Sedproxy: a forward model for sediment-archived climate proxies

Abstract

Climate reconstructions based on proxy records recovered from marine sediments, such as alkenone records or geochemical parameters measured on foraminifera, play an important role in our understanding of the climate system. They provide information about the state of the ocean ranging back hundreds to millions of years and form the backbone of paleo-oceanography.However, there are many sources of uncertainty associated with the signal recovered from sediment-archived proxies. These include seasonal or depth-habitat biases in the recorded signal; a frequency-dependent reduction in the amplitude of the recorded signal due to bioturbation of the sediment; aliasing of high-frequency climate variation onto a nominally annual, decadal, or centennial resolution signal; and additional sample processing and measurement error introduced when the proxy signal is recovered.Here we present a forward model for sediment-archived proxies that jointly models the above processes so that the magnitude of their separate and combined effects can be investigated. Applications include the interpretation and analysis of uncertainty in existing proxy records, parameter sensitivity analysis to optimize future studies, and the generation of pseudo-proxy records that can be used to test reconstruction methods. We provide examples, such as the simulation of individual foraminifera records, that demonstrate the usefulness of the forward model for paleoclimate studies. The model is implemented as an open-source R package, sedproxy, to which we welcome collaborative contributions. We hope that use of sedproxy will contribute to a better understanding of both the limitations and potential of marine sediment proxies to inform researchers about earth's past climate.

Deciphering the Variability in Mg/Ca and Stable Oxygen Isotopes of Individual Foraminifera

“…Simple models parametrizing the foraminiferal flux as a function of environmental parameters (Mix, ; Schmidt & Mulitza, ; Roche et al, ; Dolman & Laepple, ) might allow first‐order estimates of these ecological effects. Further, more complex ecosystem modeling that also includes the interaction of secondary parameters such as nutrients has the potential to provide indications on how seasonality and habitat depth change in a different climatic setting (Kretschmer et al, ; Lombard et al, ).…”

Can we use sea surface temperature and productivity proxy records to reconstruct Ekman upwelling?

“…While the first assumption that chlorophyll and primary productivity are related is probably accurate on 1st order (Henson et al, 2010), the relationship between primary productivity and export productivity is less trivial. Previous studies have identified a general relationship between export productivity, marine productivity, and sea surface temperature (Dunne et al, 2005;Laws et al, 2011). Sediment trap studies done in the Santa Barbara and Guaymas basins generally show a similar pattern (Thunell et al, 1994;Thunell, 1998), with export production correlated positively with primary productivity (organic carbon and opal in the Santa Barbara Basin; opal in the Guaymas Basin).…”

Variability in the Northern North Atlantic and Arctic Oceans Across the Last Two Millennia: A Review

“…Improved model resolution can also help proxy-model comparison in those regions where, for example, local currents are poorly resolved (Saba et al, 2016). Other major advances could come with a more extensive use of proxy system forward models (Dee et al, 2016;Dolman & Laepple, 2018;Evans et al, 2013;Kretschmer et al, 2018), in particular in the context of the last millennium. For example, one of the avenues currently explored is the explicit modeling of other parts of the climate system, such as water isotopes (Sjolte et al, 2011;Stevenson et al, 2013;Werner, Langebroek, et al, 2011).…”