Limits...
Century-Long Warming Trends in the Upper Water Column of Lake Tanganyika.

Kraemer BM, Hook S, Huttula T, Kotilainen P, O'Reilly CM, Peltonen A, Plisnier PD, Sarvala J, Tamatamah R, Vadeboncoeur Y, Wehrli B, McIntyre PB - PLoS ONE (2015)

Bottom Line: However, after accounting for spatiotemporal variation in temperature and warming rates, the TEX86 paleolimnological proxy yields lower surface temperatures (1.46 °C lower on average) and faster warming rates (by a factor of three) than in situ measurements.Based on the ecology of Thaumarchaeota (the microbes whose biomolecules are involved with generating the TEX86 proxy), we offer a reinterpretation of the TEX86 data from Lake Tanganyika as the temperature of the low-oxygen zone, rather than of the lake surface temperature as has been suggested previously.Our analyses provide a thorough accounting of spatiotemporal variation in warming rates, offering strong evidence that thermal and ecological shifts observed in this massive tropical lake over the last century are robust and in step with global climate change.

View Article: PubMed Central - PubMed

Affiliation: Center for Limnology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.

ABSTRACT
Lake Tanganyika, the deepest and most voluminous lake in Africa, has warmed over the last century in response to climate change. Separate analyses of surface warming rates estimated from in situ instruments, satellites, and a paleolimnological temperature proxy (TEX86) disagree, leaving uncertainty about the thermal sensitivity of Lake Tanganyika to climate change. Here, we use a comprehensive database of in situ temperature data from the top 100 meters of the water column that span the lake's seasonal range and lateral extent to demonstrate that long-term temperature trends in Lake Tanganyika depend strongly on depth, season, and latitude. The observed spatiotemporal variation in surface warming rates accounts for small differences between warming rate estimates from in situ instruments and satellite data. However, after accounting for spatiotemporal variation in temperature and warming rates, the TEX86 paleolimnological proxy yields lower surface temperatures (1.46 °C lower on average) and faster warming rates (by a factor of three) than in situ measurements. Based on the ecology of Thaumarchaeota (the microbes whose biomolecules are involved with generating the TEX86 proxy), we offer a reinterpretation of the TEX86 data from Lake Tanganyika as the temperature of the low-oxygen zone, rather than of the lake surface temperature as has been suggested previously. Our analyses provide a thorough accounting of spatiotemporal variation in warming rates, offering strong evidence that thermal and ecological shifts observed in this massive tropical lake over the last century are robust and in step with global climate change.

No MeSH data available.


Related in: MedlinePlus

Modeled century-long warming rate estimates (1912–2013).Each colored pixel on the maps is an estimate of the warming rate for that location in the lake based on the temperature model fit to all available in situ temperature data. Separate map panels show variation across seasons and depths in the estimated warming rate. The top row of warming estimate maps are for the dry season and the bottom row of warming rates are for the wet season. The columns indicate the depth gradient of warming rate estimates from 0–100 m. All temperature models were fit to data from more than 1.5 km from land and in locations where the water depth exceeded 100 m deep.
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pone.0132490.g002: Modeled century-long warming rate estimates (1912–2013).Each colored pixel on the maps is an estimate of the warming rate for that location in the lake based on the temperature model fit to all available in situ temperature data. Separate map panels show variation across seasons and depths in the estimated warming rate. The top row of warming estimate maps are for the dry season and the bottom row of warming rates are for the wet season. The columns indicate the depth gradient of warming rate estimates from 0–100 m. All temperature models were fit to data from more than 1.5 km from land and in locations where the water depth exceeded 100 m deep.

Mentions: According to the model of in situ temperatures, the surface of the lake has warmed on average at a rate of 0.129 ± 0.023°C decade-1 over the period 1912–2013. Water temperatures increased over the period 1912–2013 at all depths from 0–100 m across the spatial extent of the lake (Fig 2). The fastest warming rates on average can be found at depths of 50–80 m (Fig 2). The model results suggest that there is significant variation in warming rates over the surface of the lake and through the year. On average, warming rates at the nothern tip of Lake Tanganyika exceed warming rates at the southern tip by about 0.013°C decade-1 (Fig 2). This latitudinal difference is most pronounced at 50 m below the surface where the northern basin is warming 0.076°C decade-1 faster than the southern tip of the lake (Fig 2). The seasonal temperature cycle also influences the rate of temperature change. Surface warming rates vary by 0.080°C decade-1 over the seasonal cycle with the slowest surface warming rates occuring in the dry season when temperatures are typically lower (Fig 2). The opposite pattern (warming rate faster in dry season) is observed over the depth range from 20–80 m (Fig 2). The distance from shore also impacted the century-long warming rate but the effect was weaker than the effects of latitude and seasonality. The fastest surface warming rates occurred close to shore but for much of the water column (10–50 m and from 90–100 m), distance to shore was negatively related to warming rate (Fig 2).


Century-Long Warming Trends in the Upper Water Column of Lake Tanganyika.

Kraemer BM, Hook S, Huttula T, Kotilainen P, O'Reilly CM, Peltonen A, Plisnier PD, Sarvala J, Tamatamah R, Vadeboncoeur Y, Wehrli B, McIntyre PB - PLoS ONE (2015)

Modeled century-long warming rate estimates (1912–2013).Each colored pixel on the maps is an estimate of the warming rate for that location in the lake based on the temperature model fit to all available in situ temperature data. Separate map panels show variation across seasons and depths in the estimated warming rate. The top row of warming estimate maps are for the dry season and the bottom row of warming rates are for the wet season. The columns indicate the depth gradient of warming rate estimates from 0–100 m. All temperature models were fit to data from more than 1.5 km from land and in locations where the water depth exceeded 100 m deep.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4492510&req=5

pone.0132490.g002: Modeled century-long warming rate estimates (1912–2013).Each colored pixel on the maps is an estimate of the warming rate for that location in the lake based on the temperature model fit to all available in situ temperature data. Separate map panels show variation across seasons and depths in the estimated warming rate. The top row of warming estimate maps are for the dry season and the bottom row of warming rates are for the wet season. The columns indicate the depth gradient of warming rate estimates from 0–100 m. All temperature models were fit to data from more than 1.5 km from land and in locations where the water depth exceeded 100 m deep.
Mentions: According to the model of in situ temperatures, the surface of the lake has warmed on average at a rate of 0.129 ± 0.023°C decade-1 over the period 1912–2013. Water temperatures increased over the period 1912–2013 at all depths from 0–100 m across the spatial extent of the lake (Fig 2). The fastest warming rates on average can be found at depths of 50–80 m (Fig 2). The model results suggest that there is significant variation in warming rates over the surface of the lake and through the year. On average, warming rates at the nothern tip of Lake Tanganyika exceed warming rates at the southern tip by about 0.013°C decade-1 (Fig 2). This latitudinal difference is most pronounced at 50 m below the surface where the northern basin is warming 0.076°C decade-1 faster than the southern tip of the lake (Fig 2). The seasonal temperature cycle also influences the rate of temperature change. Surface warming rates vary by 0.080°C decade-1 over the seasonal cycle with the slowest surface warming rates occuring in the dry season when temperatures are typically lower (Fig 2). The opposite pattern (warming rate faster in dry season) is observed over the depth range from 20–80 m (Fig 2). The distance from shore also impacted the century-long warming rate but the effect was weaker than the effects of latitude and seasonality. The fastest surface warming rates occurred close to shore but for much of the water column (10–50 m and from 90–100 m), distance to shore was negatively related to warming rate (Fig 2).

Bottom Line: However, after accounting for spatiotemporal variation in temperature and warming rates, the TEX86 paleolimnological proxy yields lower surface temperatures (1.46 °C lower on average) and faster warming rates (by a factor of three) than in situ measurements.Based on the ecology of Thaumarchaeota (the microbes whose biomolecules are involved with generating the TEX86 proxy), we offer a reinterpretation of the TEX86 data from Lake Tanganyika as the temperature of the low-oxygen zone, rather than of the lake surface temperature as has been suggested previously.Our analyses provide a thorough accounting of spatiotemporal variation in warming rates, offering strong evidence that thermal and ecological shifts observed in this massive tropical lake over the last century are robust and in step with global climate change.

View Article: PubMed Central - PubMed

Affiliation: Center for Limnology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.

ABSTRACT
Lake Tanganyika, the deepest and most voluminous lake in Africa, has warmed over the last century in response to climate change. Separate analyses of surface warming rates estimated from in situ instruments, satellites, and a paleolimnological temperature proxy (TEX86) disagree, leaving uncertainty about the thermal sensitivity of Lake Tanganyika to climate change. Here, we use a comprehensive database of in situ temperature data from the top 100 meters of the water column that span the lake's seasonal range and lateral extent to demonstrate that long-term temperature trends in Lake Tanganyika depend strongly on depth, season, and latitude. The observed spatiotemporal variation in surface warming rates accounts for small differences between warming rate estimates from in situ instruments and satellite data. However, after accounting for spatiotemporal variation in temperature and warming rates, the TEX86 paleolimnological proxy yields lower surface temperatures (1.46 °C lower on average) and faster warming rates (by a factor of three) than in situ measurements. Based on the ecology of Thaumarchaeota (the microbes whose biomolecules are involved with generating the TEX86 proxy), we offer a reinterpretation of the TEX86 data from Lake Tanganyika as the temperature of the low-oxygen zone, rather than of the lake surface temperature as has been suggested previously. Our analyses provide a thorough accounting of spatiotemporal variation in warming rates, offering strong evidence that thermal and ecological shifts observed in this massive tropical lake over the last century are robust and in step with global climate change.

No MeSH data available.


Related in: MedlinePlus