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.
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.
M. Naulier, M. M. Savard, C. Bégin, F. Gennaretti, D. Arseneault, J. Marion, A. Nicault, and Y. Bégin Clim. Past Discuss., 11, 521-553, 2015 AbstractDiscussion Paper (PDF, 2829 KB)Interactive Discussion (Open, 1 Comment)Manuscript under review for CP
20 Feb 2015
1200 years of warm-season temperature variability in central Fennoscandia inferred from tree-ring density
Climate dependent contrast in surface mass balance in East Antarctica over the past 216 kyr
F. Parrenin, S. Fujita, A. Abe-Ouchi, K. Kawamura, V. Masson-Delmotte, H. Motoyama, F. Saito, M. Severi, B. Stenni, R. Uemura, and E. Wolff Clim. Past Discuss., 11, 377-405, 2015 AbstractDiscussion Paper (PDF, 645 KB)Interactive Discussion (Open, 1 Comment)Manuscript under review for CP
17 Feb 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.
A~regional climate palaeosimulation for Europe in the period 1501–1990 – Part II: Comparison with gridded reconstructions
J. J. Gómez-Navarro, O. Bothe, S. Wagner, E. Zorita, J. P. Werner, J. Luterbacher, C. C. Raible, and J. P. Montávez Clim. Past Discuss., 11, 307-343, 2015 AbstractDiscussion Paper (PDF, 5014 KB)Supplement (6552 KB)Interactive Discussion (Open, 1 Comment)Manuscript under review for CP
13 Feb 2015
Paleoclimate forcing by the solar De Vries/Suess cycle
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.
C. J. Hollis, B. R. Hines, K. Littler, V. Villasante-Marcos, D. K. Kulhanek, C. P. Strong, J. C. Zachos, S. M. Eggins, L. Northcote, and A. Phillips Clim. Past Discuss., 11, 243-278, 2015 AbstractDiscussion Paper (PDF, 698 KB)Supplement (235 KB)Interactive Discussion (Open, 1 Comment)Manuscript under review for CP
12 Feb 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.
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.
The effects of past climate variability on fire and vegetation in the cerrãdo savanna ecosystem of the Huanchaca Mesetta, Noel Kempff Mercado National Park, NE Bolivia
Summary: A 14,500-year, high-resolution, sedimentary record from Huanchaca Mesetta, a palm swamp located in the cerrãdo savanna in northeastern Bolivia, was analyzed for phytoliths, stable isotopes and charcoal. A non-analogue, cold-adapted vegetation community dominated the Late Glacial-Early Holocene period (14.5-9ka), that included trees and C3 Pooideae and C4 Panicoideae grasses. The Late Glacial vegetation was fire sensitive and fire activity during this period was low, likely responding to fuel ava
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.
Strong winter monsoon wind causes surface cooling over India and China in the Late Miocene
Summary: Our climate model results suggest that a stronger-than-present winter monsoon wind may account for the cooler winter temperature in southern China and northern India in the Late Miocene as indicated by the proxy data. The strong winter monsoon wind in the Late Miocene can be attributed to the lower elevation of the northern Tibetan Plateau and mountains north of it. The modern-like winter monsoon variation may not have been established in the Late Miocene.
How might the North American ice sheet influence the Northwestern Eurasian climate?
Summary: The present study investigates the potential impact of the North American ice sheet on the surface mass balance of the Eurasian ice sheet through changes in the past glacial atmospheric circulation. Using an atmospheric circulation model and an ice-sheet model, we show that the albedo of the American ice sheet favors the growth of the Eurasian ice sheet, whereas the topography of the American ice sheet leads to more ablation over the North eurasia, and therefore to a smaller Eurasian ice sheet.
New insights into the reconstructed temperature in Portugal over the last 400 years
J. A. Santos, M. F. Carneiro, A. Correia, M. J. Alcoforado, E. Zorita, and J. J. Gómez-Navarro Clim. Past Discuss., 11, 1-25, 2015 AbstractDiscussion Paper (PDF, 1345 KB)Interactive Discussion (Open, 2 Comments)Manuscript under review for CP
06 Jan 2015
Multiscale monsoon variability during the last two climatic cycles inferred from Chinese loess and speleothem records
Summary: The key finding is to decompose the orbital and millennial signals from loess and speleothem records over 260 kyr, permitting an evaluation of the relative contributions of these signals in the East Asian monsoon records. Our work suggests equivalent glacial and orbital impacts on the loess grain size changes and a dominant precession forcing in the speleothem δ18O variability. The millennial signals are evident in both proxies, and are closely linked to high-latitude Northern Hemisphere climate
Reconciling reconstructed and simulated features of the winter Pacific–North-American pattern in the early 19th century
Summary: A discrepancy exists between reconstructed and simulated Pacific North American pattern (PNA) features during the early 19th century. Pseudo-reconstructions demonstrate that the available PNA reconstruction is potentially skillful but also potentially affected by a number of sources of uncertainty and deficiencies especially at multidecadal and centennial timescales. Simulations and reconstructions can be reconciled by attributing the reconstructed PNA features to internal variability.