Estimating breakpoints in the Cenozoic Era: an econometric approach

The aim of the present study is to assess changes in the Baltic Sea climate based on different available meteorological data sources (ERA40 and ERA-INTERIM) and various published Baltic Sea climate indices. This regional assessment will be presented in relation to global climate change and assessments available from the literature. The climate of the Baltic Sea which is located between 50N and 70N is mainly influenced by the competition of westerly humid air flow and easterly continental type air masses and is therefore highly variable. We are investigating air temperature, wind speed, cloud cover, solar radiation and precipitation. Comparisons to climate indices of general relevance as the Baltic ice cover will be conducted. Using regression analysis we could confirm the following basic trends, increase in air temperature, increase in precipitation, increase in cloudiness. The increase in air temperature in the Baltic Sea area (0.02K/year) is much more rapid then the warming trend for the global air temperature (0.005K/year). The increase in cloudiness has resulted in an effective reduction of incoming solar radiation therefore the accelerated warming is not a result of increased solar radiation, but likely due to an increased net long wave radiation input. Further it has to be mentioned that not all available data sets confirmed the trend in cloudiness, ERA40 data show a nonsignificant decrease instead. No clear trend in the wind velocities could be detected, but wind velocities from ERA40 reanalysis project show an insignificant increase in wind speeds. Results from model runs with the GETM model (General Estuarine Transport Model, http://getm.eu) show sea surface warming consistent with the increase in heat flux forcing and with satellite observations. The warmer sea surface without an adequate warming in the deeper parts results in a much stronger vertical density stratification and consequently to reduced vertical mixing. A more thorough inspection of the available regional and global data provides some reasonable doubt concerning the application of least square regression analysis to the available time series. Indeed it can be shown by a test based on the F statistics that most of the analyzed time series cannot be considered as stationary and therefore drawing simple regression lines trough these datasets is statistically incorrect. Testing for structural breakpoints in these time series reveals for many investigated parameters and also for many tested climate indices the existence of such breakpoints in the 70-80ties of the last century. Therefore it has to be concluded that the simple trend estimation for many climate parameters is statistically incorrect. Instead for statistical investigations it has to be assumed that there exist either 2 different climate states with either 2 different means or alternatively with 2 different trends which have to be estimated separately.

<p>A new simple approach inspired by MacAyeal (1979) to explain the time-asymmetric ‘saw-toothed’ shape and 100,000-year quasi-period of glacial-interglacial cycles since the Middle Pleistocene Transition, is presented. Using a simple model with fast-slow dynamics, the global ice volume is taken to be a function of two independently varying parameters, the solar insolation and ‘alpha’, a secondary control parameter, the study of which is the focus this research. The steady state of the model is a partially folded surface in three-dimensional space where insolation, ‘alpha’, and global ice volume are orthogonal axes. The pleated surface allows for the gradual increase and sudden decrease in ice volume that is observed in the paleoclimate record. To derive a time series of global ice volume, the Euler integration method is used, producing a time series which replicates the ‘saw-toothed’ pattern of glacial cycles in the late Pleistocene. The second control parameter, ‘alpha’, is proposed to be related to internal dynamics of the climate system, such as ice sheet dynamics.</p><p> </p><p>Reference</p><p>D. R.  MacAyeal, ‘A Catastrophe Model of the Paleoclimate Record’ , Journal of Glaciology , Volume 24 , Issue 90 , 1979 , pp. 245 – 257.</p>

Abstract. Paleoclimate time series are often irregularly sampled and age uncertain, which is an important technical challenge to overcome for successful reconstruction of past climate variability and dynamics. Visual comparison and interpolation-based linear correlation approaches have been used to infer dependencies from such proxy time series. While the first is subjective, not measurable and not suitable for the comparison of many data sets at a time, the latter introduces interpolation bias, and both face difficulties if the underlying dependencies are nonlinear. In this paper we investigate similarity estimators that could be suitable for the quantitative investigation of dependencies in irregular and age-uncertain time series. We compare the Gaussian-kernel-based cross-correlation (gXCF, Rehfeld et al., 2011) and mutual information (gMI, Rehfeld et al., 2013) against their interpolation-based counterparts and the new event synchronization function (ESF). We test the efficiency of the methods in estimating coupling strength and coupling lag numerically, using ensembles of synthetic stalagmites with short, autocorrelated, linear and nonlinearly coupled proxy time series, and in the application to real stalagmite time series. In the linear test case, coupling strength increases are identified consistently for all estimators, while in the nonlinear test case the correlation-based approaches fail. The lag at which the time series are coupled is identified correctly as the maximum of the similarity functions in around 60–55% (in the linear case) to 53–42% (for the nonlinear processes) of the cases when the dating of the synthetic stalagmite is perfectly precise. If the age uncertainty increases beyond 5% of the time series length, however, the true coupling lag is not identified more often than the others for which the similarity function was estimated. Age uncertainty contributes up to half of the uncertainty in the similarity estimation process. Time series irregularity contributes less, particularly for the adapted Gaussian-kernel-based estimators and the event synchronization function. The introduced link strength concept summarizes the hypothesis test results and balances the individual strengths of the estimators: while gXCF is particularly suitable for short and irregular time series, gMI and the ESF can identify nonlinear dependencies. ESF could, in particular, be suitable to study extreme event dynamics in paleoclimate records. Programs to analyze paleoclimatic time series for significant dependencies are included in a freely available software toolbox.

Long paleoclimate time series combine strong persistence, multiple orbital cycles, and regime shifts, which complicates the analysis of dynamical coupling and predictability. We analyze Cenozoic variability using the Cenozoic global reference benthic foraminiferal carbon and oxygen isotope dataset, in a regime based time series framework that integrates deterministic decomposition, cyclical fractional cointegration, and regime aware forecasting. We divide the record into segments in line with the major Cenozoic climate states. Within each segment, deterministic components are estimated and removed, including linear trends, orbital forcing variables, and harmonic cycles identified via a GARMA based filtering procedure. We then apply cyclical fractional cointegration tests at shared orbital frequencies to assess whether common spectral peaks reflect a stable frequency specific linkage (cointegration) between the proxies and orbital variables. The results reveal pronounced regime dependence. The long eccentricity cycle (405 kyr) shows recurrent evidence of cointegration with both proxies across different climate states. For obliquity, an indication of frequency specific linkage is primarily found after the middle Miocene Climate Transition. Finally, we fit regime specific VAR(2) models to the residuals and report in-sample forecasts, and we generate a 100 kyr out-of-sample projection based on the Icehouse specific dynamics. Forecast behaviour varies across climate states, highlighting that non-stationarity and regime specific dynamics place strong constraints on predictability in long paleoclimate records.

Early–Middle Pleistocene transitions: Linking terrestrial and marine realms

Research Article| December 01, 1979 Possible relationships between changes in global ice volume, geomagnetic excursions, and the eccentricity of the Earth's orbit Michael R. Rampino Michael R. Rampino 1NASA, Goddard Institute for Space Studies, 2880 Broadway, New York, New York 10025 Search for other works by this author on: GSW Google Scholar Author and Article Information Michael R. Rampino 1NASA, Goddard Institute for Space Studies, 2880 Broadway, New York, New York 10025 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1979) 7 (12): 584–587. https://doi.org/10.1130/0091-7613(1979)7<584:PRBCIG>2.0.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Michael R. Rampino; Possible relationships between changes in global ice volume, geomagnetic excursions, and the eccentricity of the Earth's orbit. Geology 1979;; 7 (12): 584–587. doi: https://doi.org/10.1130/0091-7613(1979)7<584:PRBCIG>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract A possible relationship between major changes in global ice volume, geomagnetic variations, and short-term climate cooling has been investigated through a study of climate and geomagnetic records of the past 400,000 yr. Calculations suggest that redistribution of the Earth's water mass can cause rotational instabilities that lead to magnetic excursions; these magnetic variations in turn may lead to rapid coolings through several proposed mechanisms. Such double coincidences of magnetic excursions and sudden cooling and glacial advance at times of major ice-volume changes have occurred at about 13,500, 30,000, 110,000, and 180,000 B.P. The last four and possibly five times of maximum eccentricity of the Earth's orbit were closely followed by magnetic excursions; catastrophic cooling and rapid ice buildup accompanied several of these excursions. Thus, Milankovitch cycle parameters may lead to glaciation through both insolation changes and geomagnetic effects on climate. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Terrain methods on spectral analysis for paleoclimate interpretations: A novel visualization technique using python

Climate variables are known to be subject to abrupt changes when some threshold levels are surpassed. We use data for the last 798,000 years on global ice volume (Ice), atmospheric carbon dioxide level (CO2), and Antarctic land surface temperature (Temp) to model and measure those long-run nonlinear climate effects. The climate variables have very long and asymmetric cycles, created by periods of upward trends, followed by periods of downward trends driven by exogenous orbital variables. The exogenous orbital variables considered by the Milankovitch cycles are eccentricity of Earth’s orbit, obliquity, and precession of the equinox. We show that our new score-driven threshold ice-age models improve the statistical inference and forecasting performance of competing ice-age models from the literature. The drawback of using our 1000-year frequency observations, is that we cannot measure the nonlinear climate effects of humanity created during the last 250 years, which are known to have generated abrupt structural changes in the Earth’s climate, due to unprecedented high levels of CO2 and Temp, and low levels of Ice volume. On the other hand, the advantage of using low-frequency data is that they allow us to obtain long-run forecasts on what would have occurred if humanity had not burned fossil fuels since the start of the Industrial Revolution. These long-run forecasts can serve as benchmarks for the long-run evaluation of the impact of humanity on climate variables. Without the impact of humanity on climate, we predict the existence of turning points in the evolution of the three climate variables for the next 5,000 years: an upward trend in global ice volume, and downward trends in atmospheric CO2 level and Antarctic land surface temperature.

Differential ice volume and orbital modulation of Quaternary moisture patterns between Central and East Asia

Abstract. We develop the theory of cyclic Markov chains and apply it to the El Niño-Southern Oscillation (ENSO) predictability problem. At the core of Markov chain modelling is a partition of the state space such that the transition rates between different state space cells can be computed and used most efficiently. We apply a partition technique, which divides the state space into multidimensional cells containing an equal number of data points. This partition leads to mathematical properties of the transition matrices which can be exploited further such as to establish connections with the dynamical theory of unstable periodic orbits. We introduce the concept of most and least predictable states. The data basis of our analysis consists of a multicentury-long data set obtained from an intermediate coupled atmosphere-ocean model of the tropical Pacific. This cyclostationary Markov chain approach captures the spring barrier in ENSO predictability and gives insight also into the dependence of ENSO predictability on the climatic state.

Global glacial ice volume and Last Glacial Maximum duration from an extended Barbados sea level record

New oxygen isotope data and a high‐resolution carbonate record of a core from the northwest African margin are presented, in combination with geochemical (Zr/Rb ratio, Al, Ba, organic carbon, and biogenic opal fluxes) and sedimentological (median grain size) parameters, to show variations in African continental aridity, wind strength, and upwelling productivity. The carbonate record is diluted by the supply of aeolian dust from the arid Saharan region of north Africa and is seen to vary with a characteristic sawtooth pattern indicating rapid increases in dust flux followed by gradual declines. Spectral analysis of the carbonate profile and comparison with SPECMAP (stacked oxygen isotope) and ETP (solar radiation) profiles shows that the precessional (23 kyr) insolation‐induced African climate system is decoupled from global (ice volume) climate changes operating on a 100 kyr frequency. Detailed studies of glacial terminations I, II, and III confirm the presence of rapid, short timescale climatic variations (in aridity).

Global, Arctic, and Antarctic sea ice volume predictions using score-driven threshold climate models

&amp;lt;p&amp;gt;Accurate stable isotope stratigraphies are essential for understanding how past climates are influenced by orbital forcing. Deep-sea benthic foraminiferal &amp;amp;#948;&amp;lt;sup&amp;gt;18&amp;lt;/sup&amp;gt;O and &amp;amp;#948;&amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C stratigraphies can provide precise astronomical age control and record changes in past deep-sea ocean temperatures, global ice volume and the carbon cycle. Our understanding of Plio-Pleistocene climate dynamics has improved through the development of global (LR04; Lisiecki &amp;amp; Raymo, 2005) and regional stacks (Ceara Rise; Wilkens et al., 2017). However, the late Miocene climate system remains poorly understood, in part because the late Miocene benthic foraminiferal &amp;amp;#948;&amp;lt;sup&amp;gt;18&amp;lt;/sup&amp;gt;O stratigraphy is notoriously low amplitude.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Here, we present the first global late Miocene global benthic foraminiferal &amp;amp;#948;&amp;lt;sup&amp;gt;18&amp;lt;/sup&amp;gt;O compilation spanning 8.00-5.33 Ma. We formed a &amp;amp;#8220;Base Stack&amp;amp;#8221; using six continuous benthic stratigraphies from the Atlantic (ODP Sites 982 (N), 926 (E) and 1264 (S)) and Pacific Oceans (IODP Sites U1337 and U1338 (E), ODP Site 1146 (W)). To avoid misidentification of individual excursions between sites, we verified existing splices, generated isotope data where necessary and established independent astrochronologies. To accompany the &amp;amp;#8220;Base Stack&amp;amp;#8221;, we compiled a &amp;amp;#8220;Comprehensive Stack&amp;amp;#8221;, which incorporates single-hole benthic &amp;amp;#948;&amp;lt;sup&amp;gt;18&amp;lt;/sup&amp;gt;O stratigraphies to optimise global coverage.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The new global late Miocene benthic foraminiferal &amp;amp;#948;&amp;lt;sup&amp;gt;18&amp;lt;/sup&amp;gt;O stack represents a stratigraphic reference section back to 8.00 Ma. The stack is accurately tied to the Geomagnetic Polarity Time Scale between Chrons C3r and C4n.2n using the magnetostratigraphy from IODP Site U1337. We recognise 68 new &amp;amp;#948;&amp;lt;sup&amp;gt;18&amp;lt;/sup&amp;gt;O Marine Isotope Stages (MIS) between 7.7 and 6.5 Ma. An exceptional global response is imprinted on the dispersed sites between 7.7-6.9 &amp;amp; 6.4-5.4 Ma, when a strong 40 kyr heartbeat dominates the climate system. The origin of these cycles remains unclear. The influence of deep-sea temperature on the benthic &amp;amp;#948;&amp;lt;sup&amp;gt;18&amp;lt;/sup&amp;gt;O stack is explored at IODP Site U1337 using Mg/Ca data. The dominant 40-kyr &amp;amp;#948;&amp;lt;sup&amp;gt;18&amp;lt;/sup&amp;gt;O cycles are asymmetric, suggesting at least a partial ice volume imprint and raising the possibility that these cycles relate to early signs of northern hemisphere glaciation.&amp;lt;/p&amp;gt;

Milankovich theory suggested that orbitally induced summer insolation change at high-latitude region of Northern Hemisphere played a key role in driving the ice cycles during the Pleistocene. However, a significant shift of the Pleistocence climate from 41-ka to 100-ka cycles (namely mid-Pleistocene transition, MPT) cannot be simply attributed to the astronomical forcing due to insignificant insolation change induced by eccentricity forcing. Here we summarized multiple proxies generated from the ocean and land to address Pleistocene climate changes such as global ice volume, sea surface temperature, sea level, aridity of dust sources, and monsoon-related hydrological cycles. The temporal and spatial characteristics of the MPT phenomenon, in terms of the timing, duration, amplitudes and frequencies, were addressed using spectral and wavelet results. Most records reveal that the MPT was commenced as the onset of the ~100-ka cycles at ~1.2 Ma, and ended by the establishment of the dominant 100-ka cycles at ~0.7 Ma. However, some hydroclimatic proxies from the Mediterranean Sea, South China Sea and Chinese caves show a relatively strong 23-ka cycles during the middle to late Pleistocence. Such a difference may be attributable to varied sensitivity of proxy indicators to the insolation and glacial forcing. Globally, temperature and sea level signals that are affected by changing ice volume usually demonstrate a distinctive and consistent MPT. By contrast, regional hydroclimatic proxies at mid-to-low latitudes are likely dominated by the precession cycles (i.e. high-resolution, absolutely dated Chinese speleothem records). The MPT associated with the onset of ~100-ka cycles has inspired the paleocommunities to address its driving mechanism from both data and model perspectives. Several hypotheses have been proposed to explain the MPT in the past two decades, including nonlinear response to external forcing and complicated internal feedbacks. The nonlinear response to the astronomical forcing including eccentricity (100-ka cycle), interplay between obliquity (41-ka cycle) and precession (23- and 19-ka cycles) can produce the 100-ka ice-age cycles. However, model results suggest that the MPT and subsequent ″100 ka world″ are likely caused by changes in atmospheric CO2 concentration, bedrock exposure or ocean circulations. Taking these different hypotheses together, it was suggested that the solar insolation caused by changing Earth′s orbital parameters as external forcing, drives the glacial-interglacial climate cycles, whilst the nonlinear responses to atmospheric CO2 decrease and to different regolith boundary conditions as internal feedbacks have played key roles in triggering the climate transition and amplifying the glacial-interglacial oscillations. While most proxies from the land and ocean demonstrate a remarkable MPT from 41- to 100-ka cycles, regional high-resolution proxy records indicated that hydroclimatic changes at mid-to-low latitudes exhibit insignificant MPT and weak ~100-ka cycles after the MPT. In the future, more data assimilation should be focused on the hydroclimatic changes particularly in monsoon-affected regions to decipher the diverse responses in a regional scale. Meanwhile, simulations using high-resolution regional climate system models should be performed to quantify the responses of different climate parameters to external forcing and internal feedback. Through intensively data-model comparison, new insights into past climate variability and dynamics will permit a better projection of future climate change under the global warming context.