The Little Ice Age and 20th-century deep Pacific cooling

Science ◽  
2019 ◽  
Vol 363 (6422) ◽  
pp. 70-74 ◽  
Author(s):  
G. Gebbie ◽  
P. Huybers
Keyword(s):  
Long Memory ◽  
Little Ice Age ◽  
Deep Ocean ◽  
Ocean Model ◽  
Ice Age ◽  
Ocean Temperature ◽  
Temperature Changes ◽  
Surface Ocean ◽  
Proxy Records ◽  
Temperature Trends

Proxy records show that before the onset of modern anthropogenic warming, globally coherent cooling occurred from the Medieval Warm Period to the Little Ice Age. The long memory of the ocean suggests that these historical surface anomalies are associated with ongoing deep-ocean temperature adjustments. Combining an ocean model with modern and paleoceanographic data leads to a prediction that the deep Pacific is still adjusting to the cooling going into the Little Ice Age, whereas temperature trends in the surface ocean and deep Atlantic reflect modern warming. This prediction is corroborated by temperature changes identified between the HMS Challenger expedition of the 1870s and modern hydrography. The implied heat loss in the deep ocean since 1750 CE offsets one-fourth of the global heat gain in the upper ocean.

scholarly journals Effect of changing ocean circulation on deep ocean temperature in the last millennium

2020 ◽  
Author(s):  
Jeemijn Scheen ◽  
Thomas F. Stocker
Keyword(s):  
Surface Temperature ◽  
Ocean Circulation ◽  
Little Ice Age ◽  
Heat Content ◽  
Deep Ocean ◽  
Ice Age ◽  
Ocean Temperature ◽  
Meridional Heat Transport ◽  
Temperature Anomalies ◽  
The Past

Abstract. Paleoreconstructions and modern observations provide us with anomalies of surface temperature over the past millennium. The history of deep ocean temperatures is much less well-known and was simulated in a recent study for the past 2000 years under forced surface temperature anomalies. In this study, we simulate the past 800 years with an illustrative forcing scenario in the Bern3D ocean model, which enables us to assess the role of changes in ocean circulation on deep ocean temperature. We quantify the effect of changing ocean circulation by comparing transient simulations (where the ocean dynamically adjusts to anomalies in surface temperature – hence density) to simulations with fixed ocean circulation. We decompose temperature, ocean heat content and meridional heat transport into the contributions from changing ocean circulation and changing sea surface temperature (SST). In the deep ocean, the contribution from changing ocean circulation is found to be as important as the changing SST signal itself. Firstly, the small changes in ocean circulation amplify the Little Ice Age signal around 3 km depth by at least a factor of two, depending on the basin. Secondly, they fasten the arrival of this atmospheric signal in the Pacific and Southern Ocean at all depths, whereas they delay the arrival in the Atlantic between about 2.5 and 3.5 km by two centuries. This delay is explained by an initial competition between the Little Ice Age cooling and a warming due to an increase in relatively warmer North Atlantic Deep Water at the cost of Antarctic Bottom Water. Under the consecutive AMOC slowdown, this shift in water masses is inverted and aging of the water causes a late additional cooling. Our results suggest that small changes in ocean circulation can have a large impact on the amplitude and timing of ocean temperature anomalies below 2 km depth.

scholarly journals Effect of changing ocean circulation on deep ocean temperature in the last millennium

2020 ◽  
Vol 11 (4) ◽  
pp. 925-951
Author(s):  
Jeemijn Scheen ◽  
Thomas F. Stocker
Keyword(s):  
Surface Temperature ◽  
Ocean Circulation ◽  
Little Ice Age ◽  
Deep Ocean ◽  
Meridional Overturning Circulation ◽  
Ice Age ◽  
Ocean Temperature ◽  
Temperature Anomalies ◽  
The Past ◽  
The Impact

Abstract. Paleoreconstructions and modern observations provide us with anomalies of surface temperature over the past millennium. The history of deep ocean temperatures is much less well-known and was simulated in a recent study for the past 2000 years under forced surface temperature anomalies and fixed ocean circulation. In this study, we simulate the past 800 years with an illustrative forcing scenario in the Bern3D ocean model, which enables us to assess the impact of changes in ocean circulation on deep ocean temperature. We quantify the effect of changing ocean circulation by comparing transient simulations (where the ocean dynamically adjusts to anomalies in surface temperature – hence density) to simulations with fixed ocean circulation. We decompose temperature, ocean heat content and meridional heat transport into the contributions from changing ocean circulation and changing sea surface temperature (SST). In the deep ocean, the contribution from changing ocean circulation is found to be as important as the changing SST signal itself. Firstly, the small changes in ocean circulation amplify the Little Ice Age signal at around 3 km depth by at least a factor of 2, depending on the basin. Secondly, they fasten the arrival of this atmospheric signal in the Pacific and Southern Ocean at all depths, whereas they delay the arrival in the Atlantic between about 2.5 and 3.5 km by two centuries. This delay is explained by an initial competition between the Little Ice Age cooling and a warming due to an increase in relatively warmer North Atlantic Deep Water at the cost of Antarctic Bottom Water. Under the consecutive Atlantic meridional overturning circulation (AMOC) slowdown, this shift in water masses is inverted and ageing of the water causes a late additional cooling. Our results suggest that small changes in ocean circulation can have a large impact on the amplitude and timing of ocean temperature anomalies below 2 km depth.

Ice-Core Pollen Record of Climatic Changes in the Central Andes during the last 400 yr

2005 ◽  
Vol 64 (2) ◽  
pp. 272-278 ◽  
Author(s):  
Kam-biu Liu ◽  
Carl A. Reese ◽  
Lonnie G. Thompson
Keyword(s):  
Little Ice Age ◽  
Ice Core ◽  
Climatic Changes ◽  
Ice Age ◽  
Striking Similarity ◽  
Pollen Record ◽  
Dry Period ◽  
Proxy Records ◽  
Ice Cap ◽  
Ice Accumulation

AbstractThis paper presents a high-resolution ice-core pollen record from the Sajama Ice Cap, Bolivia, that spans the last 400 yr. The pollen record corroborates the oxygen isotopic and ice accumulation records from the Quelccaya Ice Cap and supports the scenario that the Little Ice Age (LIA) consisted of two distinct phases�"a wet period from AD 1500 to 1700, and a dry period from AD 1700 to 1880. During the dry period xerophytic shrubs expanded to replace puna grasses on the Altiplano, as suggested by a dramatic drop in the Poaceae/Asteraceae (P/A) pollen ratio. The environment around Sajama was probably similar to the desert-like shrublands of the Southern Bolivian Highlands and western Andean slopes today. The striking similarity between the Sajama and Quelccaya proxy records suggests that climatic changes during the Little Ice Age occurred synchronously across the Altiplano.

scholarly journals Model‐Derived Uncertainties in Deep Ocean Temperature Trends Between 1990 and 2010

2019 ◽  
Vol 124 (2) ◽  
pp. 1155-1169 ◽  
Author(s):  
F. K. Garry ◽  
E. L. McDonagh ◽  
A. T. Blaker ◽  
C. D. Roberts ◽  
D. G. Desbruyères ◽  
...  
Keyword(s):  
Deep Ocean ◽  
Ocean Temperature ◽  
Temperature Trends

Unstable Little Ice Age climate revealed by high-resolution proxy records from northwestern China

2019 ◽  
Vol 53 (3-4) ◽  
pp. 1517-1526 ◽  
Author(s):  
Jianhui Chen ◽  
Jianbao Liu ◽  
Xiaojian Zhang ◽  
Shengqian Chen ◽  
Wei Huang ◽  
...  
Keyword(s):  
High Resolution ◽  
Little Ice Age ◽  
Ice Age ◽  
Northwestern China ◽  
Proxy Records

scholarly journals Was the Little Ice Age more or less El Niño-like than the Medieval Climate Anomaly? Evidence from hydrological and temperature proxy data

2017 ◽  
Vol 13 (3) ◽  
pp. 267-301 ◽  
Author(s):  
Lilo M. K. Henke ◽  
F. Hugo Lambert ◽  
Dan J. Charman
Keyword(s):  
Little Ice Age ◽  
Large Scale ◽  
Global Climate ◽  
Ice Age ◽  
Medieval Climate Anomaly ◽  
Climate Anomaly ◽  
Proxy Data ◽  
The Past ◽  
Proxy Records

Abstract. The El Niño–Southern Oscillation (ENSO) is the most important source of global climate variability on interannual timescales and has substantial environmental and socio-economic consequences. However, it is unclear how it interacts with large-scale climate states over longer (decadal to centennial) timescales. The instrumental ENSO record is too short for analysing long-term trends and variability and climate models are unable to accurately simulate past ENSO states. Proxy data are used to extend the record, but different proxy sources have produced dissimilar reconstructions of long-term ENSO-like climate change, with some evidence for a temperature–precipitation divergence in ENSO-like climate over the past millennium, in particular during the Medieval Climate Anomaly (MCA; AD  ∼  800–1300) and the Little Ice Age (LIA; AD  ∼  1400–1850). This throws into question the stability of the modern ENSO system and its links to the global climate, which has implications for future projections. Here we use a new statistical approach using weighting based on empirical orthogonal function (EOF) to create two new large-scale reconstructions of ENSO-like climate change derived independently from precipitation proxies and temperature proxies. The method is developed and validated using model-derived pseudo-proxy experiments that address the effects of proxy dating error, resolution, and noise to improve uncertainty estimations. We find no evidence that temperature and precipitation disagree over the ENSO-like state over the past millennium, but neither do they agree strongly. There is no statistically significant difference between the MCA and the LIA in either reconstruction. However, the temperature reconstruction suffers from a lack of high-quality proxy records located in ENSO-sensitive regions, which limits its ability to capture the large-scale ENSO signal. Further expansion of the palaeo-database and improvements to instrumental, satellite, and model representations of ENSO are needed to fully resolve the discrepancies found among proxy records and establish the long-term stability of this important mode of climatic variability.

scholarly journals Mass Balance of Rhonegletscher During 1882/83–1986/87

1990 ◽  
Vol 36 (123) ◽  
pp. 199-209 ◽  
Author(s):  
Jiyang Chen ◽  
Martin Funk
Keyword(s):  
Mass Loss ◽  
Mass Balance ◽  
Confidence Level ◽  
Little Ice Age ◽  
Ice Age ◽  
Thickness Change ◽  
Temperature Changes ◽  
Covered Area ◽  
Positive Balance ◽  
Precipitation Changes

AbstractThe glaciological investigations on Rhonegletscher were started in 1874. The mass-balance data measured during 1884/85–1908/09 and during 1979/80–1981/82 are presented. Two methods are used for estimating the mass changes. During 1882/83–1968/69, the cumulative specific net balance is −24 ± 6 m w.e. at the 90% confidence level by the regression model of annual mass balance, annual precipitation, and summer air temperature (the PT model), while the thickness change revealed by the maps is −23 ± 5 m w.e. The cumulative specific net balance during 1882/83–1986/87 is −26 ± 6 m w.e. at the 90% confidence level.The study shows that Rhonegletscher generally experienced mass loss, especially during the periods from the late 1920s through the early 1960s with some short periods of positive balance. The glacier tongue retreated by 970 m during 1882–1986, that is, from 1780 ma.s.l. (1882) to 2130 ma.s.1. (1986). During 1882–1969, the ice-covered area decreased by 4.37 km2 and the volume by 4.71 × 108 m3.The PT models of Rhonegletscher and other alpine glaciers suggest that the contribution of the temperature changes to the mass balance is of more importance than that of the precipitation changes. The great mass loss reflects the climatic warming after the end of the Little Ice Age, with the warmest period occurring around the 1940s in this region.

scholarly journals Temperature changes of the past 2000 yr in China and comparison with Northern Hemisphere

2013 ◽  
Vol 9 (1) ◽  
pp. 507-523 ◽  
Author(s):  
Q. Ge ◽  
Z. Hao ◽  
J. Zheng ◽  
X. Shao
Keyword(s):  
Northern Hemisphere ◽  
Little Ice Age ◽  
Warming Trend ◽  
Warm Period ◽  
Ice Age ◽  
Global Changes ◽  
Least Squares Regression ◽  
Temperature Variations ◽  
Temperature Changes ◽  
The Past

Abstract. In this paper, we use principal components and partial least squares regression analysis to reconstruct a composite profile of temperature variations in China, and the associated uncertainties, at a decadal resolution over the past 2000 yr. Our aim is to contribute a new temperature time series to the paleoclimatic strand of the Asia2K working group, which is part of the PAGES (Past Global Changes) project. The reconstruction was developed using proxy temperature data, with relatively high confidence levels, from five locations across China, and an observed temperature dataset provided by Chinese Meteorological Administration covering the decades from the 1870s to the 1990s. Relative to the 1870s–1990s climatology, our two reconstructions both show three warm intervals during the 270s–390s, 1080s–1210s, and after the 1920s; temperatures in the 260s–400s, 560s–730s and 970s–1250s were comparable with those of the Present Warm Period. Temperature variations over China are typically in phase with those of the Northern Hemisphere (NH) after 1100, a period which covers the Medieval Climate Anomaly, Little Ice Age, and Present Warm Period. The recent rapid warming trend that developed between the 1840s and the 1930s occurred at a rate of 0.91° C/100 yr. The temperature difference between the cold spell (−0.74° C in the 1650s) during the Little Ice Age, and the warm peak of the Present Warm Period (0.08° C in the 1990s) is 0.82° C at a centennial time scale.

scholarly journals Mass Balance of Rhonegletscher During 1882/83–1986/87

1990 ◽  
Vol 36 (123) ◽  
pp. 199-209 ◽  
Author(s):  
Jiyang Chen ◽  
Martin Funk
Keyword(s):  
Mass Loss ◽  
Mass Balance ◽  
Confidence Level ◽  
Little Ice Age ◽  
Ice Age ◽  
Thickness Change ◽  
Temperature Changes ◽  
Covered Area ◽  
Positive Balance ◽  
Precipitation Changes

AbstractThe glaciological investigations on Rhonegletscher were started in 1874. The mass-balance data measured during 1884/85–1908/09 and during 1979/80–1981/82 are presented. Two methods are used for estimating the mass changes. During 1882/83–1968/69, the cumulative specific net balance is −24 ± 6 m w.e. at the 90% confidence level by the regression model of annual mass balance, annual precipitation, and summer air temperature (the PT model), while the thickness change revealed by the maps is −23 ± 5 m w.e. The cumulative specific net balance during 1882/83–1986/87 is −26 ± 6 m w.e. at the 90% confidence level.The study shows that Rhonegletscher generally experienced mass loss, especially during the periods from the late 1920s through the early 1960s with some short periods of positive balance. The glacier tongue retreated by 970 m during 1882–1986, that is, from 1780 ma.s.l. (1882) to 2130 ma.s.1. (1986). During 1882–1969, the ice-covered area decreased by 4.37 km2and the volume by 4.71 × 108m3.The PT models of Rhonegletscher and other alpine glaciers suggest that the contribution of the temperature changes to the mass balance is of more importance than that of the precipitation changes. The great mass loss reflects the climatic warming after the end of the Little Ice Age, with the warmest period occurring around the 1940s in this region.

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