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Time series of Meltwater Pulses: (a) MWP-1; (b) MWP-2; (c) MWP-3 (see text for details). The colours identify where the MWPs are applied: blue, equally at ocean gridboxes in the Atlantic zone 50–70 @BULLET N; red, equally at coastal ocean gridboxes around Antarctica.
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A new Earth System Model of Intermediate Complexity, GENIE-1, is used to simulate the most recent glacial-interglacial cycle by prescribing orbital forcing, atmospheric CO<sub>2</sub> concentration, and the time evolution of ice sheet extent and orography. A series of experiments investigates uncertainty in the amplitude, frequency and location of...
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The present paper introduces an analytical ap-proach for the description of the soil water balance dynam-ics over a schematic river basin. The model is based on a stochastic differential equation where the rainfall forcing is interpreted as an additive noise in the soil water balance. This equation can be solved assuming known the spatial distribu-...
Citations
... 4) Modeled. Theoretical models of ocean characteristics based on either physical or statistical simulations of the behavior of water (see Marsh et al. 2006). 5) Created. ...
Bringing together research on human impacts on marine environments, cultural representation, and geographic information systems (GIS), we explore new approaches to digitally representing the anthropogenic ocean. Marine environments present vexing subjects to capture digitally. Complex physical and biological oceanography, invisible boundaries, ambiguous legal controls, conflicts between multiple stakeholders over subsistence and commercial marine resources, and cultural variations in core ocean epistemologies complicate our ability to model historical and contemporary human interactions with the marine environment. Academic focus on the concept of the Anthropocene within geography, together with critical GIS studies, open new possibilities to transcend division between natural and social sciences. We propose an object-oriented, multiscalar framework for a database of anthropogenic ocean layers that represent human-ocean interactions. We outline strategies for digitally representing human experiences of maritime space and introduce a prototype GIS data structure for its delivery.
... Oxygen Isotope Stage 3 (OIS3; 60-25 thousand calendar years ago, henceforth ka cal BP) was characterized in the North Atlantic by a series of millennial-scale climate oscillations that abruptly switched from relatively cold to warm atmospheric conditions (known as Dansgaard-Oeschger or Greenland interstadials; D-O and GI) with associated environmental changes (Bond et al., 1993;Wolff et al., 2010) including massive discharges of ice rafted debris associated with the collapse of ice sheets (Heinrich or 'H-' events) (Bond et al., 1993). Although D-O events have been linked to changes in the strength of the Meridional Overturning Circulation (Marsh et al., 2006), their exact relationship to changes preserved in the Greenland ice sheet (Austin et al., 2012) and whether they were global in extent remains uncertain (EPICA, 2006;Thomas et al., 2011). Against a backdrop of rapid climate change intervals, human migration and extinction was taking place around the world (Fifield et al., 2001;Finlayson et al., 2006;Higham et al., 2011). ...
... Braconnot et al. 2007; Lunt et al. 2008 ). Transient simulations of glacial cycles have hitherto only been run with models where important climate processes such as clouds or atmospheric moisture transports are more crudely parameterised than in an AOGCM or omitted entirely (e.g. Marsh et al. 2006; Ganopolski et al. 2010; Holden et al. 2010). The heavy restrictions on the feedbacks involved in such models limit what we can learn of the evolution of the climate from them, particularly in paleoclimate states that may be significantly different from the better-known modern climates which the models are formulated to reproduce. ...
Using FAMOUS, a fast atmosphere-ocean general circulation model (AOGCM), a number of transient climate runs simulating the last 120kyr have been carried out. This is the first time such experiments have been done with an AOGCM, providing a three-dimensional simulation of both atmosphere and ocean over this period, including internally generated temporal variability over periods from days to millennia and physically detailed representations of important processes such as clouds and precipitation. Although the model is fast, computational restrictions mean that the rate of change of the forcings has been increased by a factor of 10, making each experiment 12kyr long. Atmospheric greenhouse gases (GHGs), northern hemisphere ice sheets and variations in solar radiation arising from changes in the Earth's orbit are treated as forcing factors, and are applied both separately and combined in different experiments. The long-term temperature changes on Antarctica match well with reconstructions derived from ice-core data, as does variability on timescales longer than 10kyr. Last Glacial Maximum (LGM) cooling on Greenland is reasonably well simulated, although our simulations do not reproduce the abrupt, millennial scale climate shifts seen in northern hemisphere climate proxies or their slower southern hemisphere counterparts. The spatial pattern of sea surface cooling at the LGM matches reasonably proxy reconstructions reasonably well. There is significant anti-correlated variability in the strengths of the Atlantic Meridional Overturning Circulation (AMOC) and the Antarctic Circumpolar Current (ACC) on timescales greater than 10kyr in our experiments. GHG forcing weakens the AMOC and strengths the ACC, whilst the presence of northern hemisphere icesheets strengthens the AMOC and weakens the ACC. The structure of the AMOC at the LGM is found to be sensitive to the details of the ice-sheet reconstruction used. The precessional component of the orbital forcing induces ~20kyr oscillations in the AMOC and ACC, whose amplitude is mediated by changes in the eccentricity of the Earth's orbit. These forcing influences combine, to first order, in a linear fashion to produce the ocean variability seen in the run with all forcings and set the deep-water properties of the global ocean, which is key to determining the carbon inventory of the glacial ocean.
... However, in order to understand the physical mechanisms responsible for abrupt climate change and to identify the existence of leads, lags and phase-relationships in the climate system, it is mandatory to simulate the temporal evolution of the system in response to the time-varying forcing factors. Recently the transient modeling framework has been applied to climate models to understand the Late Quaternary climate evolution and its relation to slowly-varying boundary conditions (Jackson and Broccoli, 2003;Felis et al., 2004;Lorenz and Lohmann, 2004;Charbit et al., 2005;Tuenter et al., 2005;Renssen et al., 2005;Lorenz et al., 2006;Lunt et al., 2006;Marsh et al., 2006;Timmermann et al., 2007Timmermann et al., , 2009a; Timm and Timmermann, 2007;Liu et al., 2009;Timmermann and Menviel, 2009). We recently presented a transient model solution for the Last Glacial Termination using the Earth system model of intermediate complexity LOVECLIM that was driven by changes in greenhouse gases, icesheet topography and albedo and orbitally-induced changes in solar radiation (Timm and Timmermann, 2007). ...
... The model was spun-up to equilibrium for 40,000 yr with 50 ka BP fixed boundary conditions. These include 50 ka estimated ice sheet extent and orbit (Marsh et al., 2006). Atmospheric CO 2 was prescribed at 220 ppmv (Petit et al., 1999) and relative geomagnetic intensity, M/ M 0 = 1 (Laj et al., 2004). ...
We present a new speleothem record of atmospheric Δ14C between 28 and 44 ka that offers considerable promise for resolving some of the uncertainty associated with existing radiocarbon calibration curves for this time period. The record is based on a comprehensive suite of AMS 14C ages, using new low-blank protocols, and U–Th ages using high precision MC-ICPMS procedures. Atmospheric Δ14C was calculated by correcting 14C ages with a constant dead carbon fraction (DCF) of 22.7 ± 5.9%, based on a comparison of stalagmite 14C ages with the IntCal04 (Reimer et al., 2004) calibration curve between 15 and 11 ka. The new Δ14C speleothem record shows similar structure and amplitude to that derived from Cariaco Basin foraminifera (Hughen et al., 2004, 2006), and the match is further improved if the latter is tied to the most recent Greenland ice core chronology (Svensson et al., 2008). These data are however in conflict with a previously published 14C data set for a stalagmite record from the Bahamas — GB-89-24-1 (Beck et al., 2001), which likely suffered from 14C analytical blank subtraction issues in the older part of the record. The new Bahamas speleothem ∆14C data do not show the extreme shifts between 44 and 40 ka reported in the previous study (Beck et al., 2001). Causes for the observed structure in derived atmospheric Δ14C variation based on the new speleothem data are investigated with a suite of simulations using an earth system model of intermediate complexity. Data-model comparison indicates that major fluctuations in atmospheric ∆14C during marine isotope stage 3 is primarily a function of changes in geomagnetic field intensity, although ocean–atmosphere system reorganisation also played a supporting role.
... This severe bias in the insolation forcing could lead to significantly different model interpretations. [7] With the growing number of transient paleosimulations [Jackson and Broccoli, 2003; Felis et al., 2004; Lorenz and Lohmann, 2004; Tuenter et al., 2005; Lorenz et al., 2006; Renssen et al., 2005; Charbit et al., 2005; Lunt et al., 2006; Marsh et al., 2006; Timmermann et al., 2007; Timm and Timmermann, 2007], an estimate of the time-dependent biases due to the fixed calendar becomes important. [8] In this paper we present a comparison of the differences between fixed calendar day seasons and fixed angular seasons. ...
1] Orbital forcing is a major driver of climate variability on timescales of 10,000 to 100,000 years. Changes in the orbital parameters cause variations in the length of the seasons by several days. Consequently, models using a fixed present-day calendar result in biased paleoseasons, especially in boreal autumn when the vernal equinox is used as an anchor point. The bias is estimated for temperatures and precipitation in a transient model simulation over the last 21,000 years and an accelerated simulation over the last 129,000 years. The largest differences of up to 4 K occur over the continents in high latitudes. Precipitation estimates are mostly affected in the low latitudes. The time-dependent bias is large enough to modify the temporal characteristics of temperature and precipitation indices. It is discussed to what extent the bias in one season is distorting comparisons between models and paleoproxies. The bias has minor implications for proxy-model comparisons in general. However, proxies of monsoon activity should be compared with fixed angular seasons. For process studies and climate sensitivity studies the use of fixed angular seasons is imperative. (2008), On the definition of seasons in paleoclimate simulations with orbital forcing, Paleoceanography, 23, PA2221, doi:10.1029/2007PA001461.
... [7] With the growing number of transient paleosimulations [Jackson and Broccoli, 2003;Felis et al., 2004;Lorenz and Lohmann, 2004;Tuenter et al., 2005;Lorenz et al., 2006;Renssen et al., 2005;Charbit et al., 2005;Lunt et al., 2006;Marsh et al., 2006;Timmermann et al., 2007;Timm and Timmermann, 2007], an estimate of the time-dependent biases due to the fixed calendar becomes important. ...
... The more complex GENIE-land surface plus TRIFFID have also been coupled under the EMBM, as in the UVic model (Meissner et al., 2003). The physical core of GENIE-1 using ENTS with fixed vegetation cover, and prescribed changes in ice sheet cover, orography, orbital forcing and CO 2 has been used for transient simulations of the last deglaciation (Lunt et al., 2006), and recently, the whole of the last glacial-interglacial cycle (Marsh et al., 2006). GENIE-1 has also recently been coupled to MERGE to form a detailed, consistent IAM with a closed carbon cycle. ...
... The transient paleoclimate modeling strategy has only recently been introduced to more comprehensive climate models that include at least one threedimensional component (e.g., Claussen et al. 1999;Crucifix et al. 2002;Lorenz and Lohmann 2004;Lorenz et al. 2006;Felis et al. 2004;Liu et al. 2004;Renssen et al. 2005b;Charbit et al. 2005;Lunt et al. 2006;Marsh et al. 2006). The transient simulations start from an appropriate initial state and are forced with time-varying boundary conditions. ...
The earth system model of intermediate complexity ECBilt-CLIO has been used for transient simulations of the last deglaciation and the Holocene. The forcing effects of the ice sheets, greenhouse gas concentrations, and orbital configurations are prescribed as time-varying boundary conditions. In this study two key aspects of the transient simulations are investigated, which are of broader relevance for long-term transient paleoclimate modeling: the effect of using accelerated boundary conditions and of uncertainties in the initial state. Simulations with nonaccelerated boundary conditions and an acceleration factor 10 were integrated. These simulations show that the acceleration can have a significant impact on the local climate history. In the outcropping regions of the high southern latitudes and the convective regions in the North Atlantic, the acceleration leads to damped and delayed temperature response to the boundary conditions. Furthermore, uncertainties in the initial state can strongly bias the climate trajectories in these areas over 500-700 model years. The affected oceanic regions are connected to the large heat capacities of the interior ocean, which cause a strong delay in the response to the forcing. Despite the shown difficulties with the acceleration technique, the accelerated simulations still reproduce the large-scale trend pattern of air temperatures during the Holocene from previous simulations with different models. The accelerated transient model simulation is compared with existing proxy time series at specific sites. The simulation results are in good agreement with those paleoproxies. It is shown that the transient simulations provide valuable insight into whether seasonal or annual signals are recorded in paleoproxies.
... The more complex GENIE-land surface plus TRIFFID have also been coupled under the EMBM, as in the UVic model (Meissner et al., 2003). The physical core of GENIE-1 using ENTS with fixed vegetation cover, and prescribed changes in ice sheet cover, orography, orbital forcing and CO 2 has been used for transient simulations of the last deglaciation (Lunt et al., 2006), and recently, the whole of the last glacial-interglacial cycle (Marsh et al., 2006). GENIE-1 has also recently been coupled to MERGE to form a detailed, consistent IAM with a closed carbon cycle. ...
The Grid ENabled Integrated Earth system modelling (GENIE) frame-work supports modularity (i.e. interchangeable components) and scala-bility (i.e. variable resolution of the components), which aids traceability, meaning the ability to relate the process representation and results for different module choices and/or resolutions to one another. Here for each of the main components of the Earth system, we discuss the appropriate modelling approaches for our goals and introduce the component models adopted thus far. We describe their coupling to produce a range of com-putationally efficient Earth system models (ESMs) that span a spectrum from intermediate toward full complexity, and summarise the experiments undertaken with them thus far.
