Millennial-scale precipitation variability over Easter Island (South Pacific) during MIS 3: inter-hemispheric teleconnections with North Atlantic abrupt cold events
Summary: The Rano Aroi peat record (Easter Island, 27ºS) is characterized by six major events of enhanced precipitation between 38 and 65 kyr BP coinciding with Heinrich and Dansgaard-Oeschger (DO) Stadials. These events draw a coherent regional picture involving atmospheric and oceanic reorganization. The singular location of Easter Island, filling a gap in an area where marine records are not available, contributes to understand the mechanisms behind these global rapid climatic excursions.
Clim. Past Discuss., 11, 1407-1435, doi:10.5194/cpd-11-1407-2015, 2015
Mammal faunal response to the Paleogene hyperthermals ETM2 and H2
Summary: This project describes mammal faunal response to the ETM2 and H2 hyperthermals (rapid global warming events) of the early Paleogene, including changes in faunal structure and species relative body size. Comparative analysis demonstrates that response is proportionate to the magnitude of climate change, and environmental moisture and rate of change are important moderators of response. Results permit prediction of faunal response to anthropogenically-driven warming across North America.
Clim. Past Discuss., 11, 1371-1405, doi:10.5194/cpd-11-1371-2015, 2015
Variability in terrigenous sediment supply offshore of the Rio de la Plata (Uruguay) recording the continental climatic history over the past 1200 years
Summary: The observed changes in the proxy records indicate variations in the continental runoff and the marine influence, related to regional climatic variability (the Medieval Climatic Anomaly and the Little Ice Age). Therefore, we put forward the suggestion that global atmospheric changes (mainly the latitudinal shifts of the ITCZ and the ENSO events) have made an impact on the local sedimentation regime, on the inner Uruguayan continental shelf over the past 1200 cal yr BP (750-2000 AD).
Clim. Past Discuss., 11, 1343-1369, doi:10.5194/cpd-11-1343-2015, 2015
Early warnings and missed alarms for abrupt monsoon transitions
Summary: Using a combination of speleothem records and model simulations of the East Asian Monsoon over the penultimate glacial cycle, we search for early warning signals of past tipping points. We detect a characteristic slower response to perturbations prior to an abrupt monsoon shift at the glacial termination; however, we do not detect these signals in the preceding shifts. Our results have important implications for detecting tipping points in palaeoclimate records outside glacial terminations.
Clim. Past Discuss., 11, 1313-1341, doi:10.5194/cpd-11-1313-2015, 2015
Arctic sea ice in the PlioMIP ensemble: is model performance for modern climates a reliable guide to performance for the past or the future?
Summary: Simulations of pre-industrial and Pliocene Arctic sea ice by eight GCMs are analysed. Ensemble variability of sea ice extent and thickness is greater in the Pliocene, particularly during the summer months. Weak correlations between pre-industrial sea ice and temperatures are suggested to be affected by model tuning, which along with comparisons to proxy data indicate that pre-industrial performance not necessarily a reliable guide to Pliocene performance for sea ice simulation.
Clim. Past Discuss., 11, 1263-1312, doi:10.5194/cpd-11-1263-2015, 2015
Quality assessment of chronologies in Latin American pollen records: a contribution to centennial to millennial scale studies of environmental change
Summary: We present a review of chronological dating from ca. 1100 fossil pollen records in Central and South America. Additionally, a temporal quality assessment is implemented on 292 records from northwest South-America, which include recalibrating 233 age models. This method evaluates uncertainties for inferred sample ages and chronologies. Important time windows on centennial-millennial climate variability are discussed for sample resolution (estimated years/sample) and temporal uncertainty.
Clim. Past Discuss., 11, 1219-1262, doi:10.5194/cpd-11-1219-2015, 2015
Short-term variability in the sedimentary BIT index of Lake Challa, East Africa over the past 2200 years: validating the precipitation proxy
Clim. Past Discuss., 11, 1177-1218, doi:10.5194/cpd-11-1177-2015, 2015
Parallelisms between sea surface temperature changes in the western tropical Atlantic (Guiana basin) and high latitude climate signals over the last 140 000 years
Summary: The alkenone sea surface temperatures in the Guiana basin show a rapid transmission of the climate variability from arctic-to-tropical latitudes during the last two interglacials (MIS1 and MIS5e) and warm long interstadials (MIS5d-a). In contrast, the abrupt variability of the glacial interval does not follow the North Atlantic climate but it is shaped by precessional changes. This arctic-to-tropical decoupling occurs when the Atlantic meridional overturning circulation is substantially reduced
Clim. Past Discuss., 11, 1143-1175, doi:10.5194/cpd-11-1143-2015, 2015
The simulated climate of the Last Glacial Maximum and the insights into the global carbon cycle
Summary: Global climate models provide an important tool for simulating the earth's climate. Here we present a simulation of the climate of the Last Glacial Maximum, which was obtained by setting atmospheric greenhouse gas concentrations and the earth's orbital parameters to the 21 000 years before present values. We simulate an ocean behaviour that agrees with paleoclimate reconstructions supporting our ability to model the climate system and use the model to explore the impacts on the carbon cycle.
Clim. Past Discuss., 11, 1093-1142, doi:10.5194/cpd-11-1093-2015, 2015
Terrestrial biosphere changes over the last 120 kyr and their impact on ocean δ 13C
Summary: In this paper we use two climate models to test how earth’s vegetation responded to changes in climate over the last 120 000 years, looking at warm interglacial climates like today, cold ice-age glacial climates, and intermediate climates. The models agree well with observations from pollen, showing smaller forested areas and larger desert areas during cold periods. Forests store most terrestrial carbon; the terrestrial carbon lost during cold climates was most likely relocated to the oceans.
Clim. Past Discuss., 11, 1031-1091, doi:10.5194/cpd-11-1031-2015, 2015
Radiative forcing by forest and subsequent feedbacks in the early Eocene climate
Clim. Past Discuss., 11, 997-1029, doi:10.5194/cpd-11-997-2015, 2015
Greenland Ice Sheet influence on Last Interglacial climate: global sensitivity studies performed with an atmosphere–ocean general circulation model
Summary: The Last Interglacial has been warmer with a reduced Greenland Ice Sheet (GIS) compared to the late Holocene. We analyse - through climate model simulations - the impact of a reduced GIS on the global surface air temperature and find a relatively strong warming especially in the Northern Hemisphere. These results are then compared to temperature reconstructions, indicating good agreement with respect to the pattern. However, the simulated temperatures underestimate the proxy-based temperatures.
Clim. Past Discuss., 11, 933-995, doi:10.5194/cpd-11-933-2015, 2015
Early-Holocene warming in Beringia and its mediation by sea-level and vegetation changes
Summary: The ongoing warming of the Arctic is producing changes in vegetation and hydrology, that coupled with rising sea level, could mediate the global changes. We explore this possibility using a regional climate-model simulations of a past interval of warming in Beringia, and found that the regional-scale changes do strongly mediate the responses to global changes, amplifying them in some cases, damping them in others, and, overall, generating considerable spatial heterogeneity in climate change.
Clim. Past Discuss., 11, 873-932, doi:10.5194/cpd-11-873-2015, 2015
Glacial–interglacial shifts in global and regional precipitation δ18O
Summary: In this study we compile global isotope proxy records of climate changes from the last ice age to the late-Holocene preserved in cave calcite, glacial ice and groundwater aquifers. We show that global patterns of glacial-interglacial precipitation isotope shifts are consistent with stronger-than-modern isotopic distillation of air masses during the last ice age, likely impacted by larger global temperature differences between the tropics and the poles.
Clim. Past Discuss., 11, 831-872, doi:10.5194/cpd-11-831-2015, 2015
On the occurrence of annual layers in Dome Fuji ice core early Holocene ice
Clim. Past Discuss., 11, 805-830, doi:10.5194/cpd-11-805-2015, 2015
Optimal Ranking Regime analysis of TreeFlow dendrohydrological reconstructions
Summary: A new approach to time series analysis - the ORR method- was used to evaluate reconstructed western U.S. streamflow records during 1500-2007. This method shows an interesting pattern of alternating drought and wet periods during the late 16th and 17th centuries, a period with relatively few drought or wet periods during the 18th century, and the and the reappearance of alternating dry and wet periods during the 19th and early 20th centuries.
Clim. Past Discuss., 11, 755-803, doi:10.5194/cpd-11-755-2015, 2015
Endless cold: a seasonal reconstruction of temperature and precipitation in the Burgundian Low Countries during the 15th century based on documentary evidence
Summary: This paper applies the methods of historical climatology to present a climate reconstruction for the area of the Burgundian Low Countries during the fifteenth century. The results are based on documentary evidence. Approximately 3000 written records deriving from about 100 different sources were examined and converted into seasonal seven-degree indices for temperature and precipitation.
Clim. Past Discuss., 11, 713-753, doi:10.5194/cpd-11-713-2015, 2015
Massive and permanent decline of symbiont bearing morozovellids and δ13C perturbations across the Early Eocene Climatic Optimum at the Possagno section (Southern Alps of northeastern Italy)
Summary: A major permanent decline in relative abundance of planktic forminiferal morozovellids is recorded from the Tethyan Possagno section and ODP Site 1051 (western subtropical North Atlantic) across the Early Eocene Climatic Optimum (EECO), the interval with the highest prolonged global temperatures over the past 70 Ma. Changes in relative abundances of planktic foraminifera at Possagno parallel negative shifts in both δ13C and δ18O of bulk sediment from Chron C24r to basal Chron C20r.
Clim. Past Discuss., 11, 671-712, doi:10.5194/cpd-11-671-2015, 2015
Trace metal evidence for a poorly ventilated glacial Southern Ocean
Summary: Trace metal (Ag, Cd, Re, Mo) concentrations in glacial-age, Atlantic sector Southern Ocean sediments that are similar to those found in modern sediments underlying oxygen minimum zones (e.g., Eastern Pacific) imply that the glacial Southern Ocean was significantly less well ventilated than present. These data point to a glacial equivalent of Lower Circumpolar Deep Water as the low-oxygen water mass, and the potential storage location of the ‘missing’ glacial CO2.
Clim. Past Discuss., 11, 637-670, doi:10.5194/cpd-11-637-2015, 2015
Modelled glacier equilibrium line altitudes during the mid-Holocene in the southern mid-latitudes
Summary: We examine the climatic forcing of glacier expansion in the mid-Holocene (MH) by evaluating modelled glacier equilibrium line altitude (ELA) and climate conditions during the MH compared with pre-industrial time (PI) in the mid latitudes of the Southern Hemisphere. Glaciers in both analysed regions have an ELA that is 15-33m lower than PI during the MH. We postulate that the modelled ELA changes, may help to explain larger glacier extents observed in the mid Holocene in both regions.
Clim. Past Discuss., 11, 603-636, doi:10.5194/cpd-11-603-2015, 2015
Coupled Northern Hemisphere permafrost-ice sheet evolution over the last glacial cycle
Summary: In this paper we explore the permafrost-ice sheet interaction using the fully coupled climate-ice sheet model CLIMBER-2 with the addition of a newly developed permafrost module. We find that permafrost has a moderate but significant effect on ice sheet dynamics during the last glacial cycle. In particular at the last glacial maximum the inclusion of permafrost leads to a 15 meter sea level equivalent increase in Northern Hemisphere ice volume when permafrost is included.
Clim. Past Discuss., 11, 555-601, doi:10.5194/cpd-11-555-2015, 2015
1200 years of warm-season temperature variability in central Fennoscandia inferred from tree-ring density
Clim. Past Discuss., 11, 489-519, doi:10.5194/cpd-11-489-2015, 2015
Temporal and spatial variability in precipitation trends in the Southeast Tibetan Plateau during 1961–2012
Clim. Past Discuss., 11, 447-487, doi:10.5194/cpd-11-447-2015, 2015
South-western Africa vegetation responses to atmospheric and oceanic changes during the last climatic cycle
Summary: We present a new pollen-based palaeoclimatic reconstruction covering the period between 190,000 and 24,000 years ago from a marine sediment core located off the Namibian coast. Our work identifies increased dryness during the three warmest periods of the last interglacial involving atmospheric and oceanic reorganizations in southern Africa that are linked to precession minima.
Clim. Past Discuss., 11, 345-376, doi:10.5194/cpd-11-345-2015, 2015
A~regional climate palaeosimulation for Europe in the period 1501–1990 – Part II: Comparison with gridded reconstructions
Clim. Past Discuss., 11, 307-343, doi:10.5194/cpd-11-307-2015, 2015
Obliquity forcing of low-latitude climate
Summary: Our study shows that the influence of obliquity (the tilt of Earth's rotational axis) can be explained through changes in the insolation gradient across the tropics. This explanation is fundamentally different from high-latitude mechanisms that were previously often inferred to explain obliquity signals in low-latitude paleoclimate records, for instance glacial fluctuations. Our study is based on state-of-the-art climate model experiments.
Clim. Past Discuss., 11, 221-241, doi:10.5194/cpd-11-221-2015, 2015
Scaling laws for perturbations in the ocean–atmosphere system following large CO2 emissions
Summary: In this paper we derive scaling relationships for perturbations to atmosphere and ocean variables from large transient CO2 emissions. We use a carbon cycle box model to calculate perturbations to a variety of ocean and atmosphere variables resulting from idealized emission events. The scaling laws obtained deviate from those based on simplified equilibrium considerations, mainly due to the multitude and diversity of time scales that govern the exchange of carbon between different reservoirs.
Clim. Past Discuss., 11, 95-134, doi:10.5194/cpd-11-95-2015, 2015