Antarctic climate cooling and terrestrial ecosystem response 환경계획학과 환경관리전공 김지연

Study site Antarctica including McMurdo Dry Valley ◦ S, ◦ E

( Images/images.php3?img_id=7272) - largest ice-free area - cold desert - biological activity; microbially dominated, diversity; low - largest andimals; soil invertebrates ( uplandlimestone/surface/dry_valley.html)

background The average air temperature at the Earth ’ s surface; increased by 0.06 ℃ (20 th century) per decade and by 0.19 ℃ ( ) Climate model; predicted warming in polar regions, but spatial analysis of Antarctica demonstrates a net cooling particularly summer and autumn. Summer cooling is important to Antarctic terrestiral ecosystem.

objective To represent evidence of rapid terrestrial ecosystem response to climate cooling in Antarctica, including primary productivity of lakes, numbers of soil invertebrates

Methods 1.Dry valley ecosystem parameters -meteorological data; air temperature, wind speed, solar flux, relative humidity, stream flow ; using Campbell Scientific data loggers 1) air temperature; cllected using a fenwall-type theimistor and caluculated using Steinhart-Hart equation 2) wind speed; measured using speed sensor and wind direction sensor 3) solar flux; measured using LiCor model LI-200 pyranometers 4) relative humidity; measured using Phis-Chem humidity transducers in Cambell Scientific 207 probes 5) stream flow; measured using pressure transducers in flumes

2. soil moisture; determined from 50g soil samples collected in the field 3. Irradiance in water; measured with a Li-Cor model 193 spherical quantum( nm) sensor 4. Primary productivity; measured using the 14C method 5. Nematode; for analysis, soil samples were collected and transported in insulated coolers(4 ℃ ), then nematodes were extracted from the soils and modified. Extracted nematodes were identified to genus level. All nematode counts were adjusted for soil moisture to give number of nematodes /kg dry soil Methods

6. Continental temperature trend ; continental temperature trend map ; computed from data set. Methods

Air temperature Seasonally averaged surface air temperature; decreased by 0.7 ℃ per decade Summer and autumn; decreased prononcely Winter and spring; increased slighthly result

Dry valley cooling, its seasonal pattern → reflect longer term continental Antarctic cooling( ) ; consistent with maps of individual station trends( ) in IPCC report

Wind speed - Seasonally averaged wind speed ; decreased by 0.23m/s per decade at Lake Hoare - correlated with seasonally averaged temperature decrease ; Annual temperature; controlled by exposure to wind → long-term temperature change in coastal Antarctica; synoptic controls on surface, wind variability result

Solar radiation - Seasonally averaged solar radiation ; increased 8.1 w/m 2 ( ) -summer; decreased with increasing wind speed -Spring and autumn; increased with increasing wind speed -high wind; coudiness → increased solar radiation ; related to decreased wind, associated cloudiness result

Moisture indices 1)Relative humidity, precipitation; inconclusive 2)Snow accumulation; no clear trend 3)Cloudiness; decreased 4)Soil moisture; decreased 0.8%(by weight) result

hydrology - discharges from the eight inflow streams ; decreased nonlinearly by an average rate of ㎥ /yr -discharge; glacial melt, snow banks(a little) ← Dependent on summer temperature, solar radiation stream result

hydrolgy Lake level - the thickness of lake ice ; increased at an average rate of 11cm/yr ; in response to the lower temperature Lake ice - lake level ; receded in response to cooler summers result

Ecosystem properties - Underwater irradiance; reduced by 0.055mol/phtons m 2 d ← phytoplankton primary production in lakes is limited by light - The rate of primary productivity; decreased ← decrease in radiance ⇒ reduced primary production; exacerbate this situation, may play a role of CO 2 source, become depleted in organic carbon stores result

Soil invertebrate communities - Changes in abundance in tardigfades, nematodes ;decreased → shifts in the diversity, life cycles, trophic relationships and functioning of dry valley soils. result

conclusion Rapid terrestrial ecosystem response to climate cooling in Antarctica → decreased primary productivity of lakes, declining numbers of soil invertebrates. Cooling trend is correlated with decreased winds and increased clear-sky conditions. Prolonged summer cooling will diminish aquatic and soil biological assemblages throughout the valleys, Antarctic ecosystems. Summer temperatures are the critical driver of Antarctic terrestrial ecosystems

reference Doran, P.T. and others Antarctic climate cooling and terrestrial ecosystem response. Nature 415: