Download Rapid Climate Change During the Holocene

Chapter 16 – Rapid Climate Change During the Holocene
16.1 Introduction to the Holocene
 The last 10,000 of the Pleistocene are commonly referred to as the Holocene
Epoch, or simply, the “Recent”
 Ice core studies indicate that natural climate change during the Holocene has often
been quite abrupt and rapid
o Such climate change is now understood to occur at sub-Milankovitch time
scales (over time spans less than a few thousand years down to durations
as short as decades of less
16.2 Beginning of the Holocene
 Sea-Level Rise
o The Holocene is marked by sea-level rise, augmented in some localities by
isostatic rebound
o Rapid sea-level rise may occur catastrophically for various reasons, such
as collapse of the Antarctic ice sheets
 Younger Dryas
o The Holocane actually began twice; as the world began to warm, it
suddenly turned cold again during the Younger Dryas interval
o Named for a cold-tolerant flowering plant represented by abundant pollen
in sediments from about 13,000 years ago, the interval lasted roughly 1000
years
o It have had a rapid onset, with much of the initial cooling in as little as a
decade
o The cooing may have been caused by a freshwater layer preventing the
formation and sinking of North Atlantic Deep Water, which increased
ocean productivity and the drawdown of CO2
16.3 Rapid Climate Change on Millennial Time Scales
 Rapid Climate Change Involving the Oceans
o Evidence shows that meltwater pulses like the Younger Dryas occurred
repeatedly during the Holocene
o These are indicated by layers of ice-rafted debris called Heinrich events,
which occur every 1500 years
o Ice-rafting events also occurred before the Holocene, so other factors may
be involved, such as changes in solar radiation
 Rapid Climate Change on Land
o Speleothems (cave-deposited travertine) provide records of changes in
temperature and precipitation reflecting shifts in air masses over land
o The oxygen isotope record from speleothems corresponds to welldocumented changes in vegetation; these in turn reflect changes in
precipitation
16.4 Rapid Climate Change on Centennial Time Scales
 Newly emerging evidence indicates that climate fluctuates significantly on
centennial (century) time scales
o There is a growing realization that the sun may be involved
o Sunspots appear to be related to gigantic magnetic storms on the sun’s
surface; they have an 11-year-long activity cycle
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o Longer cycles of sunspot minima may occur during prolonged intervals of
harsher climate, such as the “Little Ice Age” (1850-1880 A.D.)
16.5 Rapid Climate Change on Interdecadal to Multidecadal Time Scales
 Rapid climate change on interdecadal to multidecadal scales represent attempts by
Earth’s systems to redistribute heat by atmospheric and oceanic currents
o The resulting fluctuation of the convection cells associated with these
changes has led to these phenomena being referred to as “oscillations”
o These oscillations and other ocean-atmospheric phenomena are linked by
long-distance teleconnections
o The oscillations and teleconnections may be influenced by changes in soar
radiation and anthropogenic activities, although this is complex and
remains poorly understood
o The El Niño-Southern Oscillation (ENSO) is one of the best understood
oscillations; La Niñas, in which conditions reverse themselves, sometimes
follow El Niño events
16.6 Climatic Modes and Climatic Irreversibility
 Given the complexity of the systems involved in regulating Earth’s climate, it is
difficult to predict the exact mode that Earth’s climate will occupy in the immediate
future
o Climate scientists state that anthropogenic production of carbon dioxide
has caused some of the warming during the 20th century
o Anthropogenic warming may dominate climate during the next few
centuries or longer
o Carbon dioxide may accumulate in Earth’s atmosphere with relatively
little effect until a threshold is crossed and climate suddenly shifts into an
entirely new mode
© 2013 Jones and Bartlett Learning, LLC