Abstract
The southwest monsoon is responsible for a summer precipitation maximum for much of the southwest U.S. Biostratigraphies of pollen, plant macrofossils, and aquatic fossils in lakes from near modern monsoon boundaries in conjunction with climate modelling suggests variations in strength of the monsoon system during the late Quaternary. At Montezuma Well, Arizona, high percentages of Pinus and Juniperus pollen as well as maximum influxes of Quercus and Gramineae pollen suggest a shift from dominantly winter to summer precipitation between ca. 12,000 and 9000 yr BP. Maximum aridity occurred 7000-4000 yr BP, coincident with lowest lake levels. In the High Plateaus region of the Colorado Plateau, high Artemisia to Chenopodiaceae-Amaranthus pollen ratios suggests precipitation maxima until ca. 6000 yr BP at Fryingpan Lake and 5000 yr BP at Posy Lake. Pollen records suggest that Pinus edulis, P. ponderosa, and Quercus gambelii, were present on the western Colorado Plateau throughout the Holocene. Expansion of shadscale steppe vegetation at low elevations and upslope movement of ecotones for Pinus edulis, P. ponderosa, and Q. gambelii after ca. 6000 yr BP and low lake levels ca. 5000-3700 yr BP, suggest a period of maximum aridity from decreased summer precipitation. In the San Luis Valley, Colorado, pollen records from Head Lake on the basin floor suggest an expansion of oaks and junipers at the Pleistocene/Holocene boundary that may indicate increased summer precipitation. Lake levels of Head Lake fell sharply after ca. 9500 yr BP. Pollen records from Como Lake in the Sangre de Cristo Mountains suggest that Pinus ponderosa was established in the area by ca. 12,000 yr BP and Pinus edulis by ca. 9500 yr BP. Highland regions such as the High Plateaus (until ca. 6000-5000 yr BP) and central Colorado (until ca. 4000 yr BP) may have experienced Holocene summer precipitation maxima later into the Holocene than sites in lower elevation regions. Regional orographic uplift as a catalyst for convective summer precipitation may be responsible for the duration of summer precipitation maxima in these regions. On a longitudinal gradient, sites to the west such as in the southern Great Basin and Mohave Desert may have recorded enhanced summer precipitation earlier, reflecting different histories of the low-level jets in the southwest. The paleoecologic record generally confirm predictions of general circulation models (GCMs) that southwest monsoon circulation was enhanced from 12,000-6000 yr BP in response to peaks in annual (11,500-11,000 yr BP) and summer insolation (10,000-9000 yr BP) during the late Quaternary.
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Claims 19
Claim · model-written summary
High percentages of Pinus and Juniperus pollen at Montezuma Well suggest a shift from winter to summer precipitation between ca. 12,000 and 9000 yr BP.
- Outcome
- percentages of Pinus and Juniperus pollene0
- Direction
- highe0
- Qualifier
- a shift from dominantly winter to summer precipitation between ca. 12,000 and 9000 yr BPe0
- Setting
- Montezuma Well, Arizonae0
Pinus
JuniperusOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At Montezuma Well, Arizona, high percentages of Pinus and Juniperus pollen as well as maximum influxes of Quercus and Gramineae pollen suggest a shift from dominantly winter to summer precipitation between ca. 12,000 and 9000 yr BP. Maximum aridity occurred 7000-4000 yr BP, coincident with lowest lake levels.”
Claim · model-written summary
Maximum influxes of Quercus and Gramineae pollen at Montezuma Well suggest a shift to summer precipitation between ca. 12,000 and 9000 yr BP.
- Outcome
- influxes of Quercus and Gramineae pollene0
- Direction
- maximume0
- Qualifier
- between ca. 12,000 and 9000 yr BPe0
- Setting
- Montezuma Well, Arizonae0
QuercusOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At Montezuma Well, Arizona, high percentages of Pinus and Juniperus pollen as well as maximum influxes of Quercus and Gramineae pollen suggest a shift from dominantly winter to summer precipitation between ca. 12,000 and 9000 yr BP. Maximum aridity occurred 7000-4000 yr BP, coincident with lowest lake levels.”
Claim · model-written summary
Maximum aridity occurred between 7000 and 4000 yr BP, coincident with the lowest lake levels.
Not reportedTaxon
Verbatim
e0“At Montezuma Well, Arizona, high percentages of Pinus and Juniperus pollen as well as maximum influxes of Quercus and Gramineae pollen suggest a shift from dominantly winter to summer precipitation between ca. 12,000 and 9000 yr BP. Maximum aridity occurred 7000-4000 yr BP, coincident with lowest lake levels.”
Claim · model-written summary
High Artemisia to Chenopodiaceae-Amaranthus pollen ratios at Fryingpan Lake suggest precipitation maxima until ca. 6000 yr BP.
- Outcome
- Artemisia to Chenopodiaceae-Amaranthus pollen ratiose1
- Direction
- highe1
- Qualifier
- precipitation maxima until ca. 6000 yr BP at Fryingpan Lakee1
- Setting
- High Plateaus region of the Colorado Plateaue1
ArtemisiaOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In the High Plateaus region of the Colorado Plateau, high Artemisia to Chenopodiaceae-Amaranthus pollen ratios suggests precipitation maxima until ca. 6000 yr BP at Fryingpan Lake and 5000 yr BP at Posy Lake.”
Claim · model-written summary
High Artemisia to Chenopodiaceae-Amaranthus pollen ratios at Posy Lake suggest precipitation maxima until ca. 5000 yr BP.
- Outcome
- Artemisia to Chenopodiaceae-Amaranthus pollen ratiose1
- Direction
- highe1
- Qualifier
- 5000 yr BP at Posy Lakee1
- Setting
- High Plateaus region of the Colorado Plateaue1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In the High Plateaus region of the Colorado Plateau, high Artemisia to Chenopodiaceae-Amaranthus pollen ratios suggests precipitation maxima until ca. 6000 yr BP at Fryingpan Lake and 5000 yr BP at Posy Lake.”
Claim · model-written summary
Pinus edulis, P. ponderosa and Quercus gambelii were present on the western Colorado Plateau throughout the Holocene.
- Taxon
- Pinus edulis, P. ponderosa, and Quercus gambelii
Pinus edulis
Pinus ponderosa_(Warner_Point_Trail%2C_Black_Canyon_of_the_Gunnison_National_Park%2C_Colorado%2C_USA)_1_(19684871270).jpg?width=60)
Quercus gambeliie2 - Outcome
- presente2
- Qualifier
- throughout the Holocenee2
- Setting
- western Colorado Plateaue2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
_(Warner_Point_Trail%2C_Black_Canyon_of_the_Gunnison_National_Park%2C_Colorado%2C_USA)_1_(19684871270).jpg?width=500)
Verbatim
e2“Pollen records suggest that Pinus edulis, P. ponderosa, and Quercus gambelii, were present on the western Colorado Plateau throughout the Holocene. Expansion of shadscale steppe vegetation at low elevations and upslope movement of ecotones for Pinus edulis, P. ponderosa, and Q. gambelii after ca. 6000 yr BP and low lake levels ca. 5000-3700 yr BP, suggest a period of maximum aridity from decreased summer precipitation.”
Claim · model-written summary
Ecotones of Pinus edulis, P. ponderosa and Q. gambelii moved upslope after ca. 6000 yr BP.
- Taxon
- Pinus edulis, P. ponderosa, and Q. gambeliiPinus edulisPinus ponderosaQuercus gambeliie2
- Outcome
- upslope movement of ecotonese2
- Direction
- upslope movemente2
- Qualifier
- after ca. 6000 yr BPe2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“Pollen records suggest that Pinus edulis, P. ponderosa, and Quercus gambelii, were present on the western Colorado Plateau throughout the Holocene. Expansion of shadscale steppe vegetation at low elevations and upslope movement of ecotones for Pinus edulis, P. ponderosa, and Q. gambelii after ca. 6000 yr BP and low lake levels ca. 5000-3700 yr BP, suggest a period of maximum aridity from decreased summer precipitation.”
Claim · model-written summary
Expansion of shadscale steppe vegetation at low elevations suggests a period of maximum aridity from decreased summer precipitation.
Verbatim
e2“Pollen records suggest that Pinus edulis, P. ponderosa, and Quercus gambelii, were present on the western Colorado Plateau throughout the Holocene. Expansion of shadscale steppe vegetation at low elevations and upslope movement of ecotones for Pinus edulis, P. ponderosa, and Q. gambelii after ca. 6000 yr BP and low lake levels ca. 5000-3700 yr BP, suggest a period of maximum aridity from decreased summer precipitation.”
Claim · model-written summary
Low lake levels between ca. 5000 and 3700 yr BP suggest a period of maximum aridity.
Not reportedTaxon
Verbatim
e2“Pollen records suggest that Pinus edulis, P. ponderosa, and Quercus gambelii, were present on the western Colorado Plateau throughout the Holocene. Expansion of shadscale steppe vegetation at low elevations and upslope movement of ecotones for Pinus edulis, P. ponderosa, and Q. gambelii after ca. 6000 yr BP and low lake levels ca. 5000-3700 yr BP, suggest a period of maximum aridity from decreased summer precipitation.”
Claim · model-written summary
Pollen records from Head Lake suggest an expansion of oaks and junipers at the Pleistocene/Holocene boundary that may indicate increased summer precipitation.
- Outcome
- expansion of oaks and juniperse3
- Direction
- expansione3
- Qualifier
- at the Pleistocene/Holocene boundarye3
- Setting
- San Luis Valley, Coloradoe3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e3“In the San Luis Valley, Colorado, pollen records from Head Lake on the basin floor suggest an expansion of oaks and junipers at the Pleistocene/Holocene boundary that may indicate increased summer precipitation. Lake levels of Head Lake fell sharply after ca. 9500 yr BP.”
Claim · model-written summary
Lake levels of Head Lake fell sharply after ca. 9500 yr BP.
Not reportedTaxon
Verbatim
e3“In the San Luis Valley, Colorado, pollen records from Head Lake on the basin floor suggest an expansion of oaks and junipers at the Pleistocene/Holocene boundary that may indicate increased summer precipitation. Lake levels of Head Lake fell sharply after ca. 9500 yr BP.”
Claim · model-written summary
Pinus ponderosa was established in the Como Lake area by ca. 12,000 yr BP.
- Taxon
- Pinus ponderosaPinus ponderosae4
- Outcome
- established in the areae4
- Qualifier
- by ca. 12,000 yr BPe4
- Setting
- Como Lake in the Sangre de Cristo Mountainse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e4“Pollen records from Como Lake in the Sangre de Cristo Mountains suggest that Pinus ponderosa was established in the area by ca. 12,000 yr BP and Pinus edulis by ca. 9500 yr BP.”
Claim · model-written summary
Pinus edulis was established in the Como Lake area by ca. 9500 yr BP.
- Taxon
- Pinus edulisPinus edulise4
- Outcome
- established in the areae4
- Qualifier
- by ca. 9500 yr BPe4
- Setting
- Como Lake in the Sangre de Cristo Mountainse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e4“Pollen records from Como Lake in the Sangre de Cristo Mountains suggest that Pinus ponderosa was established in the area by ca. 12,000 yr BP and Pinus edulis by ca. 9500 yr BP.”
Claim · model-written summary
Summer precipitation maxima may have lasted later into the Holocene on the High Plateaus, until ca. 6000-5000 yr BP.
- Outcome
- summer precipitation maximae5
- Direction
- latere5
- Qualifier
- until ca. 6000-5000 yr BPe5
- Setting
- High Plateause5
Not reportedTaxon
Verbatim
e5“Highland regions such as the High Plateaus (until ca. 6000-5000 yr BP) and central Colorado (until ca. 4000 yr BP) may have experienced Holocene summer precipitation maxima later into the Holocene than sites in lower elevation regions.”
Claim · model-written summary
Summer precipitation maxima may have lasted later into the Holocene in central Colorado, until ca. 4000 yr BP.
- Outcome
- summer precipitation maximae5
- Direction
- latere5
- Qualifier
- until ca. 4000 yr BPe5
- Setting
- central Coloradoe5
Not reportedTaxon
Verbatim
e5“Highland regions such as the High Plateaus (until ca. 6000-5000 yr BP) and central Colorado (until ca. 4000 yr BP) may have experienced Holocene summer precipitation maxima later into the Holocene than sites in lower elevation regions.”
Claim · model-written summary
Regional orographic uplift may be responsible for the duration of summer precipitation maxima in the highland regions.
- Outcome
- duration of summer precipitation maximae6
- Qualifier
- Regional orographic uplift as a catalyst for convective summer precipitatione6
Not reportedTaxon
Verbatim
e6“Regional orographic uplift as a catalyst for convective summer precipitation may be responsible for the duration of summer precipitation maxima in these regions. On a longitudinal gradient, sites to the west such as in the southern Great Basin and Mohave Desert may have recorded enhanced summer precipitation earlier”
Claim · model-written summary
Sites in the southern Great Basin and Mohave Desert may have recorded enhanced summer precipitation earlier than highland sites.
- Outcome
- enhanced summer precipitatione6
- Direction
- earliere6
- Setting
- southern Great Basin and Mohave Deserte6
Not reportedTaxon
Verbatim
e6“Regional orographic uplift as a catalyst for convective summer precipitation may be responsible for the duration of summer precipitation maxima in these regions. On a longitudinal gradient, sites to the west such as in the southern Great Basin and Mohave Desert may have recorded enhanced summer precipitation earlier”
Claim · model-written summary
The paleoecologic record generally confirms model predictions that southwest monsoon circulation was enhanced from 12,000 to 6000 yr BP.
- Outcome
- southwest monsoon circulation was enhancede7
- Direction
- enhancede7
- Qualifier
- from 12,000-6000 yr BPe7
Not reportedTaxon
Verbatim
e7“The paleoecologic record generally confirm predictions of general circulation models (GCMs) that southwest monsoon circulation was enhanced from 12,000-6000 yr BP in response to peaks in annual (11,500-11,000 yr BP) and summer insolation (10,000-9000 yr BP) during the late Quaternary.”
Claim · model-written summary
Southwest monsoon circulation was enhanced from 12,000 to 6000 yr BP in response to insolation peaks.
- Outcome
- southwest monsoon circulation was enhancede7
- Qualifier
- in response to peaks in annual (11,500-11,000 yr BP) and summer insolation (10,000-9000 yr BP)e7
Not reportedTaxon
Verbatim
e7“The paleoecologic record generally confirm predictions of general circulation models (GCMs) that southwest monsoon circulation was enhanced from 12,000-6000 yr BP in response to peaks in annual (11,500-11,000 yr BP) and summer insolation (10,000-9000 yr BP) during the late Quaternary.”