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, 0 Comments)Manuscript under review for CP
06 Jan 2015
Eastern Mediterranean Sea circulation inferred from the conditions of S1 sapropel deposition
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
The sharp decline of East Asian summer monsoon at mid-Holocene indicated by the lake-wetland transition in the Sanjiang Plain, northeastern China
Summary: The results show that the shallow-water lakes have developed in low-lying areas of the plain before 4600 yr BP, corresponding to the Holocene monsoon maximum. Thereafter, the wetlands began to initiate with the extinction of the paleolakes, marking a lake-shrinking stage with the relative dry climate.We suggest the lake-wetland transition at 4600 yr BP indicate a sharp decline of the summer monsoon.
Thermal evolution of the western South Atlantic and the adjacent continent during Termination 1
Summary: Here we show that temperatures in the western South Atlantic increased markedly during the major slowdown event of the Atlantic meridional overturning circulation (AMOC) of the last deglaciation. Over the adjacent continent, however, temperatures followed the rise in atmospheric carbon dioxide, lagging changes in oceanic temperature. Our records corroborate the notion that the long duration of the major slowdown event of the AMOC was fundamental to drive the Earth out of the last glacial.
Technical Note: Probabilistically constraining proxy age–depth models within a Bayesian hierarchical reconstruction model
Summary: We present a Bayesian approach to simultaneously constrain the age models associated with time-uncertain proxies and inferring past climate in space and time. For the sake of exposition, discussion focusses on annually resolved climate archives, such as varved lakes, corals and tree rings, with dating by layer counting. Numerical experiments show that updating the probabilities associated with an ensemble of possible age models reduces uncertainty in the inferred 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.