Table 1: Summary of groove parameters from observations.

date	range N	range S	center	depth N	depth S
1996.43	25.1	-33.0	-7.0	1.37	1.23
1996.93	28.7	-39.2	-8.0	1.31	1.25
1997.43	28.9	-35.7	-6.0	1.39	1.25
1997.93	29.4	-39.9	-8.0	1.41	1.26
1998.43	40.4	-38.4	-1.0	1.29	1.22
1998.93	41.3	-47.4	-9.0	1.40	1.24
1999.43	44.1	-62.0	-33.0
1999.93	34.9	-61.2	-24.0