Vegetation, disturbance, and climate history since the onset of ice-free conditions in the Lago Rosselot sector of Chiloé continental (44°S), northwestern Patagonia

Antarctic climate changes have been reconstructed from ice and sediment cores and numerical models (which also predict future changes). Major ice sheets first appeared 34 million years ago (Ma) and fluctuated throughout the Oligocene, with an overall cooling trend. Ice volume more than doubled at the Oligocene-Miocene boundary. Fluctuating Miocene temperatures peaked at 17–14 Ma, followed by dramatic cooling. Cooling continued through the Pliocene and Pleistocene, with another major glacial expansion at 3–2 Ma. Several interacting drivers control Antarctic climate. On timescales of 10,000–100,000 years, insolation varies with orbital cycles, causing periodic climate variations. Opening of Southern Ocean gateways produced a circumpolar current that thermally isolated Antarctica. Declining atmospheric CO2 triggered Cenozoic glaciation. Antarctic glaciations affect global climate by lowering sea level, intensifying atmospheric circulation, and increasing planetary albedo. Ice sheets interact with ocean water, forming water masses that play a key role in global ocean circulation.

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The diversity of opsins in Lake Baikal amphipods (Amphipoda: Gammaridae)

BMC Ecology and Evolution ◽

10.1186/s12862-021-01806-9 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Polina Drozdova ◽

Alena Kizenko ◽

Alexandra Saranchina ◽

Anton Gurkov ◽

Maria Firulyova ◽

...

Keyword(s):

Lake Baikal ◽

Visual Pigments ◽

Ancient Lake ◽

Climate History ◽

Habitat Depth ◽

Long Wavelength ◽

Evolutionary Scenario ◽

Evolutionary Changes ◽

Evolutionary Success ◽

Multiple Species

Abstract Background Vision is a crucial sense for the evolutionary success of many animal groups. Here we explore the diversity of visual pigments (opsins) in the transcriptomes of amphipods (Crustacea: Amphipoda) and conclude that it is restricted to middle (MWS) and long wavelength-sensitive (LWS) opsins in the overwhelming majority of examined species. Results We evidenced (i) parallel loss of MWS opsin expression in multiple species (including two independently evolved lineages from the deep and ancient Lake Baikal) and (ii) LWS opsin amplification (up to five transcripts) in both Baikal lineages. The number of LWS opsins negatively correlated with habitat depth in Baikal amphipods. Some LWS opsins in Baikal amphipods contained MWS-like substitutions, suggesting that they might have undergone spectral tuning. Conclusions This repeating two-step evolutionary scenario suggests common triggers, possibly the lack of light during the periods when Baikal was permanently covered with thick ice and its subsequent melting. Overall, this observation demonstrates the possibility of revealing climate history by following the evolutionary changes in protein families.

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Middle Holocene Climate Oscillations Recorded in the Western Dvina Lakeland

Water ◽

10.3390/w13111611 ◽

2021 ◽

Vol 13 (11) ◽

pp. 1611

Author(s):

Agnieszka Mroczkowska ◽

Dominik Pawłowski ◽

Emilie Gauthier ◽

Andrey Mazurkevich ◽

Tomi P. Luoto ◽

...

Keyword(s):

River System ◽

Summer Temperature ◽

Human Occupation ◽

Holocene Climate ◽

Climate History ◽

Remarkable Feature ◽

Climate Oscillations ◽

Climate Fluctuations ◽

The North ◽

The North Atlantic Oscillation

Although extensive archeological research works have been conducted in the Serteya region in recent years, the Holocene climate history in the Western Dvina Lakeland in Western Russia is still poorly understood. The Neolithic human occupation of the Serteyka lake–river system responded to climate oscillations, resulting in the development of a pile-dwelling settlement between 5.9 and 4.2 ka cal BP. In this paper, we present the quantitative paleoclimatic reconstructions of the Northgrippian stage (8.2–4.2 ka cal BP) from the Great Serteya Palaeolake Basin. The reconstructions were created based on a multiproxy (Chironomidae, pollen and Cladocera) approach. The mean July air temperature remained at 17–20 °C, which is similar to the present temperature in the Smolensk Upland. The summer temperature revealed only weak oscillations during 5.9 and 4.2 ka cal BP. A more remarkable feature during those events was an increase in continentality, manifested by a lower winter temperature and lower annual precipitation. During the third, intermediate oscillation in 5.0–4.7 ka cal BP, a rise in summer temperature and stronger shifts in continental air masses were recorded. It is still unclear if the above-described climate fluctuations are linked to the North Atlantic Oscillation and can be interpreted as an indication of Bond events because only a few high-resolution paleoclimatic reconstructions from the region have been presented and these reconstructions do not demonstrate explicit oscillations in the period of 5.9 and 4.2 ka cal BP.

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Modeling the effects of vegetation on Mediterranean climate during the Roman Classical Period Part I: Climate history and model sensitivity

Global and Planetary Change ◽

10.1016/s0921-8181(00)00002-3 ◽

2000 ◽

Vol 25 (3-4) ◽

pp. 163-184 ◽

Cited By ~ 63

Author(s):

O Reale

Keyword(s):

Mediterranean Climate ◽

Classical Period ◽

Model Sensitivity ◽

Climate History

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Holocene climate change in the Bransfield Basin, Antarctic Peninsula: evidence from sediment and diatom analysis

Antarctic Science ◽

10.1017/s0954102007000788 ◽

2007 ◽

Vol 20 (1) ◽

pp. 69-87 ◽

Cited By ~ 44

Author(s):

David C. Heroy ◽

Charlotte Sjunneskog ◽

John B. Anderson

Keyword(s):

Ocean Circulation ◽

Sediment Accumulation ◽

Sedimentary Facies ◽

Ice Shelf ◽

Diatom Analysis ◽

Climate History ◽

Radiocarbon Dates ◽

Sedimentary Environments ◽

Unstable Surface ◽

Bransfield Basin

AbstractWe present the first study from the Bransfield Basin that extends through the Holocene, recording the variable climate history back to the decoupling of the ice sheet from the continental shelf ~10 650 calendar years before present (cal yr bp). Detailed sediment analysis reveals three stratigraphic units in PC-61 concomitant with three sedimentary environments, similar to sedimentary facies reported elsewhere: 1) subglacial, 2) glacial proximal/sub-ice shelf, and 3) open marine. These interpretations are based on a variety of sedimentological criteria, supported by ten AMS radiocarbon dates and detailed diatom analysis. We note two significant volcanic ash layers (tephra) at 3870 and 5500 cal yr bp from nearby Deception Island. Based on diatom assemblage analysis, we identify five separate climate regimes, highlighting a significantly shorter Mid-Holocene Climatic Optimum than reported by other studies (6800–5900 cal yr bp). This period is marked by the highest Eucampia antarctica var. antarctica and Fragilariopsis curta abundance, total diatom abundance, sediment accumulation rates, and low magnetic susceptibility. We also identify a less pronounced Neoglacial period relative to other studies, which includes an increase of Cocconeis/Rhizosolenia spp. assemblage related to unstable surface water conditions. Such observations probably reflect important regional variations in atmospheric or ocean circulation patterns.

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