Chapter 12: Polar Regions Flashcards
what percent of the earth’s surface is made up of pack ice at its maxium extent?
13%
how are people able to research polar regions?
by setting up ice camps and drift stations
where do icebergs originate from?
broken-off pieces of FW glaciers and ice shelves
what is pack ice?
formed from the freezing seawater in autumn
- ice crystals form to GREASE ICE
- form ICE PANCAKES
- form SUPER PANCAKES
- raft together from wind and waves, freeze.
how cold does the water have to be to form pack ice?
-1.8*C
how big are ice pancakes?
5-10cm in dia
what are the differences btwn arctic and Antarctic pack ice?
- arctic ocean has more ice
- arctic basin is almost enclosed entirely
- southern ocean is circumpolar
- arctic ice last for up to 10 years
- arctic ocean only has a mean depth of 1800m
- Antarctic pack ice zone range between 4000-6500m deep
- lots of FW rivers run-off in the arctic basin
what percentage of the total southern ocean primary productivity occurs in the sea ice?
up to 5%
what is the main microbiota found?
pennate diatoms
how do microbes survive in the ice sheets?
brine channels within ice creates refuges
what are physiological pre-requisites for survival in a block of ice?
adaptations to low light, low temp and high salinities
what important nutrient source does bacteria and microalgae produce?
PUFAs
-poly unsaccharied fatty acids
what happens when sea ice melts?
- FW release lowers salinity levels
- stabelizes upper water column
- creates frontal system
- algal blooms
- higher rates of grazing
how does the algal blooms influence other habitats?
- feeding ground for entire food webs
- faecal pellet production results in a large downward flux of biogenic material to the underlying sediments
strong ________ in the open arctic waters
pynocline
high concentrations of _____ ____ in the southern ocean
inorganic nutrients
large variation in ____ _______ in the arctic
latitudinal gradients
what is the relationship between krill, whales, iron, and ocean productivity?
if whales are able to recover, the result will be an increase of iron in the ocean, therefore increasing ocean’s productivity. The amount of iron in krill is so high that the fecal matter of whales are particularily iron-rich.
what occurs with the grounding of icebergs?
- considerable damage to the benthic communities
- scour
- sessile species eradicated and pioneer spp grow in high abundances
the largest proportion
of the Antarctic shelf benthos is made up of what?
sessile suspension-feeders (sponges, cniderians, bryozoans, echninoderms)
how do organisms feed during winter months when there is no primary productivity?
- resuspension of sediments
- lateral advection of organic rich material
what percentage of fish genera and species are endemic in the antarctic?
70% fish genera
95% fish spp
why are there so many endemic spp in the arctic, Antarctic?
- greater age
- longer isolation
why gigantism in polar regions?
- low water temp = low metabolic rates
- growth rates slow enough to enable them to live longer
- higher DO concentration in water
