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
A millennial summer temperature reconstruction for northeastern Canada using oxygen isotopes in subfossil trees
Summary: This paper presents a millennial δ18O series and the reconstruction of the maximal temperature. The maximal replication and annual resolution have been obtained by using cohort sampling method. Three contrasted climatic periods have been identified: the medieval warm period (~997-1250; the warmest), the little ice age (~1450-1880) and the modern period (1970-2000) that is one of the fastest warming over the last millenium.The solar activity is proposed to being the main forcing on temperature minima.
Clim. Past Discuss., 11, 521-553, doi:10.5194/cpd-11-521-2015, 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
Volcanic synchronization of Dome Fuji and Dome C Antarctic deep ice cores over the past 216 kyr
Clim. Past Discuss., 11, 407-445, doi:10.5194/cpd-11-407-2015, 2015
Climate dependent contrast in surface mass balance in East Antarctica over the past 216 kyr
Clim. Past Discuss., 11, 377-405, doi:10.5194/cpd-11-377-2015, 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
Paleoclimate forcing by the solar De Vries/Suess cycle
Clim. Past Discuss., 11, 279-305, doi:10.5194/cpd-11-279-2015, 2015
Onset of the Paleocene–Eocene Thermal Maximum in the southern Pacific Ocean (DSDP Site 277, Campbell Plateau)
Summary: Re-examination of a Deep Sea Drilling Project sediment core (DSDP Site 277) from the western Campbell Plateau has identified the initial phase of the Paleocene-Eocene Thermal Maximum (PETM) within nannofossil chalk, the first record of the PETM in an oceanic setting in the southern Pacific Ocean (paleolatitude of ~65°S). Geochemical proxies indicate that intermediate and surface waters warmed by ~6° at the onset of the PETM prior to the full development of the negative δ13C excursion.
Clim. Past Discuss., 11, 243-278, doi:10.5194/cpd-11-243-2015, 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
Tropical cyclone genesis across palaeoclimates
Summary: Here we diagnose patterns associated with the formation of tropical cyclones (such as hurricanes and typhoons) in model simulations of the past. The global number of storms formed each year is pretty constant, despite the dramatic changes in temperature of say the last glacial maximum or the warm Pliocene. There are, however, coherent shifts in the relative strength of the storm regions. Little connections appears the past storm behaviour in the five models studied and their future projections.
Clim. Past Discuss., 11, 181-220, doi:10.5194/cpd-11-181-2015, 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