WordNet (r) 3.0 (2006):

upsurge
    n 1: a sudden forceful flow [syn: rush, spate, surge,
         upsurge]
    2: a sudden or abrupt strong increase; "stimulated a surge of
       speculation"; "an upsurge of emotion"; "an upsurge in violent
       crime" [syn: surge, upsurge]

Moby Thesaurus II by Grady Ward, 1.0:

127 Moby Thesaurus words for "upsurge":
   access, accession, accretion, accrual, accruement, accumulation,
   addition, advance, aggrandizement, amplification, anabasis,
   appreciation, arise, ascend, ascension, ascent, augment,
   augmentation, ballooning, bloating, boom, boost, broadening, build,
   buildup, clamber, climb, climbing, come up, crescendo,
   curl upwards, development, edema, elevation, enlarge, enlargement,
   escalade, expand, expansion, extension, flood, fountain, gain,
   go up, greatening, grow up, growth, gush, gyring up, heighten,
   hike, increase, increment, inflation, jet, jump, leap, levitate,
   levitation, loom, mount, mounting, multiplication, multiply,
   productiveness, proliferation, raise, rear, rear up, rise, rise up,
   rising, rocketing up, saltation, shooting up, snowballing, soaring,
   spiral, spire, spout, spread, spring, spurt, stand up, surge,
   swarm up, sweep up, swelling, takeoff, taking off, tower,
   tumescence, up, upclimb, upcoming, updraft, upgang, upgo, upgoing,
   upgrade, upgrow, upgrowth, upheave, uphill, upleap, uplift, upping,
   uprisal, uprise, uprising, uprush, upshoot, upslope, upspin,
   upstream, upsurgence, upswarm, upsweep, upswing, uptrend, upturn,
   upwind, vault, wax, waxing, widening, zooming