Conference papers by Jacob Warner
100th Annual Meeting for the American Geophysical Union, 2018
This paper is co-authored by Jacob Warner, Kristine DeLong, David Chicoine, Alan Wanamaker, C. F... more This paper is co-authored by Jacob Warner, Kristine DeLong, David Chicoine, Alan Wanamaker, C. Fred T. Andrus, and Kaustubh Thirumalai.
American Geophysical Union, Fall Meeting, 2020
Reconstructions of the El Niño-Southern Oscillation (ENSO) suggest a decrease in intensity and va... more Reconstructions of the El Niño-Southern Oscillation (ENSO) suggest a decrease in intensity and variability during the middle Holocene, but disagree as to when modern conditions began. Most studies report an increase in ENSO intensity beginning around 3000-1000 BCE, but conflicting perspectives exist in eastern and western Pacific archives. We use δ18O signals, a proxy for sea surface temperature (SST) and salinity (SSS), from two short-lived (<5 years) bivalve (SLB) species, Mesodesma donacium and Donax obesulus, recovered from Caylán (9.18°S, 78.38°W), an archaeological site in coastal Peru to reconstruct ENSO variance. These two species exhibit complimentary tolerances to SST at both extreme ends of ENSO phases: D. obesulus being vulnerable to die-offs in the colder SSTs of La Niña events and surviving during El Niño warmth whereas M. donacium, on the other hand is vulnerable to the warmer SSTs of El Niños and thrives during La Niño cooling. We examine the variance of the annual range of δ18O in both species as a “snapshot” of ENSO variability. In doing so, we aim to fill a temporal gap in existing SLB reconstructions from coastal Peru. We analyzed ~monthly-resolved δ18O samples from 20 shells (12 D. obesulus, 8 M. donacium) from Caylán dating 400–200 BCE. We compared these samples to the variance of the annual range of SST of an in situ record from Chicama, Peru (7.69°S, 79.43°W) spanning the years 1925–2019. We found that the sampled shells likely represent all three phases of ENSO (La Niña, neutral, and El Niño), and the reconstructed variance of the annual range of SST from both species combined was similar at 400–200 BCE to that of the 20th–21st century in situ SST record suggesting modern like conditions unlike the quiescent in the mid-Holocene. We conducted a principal component analysis (PCA) on the shell population to understand which δ18O signals were driving the variance. Two D. obesulus shells, MA197-2 and MA197-27, exhibited the strongest loadings along principle component 1. Both of these shells’ δ18O profiles represent temperature ranges >10°C, or equivalent to a major El Niño event akin to 1982-83 and 1997-98. Our results suggest that strong El Niño events dominated ENSO variability from 400–200 BCE, in agreement with other reconstructions suggesting increased ENSO activity during this interval.
American Geophysical Union, Fall Meeting, 2017
The January-April 2017 El Niño-costero, which brought elevated sea surface temperatures (SSTs) to... more The January-April 2017 El Niño-costero, which brought elevated sea surface temperatures (SSTs) to the Niño 1+2 region and sudden rainfall, highlights the need for eastern Pacific oriented El Niño-Southern Oscillation (ENSO) proxies along the Peruvian coast. Unfortunately paleoclimatological archive options for this coast are limited because there are few long-lived (>50 years) organisms suitable for reconstructions; however, short-lived (<5 years) intertidal bivalve species are abundant. Monte Carlo simulations suggest that these bivalves live long enough to record seasonal and thus ENSO variability. Reconstructions have been created using Mesodesma donacium, an intertidal clam; however, M. donacium populations are vulnerable to die-offs from warmer SSTs during El Niño events, possibly biasing its seasonal δ18O cycle towards ENSO-neutral and La Niña conditions. M. donacium are also functionally extinct north of 14°S, limiting the geographic range for modern analog studies. Here we present another short-lived intertidal clam species, Donax obesulus, as a complimentary archive to M. donacium for reconstructing ENSO variability in modern and prehistoric Peru. D. obesulus lives in warmer SSTs and survives north of 14°S, yet may be sensitive to colder La Niña conditions. Both clam species are found in archaeological sites along the north-central coast of Peru, providing a comparison between modern and prehistoric ENSO variability in an under-researched area. We collected D. obesulus from the Nepeña Valley, department of Ancash, Peru, in 2012, 2014, and 2016 (La Niña, ENSO-neutral, and El Niño years, respectively) for a modern analog study. We also obtained M. donacium and D. obesulus specimens excavated from a prehistoric ( 2300±100 BP) site (Caylán) in the same valley for comparison to modern ENSO conditions. Our results indicate that modern D. obesulus have a seasonal δ18O range of 0.8‰, which is less than modern M. donacium from previous studies (1.1‰). Archaeological D. obesulus had a larger seasonal δ18O range ( 1.8‰), indicating greater ENSO variability. Caylán M. donacium have a seasonal range of 1.1‰, within the range of previous studies (seasonal δ18O range = 0.3-1.3‰, 2900 BP). Our results also indicate a shift in modern D. obesulus mean shell δ18O (+0.77‰) compared to 2300 BP at Caylán.
American Geophysical Union, Fall Meeting , 2019
As researchers extend the history of El Niño-Southern Oscillation (ENSO), we find time periods an... more As researchers extend the history of El Niño-Southern Oscillation (ENSO), we find time periods and regions that contain data gaps including coastal Peru from 1000–0 BCE. Though there are no long-lived organisms suitable for climate reconstructions in that area, short-lived (<5 year) marine bivalves, which are abundant in archaeological sites in Peru, can provide “snapshots” of past climate variability, similar to the single foraminifera approach. We sampled Donax obesulus and Mesodesma donacium shells from an archaeological site (Caylán) in the Nepeña Valley, Peru dated to ~400 BCE and modern shells collected nearby during different ENSO phases to examine ENSO variability. Paleoclimate models, sediment cores, and reconstructions from other regions find ENSO strength increasing during the first millennium BCE compared to the period of reduced to non-existent ENSO activity during the mid-Holocene. Previous reconstructions using M. donacium, a short-lived intertidal bivalve preferring colder waters, are restricted to areas south of ~16°S due to warmer waters and more frequent El Niños. We use D. obesulus as a complimentary archive to M. donacium for reconstructing ENSO variability, as modern D. obesulus are present along the entire coastline of Peru and prefer warmer waters, though they undergo die-offs in strong La Niñas.
We find the seasonal variations in δ18O of D. obesulus shells faithfully record sea surface temperature (SST) and salinity (SSS) during ENSO-Neutral (2014) and El Niño (2016) years, but underestimate La Niña (2012) events possibly due to biological temperature limits (i.e., colder SST). Modern D. obesulus trace elemental ratios (Sr/Ca, Mg/Ca) correlate with SST, which helps us constrain changes in δ18Owater in our shell δ18O. Geochemical data from archaeological shells of both species indicate an overall colder (2.5–3.3°C) SST mean shift and a wider range in seasonal variability compared to modern (2012–2016) shells suggesting colder and/or drier conditions for ~400 BCE. This seasonal SST variability includes anomalous warm signals, which we interpret as El Niño events. Our analysis finds ENSO other reconstructions in coastal Peru may have missed this increasing ENSO variability, i.e., more frequent and stronger ENSO events, during the 1st millennium BCE.
American Association of Geographers, 2018
This paper is co-authored by Jacob Warner, Kristine DeLong, David Chicoine, Alan Wanamaker Jr., ... more This paper is co-authored by Jacob Warner, Kristine DeLong, David Chicoine, Alan Wanamaker Jr., and Kaustubh Thirumalai. There is a need for precise El Niño-Southern Oscillation (ENSO) proxies along the Peruvian coast. Unfortunately few long-lived (>50 years) organisms suitable for sclerochronological research exist along this coast. However, short-lived (<5 years) intertidal bivalves abound. Monte Carlo simulations suggest these species live long enough to record ENSO variability. However, Mesodesma donacium (one such intertidal bivalve clam used for reconstructions) is vulnerable to El Niños, possibly biasing seasonal δ18O cycles towards ENSO-neutral and La Niñas. M. donacium are functionally extinct north of ~14°S, limiting the geographic range of modern studies. We present another short-lived intertidal clam as complimentary to M. donacium for reconstructing ENSO variability. Donax obesulus lives in warmer SSTs north of ~14°S, yet may be sensitive to La Niñas. Both species are found in archaeological sites along the north-central coast of Peru, allowing comparison between modern and prehistoric ENSO variability. We collected D. obesulus from the Nepeña Valley, Ancash, Peru, in 2012, 2014, and 2016 (La Niña, ENSO-neutral, and El Niño, respectively) and obtained M. donacium and D. obesulus excavated from a prehistoric (~2300 ±100 BP) site (Caylán) in the same valley. Modern La Niña D. obesulus seasonal δ18O range is 0.8‰, less than modern M. donacium (1.1‰). Archaeological D. obesulus seasonal δ18O range is ~1.8‰, indicating greater ENSO variability than modern. Caylán M. donacium seasonal range is ~1.1‰, within previous studies (~0.3 to 1.3‰, ~2900 BP), suggesting possible bias. Modern D. obesulus also show a mean δ18O shift (+0.77‰) compared to Caylán suggesting shifts in seawater δ18O.
Annual Meeting of the Society for American Archaeology, 2013
This poster is co-authored by Jacob Warner and David Chicoine. The disciplines of behavioral arch... more This poster is co-authored by Jacob Warner and David Chicoine. The disciplines of behavioral archaeology and garbology have been applied to various sites both ancient and modern in an attempt to explain the cultural practices and habitation patterns of various groups. A variety of settlement types have been studied across several continents and involving different ethnic groups. However, very few studies have been applied to South America, especially relating to the development of urban sites and social structure, despite the plethora of available archaeological sites.
This project intends to apply behavioral archaeology as well as some aspects of garbology to understanding the actual social structure and physical layout of the site of Caylan, an Early Horizon urban settlement located along the north-central Peruvian coast. Specifically, how did the settlers at Caylan dispose of their waste material, as well as trying to understand how such discard patterns can related to lifestyle and habitation practices, including the seasonality of residence at the site.
Meeting of the AGU, ASLO and Oceanography Society, 2016
This paper is co-authored by Jacob Warner, Kristine DeLong, David Chicoine, Alan Wanamaker, Jr., ... more This paper is co-authored by Jacob Warner, Kristine DeLong, David Chicoine, Alan Wanamaker, Jr., and Kaustubh Thirumalai.
Book Reviews by Jacob Warner
Anthropology Book Forum, 2020
Are the islands off the coast of California “marginal” environments? How could seemingly “depaupe... more Are the islands off the coast of California “marginal” environments? How could seemingly “depauperate” places have sustained human settlements for thousands of years? In An Archaeology of Abundance: Reevaluating the Marginality of California’s Islands, edited by
Kristina M. Gill, Mikael Fauvelle, and Jon M. Erlandson, archaeologists and other scholars argue that our understanding of the resource bases of the California islands is biased by years of Euroamerican impacts. By integrating archaeological and ethnohistoric data with paleoecological reconstructions, the authors reexamine life on these islands before European contact and subsequent environmental degradation.
Papers by Jacob Warner
Anthropology Book Forum, May 31, 2021
emphasized the importance of maritime resources to the development of social complexity in the An... more emphasized the importance of maritime resources to the development of social complexity in the Andean region in his theory articulated in his Maritime Foundations of Andean Civilization (1975), which became a central (and controversial) text in the field. This volume builds on his and others' foundational work and asks, "how did ancient Andean coastal communities build themselves, and their identities, around their proximity to the Pacific Ocean"? Maritime Communities of the Ancient Andes, edited by Gabriel Prieto and Daniel Sandweiss, is based on a session conducted at the 2014 Society for American Archaeology annual meeting. The book contains an introductory chapter followed by 14 chapters in four sections organized by time interval, beginning with the first human occupations of the Pacific littoral of western South America and culminating in the 17 th century CE colonial period.
Goldschmidt2022 abstracts
AGU Fall Meeting Abstracts, Dec 1, 2019
As researchers extend the history of El Niño-Southern Oscillation (ENSO), we find time periods an... more As researchers extend the history of El Niño-Southern Oscillation (ENSO), we find time periods and regions that contain data gaps including coastal Peru from 1000–0 BCE. Though there are no long-lived organisms suitable for climate reconstructions in that area, short-lived (&lt;5 year) marine bivalves, which are abundant in archaeological sites in Peru, can provide “snapshots” of past climate variability, similar to the single foraminifera approach. We sampled Donax obesulus and Mesodesma donacium shells from an archaeological site (Caylán) in the Nepeña Valley, Peru dated to ~400 BCE and modern shells collected nearby during different ENSO phases to examine ENSO variability. Paleoclimate models, sediment cores, and reconstructions from other regions find ENSO strength increasing during the first millennium BCE compared to the period of reduced to non-existent ENSO activity during the mid-Holocene. Previous reconstructions using M. donacium, a short-lived intertidal bivalve preferring colder waters, are restricted to areas south of ~16°S due to warmer waters and more frequent El Niños. We use D. obesulus as a complimentary archive to M. donacium for reconstructing ENSO variability, as modern D. obesulus are present along the entire coastline of Peru and prefer warmer waters, though they undergo die-offs in strong La Niñas. We find the seasonal variations in δ18O of D. obesulus shells faithfully record sea surface temperature (SST) and salinity (SSS) during ENSO-Neutral (2014) and El Niño (2016) years, but underestimate La Niña (2012) events possibly due to biological temperature limits (i.e., colder SST). Modern D. obesulus trace elemental ratios (Sr/Ca, Mg/Ca) correlate with SST, which helps us constrain changes in δ18Owater in our shell δ18O. Geochemical data from archaeological shells of both species indicate an overall colder (2.5–3.3°C) SST mean shift and a wider range in seasonal variability compared to modern (2012–2016) shells suggesting colder and/or drier conditions for ~400 BCE. This seasonal SST variability includes anomalous warm signals, which we interpret as El Niño events. Our analysis finds ENSO other reconstructions in coastal Peru may have missed this increasing ENSO variability, i.e., more frequent and stronger ENSO events, during the 1st millennium BCE.
American Geophysical Union eBooks, Feb 1, 2016
AGU Fall Meeting Abstracts, Dec 1, 2020
Anthropology Book Forum, Apr 13, 2020
The Journal of Island and Coastal Archaeology, 2022
Climate (in)stability can manifest in the size of mollusks attesting to variable impacts on growt... more Climate (in)stability can manifest in the size of mollusks attesting to variable impacts on growth, seasonal exploitation, and cultural persistence. We present population statistics of the height of a bivalve species (Donax obesulus) collected from sites dating to the Early Horizon (EH, 900-200 BCE) in the Nepeña Valley and the Middle Horizon (MH, 600-1000 CE) in the Jequetepeque Valley of northern coastal Peru and compare them with a paleoclimate record and a sample of modern shells (collected in 2012, 2014, and 2016) from the Nepeña Valley. We observe diachronic variation in the size of D. obesulus with larger bivalves during the EH and smaller shells during the MH and in the modern sample. D. obesulus size remains relatively static during the MH at one site through two sub-phases. These bivalve populations were likely impacted by both climate and cultural circumstances. A proxy for runoff from El Niño related rainfall (%lithic flux) from a previously published nearby marine sediment core is elevated during the EH and Late Moche phase of the MH and correlates with shell height. During the Transitional phase of the MH and the modern interval, however, there are periods of comparatively reduced El Niño activity and shell height compared to the EH.
The January-April 2017 El Niño-costero, which brought elevated sea surface temperatures (SSTs) to... more The January-April 2017 El Niño-costero, which brought elevated sea surface temperatures (SSTs) to the Niño 1+2 region and sudden rainfall, highlights the need for eastern Pacific oriented El Niño-Southern Oscillation (ENSO) proxies along the Peruvian coast. Unfortunately paleoclimatological archive options for this coast are limited because there are few long-lived (&gt;50 years) organisms suitable for reconstructions; however, short-lived (&lt;5 years) intertidal bivalve species are abundant. Monte Carlo simulations suggest that these bivalves live long enough to record seasonal and thus ENSO variability. Reconstructions have been created using Mesodesma donacium, an intertidal clam; however, M. donacium populations are vulnerable to die-offs from warmer SSTs during El Niño events, possibly biasing its seasonal δ18O cycle towards ENSO-neutral and La Niña conditions. M. donacium are also functionally extinct north of 14°S, limiting the geographic range for modern analog studies. Here we present another short-lived intertidal clam species, Donax obesulus, as a complimentary archive to M. donacium for reconstructing ENSO variability in modern and prehistoric Peru. D. obesulus lives in warmer SSTs and survives north of 14°S, yet may be sensitive to colder La Niña conditions. Both clam species are found in archaeological sites along the north-central coast of Peru, providing a comparison between modern and prehistoric ENSO variability in an under-researched area. We collected D. obesulus from the Nepeña Valley, department of Ancash, Peru, in 2012, 2014, and 2016 (La Niña, ENSO-neutral, and El Niño years, respectively) for a modern analog study. We also obtained M. donacium and D. obesulus specimens excavated from a prehistoric ( 2300±100 BP) site (Caylán) in the same valley for comparison to modern ENSO conditions. Our results indicate that modern D. obesulus have a seasonal δ18O range of 0.8‰, which is less than modern M. donacium from previous studies (1.1‰). Archaeological D. obesulus had a larger seasonal δ18O range ( 1.8‰), indicating greater ENSO variability. Caylán M. donacium have a seasonal range of 1.1‰, within the range of previous studies (seasonal δ18O range = 0.3-1.3‰, 2900 BP). Our results also indicate a shift in modern D. obesulus mean shell δ18O (+0.77‰) compared to 2300 BP at Caylán.
Chemical Geology, 2022
The coastline of Peru lacks long-lived marine organisms useful for paleoclimatic reconstructions ... more The coastline of Peru lacks long-lived marine organisms useful for paleoclimatic reconstructions generating a need for novel archives. Short-lived (&lt;5 years) bivalves are commonly found in geological and archaeological deposits and thus can provide “snapshots” of past climatic variability (i.e., seasonal range), similar to data obtained by individual foraminifera analysis, rather than continuous, cross-dated time series (e.g., trees and corals). Previous studies have found success using the short-lived intertidal clam Mesodesma donacium. However, M. donacium are vulnerable to die-offs from the warmer sea surface temperatures (SST) associated with El Niño events and are functionally extinct in northern Peru thus limiting the possibility of modern analog studies for that region. Here we investigate the short-lived (1–3 years) surf clam, Donax obesulus, commonly found in northern Peru, as a paleoclimate archive. Donax obesulus populations are able to survive the warmer SSTs present during El Niño years although they are vulnerable to colder SSTs associated with La Niñas. We assessed the environmental drivers underlying subannual δ18O variability in D. obesulus from live collected shells from fish markets and coastal beaches near the Nepeña Valley, Peru in 2012 (La Niña), 2014 (ENSO-neutral), and 2016 (El Niño). Forward modeling of pseudo-shell δ18O reveals that SST variations are a dominant driver with secondary contributions from seasonally-varying seawater δ18O (δ18Osw). By accounting for varying δ18Osw, we isolated the temperature dependent variable resulting in a paleotemperature equation for D. obesulus δ18O. We verified our results with the δ18O record of a D. obesulus shell collected in 2006. Our results suggest that the paleotemperature equation we developed is useful for reconstructing El Niño-Southern Oscillation (ENSO)-related climatic variations in this region and the pseudo-shell approach may be useful for understanding shell δ18O in other locations.
The Casma polity emerged during the Middle Horizon (AD 600-1000) in coastal Peru, spanning from t... more The Casma polity emerged during the Middle Horizon (AD 600-1000) in coastal Peru, spanning from the Chao to Huarmey Valleys. Our understanding of the political economy/ecology of the polity, especially interaction between Casma settlements, is limited to a few sites. There is also a question of Casma interaction with other Middle Horizon political entities/ideologies (Late Moche, Wari, Chimu, Sican/Lambayeque).Thus, there is a need for information from settlements associated with the Casma polity, both within the Casma valley and in other areas, to reconstruct economic networks.
Poster presented at the 84th Annual Meeting of the Society for American Archaeology, 2019
The Casma polity emerged during the Middle Horizon (AD 600-1000) in coastal Peru, spanning from t... more The Casma polity emerged during the Middle Horizon (AD 600-1000) in coastal Peru, spanning from the Chao to Huarmey Valleys. Our understanding of the political economy/ecology of the polity, especially interaction between Casma settlements, is limited to a few sites. There is also a question of Casma interaction with other Middle Horizon political entities/ideologies (Late Moche, Wari, Chimu, Sican/Lambayeque).Thus, there is a need for information from settlements associated with the Casma polity, both within the Casma valley and in other areas, to reconstruct economic networks.
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Conference papers by Jacob Warner
We find the seasonal variations in δ18O of D. obesulus shells faithfully record sea surface temperature (SST) and salinity (SSS) during ENSO-Neutral (2014) and El Niño (2016) years, but underestimate La Niña (2012) events possibly due to biological temperature limits (i.e., colder SST). Modern D. obesulus trace elemental ratios (Sr/Ca, Mg/Ca) correlate with SST, which helps us constrain changes in δ18Owater in our shell δ18O. Geochemical data from archaeological shells of both species indicate an overall colder (2.5–3.3°C) SST mean shift and a wider range in seasonal variability compared to modern (2012–2016) shells suggesting colder and/or drier conditions for ~400 BCE. This seasonal SST variability includes anomalous warm signals, which we interpret as El Niño events. Our analysis finds ENSO other reconstructions in coastal Peru may have missed this increasing ENSO variability, i.e., more frequent and stronger ENSO events, during the 1st millennium BCE.
This project intends to apply behavioral archaeology as well as some aspects of garbology to understanding the actual social structure and physical layout of the site of Caylan, an Early Horizon urban settlement located along the north-central Peruvian coast. Specifically, how did the settlers at Caylan dispose of their waste material, as well as trying to understand how such discard patterns can related to lifestyle and habitation practices, including the seasonality of residence at the site.
Book Reviews by Jacob Warner
Kristina M. Gill, Mikael Fauvelle, and Jon M. Erlandson, archaeologists and other scholars argue that our understanding of the resource bases of the California islands is biased by years of Euroamerican impacts. By integrating archaeological and ethnohistoric data with paleoecological reconstructions, the authors reexamine life on these islands before European contact and subsequent environmental degradation.
Papers by Jacob Warner
We find the seasonal variations in δ18O of D. obesulus shells faithfully record sea surface temperature (SST) and salinity (SSS) during ENSO-Neutral (2014) and El Niño (2016) years, but underestimate La Niña (2012) events possibly due to biological temperature limits (i.e., colder SST). Modern D. obesulus trace elemental ratios (Sr/Ca, Mg/Ca) correlate with SST, which helps us constrain changes in δ18Owater in our shell δ18O. Geochemical data from archaeological shells of both species indicate an overall colder (2.5–3.3°C) SST mean shift and a wider range in seasonal variability compared to modern (2012–2016) shells suggesting colder and/or drier conditions for ~400 BCE. This seasonal SST variability includes anomalous warm signals, which we interpret as El Niño events. Our analysis finds ENSO other reconstructions in coastal Peru may have missed this increasing ENSO variability, i.e., more frequent and stronger ENSO events, during the 1st millennium BCE.
This project intends to apply behavioral archaeology as well as some aspects of garbology to understanding the actual social structure and physical layout of the site of Caylan, an Early Horizon urban settlement located along the north-central Peruvian coast. Specifically, how did the settlers at Caylan dispose of their waste material, as well as trying to understand how such discard patterns can related to lifestyle and habitation practices, including the seasonality of residence at the site.
Kristina M. Gill, Mikael Fauvelle, and Jon M. Erlandson, archaeologists and other scholars argue that our understanding of the resource bases of the California islands is biased by years of Euroamerican impacts. By integrating archaeological and ethnohistoric data with paleoecological reconstructions, the authors reexamine life on these islands before European contact and subsequent environmental degradation.