth interaction emulates the 1470-year climate change cycle. The sunspot cycle and gravitational impact of the Sun and Moon on Earth’s spinning axis appear to play important roles in this cycle, affecting the orientation and proximity of climatically sensitive geographic regions capable of responding to astronomical forcing. Astronomical data suggest nutation affects incoming solar insolation patterns as solar and lunar declination wobbles match spectral frequencies in isotopic data.
Clim. Past Discuss., 11, 4895-4915, doi:10.5194/cpd-11-4895-2015, 2015
A Bayesian hierarchical model for reconstructing relative sea level: from raw data to rates of change
Summary: We propose a holistic Bayesian model for the reconstruction and analysis of former sea levels. The model provides a single, unifying framework for reconstructing and analysing sea level through time with fully quantified uncertainty. We illustrate our approach using a case study of Common Era (last 2000 years) sea levels from New Jersey. When compared with an existing method for sea level reconstruction, our method produces a reconstruction that has both an increased accuracy and precision.
Clim. Past Discuss., 11, 4851-4893, doi:10.5194/cpd-11-4851-2015, 2015
Solar modulation of flood frequency in Central Europe during spring and summer on inter-annual to millennial time-scales
Summary: Integrating discharge data of River Ammer back to 1926 and a 5500-year flood layer record from an annually laminated sediment core of the downstream Lake Ammersee allowed investigating changes in the frequency of major floods in Central Europe on inter-annual to millennial time-scales. Significant correlations between flood frequency variations in both archives and changes in the activity of the Sun suggest a solar influence on the frequency of these hydrometeorological extremes.
Clim. Past Discuss., 11, 4833-4850, doi:10.5194/cpd-11-4833-2015, 2015
Climate-driven expansion of blanket bogs in Britain during the Holocene
Summary: It has become a well-established paradigm that blanket bog landscapes in the British Isles are a result of forest clearance by early human populations. We provide a novel test of this hypothesis using results from bioclimatic modelling driven by cimate reconstructions compared with a database of peat initiation dates. Both results show similar patterns of peat initiation over time and space. This suggests that climate was the main driver of blanket bog inception and not human disturbance.
Clim. Past Discuss., 11, 4811-4832, doi:10.5194/cpd-11-4811-2015, 2015
The effect of low ancient greenhouse climate temperature gradients on the ocean's overturning circulation
Summary: The polar warmth of the greenhouse climates in the Earth's past represents a fundamentally different climate state to that of today, with a strongly reduced temperature difference between the equator and the poles. It is commonly thought that this would lead to a more quiescent ocean, with much reduced ventilation of the abyss. Surprisingly, using a Cretaceous cimate model, we find that ocean overturning is not weaker under a reduced temperature gradient arising from amplified polar heat.
Clim. Past Discuss., 11, 4787-4810, doi:10.5194/cpd-11-4787-2015, 2015
Holocene Asian monsoon evolution revealed by a pollen record from an alpine lake on the southeastern margin of the Qinghai-Tibetan Plateau, China
Clim. Past Discuss., 11, 4751-4786, doi:10.5194/cpd-11-4751-2015, 2015
Technical Note: Estimating unbiased transfer-function performances in spatially structured environments
Clim. Past Discuss., 11, 4729-4749, doi:10.5194/cpd-11-4729-2015, 2015
On reconstruction of time series in climatology
Clim. Past Discuss., 11, 4701-4728, doi:10.5194/cpd-11-4701-2015, 2015
Hosed vs. unhosed: global response to interruptions of the Atlantic Meridional Overturning, with and without freshwater forcing
Summary: A full complexity Earth System model is used to explore potential causes of abrupt climate change during glacial periods. The model is one of a few that exhibit spontaneous oscillations of the Atlantic Meridional Overturning Circulation (AMOC). We find that whether a reduction of AMOC is forced by freshwater or not, the impact on global climate patterns is very similar. A difference lies in the Southern Ocean halocline, which influences the Antarctic air temperature response.
Clim. Past Discuss., 11, 4669-4700, doi:10.5194/cpd-11-4669-2015, 2015
Atmospheric circulation patterns associated to the variability of River Ammer floods: evidence from observed and proxy data
Clim. Past Discuss., 11, 4483-4504, doi:10.5194/cpd-11-4483-2015, 2015
Probabilistic precipitation and temperature downscaling of the Twentieth Century Reanalysis over France
Clim. Past Discuss., 11, 4425-4482, doi:10.5194/cpd-11-4425-2015, 2015
Impact of ice sheet meltwater fluxes on the climate evolution at the onset of the Last Interglacial
Clim. Past Discuss., 11, 4391-4423, doi:10.5194/cpd-11-4391-2015, 2015
Stable isotope and calcareous nannofossil assemblage records for the Cicogna section: toward a detailed template of late Paleocene and early Eocene global carbon cycle and nannoplankton evolution
Clim. Past Discuss., 11, 4329-4389, doi:10.5194/cpd-11-4329-2015, 2015
Technical Note: The Linked Paleo Data framework – a common tongue for paleoclimatology
Summary: The lack of accepted data formats and data standards in paleoclimatology is a growing problem that slows progress in the field. Here, we propose a preliminary data standard for paleoclimate data, general enough to accommodate all the proxy and measurement types encountered in a large international collaboration (PAGES2K). We also introduce a "container" for such structured data (Linked Paleo Data, or LiPD), leveraging recent advances in knowledge representation (Linked Open Data).
Clim. Past Discuss., 11, 4309-4327, doi:10.5194/cpd-11-4309-2015, 2015
Palaeoceanographic changes in Hornsund Fjord (Spitsbergen, Svalbard) over the last millennium: new insights from ancient DNA
Summary: The presented study focuses on the last millennium of the palaeoclimatic history of Svalbard region. The investigation was based on classical paleoceanographic proxies, strengthened by the analysis of ancient foraminiferal DNA in down-core sediment samples. This study is the first attempt to implement the aDNA record in the paleoenvironmental reconstruction. The aDNA data revealed even small environmetal changes, that were not evidenced in the sedimentological and micropaleontological record.
Clim. Past Discuss., 11, 3665-3698, doi:10.5194/cpd-11-3665-2015, 2015
Impact of the oceanic geothermal heat flux on a glacial ocean state
Summary: We investigate the impact of the ocean geothermal heating (OGH) on a glacial ocean state using numerical simulations. We found that the OGH is a significant forcing of the abyssal ocean and thermohaline circulation. Applying the OGH warms the Antarctic Bottom Water by ~0.4°C and strengthens the deep circulation by 15% to 30%. The geothermally heated waters are advected from the Indo-Pacific to the North Atlantic basin, indirectly favouring the deep convection in the North Atlantic.
Clim. Past Discuss., 11, 3597-3624, doi:10.5194/cpd-11-3597-2015, 2015