Earth System Components Research Articles

Importance of structure and its measurement in quantifying function of forest ecosystems

The structure of forests, the three‐dimensional arrangement of individual trees, has a profound effect on how ecosystems function and cycle carbon, water, and nutrients. The increased need to understand local to global dynamics of ecosystems, a prerequisite to understand the coupling of the biosphere to other components of Earth systems, has created a demand for extensive ecosystem structure data. Repeated satellite observations of vegetation patterns in two dimensions have made significant contributions to our understanding of the state and dynamics of the global biosphere. Recent advances in remote sensing technology allow us to view the biosphere in three dimensions and provide us with refined measurements of horizontal, as well as vertical, structure of forests. This paper provides an introductory review of the importance of the three‐dimensional characterization of terrestrial ecosystem structure of forests and woodlands and its potential measurement from space. We discuss the relevance of these measurements for reducing the uncertainties of terrestrial carbon cycle and the response of ecosystems to future climate. By relating the 3‐D structure to forest biomass, carbon content, disturbance characteristics, and habitat diversity, we examine the requirements for future satellite sensors in terms of precision and spatial and temporal resolutions. In particular, we focus this review on measurements from lidar and radar sensors that provide vertical and horizontal characterization of vegetation and are currently recommended for next generation of NASA's Earth observing and European Earth Explorer systems.

Tipping elements in the Earth System

The Earth System (ES) is defined as the conglomerate formed by human civilization and its planetary matrix (i.e., all parts of the Earth that interact with the members and manifestations of our species) (1, 2). Thus, eminently complex systems like the global economy or the human brain are just components of the ES, contributing to its overall evolution. The climate machinery is another formidable subsystem that comprises vast domains of the atmosphere, hydrosphere, biosphere, and pedosphere, involves innumerable intertwined processes, and generates fairly robust dynamical patterns like the Hadley cell. This machinery still operates in the “Holocene mode,” which emerged ≈10 ka ago and is characterized by a distinctive distribution of ice sheets, wind regimes, ocean currents, biomes, and deserts, something that can be perceived as the environmental face of the Earth. Although one of the ES components mentioned above, the global economy, is about to inadvertently transform that face through massive emissions of greenhouse gases (GHGs) and the so-induced planetary warming, one other crucial component, the human brain, struggles to advertently preserve it by constructing clumsy institutions like the United Nations Framework Convention on Climate Change (http://unfccc.int/resource/docs/convkp/conveng.pdf). The ultimate objective of this convention is to avoid dangerous climate change, a target that can be operationalized with the help of recent scientific evidence including the results presented in this Special Feature. Now, what features establish the identity of a face; what distortions erase that identity beyond recognition? The first question can be best answered by cartoonists, whereas the second related one can be addressed in terms of mathematical mapping. An affine (i.e., linear) transformation may stretch or shear the face but cannot wipe out its character. Smooth nonlinear … 1E-mail: director{at}pik-potsdam.de

Multidisciplinary Perspectives in Marine Biogeochemistry and Ecology: Fourth Annual Ocean Carbon and Biogeochemistry Summer Workshop; Woods Hole, Massachusetts, 20–23 July 2009

The Ocean Carbon and Biogeochemistry (OCB) program is a coordinating body for the U.S. research community that focuses on the ocean's role as a component of the global Earth system, bringing together research in geochemistry, ocean physics, and ecology. The fourth annual Ocean Carbon and Biogeochemistry summer workshop convened 147 participants at Woods Hole Oceanographic Institution, in Massachusetts.The workshop opened with a session on the next U.S. Carbon Cycle Science Plan (CCSP) that included presentations highlighting the priorities of the next CCSP and providing atmospheric, oceanic, terrestrial, social science, and decision support perspectives. An interdisciplinary panel of CCSP working group members then fielded audience questions and solicited feedback from the OCB community, which focused primarily on CCSP scope, ocean research and observing system priorities, and more effective integration with social science and decision support communities.

Separation of atmosphere‐ocean‐vegetation feedbacks and synergies for mid‐Holocene climate

We determine both the impact of atmosphere‐ocean and atmosphere‐vegetation feedback, and their synergy on northern latitude climate in response to the orbitally‐induced changes in mid‐Holocene insolation. For this purpose, we present results of eight simulations using the general circulation model ECHAM5‐MPIOM including the land surface scheme JSBACH with a dynamic vegetation module. The experimental set‐up allows us to apply a factor‐separation technique to isolate the contribution of dynamic Earth system components (atmosphere, atmosphere‐ocean, atmosphere‐vegetation, atmosphere‐ocean‐vegetation) to the total climate change signal. Moreover, in order to keep the definition of seasons consistent with insolation forcing, we define the seasons on an astronomical basis. Our results reveal that north of 40°N atmosphere‐vegetation feedback (maximum in spring of 0.08°C) and synergistic effects (maximum in winter of 0.25°C) are weaker than in previous studies. The most important modification of the orbital forcing is related to the atmosphere‐ocean component (maximum in autumn of 0.78°C).

Climate change mitigation: trade-offs between delay and strength of action required

Climate change mitigation via a reduction in the anthropogenic emissions of carbon dioxide (CO2) is the principle requirement for reducing global warming, its impacts, and the degree of adaptation required. We present a simple conceptual model of anthropogenic CO2 emissions to highlight the trade off between delay in commencing mitigation, and the strength of mitigation then required to meet specific atmospheric CO2 stabilization targets. We calculate the effects of alternative emission profiles on atmospheric CO2 and global temperature change over a millennial timescale using a simple coupled carbon cycle-climate model. For example, if it takes 50 years to transform the energy sector and the maximum rate at which emissions can be reduced is −2.5% \(\text{year}^{-1}\), delaying action until 2020 would lead to stabilization at 540 ppm. A further 20 year delay would result in a stabilization level of 730 ppm, and a delay until 2060 would mean stabilising at over 1,000 ppm. If stabilization targets are met through delayed action, combined with strong rates of mitigation, the emissions profiles result in transient peaks of atmospheric CO2 (and potentially temperature) that exceed the stabilization targets. Stabilization at 450 ppm requires maximum mitigation rates of −3% to −5% \(\text{year}^{-1}\), and when delay exceeds 2020, transient peaks in excess of 550 ppm occur. Consequently tipping points for certain Earth system components may be transgressed. Avoiding dangerous climate change is more easily achievable if global mitigation action commences as soon as possible. Starting mitigation earlier is also more effective than acting more aggressively once mitigation has begun.

Ocean Carbon Cycling and Climate Impacts on Marine Ecosystems: Third Annual Ocean Carbon and Biogeochemistry Summer Science Workshop 2008; Woods Hole, Massachusetts, 21–24 July 2008

The Ocean Carbon and Biogeochemistry (OCB) program is a coordinating body for the U.S. research community that focuses on the ocean's role as a component of the global Earth system, bringing together research in geochemistry, ocean physics, and ecology to advance our understanding of ocean biogeochemistry. The third annual OCB summer science workshop, sponsored by the U.S. National Science Foundation, took place at Woods Hole Oceanographic Institution, convening 147 participants.Daily plenary and poster sessions focused on three interdisciplinary themes: (1) climate sensitivity of ecosystem structure and associated impacts on biogeochemical cycles, (2) carbon uptake and storage, and (3) temporal trends in ecosystem variability.

Advancing the Integration of Marine Ecosystem Dynamics and Biogeochemistry: Second Annual Ocean Carbon and Biogeochemistry Summer Workshop; Woods Hole, Massachusetts, 23–26 July 2007

The Ocean Carbon and Biogeochemistry (OCB) program, a scientific community‐driven coordinating body designed to promote U.S. research and international cooperation, focuses on the ocean's role as a component of the global Earth system, bringing together research in geochemistry, ocean physics, and ecology to advance our understanding of ocean biogeochemistry. The second annual OCB summer science workshop, sponsored by the National Science Foundation, took place at Woods Hole Oceanographic Institution, convening 155 participants.Plenary sessions focused on three broad interdisciplinary themes: (1) interplay between biotic structure and biogeochemical cycles, (2) changing ocean biogeochemistry, and (3) terrestrial/coastal ocean cross‐boundary fluxes.

Evidence for last interglacial chronology and environmental change from Southern Europe.

Establishing phase relationships between earth-system components during periods of rapid global change is vital to understanding the underlying processes. It requires records of each component with independent and accurate chronologies. Until now, no continental record extending from the present to the penultimate glacial had such a chronology to our knowledge. Here, we present such a record from the annually laminated sediments of Lago Grande di Monticchio, southern Italy. Using this record we determine the duration (17.70 +/- 0.20 ka) and age of onset (127.20 +/- 1.60 ka B.P.) of the last interglacial, as reflected by terrestrial ecosystems. This record also reveals that the transitions at the beginning and end of the interglacial spanned only approximately 100 and 150 years, respectively. Comparison with records of other earth-system components reveals complex leads and lags. During the penultimate deglaciation phase relationships are similar to those during the most recent deglaciation, peaks in Antarctic warming and atmospheric methane both leading Northern Hemisphere terrestrial warming. It is notable, however, that there is no evidence at Monticchio of a Younger Dryas-like oscillation during the penultimate deglaciation. Warming into the first major interstadial event after the last interglacial is characterized by markedly different phase relationships to those of the deglaciations, warming at Monticchio coinciding with Antarctic warming and leading the atmospheric methane increase. Diachroneity is seen at the end of the interglacial; several global proxies indicate progressive cooling after approximately 115 ka B.P., whereas the main terrestrial response in the Mediterranean region is abrupt and occurs at 109.50 +/- 1.40 ka B.P.

Potential impact of climate change on marine export production

Future climate change will affect marine productivity, as well as other many components of Earth system. We have investigated the response of marine productivity to global warming with two different ocean biogeochemical schemes and two different atmosphere‐ocean coupled general circulation models (GCM). Both coupled GCMs were used without flux correction to simulate climate response to increased greenhouse gases (+1% CO2/yr for 80 years). At 2×CO2, increased stratification leads to both reduced nutrient supply and increased light efficiency. Both effects drive a reduction in marine export production (−6%), although regionally changes can be both negative and positive (from −15% zonal average in the tropics to +10% in the Southern Ocean). Both coupled models and both biogeochemical schemes simulate a poleward shift of marine production due mainly to a longer growing season at high latitudes. At low latitudes, the effect of reduced upwelling prevails. The resulting reduction in marine productivity, and other marine resources, could become detectable in the near future, if appropriate long‐term observing systems are implemented.

The Response of the Coupled Arctic Sea Ice–Atmosphere System to Orbital Forcing and Ice Motion at 6 kyr and 115 kyr BP

Abstract A coupled atmosphere–mixed layer ocean GCM (GENESIS2) is forced with altered orbital boundary conditions for paleoclimates warmer than modern (6 kyr BP) and colder than modern (115 kyr BP) in the high-latitude Northern Hemisphere. A pair of experiments is run for each paleoclimate, one with sea-ice dynamics and one without, to determine the climatic effect of ice motion and to estimate the climatic changes at these times. At 6 kyr BP the central Arctic ice pack thins by about 0.5 m and the atmosphere warms by 0.7 K in the experiment with dynamic ice. At 115 kyr BP the central Arctic sea ice in the dynamical version thickens by 2–3 m, accompanied by a 2 K cooling. The magnitude of these mean-annual simulated changes is smaller than that implied by paleoenvironmental evidence, suggesting that changes in other earth system components are needed to produce realistic simulations. Contrary to previous simulations without atmospheric feedbacks, the sign of the dynamic sea-ice feedback is complicated and...

Taking a clear look at cloud‐covered oceanic islands on a seasonal basis

All‐weather spaceborne imaging of isolated oceanic islands is opening the door to some new, previously unfeasible studies of global environmental change.The first orbital synthetic aperture radar (SAR) views of some relatively small,yet important islands have provided icecover and other data that until recently have been impossible to gather.These islands, whose geologic histories are dominated by the interactions of volcanism, glacier dynamics, and marine erosion, are often cloud enshrouded but can be monitored by SAR regardless of cloud cover or solar illumination.Oceanic islands are often overlooked components of the global Earth system. Yet their landscapes and ecosystems provide natural laboratories for investigating the effects of various natural and anthropogenic forcing factors in an essentially closed, controlled environment.

Perspectives for regional earth system modeling

The recent development of regional climate models which can potentially produce long-term (multi-year to multi-decadal) simulations at high spatial resolution (5–50 km), opens a range of possibilities for interactive coupling with ecosystem, hydrology, ocean-sea-ice and chemistry models on the regional scale. Such coupling offers two primary advantages: (1) It is accomplished at scales more consistent with regional processes and available models; (2) It allows the explicit description of fine scale interactions between different Earth System components. A discussion of available models, strategies for coupling and issues which would especially benefit from an integrated regional modeling approach is presented.

Terrestrial biogeochemical cycles: global interactions with the atmosphere and hydrology

Ecosystem scientists have developed a body of theory to predict the behavior of biogeochemical cycles when exchanges with other ecosystems are small or prescribed. Recent environmental changes make it clear that linkages between ecosystems via atmospheric and hydrological transport have large effects on ecosystem dynamics when considered over time periods of a decade to a century, time scales relevant to contemporary humankind. Our ability to predict behavior of ecosystems coupled by transport is limited by our ability (1) to extrapolate biotic function to large spatial scales and (2) to measure and model transport. We review developments in ecosystem theory, remote sensing, and geographical information systems (GIS) that support new efforts in spatial modeling. A paradigm has emerged to predict behavior of ecosystems based on understanding responses to multiple resources (e.g., water, nutrients, light). Several ecosystem models couple primary production to decomposition and nutrient availability using the above paradigm. These models require a fairly small set of environmental variables to simulate spatial and temporal variation in rates of biogeochemical cycling. Simultaneously, techniques for inferring ecosystem behavior from remotely measured canopy light interception are improving our ability to infer plant activity from satellite observations. Efforts have begun to couple models of transport in air and water to models of ecosystem function. Preliminary work indicates that coupling of transport and ecosystem processes alters the behavior of earth system components (hydrology, terrestrial ecosystems, and the atmosphere) from that of an uncoupled mode. DOI: 10.1034/j.1600-0889.1991.t01-1-00017.x

Terrestrial biogeochemical cycles: global interactions with the atmosphere and hydrology

Ecosystem scientists have developed a body of theory to predict the behavior of biogeochemical cycles when exchanges with other ecosystems are small or prescribed. Recent environmental changes make it clear that linkages between ecosystems via atmospheric and hydrological transport have large effects on ecosystem dynamics when considered over time periods of a decade to a century, time scales relevant to contemporary humankind. Our ability to predict behavior of ecosystems coupled by transport is limited by our ability (1) to extrapolate biotic function to large spatial scales and (2) to measure and model transport. We review developments in ecosystem theory, remote sensing, and geographical information systems (GIS) that support new efforts in spatial modeling. A paradigm has emerged to predict behavior of ecosystems based on understanding responses to multiple resources (e.g., water, nutrients, light). Several ecosystem models couple primary production to decomposition and nutrient availability using the above paradigm. These models require a fairly small set of environmental variables to simulate spatial and temporal variation in rates of biogeochemical cycling. Simultaneously, techniques for inferring ecosystem behavior from remotely measured canopy light interception are improving our ability to infer plant activity from satellite observations. Efforts have begun to couple models of transport in air and water to models of ecosystem function. Preliminary work indicates that coupling of transport and ecosystem processes alters the behavior of earth system components (hydrology, terrestrial ecosystems, and the atmosphere) from that of an uncoupled mode. DOI: 10.1034/j.1600-0889.1991.t01-1-00017.x