Difference between revisions of "Climate Proxy"
From Linked Earth Wiki
| Line 1: | Line 1: | ||
| − | Observations of past climates are necessarily indirect. | + | Observations of past climates are necessarily indirect. These observations are made on climate '''proxies''' in various geological (e.g. lake or marine sediments, living or fossil coral reefs, cave deposits), glaciological (ice cores or snow pits) or biological (trees) [[archive]]s. Many data streams can be collected from these archives, each '''sensing''' a different aspect of the environment (sometimes, several aspects at once). A paleoclimate dataset is almost always a [https://en.wikipedia.org/wiki/Time_series time series] of observations made on a proxy system. |
[http://one.geol.umd.edu/preprints/psm13.pdf Evans et al, (2013)] define a proxy system as comprised of three components: | [http://one.geol.umd.edu/preprints/psm13.pdf Evans et al, (2013)] define a proxy system as comprised of three components: | ||
| − | + | * The [[sensor]] comprises physical, chemical and/or biological components that react to environmental conditions. Sensors are often multivariate (i.e. sensitive to more than one environmental [[variable]]), seasonal and/or nonlinear or thresholded (record only part of the range of environmental conditions), or do so nonlinearly. For instance, [[Mg/Ca]] is often used sensor for temperature but depends also on salinity and pH [http://onlinelibrary.wiley.com/doi/10.1002/2015GC005844/abstract (Khider et al., 2015)]. Its temperature dependence is exponential (reference). It is thus a multivariate and nonlinear sensor. | |
| − | + | * The [[archive]] is the medium in which the response of a sensor to environmental forcing is recorded (Fig. 1). [Marine sediments] are a type of archive, on which many sensors may be measured (e.g. Mg/Ca, \delta^{18}O, Uk37, TEX86, \deltaD) | |
| − | + | * [[observation]]s are made on archives, and involve several processes: | |
| + | ** sampling is the process where the subsets of the archive are extracted, usually via coring or drilling. | ||
| + | ** often, the observations are made on a purified, chemically transformed (.e.g leached) form of the sampled material | ||
| + | ** what else? | ||
| − | These components | + | These three major components may be individually modeled, and linked together within a [[Proxy System Model]] (e.g. [http://one.geol.umd.edu/preprints/psm13.pdf Evans et al, (2013)], [http://onlinelibrary.wiley.com/doi/10.1002/2015MS000447/full Dee et al (2015)] ) |
Revision as of 17:44, 13 January 2016
Observations of past climates are necessarily indirect. These observations are made on climate proxies in various geological (e.g. lake or marine sediments, living or fossil coral reefs, cave deposits), glaciological (ice cores or snow pits) or biological (trees) archives. Many data streams can be collected from these archives, each sensing a different aspect of the environment (sometimes, several aspects at once). A paleoclimate dataset is almost always a time series of observations made on a proxy system.
Evans et al, (2013) define a proxy system as comprised of three components:
- The sensor comprises physical, chemical and/or biological components that react to environmental conditions. Sensors are often multivariate (i.e. sensitive to more than one environmental variable), seasonal and/or nonlinear or thresholded (record only part of the range of environmental conditions), or do so nonlinearly. For instance, Mg/Ca is often used sensor for temperature but depends also on salinity and pH (Khider et al., 2015). Its temperature dependence is exponential (reference). It is thus a multivariate and nonlinear sensor.
- The archive is the medium in which the response of a sensor to environmental forcing is recorded (Fig. 1). [Marine sediments] are a type of archive, on which many sensors may be measured (e.g. Mg/Ca, \delta^{18}O, Uk37, TEX86, \deltaD)
- observations are made on archives, and involve several processes:
- sampling is the process where the subsets of the archive are extracted, usually via coring or drilling.
- often, the observations are made on a purified, chemically transformed (.e.g leached) form of the sampled material
- what else?
These three major components may be individually modeled, and linked together within a Proxy System Model (e.g. Evans et al, (2013), Dee et al (2015) )
