Long-Term Changes Flashcards
What does the climate record over the last million years show?
The climate record over the last million years shows that the Earth’s climate has been highly unstable, with large fluctuations in global temperatures occurring at regular intervals.
How many major glacial cycles have occurred in the past 400,000 years?
In the past 400,000 years, there have been four major glacial cycles.
What are the characteristics of these glacial cycles?
The glacial cycles consist of cold glacials followed by warmer inter-glacials, each lasting around 100,000 years.
What were the average annual temperatures in the British Isles during the last glacial period?
At the height of the last glacial, 20,000 years ago, average annual temperatures in the British Isles were 5°C lower than today.
How much ice covered Scotland, Wales, northern England, and Ireland during the last glacial period?
During the last glacial period, Scotland, Wales, most of northern England, and Ireland were submerged by ice up to 1 km thick.
How do temperatures during warm inter-glacial periods compare to today’s temperatures?
During warm inter-glacial periods, temperatures were similar to those of today.
How extreme were global temperatures 250 million years ago compared to today?
250 million years ago, average global temperatures reached 22 °C, which is at least 7-8°C higher than today’s temperatures.
What impacts did the climatic shifts have on the water and carbon cycles?
The climatic shifts had a major impact on the water and carbon cycles.
What happens to the water cycle during glacial periods?
During glacial periods, there is a net transfer of water from the ocean reservoir to storage in ice sheets, glaciers, and permafrost. As a result, the sea level worldwide falls by 100-130 m, and ice sheets and glaciers expand to cover around one-third of the continental land mass. The destruction of forest and grassland occurs as ice sheets advance equatorwards, while in the tropics, the climate becomes drier and deserts and grasslands replace rainforests.
How do glacial phases affect evapotranspiration and water exchange?
Lower rates of evapotranspiration during glacial phases reduce exchanges of water between the atmosphere and the oceans, biosphere, and soils.
What is the most striking feature of the carbon cycle during glacial periods?
The most striking feature of the carbon cycle during glacial periods is the dramatic reduction in atmospheric CO₂ concentrations.
What is the correlation between temperature and atmospheric CO₂ over the past 400,000 years?
There is a close correlation between temperature and atmospheric CO₂ over the past 400,000 years.
What are the atmospheric CO₂ concentrations during glacial maxima and warmer inter-glacial periods?
During glacial maxima, CO₂ concentrations fall to around 180 ppm, while in warmer inter-glacial periods, they are 100 ppm higher.
Is there a clear explanation for the drop in atmospheric CO₂ during glacial periods?
No clear explanation exists for the drop in atmospheric CO₂ during glacial periods.
How does excess CO₂ find its way from the atmosphere to the deep ocean during glacial periods?
One possible mechanism is changes in ocean circulation during glacials that bring nutrients to the surface and stimulate phytoplankton growth. Phytoplankton fix large amounts of CO₂ through photosynthesis before dying and sinking to the deep ocean, where the carbon is stored. Lower ocean temperatures also make CO₂ more soluble in surface waters, facilitating its transfer to the deep ocean.
